E4407B Tracking Generator Repair

[analogRF]

these 2 Sot-23's marked 8F I think are 5.1v zeners but 8F can be a NPN transistor as well
both read strange but reading is in-circuit.  one reads 24.7K forward and reverse and other is like 30meg forward and reverse.   I'll get them out of circuit to test but they are connected to V1/V2

clearly they are not transistors (they are marked by CRxx) and they are definitely diodes. seems to be used for clipping/clamping a signal or a dc voltage (from top and bottom)

use diode test mode not resistance mode in your multimeter

[analogRF]

Here's another area.   all but the one with a ? is identified but  I marked one component that looks damaged?   any thoughts on that?

the ? element looks like RF amp but it has an extra supply pin (other than the usual one that is connected through a ferrite bead) that is a bit puzzling
maybe it has a on/off  switch in it too? there must be a marking on that package. what is the marking??

the discolored element does look like damaged but at that point i dont think there is anything stressful to elements, maybe it can be cleaned? can you try to clean it? looks like a capacitor of course but it could be a resistor so check with multimeter

after those you have a bandpass filter at 784MHz I think..

[smgvbest]

Looking for help in identifying some components
in PICT0007.jpg   looking to identify all marked ones.  the one I put a D on,  the D is the only marking on the component.   I think this is a dual diode package for the peak detector.

I loose allot of power at the point of this component.   like -25dB.   this is suppling the 786.5hz RF to the Mixer (5x that but I can't measure on my 1.5Ghz SA)
in  IMG_2867-1.jpg

the white elements are most likely resistors. you can check with multimeter
the "D" element is most likely HMPP-3890 single schottky diode by Agilent/Avago but are you 100% sure about the marking? sometimes it is tricky to read the labels
seems that all 4 pins of it have been used  also for a good temperature compensated peak detector it makes sense to have two diodes in one package but if the marking is only a "D" then I couldn't find anything other than HMPP-3890 which is still applicable...

the element with red dot is what is used to generate 5th harmonic if i remember correctly from previous discussions, so it is probably a diode of some kind.

The White elements do read as resistors of 50 and 125 ohm

for the part with the D marking.   see image for best I could get 
Using the Diode test here are reading for all 4 pins (see image for pin numbering used)  all reading Vdc

1-2  1.3908v/1.447v
3-4  1.6304v/0.1447v
1-3  0.0691c/0.0691v
2-4  1.4398v/1.3723v

for the damaged element

Did multiple checks
Resistance Open
Capacitance 0
Diode open

see image for better view

[smgvbest]

heres image of damaged part

[smgvbest]

these 2 Sot-23's marked 8F I think are 5.1v zeners but 8F can be a NPN transistor as well
both read strange but reading is in-circuit.  one reads 24.7K forward and reverse and other is like 30meg forward and reverse.   I'll get them out of circuit to test but they are connected to V1/V2

clearly they are not transistors (they are marked by CRxx) and they are definitely diodes. seems to be used for clipping/clamping a signal or a dc voltage (from top and bottom)

use diode test mode not resistance mode in your multimeter

Here are reading for CR1/CR2 Forward and reverse voltages  meter set for 15V test

CR1  0.789v/2.773v
CR2  0.789v/2.763v

[analogRF]

Looking for help in identifying some components
in PICT0007.jpg   looking to identify all marked ones.  the one I put a D on,  the D is the only marking on the component.   I think this is a dual diode package for the peak detector.

I loose allot of power at the point of this component.   like -25dB.   this is suppling the 786.5hz RF to the Mixer (5x that but I can't measure on my 1.5Ghz SA)
in  IMG_2867-1.jpg

the white elements are most likely resistors. you can check with multimeter
the "D" element is most likely HMPP-3890 single schottky diode by Agilent/Avago but are you 100% sure about the marking? sometimes it is tricky to read the labels
seems that all 4 pins of it have been used  also for a good temperature compensated peak detector it makes sense to have two diodes in one package but if the marking is only a "D" then I couldn't find anything other than HMPP-3890 which is still applicable...

the element with red dot is what is used to generate 5th harmonic if i remember correctly from previous discussions, so it is probably a diode of some kind.

The White elements do read as resistors of 50 and 125 ohm

for the part with the D marking.   see image for best I could get 
Using the Diode test here are reading for all 4 pins (see image for pin numbering used)  all reading Vdc

1-2  1.3908v/1.447v
3-4  1.6304v/0.1447v
1-3  0.0691c/0.0691v
2-4  1.4398v/1.3723v

for the damaged element

Did multiple checks
Resistance Open
Capacitance 0
Diode open

see image for better view

see the picture for my comments.
are you sure about the diode test voltages? you have a 1.447 and a 0.1447? which one is correct?
what was the test current of your multimeter diode test? 1mA as usual? in that case you are reading 69 ohm between 1 and 3 but I think that's because of the outside resistors forming a loop. I think 1 and 3 are in fact not connected in the device

w.r.t. the discolored component it is definitely a capacitor and it cannot be zero of course. if you want, you need to measure it with a LCR meter
with at least 10KHz or above because it is definitely just a few pF or maybe several 10s of pF
I dont think it is damaged otherwise your TG wouldn't work at all.

[analogRF]

these 2 Sot-23's marked 8F I think are 5.1v zeners but 8F can be a NPN transistor as well
both read strange but reading is in-circuit.  one reads 24.7K forward and reverse and other is like 30meg forward and reverse.   I'll get them out of circuit to test but they are connected to V1/V2

clearly they are not transistors (they are marked by CRxx) and they are definitely diodes. seems to be used for clipping/clamping a signal or a dc voltage (from top and bottom)

use diode test mode not resistance mode in your multimeter

Here are reading for CR1/CR2 Forward and reverse voltages  meter set for 15V test

CR1  0.789v/2.773v
CR2  0.789v/2.763v

so they are 2.7V zener diodes.

what is your multimeter by the way?

[smgvbest]

these 2 Sot-23's marked 8F I think are 5.1v zeners but 8F can be a NPN transistor as well
both read strange but reading is in-circuit.  one reads 24.7K forward and reverse and other is like 30meg forward and reverse.   I'll get them out of circuit to test but they are connected to V1/V2

clearly they are not transistors (they are marked by CRxx) and they are definitely diodes. seems to be used for clipping/clamping a signal or a dc voltage (from top and bottom)

use diode test mode not resistance mode in your multimeter

Here are reading for CR1/CR2 Forward and reverse voltages  meter set for 15V test

CR1  0.789v/2.773v
CR2  0.789v/2.763v

so they are 2.7V zener diodes.

what is your multimeter by the way?

in this case I'm using the eevblog 121GW

on the 2.7 zener though.  isn't a 8F a 5.1V zener?

[smgvbest]

at peak detector I did have a typo
this is the correct value
1-2   1.3908v/0.1447v

in PICT0042-1.jpg

the Cap did clean up as seen and the LCR at 10Khz says 9.65pF

[smgvbest]

Would this be of any value in doing.

my Rigol 815 only goes to 1.5Ghz.
I need to look at signals up to 6hgz (LO)

I go have a Divide by 4 that's good up 8Ghz
what if I ran my probe into the /4 then into the SA. adjust reference to give good readings

The 3.92Ghz would come out at 981.875Mhz if present.   

I would also be able to see the LO sweeping

I know its not ideal but working with what I have would that be useful to do?

[smgvbest]

here's an update RF board where signals go
note the labels PD+/PD- in the peak detector that go to the AD620.

[analogRF]

Would this be of any value in doing.

my Rigol 815 only goes to 1.5Ghz.
I need to look at signals up to 6hgz (LO)

I go have a Divide by 4 that's good up 8Ghz
what if I ran my probe into the /4 then into the SA. adjust reference to give good readings

The 3.92Ghz would come out at 981.875Mhz if present.   

I would also be able to see the LO sweeping

I know its not ideal but working with what I have would that be useful to do?

why do you need to do this? I think we concluded long ago that LO was present and working
in fact your TG is working normally most of the time except some short dips in amplitude
which you must find out their correlation with other signals to see what is causing them
other than that between those blips, the TG is working normally. Obviously if you didnt have LO coming in
this would not have worked at all
So i dont see the point of this test. Besides, if anything, you would need to know the precise amplitude of coming LO
which this test will not tell you but you measured that with power meter and it was alright.

[analogRF]

at peak detector I did have a typo
this is the correct value
1-2   1.3908v/0.1447v

in PICT0042-1.jpg

the Cap did clean up as seen and the LCR at 10Khz says 9.65pF

so there are two separate schottky diodes in one package, one for peak detection and one for the temp and V_fwd compensation. It's a classic RF peak detector circuit. But the part number I could find for "D" was a single diode which makes no sense so it must be a different part...

[analogRF]

here's an update RF board where signals go
note the labels PD+/PD- in the peak detector that go to the AD620.

B1 and B2 are power supplies for the RF ampliiers.

C8 is the output of peak detector and must eventually become ALC_MON after further processing on the other board

you need to find out the relationship between V1/V2 and PWR_LVL signal coming from A2A1

is there any jump/dip in OSC_PWR consistent with the dips in the TG output power?

[analogRF]

Looking for help in identifying some components
in PICT0007.jpg   looking to identify all marked ones.  the one I put a D on,  the D is the only marking on the component.   I think this is a dual diode package for the peak detector.

I loose allot of power at the point of this component.   like -25dB.   this is suppling the 786.5hz RF to the Mixer (5x that but I can't measure on my 1.5Ghz SA)
in  IMG_2867-1.jpg

the white elements are most likely resistors. you can check with multimeter
the "D" element is most likely HMPP-3890 single schottky diode by Agilent/Avago but are you 100% sure about the marking? sometimes it is tricky to read the labels
seems that all 4 pins of it have been used  also for a good temperature compensated peak detector it makes sense to have two diodes in one package but if the marking is only a "D" then I couldn't find anything other than HMPP-3890 which is still applicable...

the element with red dot is what is used to generate 5th harmonic if i remember correctly from previous discussions, so it is probably a diode of some kind.

The White elements do read as resistors of 50 and 125 ohm

for the part with the D marking.   see image for best I could get 
Using the Diode test here are reading for all 4 pins (see image for pin numbering used)  all reading Vdc

1-2  1.3908v/1.447v
3-4  1.6304v/0.1447v
1-3  0.0691c/0.0691v
2-4  1.4398v/1.3723v

for the damaged element

Did multiple checks
Resistance Open
Capacitance 0
Diode open

see image for better view

I dont think the marking on the dual diode package is "D". It must be 2 letters and "D" seems to be the second letter which is a date code
there is a very faint letter before "D" it's either "B" or "C" i think
you need to look carefully at proper angle

[smgvbest]

I dont think the marking on the dual diode package is "D". It must be 2 letters and "D" seems to be the second letter which is a date code
there is a very faint letter before "D" it's either "B" or "C" i think
you need to look carefully at proper angle

I have twisted and contorted in every possible way so see and what I posted is the best I can get

why do you need to do this? I think we concluded long ago that LO was present and working
in fact your TG is working normally most of the time except some short dips in amplitude
which you must find out their correlation with other signals to see what is causing them
other than that between those blips, the TG is working normally. Obviously if you didnt have LO coming in
this would not have worked at all
So i dont see the point of this test. Besides, if anything, you would need to know the precise amplitude of coming LO
which this test will not tell you but you measured that with power meter and it was alright.

This was to look at the 768.5Mhz getting multiplied by 5x and where it happened is all.

If I didn't already say so I'm also documenting as much as possible about the BITG for others in the future. (you can still get the BITG from Keysight for a mere $4500 
This is why the boat load of pics and sometimes extraneous information

B1 and B2 are power supplies for the RF ampliiers.

C8 is the output of peak detector and must eventually become ALC_MON after further processing on the other board

you need to find out the relationship between V1/V2 and PWR_LVL signal coming from A2A1

is there any jump/dip in OSC_PWR consistent with the dips in the TG output power?

working on the other board to trace the signals around
i did not note any DIPs in OSC_PWR.  it is very stable.

unrelated,   now is the only time I regret having done lasic eye surgery.   my near vision it shot and everything I do is under a microscope.
wouldn't change having done it but this does get frustrating at times

[smgvbest]

Here's another part I'm having trouble finding
Marking is a Linear Technologies 531 (LT531) but I can find no such beast.

Anyone recognize this 8 pin guy?

[analogRF]

Here's another part I'm having trouble finding
Marking is a Linear Technologies 531 (LT531) but I can find no such beast.

Anyone recognize this 8 pin guy?

531 is the date code (2005/ week 31)
This is LT1021 precision reference 10.000V

[smgvbest]

Here's another part I'm having trouble finding
Marking is a Linear Technologies 531 (LT531) but I can find no such beast.

Anyone recognize this 8 pin guy?

531 is the date code (2005/ week 31)
This is LT1021 precision reference 10.000V

Thank you very much.
That would make sense where it is in the circuit.
i don't see how how to get from the marking 2110 i guess to a LT1021,  is this some vodoo magic or am I (very likely) missing something simple)?

[analogRF]

Here's another part I'm having trouble finding
Marking is a Linear Technologies 531 (LT531) but I can find no such beast.

Anyone recognize this 8 pin guy?

531 is the date code (2005/ week 31)
This is LT1021 precision reference 10.000V

Thank you very much.
That would make sense where it is in the circuit.
i don't see how how to get from the marking 2110 i guess to a LT1021,  is this some vodoo magic or am I (very likely) missing something simple)?

I already knew that part because I had seen and used it before myself but if you search for Linear Technology 2110 SOIC
you'll find it after a little while 

[smgvbest]

Here's another part I'm having trouble finding
Marking is a Linear Technologies 531 (LT531) but I can find no such beast.

Anyone recognize this 8 pin guy?

531 is the date code (2005/ week 31)
This is LT1021 precision reference 10.000V

Thank you very much.
That would make sense where it is in the circuit.
i don't see how how to get from the marking 2110 i guess to a LT1021,  is this some vodoo magic or am I (very likely) missing something simple)?

I already knew that part because I had seen and used it before myself but if you search for Linear Technology 2110 SOIC
you'll find it after a little while 

Yeh,   like the first result returned.   oye
Thanks again

still working on reversing the control board (A2A2-BITG)
Making progress slowly.   
Don't know how many layers this board is but its' more than 2

[smgvbest]

Just a quick update.

while reversing the board.   I decided to go ahead and replace the H346 on the RF board.    while this did not fix the issue it did have an impact on the output
the dB steps are now much more visiable and it much more consistent.   for every 6db (1-6) on the H346 its unlevel then for 2db (7-8) it's level.   this is now consistent all the way down to -66db (limit of the TG).

I also pulled the 2 zenners to check out of circuit.   they are 5v zeners and working ok

I also pulle Q1 an tested it out of circuit.    this is a LS312 Dual NPN transistor.   one Transistor has a hfe of 285 the other of 108.    I had ordered 2 LS312s just in case and the new ones are hfe of 276 and 277
so I'm going to replace Q1.

Next.  I pulled all 5 trimming pots and inspected them
R2/R3 have been messed with
PWR_LVL goes into R3 before going to U7 TL074 and the other input of this opamp (+12,-13 and out14) is the output of the peak detector.
this then goes to ALC_MON and thru R4 to U5 which controls V2.  R5 looks to set the reference for one opamp on U5.   U5 other opamp handles V1 which uses R1 and R2.

just for reference I'm attaching a image of the board with the trimmers and Q1 removed.
I also did record the settings for each Pot (R1-R5) just in case

NOTE:   replacing Q1 had no noticeable effect

[analogRF]

Just a quick update.

while reversing the board.   I decided to go ahead and replace the H346 on the RF board.    while this did not fix the issue it did have an impact on the output
the dB steps are now much more visiable and it much more consistent.   for every 6db (1-6) on the H346 its unlevel then for 2db (7-8) it's level.   this is now consistent all the way down to -66db (limit of the TG).

I also pulled the 2 zenners to check out of circuit.   they are 5v zeners and working ok

I also pulle Q1 an tested it out of circuit.    this is a LS312 Dual NPN transistor.   one Transistor has a hfe of 285 the other of 108.    I had ordered 2 LS312s just in case and the new ones are hfe of 276 and 277
so I'm going to replace Q1.

Next.  I pulled all 5 trimming pots and inspected them
R2/R3 have been messed with
PWR_LVL goes into R3 before going to U7 TL074 and the other input of this opamp (+12,-13 and out14) is the output of the peak detector.
this then goes to ALC_MON and thru R4 to U5 which controls V2.  R5 looks to set the reference for one opamp on U5.   U5 other opamp handles V1 which uses R1 and R2.

just for reference I'm attaching a image of the board with the trimmers and Q1 removed.
I also did record the settings for each Pot (R1-R5) just in case

NOTE:   replacing Q1 had no noticeable effect

I would never start replacing components at random for no reason unless there is evidence it is not working. Not only this will not achieve anything and waste a lot of time you end up tampering with the calibration of instrument. Q1 was already tested fine, so no surprise there.
and why did you take out all the potentiometers?

if you are sure R2/R3 have been messed with and PWR_LVL and peak detector are related to them, that's your clue! 
that could very well be the cause of your problem because so far there does not seem to be any defective component anywhere.

i would like to see a schematic of that board (not the RF section which is quite clear already)

[smgvbest]

I did not replace randomly anything

H346 when looking at it the RF IN was at -60db after the filter and into the H346.  without the H346 it was at about -10db.   I replaced it because it appeared to be pulling down the RFin
Q1 is a matched pair of NPN transistors   HFE's that different are not matched.  which is why I pull it and replaced it.
the Pots where pulled to inspect out of circuit due to tampering.  They did not remove the silistic on the adjustment screw and where visibly damaged. I wanted to be sure they were ok and while out I got a good read on how they where set. as well as a pic of the board.

I've hand drawn it in various parts.  I'm now putting it all together and will verify it against the board then plan to post when it's done

[analogRF]

I did not replace randomly anything

H346 when looking at it the RF IN was at -60db after the filter and into the H346.  without the H346 it was at about -10db.   I replaced it because it appeared to be pulling down the RFin

how did you measure the 3.92GHz signal at the RF pin of HMC346? how much was the output amplitude?
it is critical how you measure it and besides when you leave that open circuit
(by removing the chip) that changes the whole dynamics...it will be a totally different reading of course....