HP 3458A - Fails Slave Test - Convergence

[Dr. Frank]

Managed to purchase maybe 5 years ago , upon trying to power on at that time I found the inguard board was burnt around CR11,CR12 maybe caused by the incorrect power setting from the previous owners. These were replaced and the system powered on, but due to travelling allot at the time it was switched off and left for 2-3 years.


Many tx Ade.

Hello Ade,
I'm trying to get some light in your recent descriptions..

CR11 and CR 12 are on A1, SENTRY, Input Signal Conditioning, and on A4, inguard power supply (an "Inguard board" is not existent).
That's very confusing.

Please name all components correctly,  best would be using the BOM designator, like A1CR11 and A1CR12, or A4CR11, A4CR12, and so on.
Please describe in detail, which components were damaged at that time, A4CR11 + CR12 only?

Frank (to be continued)

[Dr. Frank]

Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again.

Ive checked the Convergence circuit with my very limited understanding of the circuit.    FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working.

As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in]   

@ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle.
Therefore it's completely normal, that you see varying voltages on that pin.
If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle.

If you switch off AZ, then the 10V should be visible continuously @ TP11.

Please try that out

[Dr. Frank]

update

So I guess the dallas chips are from 1995 week 38 / 47 after watching videos about them, ill order replacements and hope you can clarify how i can download and replace.

I also found an old communication from TiN re the TARM command, OMW , after doing this the meter came to life and did a few samples before stopping again [but it is repeatable]. With nothing connected im getting various voltages between +5.xxx and +10.xxx , If you do an autozero i then get +10.xxxxv.

What PCB / TP are you talking about?
Where do you measure these signals?

[Dr. Frank]

I checked U181 and this looks fine,

All signals are fine except pin 3 where it toggles only to 7v during a DCV cal then fails / stops sampling, or 10v when it does a little more sampling and the output jumps to 5v [plus relay clicks on].

U142 , again I believe is ok, the output is toggling between 0 and 5v, however if I scope the input pin 3 the sampling fails [TP140] , its as if the system doesn't like the extra load, which is strange as its only a normal scope probe.

How did you confirm / measure, that the EL2018 are working ok?
Did you scope  on their outputs?

[Dr. Frank]

Todays update

only samples if i manually trigger TARM command, no idea why.

when i initially started to look inside i found the voltage on U100 pin 6 is slowly drifting up , its still doing it now. Unfortunately I damaged Q106 but was able to replace so didnt think any more about it, but today I find myself again back here as the signal DC_AD is slowly rising and is reflected on the screen [least I know the DAC is ok]

Have you applied a fixed input voltage (only at the input jacks, of course!) for that test?
Use TP100, instead of A1U100 - pin6. switch AZ off for that test.
If you apply fixed 10V in 10V range, then you should see that 10V at TP100.
apply 1V in 1V range, you should see 10V as well, repeat that for 100mV in 100mV range, please

screen readings

DCV volts ? +0.689 max then freezes - error message time out read A/D 108 [but it cant be the DAC]
ACV mv samples for ever 1.945mv AC
ACV 000.081 and rising VAC
OHMS +0.VLD GOHM
OHMS +OVL.D MOHM stops sampling
OHMS +OV.LD KOHM
OHMS +OV.LD OHM
DCI nA 000.173
DCI uA 0.000159 stops sampling
DCI mA 0.0000248
DCI A 0.0000135
ACI uA 000.0434
ACI mA 0.000286
ACI A 0.000268
FREQ 50.xxx HZ

Data error matches system asking for DCV and OHMS calibration

Any support most welcome please

Tx Ade

Please explain, what are you doing here, I do not know (or can't guess) what you mean with screen display, which sources you apply, and what mode / range you select in each case

[Dr. Frank]

For some strange reason when you inject 10V and manually cycle through  the X1, X10 , initially when you selected mv the meter wouldn't do anything now it states overload and samples , no idea why.

Monitoring A1 TP100

X1 10V I/P 10V TP100
X10 10V I/P 1V TP100
x100 10V I/P 0.1V TP100

Below X1 [mV ?] 10V I/P Overload [ sampling] TP100 = 17.39V

I thought the input to the A3 would never exceed 10V , is this incorrect.

Ive also noticed that if you remove the 10V I/P and set to X1 TP100 starts to drive up towards 17.39V, is this normal.

Also removed Jumper P100 and there is no input via P102 and still does it.

Any idea where to check next please, I hope that because the voltage from A1 if above 10V the A-D will not sample and there is some limit circuit stopping 17V damaging the device.

 Trying to be logical and methodical in finding what is wrong.

TP100 (w/o AZ) is the input signal times the range amplification, i.e. x1, for 10V range, x10 for 1V range and x100 for the 100mV range.
Where did you inject the 10V?
At the input jacks only, hopefully.
If you overload the amplifier, then of course you get +/-17V something out of U100.
The input to the ADC can of course be +/-12V for full scale.

[Dr. Frank]

Hi 3458A knowledge group, so after ordering spare parts and fitting things still look bad. I really don't know what happened to the unit, be it a surge or something I really don't know;

Status

Repositioned JMP600 to pin 1-2 [Right side] Front of meter facing me - Calibration security code

Fitted NEW U105 --> LT1008CN8 out put was floating/drifting 

Replaced Q106 - Damaged CAN
Replaced Q107 with  J112      [Found the resistance between the Gate and Drain on a meter changes over time] - Causing TP100 to rise in voltage to 17V or so.
Replaced Q108 with J112       [ Not 100% sure before removing both which was causing the voltage on TP100 to rise.

Now

Original error still there.
Input connected to +10V, +10V now read on TP100 [x10 = 1v , x100 = 0.1].
Short input pins TP100 = 0V

Set DC to mV [No short input floating] X1 or X 10 - DC TP100 now ready +17V !

DC X1 ~ +1.5V , X10 +0.042, X100 +0.004V

Not sure where the +17V is being generated from [High voltage relays not used I assume]

If I try and do a CAL 0 the meter does something then beeps

If I try and do and CAL from the manual nothing changes

If I try AUTOCAL DCV nothing changes

Im therefor not sure where to check next.

Any advice would be so very much received please as I have no idea what to check next.

New error message

Select mV
Enable TARM
System now samples with overvoltage error - TP100 = +17V
Select X1 - TP100 = +10V , no sample [ ERRSTR 101,"CALIBRATION ERROR"

why have you changed A1Q107 / Q108?
Put in the original transistors, please.
Hopefully you now understand, how this circuit part works?

[Dr. Frank]

Hello Frank,

Not sure if you can answer ; if i have access to another unit , would board swapping cause issues with the other unit, not ideal but run out of ideas before asking for a quote from the OEM.

Im stuck, I don't seem to be able to find out anywhere where it states the system will still sample even if U180 is dead. It will sample if TRAM is activated , no input and DCV dropped to mV but im not sure why this happens but not in volt range.

OVLD signal on U228 is working fine.

You have probably damaged A1 with all your component changes and measuring / injecting signals (I'm partly confused about your descriptions so far.).

U180 rarely fails completely. That didn't seem to be the problem, initially.

As the comparators A3U110, U11, U112, 140 are fully overloaded, is A1P100 set correctly?
Have you touched the LTZ1000 reference board, and are its voltages and potential applied correctly, especially reference zero?

Is the input amplifier with U100 / TP100 now working correctly, as described above?

If you apply input signal of 10V in 10V range, w/o AZ,does that appear correctly @ DC_AD on A3 board?

What are the voltages on A3U110, pin 2 +3?

As long as you can't confirm that A1 is working properly, I would not swap any boards any more.

In your situation, I would not jeopardize the other working boards by swapping, to write it in a polite manner.

Frank

[Ade911]

Hello Kleinstein, yes its my sons so i dont think he would be very happy if something broke, I will not do any board swapping , just a thought before doing some thing drastic like sending to keysight.

[Ade911]

Managed to purchase maybe 5 years ago , upon trying to power on at that time I found the inguard board was burnt around CR11,CR12 maybe caused by the incorrect power setting from the previous owners. These were replaced and the system powered on, but due to travelling allot at the time it was switched off and left for 2-3 years.


Many tx Ade.

Hello Ade,
I'm trying to get some light in your recent descriptions..

CR11 and CR 12 are on A1, SENTRY, Input Signal Conditioning, and on A4, inguard power supply (an "Inguard board" is not existent).
That's very confusing.

Please name all components correctly,  best would be using the BOM designator, like A1CR11 and A1CR12, or A4CR11, A4CR12, and so on.
Please describe in detail, which components were damaged at that time, A4CR11 + CR12 only?

Frank (to be continued)

Sorry for the confusion.

A4 Inguard power supply - A4CR11 + A4CR12 were replaced as they were damaged [PCB is slightly damaged as well but repaired and working.

[Ade911]

Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again.

Ive checked the Convergence circuit with my very limited understanding of the circuit.    FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working.

As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in]   

@ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle.
Therefore it's completely normal, that you see varying voltages on that pin.
If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle.

If you switch off AZ, then the 10V should be visible continuously @ TP11.

Please try that out

when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts.

[Ade911]

update

So I guess the dallas chips are from 1995 week 38 / 47 after watching videos about them, ill order replacements and hope you can clarify how i can download and replace.

I also found an old communication from TiN re the TARM command, OMW , after doing this the meter came to life and did a few samples before stopping again [but it is repeatable]. With nothing connected im getting various voltages between +5.xxx and +10.xxx , If you do an autozero i then get +10.xxxxv.

What PCB / TP are you talking about?
Where do you measure these signals?

This doesn't work now but when the meter would not sample, if i selected TARM i could at that time get a voltage at A1 TP100. it varied , this is why i looked at the circuit around A1 Q106, Q107 and Q108. Monitoring At TP100 without TARM enabled , the voltage would over 1-2 minuets rise to 10 Volts. After replacing A1 Q106 as it had a dent in the can ? , no change which was expected. I then removed  A1 Q107 and A1 Q108, checking I found low resistance between S and G of Q107. As both devices were out the board I replaced with 112 devices which others had suggested. After powering back up the voltage drift disappeared, A1 TP100 is now stable.
 

[Ade911]

I checked U181 and this looks fine,

All signals are fine except pin 3 where it toggles only to 7v during a DCV cal then fails / stops sampling, or 10v when it does a little more sampling and the output jumps to 5v [plus relay clicks on].

U142 , again I believe is ok, the output is toggling between 0 and 5v, however if I scope the input pin 3 the sampling fails [TP140] , its as if the system doesn't like the extra load, which is strange as its only a normal scope probe.

How did you confirm / measure, that the EL2018 are working ok?
Did you scope  on their outputs?

when the unit was reading some random voltage , yes I scoped the input and out put of EL2018 , as I also mentioned later on I removed and tested on bread board A3 U111, A3 U112 and A3 U140. All three devices did work but U140 exceeded the current drawn as stated on the manufacturers datasheet. I managed to purchase replacement devices for A3 U111 and U140 but need to use U112 as I cant purchase a replacement even though its still running very hot [greater than finger hot]

[Ade911]

Todays update

only samples if i manually trigger TARM command, no idea why.

when i initially started to look inside i found the voltage on U100 pin 6 is slowly drifting up , its still doing it now. Unfortunately I damaged Q106 but was able to replace so didnt think any more about it, but today I find myself again back here as the signal DC_AD is slowly rising and is reflected on the screen [least I know the DAC is ok]

Have you applied a fixed input voltage (only at the input jacks, of course!) for that test?
Use TP100, instead of A1U100 - pin6. switch AZ off for that test.
If you apply fixed 10V in 10V range, then you should see that 10V at TP100.
apply 1V in 1V range, you should see 10V as well, repeat that for 100mV in 100mV range, please

screen readings

DCV volts ? +0.689 max then freezes - error message time out read A/D 108 [but it cant be the DAC]
ACV mv samples for ever 1.945mv AC
ACV 000.081 and rising VAC
OHMS +0.VLD GOHM
OHMS +OVL.D MOHM stops sampling
OHMS +OV.LD KOHM
OHMS +OV.LD OHM
DCI nA 000.173
DCI uA 0.000159 stops sampling
DCI mA 0.0000248
DCI A 0.0000135
ACI uA 000.0434
ACI mA 0.000286
ACI A 0.000268
FREQ 50.xxx HZ

Data error matches system asking for DCV and OHMS calibration

Any support most welcome please

Tx Ade

Please explain, what are you doing here, I do not know (or can't guess) what you mean with screen display, which sources you apply, and what mode / range you select in each case

Sorry Frank, I dont recall , I believe I was checking all functions on the front panel and reading the main value on the front screen. Now nothing so I can not check sorry.

[Ade911]

For some strange reason when you inject 10V and manually cycle through  the X1, X10 , initially when you selected mv the meter wouldn't do anything now it states overload and samples , no idea why.

Monitoring A1 TP100

X1 10V I/P 10V TP100
X10 10V I/P 1V TP100
x100 10V I/P 0.1V TP100

Below X1 [mV ?] 10V I/P Overload [ sampling] TP100 = 17.39V

I thought the input to the A3 would never exceed 10V , is this incorrect.

Ive also noticed that if you remove the 10V I/P and set to X1 TP100 starts to drive up towards 17.39V, is this normal.

Also removed Jumper P100 and there is no input via P102 and still does it.

Any idea where to check next please, I hope that because the voltage from A1 if above 10V the A-D will not sample and there is some limit circuit stopping 17V damaging the device.

 Trying to be logical and methodical in finding what is wrong.

TP100 (w/o AZ) is the input signal times the range amplification, i.e. x1, for 10V range, x10 for 1V range and x100 for the 100mV range.
Where did you inject the 10V?
At the input jacks only, hopefully.
If you overload the amplifier, then of course you get +/-17V something out of U100.
The input to the ADC can of course be +/-12V for full scale.

I only inject via the front panel , never in circuit as I dont know it that well.

At present I get what you have stated above , good to see +17 V is normal as well , I thought this may kill the A/D.

Also no voltage drift since changing the FETs on A1 Q106,7,8

[Ade911]

Hello Frank,

Not sure if you can answer ; if i have access to another unit , would board swapping cause issues with the other unit, not ideal but run out of ideas before asking for a quote from the OEM.

Im stuck, I don't seem to be able to find out anywhere where it states the system will still sample even if U180 is dead. It will sample if TRAM is activated , no input and DCV dropped to mV but im not sure why this happens but not in volt range.

OVLD signal on U228 is working fine.

You have probably damaged A1 with all your component changes and measuring / injecting signals (I'm partly confused about your descriptions so far.).

U180 rarely fails completely. That didn't seem to be the problem, initially.

Ade > Correct, something failed slowly over a couple of days , firstly try Autocal , I would read 10V then the autocal would fail, leave for 10 min try again ,10v would pass, the 1 volt would pass , then next test may pass or fail and so on. Thats when I made the mistake of changing components on A1 PCB

As the comparators A3U110, U11, U112, 140 are fully overloaded, is A1P100 set correctly?

Ade > I believe yes, between Pin 2 & 5

Have you touched the LTZ1000 reference board, and are its voltages and potential applied correctly, especially reference zero?

Ade > no not touched , voltage out reads 7.2 volts

Is the input amplifier with U100 / TP100 now working correctly, as described above?

Ade > I believe yes

If you apply input signal of 10V in 10V range, w/o AZ,does that appear correctly @ DC_AD on A3 board?

Ade > AZ OFF DC_AD signal on A3 = + 10V

What are the voltages on A3U110, pin 2 +3?

Pin 2 Zero Volts
Pin 3 Zero Volts

As long as you can't confirm that A1 is working properly, I would not swap any boards any more.

In your situation, I would not jeopardize the other working boards by swapping, to write it in a polite manner.

Frank

Please see my comments Ade > xxxx

Is there a signal that shuts down the A/D if the voltage is to high or should the A3 board sample continuedly , its like something is blocking the A3 board reading voltage.

Thanks Frank.

[Dr. Frank]

Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again.

Ive checked the Convergence circuit with my very limited understanding of the circuit.    FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working.

As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in]   

@ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle.
Therefore it's completely normal, that you see varying voltages on that pin.
If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle.

If you switch off AZ, then the 10V should be visible continuously @ TP11.

Please try that out

when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts.

Which NPLC length do you use?
For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi.
Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly.
Under these conditions, that same signal should be visible @ TP100.

If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message.
Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1.
Or try sampling with APER 1.
Frank

[Ade911]

Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again.

Ive checked the Convergence circuit with my very limited understanding of the circuit.    FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working.

As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in]   

@ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle.
Therefore it's completely normal, that you see varying voltages on that pin.
If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle.

If you switch off AZ, then the 10V should be visible continuously @ TP11.

Please try that out

when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts.

Which NPLC length do you use?

Ade > Default value at switch ON.

For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi.

I set AZERO ON and NPLC to 10, 100 , measuring at A1TP11 I jut see +10VDC, no oscillation as you say it should be.

Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly.
Under these conditions, that same signal should be visible @ TP100.

Ade> TP100 = +10VDC

If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message.
Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1.
Or try sampling with APER 1.

NPLC set to 0.001 still +10VDC on A1 TP10
APER =1 still +10VDC on A1 TP10

Frank

Evening Frank,

The error messages I get at present when turning the unit on are

202 Hardware failure - Slave test convergence
110 Calibration Required - SCAL
0 No Error

I too think the system is frozen somehow, this is why I also checked A1 U10 Pin3 , this is sitting at +5V, I thought this may have caused measurements to stop but guess not.

If I enable TARM [beeps as well]
Inject +10VDC to the front of the unit
Scroll to mV I then get +0.VLD but the system is sampling on the front screen A1 TP10 still at +10VDC

Error message
114 System Error - balanced rundown convergence
0 No Error

If I enable TARM [beeps as well]
Inject +1mVDC to the front of the unit
Scroll to mV I then get NO +0.VLD and the system is NOT sampling on the front screen A1 TP10 noise but no smooth voltage> 20mV [Noise could be from the power supply I am using ?]

The unit only samples when the voltage is too high for the from screen, in auto  nothing works.

Is there another A->D that says the input is too high or ??

[Dr. Frank]

Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again.

Ive checked the Convergence circuit with my very limited understanding of the circuit.    FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working.

As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in]   

@ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle.
Therefore it's completely normal, that you see varying voltages on that pin.
If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle.

If you switch off AZ, then the 10V should be visible continuously @ TP11.

Please try that out

when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts.

Which NPLC length do you use?

Ade > Default value at switch ON.

For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi.

I set AZERO ON and NPLC to 10, 100 , measuring at A1TP11 I jut see +10VDC, no oscillation as you say it should be.

Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly.
Under these conditions, that same signal should be visible @ TP100.

Ade> TP100 = +10VDC

If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message.
Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1.
Or try sampling with APER 1.

NPLC set to 0.001 still +10VDC on A1 TP10
APER =1 still +10VDC on A1 TP10

Frank

Evening Frank,

The error messages I get at present when turning the unit on are

202 Hardware failure - Slave test convergence
110 Calibration Required - SCAL
0 No Error

I too think the system is frozen somehow, this is why I also checked A1 U10 Pin3 , this is sitting at +5V, I thought this may have caused measurements to stop but guess not.

If I enable TARM [beeps as well]
Inject +10VDC to the front of the unit
Scroll to mV I then get +0.VLD but the system is sampling on the front screen A1 TP10 still at +10VDC

Error message
114 System Error - balanced rundown convergence
0 No Error

If I enable TARM [beeps as well]
Inject +1mVDC to the front of the unit
Scroll to mV I then get NO +0.VLD and the system is NOT sampling on the front screen A1 TP10 noise but no smooth voltage> 20mV [Noise could be from the power supply I am using ?]

The unit only samples when the voltage is too high for the from screen, in auto  nothing works.

Is there another A->D that says the input is too high or ??

No. There is an analog overload detection / clamp circuit on sheet 4 / 5 for protection of the fast input DCV path, A1R17/18.
This is centered around A1U10, Q26/Q27 as low leakage diodes.
This circuit has to switch off the input relays very fast to unload the DCV input.

Have you already tried to use a very short NPLC number, like NPLC 0.01, 0.001, or so?
There was a difference between the slow and fast sampling.

All these rundown convergence error point towards A3, most probably the EL2018, maybe U180.

But anyhow, as the input amplifier and the MUX might not work at all/incorrectly, maybe the control shift register chain is defect. Please check those on input / output DATA, like A1U105, sheet 3/5, and U6, U17, U9, U201, 203, U1, U4.. sorry, you have to search for the whole chain by yourself.. I don't know where this begins, and how it ends.
I would trace from behind, maybe there is already a break in between..

Frank

[Ade911]

Monitoring TP11 on A1 I can see a signal jumping from zero to around 7 volts, the screen also shows its sampling, then it beeps and stops , or some times it will sample , a relay will click and TP11 will jump to 10V before failing again.

Ive checked the Convergence circuit with my very limited understanding of the circuit.    FETs are on and off , ive cycled functions to see if the FET will change state just to see if its working.

As the test sometimes goes further than other times I took the decision to replace U7,8,9,20,17, 14,11 [I know some chips don't need changing but desperation cut in]   

@ TP11 / A1 you measure behind the input multiplexer, which applies DCV input, then zero for the AZ cycle.
Therefore it's completely normal, that you see varying voltages on that pin.
If you apply 10V to the input jacks in the 10V range, you should see 10V / 0V , with about 200ms time for each cycle.

If you switch off AZ, then the 10V should be visible continuously @ TP11.

Please try that out

when I apply +10V to the input with Auto Zero ON or OFF i only see a constant +10V on A1 TP11, its not dropping to zero volts.

Which NPLC length do you use?

Ade > Default value at switch ON.

For AZERO ON and NPLC 10, NPLC 100, you should always see a switching signal @ A1TP11, between 0V and 10V, for 50Hz => 200ms Lo, 200ms Hi.

I set AZERO ON and NPLC to 10, 100 , measuring at A1TP11 I jut see +10VDC, no oscillation as you say it should be.

Sorry, I can't check that in situ, but that's exactly how Auto Zero is working, if the DMM is running correctly.
Under these conditions, that same signal should be visible @ TP100.

Ade> TP100 = +10VDC

If the whole system is stalled somehow, as it might the case, then you should read out the ERR? message.
Maybe you try NPLC 0.001,, or so, i.e much shorter than NPLC 1.
Or try sampling with APER 1.

NPLC set to 0.001 still +10VDC on A1 TP10
APER =1 still +10VDC on A1 TP10

Frank

Evening Frank,

The error messages I get at present when turning the unit on are

202 Hardware failure - Slave test convergence
110 Calibration Required - SCAL
0 No Error

I too think the system is frozen somehow, this is why I also checked A1 U10 Pin3 , this is sitting at +5V, I thought this may have caused measurements to stop but guess not.

If I enable TARM [beeps as well]
Inject +10VDC to the front of the unit
Scroll to mV I then get +0.VLD but the system is sampling on the front screen A1 TP10 still at +10VDC

Error message
114 System Error - balanced rundown convergence
0 No Error

If I enable TARM [beeps as well]
Inject +1mVDC to the front of the unit
Scroll to mV I then get NO +0.VLD and the system is NOT sampling on the front screen A1 TP10 noise but no smooth voltage> 20mV [Noise could be from the power supply I am using ?]

The unit only samples when the voltage is too high for the from screen, in auto  nothing works.

Is there another A->D that says the input is too high or ??

No. There is an analog overload detection / clamp circuit on sheet 4 / 5 for protection of the fast input DCV path, A1R17/18.
This is centered around A1U10, Q26/Q27 as low leakage diodes.
This circuit has to switch off the input relays very fast to unload the DCV input.

Have you already tried to use a very short NPLC number, like NPLC 0.01, 0.001, or so?
There was a difference between the slow and fast sampling.

All these rundown convergence error point towards A3, most probably the EL2018, maybe U180.

But anyhow, as the input amplifier and the MUX might not work at all/incorrectly, maybe the control shift register chain is defect. Please check those on input / output DATA, like A1U105, sheet 3/5, and U6, U17, U9, U201, 203, U1, U4.. sorry, you have to search for the whole chain by yourself.. I don't know where this begins, and how it ends.
I would trace from behind, maybe there is already a break in between..

Frank

Hello Frank,

No input, activating the Reset on the front panel

All inputs now checked, On all devices you listed pin 1 gives 2 10us pulses from 0V to 4V, Pin 2 shows data stream, Pin 3 I cant read the clock maybe too fast for my old scope so sits high [+5v] and pin 15 is high [+5v] , started to try and test outputs which is difficult to achieve.

Maybe  its not a problem, A1 U10C, Im checking data coming from A1  U17 to the DAC but I dont see a W/R signal. U10 Pin 9 is connected to all devices just checked - PIN 1, I see 2 10us pulses as before , Pin 10 is sitting at 2V , the output A1 U10 Pin 15 just sits high even when Pin 9 goes above the 2V threshold , is this normal , I though being a comparator it would flip and drive to 0V.

Anyhow Ill carry on checking the other outputs where I can of the devices you mentioned.

Many thanks

[Dr. Frank]

Hello Frank,

No input, activating the Reset on the front panel

All inputs now checked, On all devices you listed pin 1 gives 2 10us pulses from 0V to 4V, Pin 2 shows data stream, Pin 3 I cant read the clock maybe too fast for my old scope so sits high [+5v] and pin 15 is high [+5v] , started to try and test outputs which is difficult to achieve.

Maybe  its not a problem, A1 U10C, Im checking data coming from A1  U17 to the DAC but I dont see a W/R signal. U10 Pin 9 is connected to all devices just checked - PIN 1, I see 2 10us pulses as before , Pin 10 is sitting at 2V , the output A1 U10 Pin 15 just sits high even when Pin 9 goes above the 2V threshold , is this normal , I though being a comparator it would flip and drive to 0V.

Anyhow Ill carry on checking the other outputs where I can of the devices you mentioned.

Many thanks

Hi Ade,
what kind of old scope do you have? Should be at least 20MHz BW, hopefully.
The SR data might be clocked with 10MHz; I don't find the clock generator, or there should be a Hi speed UART on the analog side, which complements the UART A5U700, restoring clock and data, somehow. Well, that's the GA_Chip, A5U210, which serializes the data and creates all necessary signals for the different SR chains. It's clocked with 20MHz, so you should use a scope which has 60MHz Bw at least.
This clock should be visible on all SR clock, and U10C serves as a simple inverter, delivering inverted clock for the DAC. Btw. there are ten SR '4094 in series on A1, in the following order: U1, U106, U307, U4, U14, U17, U6, U9, U201, U203. Check U203, pin 9, which is
SERIAL OUT for the whole chain.

If the clock signal is not present at all, and no data out at the last SR, then we might have found the problem.
Frank 

[Ade911]

Hello Frank,

No input, activating the Reset on the front panel

All inputs now checked, On all devices you listed pin 1 gives 2 10us pulses from 0V to 4V, Pin 2 shows data stream, Pin 3 I cant read the clock maybe too fast for my old scope so sits high [+5v] and pin 15 is high [+5v] , started to try and test outputs which is difficult to achieve.

Maybe  its not a problem, A1 U10C, Im checking data coming from A1  U17 to the DAC but I dont see a W/R signal. U10 Pin 9 is connected to all devices just checked - PIN 1, I see 2 10us pulses as before , Pin 10 is sitting at 2V , the output A1 U10 Pin 15 just sits high even when Pin 9 goes above the 2V threshold , is this normal , I though being a comparator it would flip and drive to 0V.

Anyhow Ill carry on checking the other outputs where I can of the devices you mentioned.

Many thanks

Hi Ade,
what kind of old scope do you have? Should be at least 20MHz BW, hopefully.
The SR data might be clocked with 10MHz; I don't find the clock generator, or there should be a Hi speed UART on the analog side, which complements the UART A5U700, restoring clock and data, somehow. Well, that's the GA_Chip, A5U210, which serializes the data and creates all necessary signals for the different SR chains. It's clocked with 20MHz, so you should use a scope which has 60MHz Bw at least.
This clock should be visible on all SR clock, and U10C serves as a simple inverter, delivering inverted clock for the DAC. Btw. there are ten SR '4094 in series on A1, in the following order: U1, U106, U307, U4, U14, U17, U6, U9, U201, U203. Check U203, pin 9, which is
SERIAL OUT for the whole chain.

If the clock signal is not present at all, and no data out at the last SR, then we might have found the problem.
Frank

Hi Frank,

Yes the clock is missing from U210 Pin 31, i traced and checked each signal back to the rear of U210 through R270,1,2 and the signal is missing [BTW you said A5 Bd but this should be the A3 bd i could only find U210 on A3, please confirm if I had another snr moment].

All tests carried out on A3.

Im still not sure if the clock signal runs freely or is it looking for a good state from U220. I ask as Im getting ripple on the supply on U220. The main incoming feed is smooth but on pin 40 / 20 I get 20mv ripple , even if I short out L222 & L223.The lines between U220 & U210 look fine , either +5V or 0V or 20mv Ripple.

I think unless there is an interlock stopping the clock I can only assume U210 is dead.

If you agree then Ill send out a request for a broken A3 Bd and see if I can exchange U220 which will be fun.

Many thanks,

Ade.

[Dr. Frank]

Hello Frank,

No input, activating the Reset on the front panel

All inputs now checked, On all devices you listed pin 1 gives 2 10us pulses from 0V to 4V, Pin 2 shows data stream, Pin 3 I cant read the clock maybe too fast for my old scope so sits high [+5v] and pin 15 is high [+5v] , started to try and test outputs which is difficult to achieve.

Maybe  its not a problem, A1 U10C, Im checking data coming from A1  U17 to the DAC but I dont see a W/R signal. U10 Pin 9 is connected to all devices just checked - PIN 1, I see 2 10us pulses as before , Pin 10 is sitting at 2V , the output A1 U10 Pin 15 just sits high even when Pin 9 goes above the 2V threshold , is this normal , I though being a comparator it would flip and drive to 0V.

Anyhow Ill carry on checking the other outputs where I can of the devices you mentioned.

Many thanks

Hi Ade,
what kind of old scope do you have? Should be at least 20MHz BW, hopefully.
The SR data might be clocked with 10MHz; I don't find the clock generator, or there should be a Hi speed UART on the analog side, which complements the UART A5U700, restoring clock and data, somehow. Well, that's the GA_Chip, A5U210, which serializes the data and creates all necessary signals for the different SR chains. It's clocked with 20MHz, so you should use a scope which has 60MHz Bw at least.
This clock should be visible on all SR clock, and U10C serves as a simple inverter, delivering inverted clock for the DAC. Btw. there are ten SR '4094 in series on A1, in the following order: U1, U106, U307, U4, U14, U17, U6, U9, U201, U203. Check U203, pin 9, which is
SERIAL OUT for the whole chain.

If the clock signal is not present at all, and no data out at the last SR, then we might have found the problem.
Frank

Hi Frank,

Yes the clock is missing from U210 Pin 31, i traced and checked each signal back to the rear of U210 through R270,1,2 and the signal is missing [BTW you said A5 Bd but this should be the A3 bd i could only find U210 on A3, please confirm if I had another snr moment].

All tests carried out on A3.

Im still not sure if the clock signal runs freely or is it looking for a good state from U220. I ask as Im getting ripple on the supply on U220. The main incoming feed is smooth but on pin 40 / 20 I get 20mv ripple , even if I short out L222 & L223.The lines between U220 & U210 look fine , either +5V or 0V or 20mv Ripple.

I think unless there is an interlock stopping the clock I can only assume U210 is dead.

If you agree then Ill send out a request for a broken A3 Bd and see if I can exchange U220 which will be fun.

Many thanks,

Ade.

Hi Ade,
sure, should be on A3 board, sorry for that mistake.... you're really quick on the trigger to replace components.
Please probe around that IC, if any other part is faulty, like U230, U131.. I can't hardly imagine, that such a part is gone. There's a 20MHz oscillator, search if you can find comprehensive signals around that.
Please check pin 73, labeled IGCLK, if there's a clock available.

[Ade911]

Hello Frank,

No input, activating the Reset on the front panel

All inputs now checked, On all devices you listed pin 1 gives 2 10us pulses from 0V to 4V, Pin 2 shows data stream, Pin 3 I cant read the clock maybe too fast for my old scope so sits high [+5v] and pin 15 is high [+5v] , started to try and test outputs which is difficult to achieve.

Maybe  its not a problem, A1 U10C, Im checking data coming from A1  U17 to the DAC but I dont see a W/R signal. U10 Pin 9 is connected to all devices just checked - PIN 1, I see 2 10us pulses as before , Pin 10 is sitting at 2V , the output A1 U10 Pin 15 just sits high even when Pin 9 goes above the 2V threshold , is this normal , I though being a comparator it would flip and drive to 0V.

Anyhow Ill carry on checking the other outputs where I can of the devices you mentioned.

Many thanks

Hi Ade,
what kind of old scope do you have? Should be at least 20MHz BW, hopefully.
The SR data might be clocked with 10MHz; I don't find the clock generator, or there should be a Hi speed UART on the analog side, which complements the UART A5U700, restoring clock and data, somehow. Well, that's the GA_Chip, A5U210, which serializes the data and creates all necessary signals for the different SR chains. It's clocked with 20MHz, so you should use a scope which has 60MHz Bw at least.
This clock should be visible on all SR clock, and U10C serves as a simple inverter, delivering inverted clock for the DAC. Btw. there are ten SR '4094 in series on A1, in the following order: U1, U106, U307, U4, U14, U17, U6, U9, U201, U203. Check U203, pin 9, which is
SERIAL OUT for the whole chain.

If the clock signal is not present at all, and no data out at the last SR, then we might have found the problem.
Frank

Hi Frank,

Yes the clock is missing from U210 Pin 31, i traced and checked each signal back to the rear of U210 through R270,1,2 and the signal is missing [BTW you said A5 Bd but this should be the A3 bd i could only find U210 on A3, please confirm if I had another snr moment].

All tests carried out on A3.

Im still not sure if the clock signal runs freely or is it looking for a good state from U220. I ask as Im getting ripple on the supply on U220. The main incoming feed is smooth but on pin 40 / 20 I get 20mv ripple , even if I short out L222 & L223.The lines between U220 & U210 look fine , either +5V or 0V or 20mv Ripple.

I think unless there is an interlock stopping the clock I can only assume U210 is dead.

If you agree then Ill send out a request for a broken A3 Bd and see if I can exchange U220 which will be fun.

Many thanks,

Ade.

Hi Ade,
sure, should be on A3 board, sorry for that mistake.... you're really quick on the trigger to replace components.
Please probe around that IC, if any other part is faulty, like U230, U131.. I can't hardly imagine, that such a part is gone. There's a 20MHz oscillator, search if you can find comprehensive signals around that.
Please check pin 73, labeled IGCLK, if there's a clock available.

Hello Frank,

Sorry I should have shared more testing results.
A3 Board

U230 20M oscillator OK, U131 OK , signal CK10 OK [ Not a square wave but still a clock pulse] .

U211 , 212 change state during reset or changing front panel buttons, not sure if they have anything to do with how U210 functions.

Unplugged P2 and P1 from the AC board to see if anything was affecting the signal DCCK_F [sitting at 5V]

Where can I find the pin configuration of U210, I tried google but failed, guess Pin 11 U220 is acceptable - no clock , sitting at + 5V. U220 Pin 19 has a +5V clock pulse [more like a saw tooth]

Good catch Frank, still learning from the master.

Is this signal generated in U210 or U220 ?

Tx Ade.

[Dr. Frank]

Hello Frank,

Sorry I should have shared more testing results.
A3 Board

U230 20M oscillator OK, U131 OK , signal CK10 OK [ Not a square wave but still a clock pulse] .

U211 , 212 change state during reset or changing front panel buttons, not sure if they have anything to do with how U210 functions.

Unplugged P2 and P1 from the AC board to see if anything was affecting the signal DCCK_F [sitting at 5V]

Where can I find the pin configuration of U210, I tried google but failed, guess Pin 11 U220 is acceptable - no clock , sitting at + 5V. U220 Pin 19 has a +5V clock pulse [more like a saw tooth]

Good catch Frank, still learning from the master.

Is this signal generated in U210 or U220 ?

Tx Ade.

Pin configuration of U210???
It's on sheet 1 / 2of A3. What do you expect more?
It's a hp programmed Gate Array, in my 3458A it's an ORBIT 6968A, don't know anything about this device.
I have not measured inside my 3458A, but maybe the clock Pin 31 for the SR chain is only output, when needed. (*) Please scope on that pin, while you RESET the instrument, if there is an initial activity.
What about pin 73, now? Is there a clock, or not?
The 3458A currently does not work at all, anymore?

Frank

(*) That might be reasonable, so not to disturb the analog part by RF emission, during sampling.