Agilent 33220A Generator, FPGA not repairable

[HighVoltage]

This Agilent 33220A was bought used and broken and now I am trying to repair it.

Error message: "Reference phase-lock loop is UNLOCKED"
Like usual, I checked all the rails and the -15V rail only has -13.1 V
So, I suspected the evil yellow tantalum caps, but they are not the culprits.

If I remove the 0 Ohm resistor right at the output of the -15V regulator, I have perfect -15V
It seems that some component is pulling too much current from the -15V regulator.
But nothing is getting hot to an usual level.

Any suggestions would be appreciated.
The manual can be found here: http://cp.literature.agilent.com/litweb/pdf/33220-90012.pdf

[Quarlo Klobrigney]

So you suspect the tantalums but you know they are not the problem how?

And how much current is too much current? Have you measured it and is it below the 1A specified for the 7915?

[HighVoltage]

So you suspect the tantalums but you know they are not the problem how?

Because I removed them and replaced the temporarily with some electrolytic caps.

And how much current is too much current? Have you measured it and is it below the 1A specified for the 7915?

This is the weird thing.
If I use my DC load, I can pull 450 mA out of the 7915 and the voltage stays at -15.0V
The instrument is pulling "only" 200 mA from the 7915 and the voltage drops to -13.1 V.

[Quarlo Klobrigney]

By: "The instrument is pulling "only" 200 mA from the 7915 and the voltage drops to -13.1 V."
You mean the actual circuit that the regulator is mounted or supplying to.
I would change the 7915, the 2 series diodes, the electrolytics need to be checked or replaced.

When I was talking about the tantalums, I was assuming there were more on the external circuit at the IC's on the board. Are there any near the IC's?
Also the rectangular SMD ones are usually OK, it's the dipped ones that are crap.

[AF6LJ]

Have you looked at the 7915's output on a scope, almost sounds like the regulator is oscillating.

[HighVoltage]

Have you looked at the 7915's output on a scope, almost sounds like the regulator is oscillating.

Yes, I did and the output of the 7915 is very smooth.

OK, after some more checking, it seems the -15V rail is only a symptom and not the reason for failure.
I injected -15V manually from an external PSU and still have the very same problem and error message
The external PSU supplies about 200 mA to the circuit and stays stable.
 

[HighVoltage]

OK, I did not notice this right away, but after I injected the -15V from an external PSU, I am getting a new Error 606, which is explained in the service manual as:

This error indicates that the cross-isolation interface between the main
processor (U101) and Synthesis IC (U501) has failed, or that the
synthesis IC itself has failed.


It seems this is beyond repair, because the U501 is the main FPGA.

Thanks for all your help, but I am now giving up on this repair.


 

[AF6LJ]

One quick thing you might try.
Put 10MHZ into the timebase input in the back of the unit.
The manual says it will automatically switch to the external 10MHZ timebase.
Run the signal in there power up the unit and see if the error clears.

[Quarlo Klobrigney]

EP1C6Q240C8

[HighVoltage]

One quick thing you might try.
Put 10MHZ into the timebase input in the back of the unit.
The manual says it will automatically switch to the external 10MHZ timebase.
Run the signal in there power up the unit and see if the error clears.

Did not work!
I also tried to get it started through GPIB but the same problem stays.

[HighVoltage]

EP1C6Q240C8

Thanks.
It seems, U501 is available and it will probably work.
But this is too much for me, since I do not have the tools to solder such a part in correctly.
I will leave this to someone else and offer this Agilent Generator for sale in the "Sell/Buy' section of this forum.

[plesa]

replace the this size is possible with piece of kapton tape and heat gun or contact some repair center they can do it for you for 20-40 EUR.

[vaualbus]

Could be also somethingh else. I think if the main FPGA is broken the instrument won't turn on.
Does it output a signal?
I would ceck for short component before call it a unrepair!

[AF6LJ]

From The Potentially Stupid Question Department...
If you buy this FPGA, how do you get it programmed or for that matter do you need to have it programmed??

[HighVoltage]

Could be also somethingh else. I think if the main FPGA is broken the instrument won't turn on.
Does it output a signal?
I would ceck for short component before call it a unrepair!

You might be right, but I leave this to someone else to find out.

I can switch the frequencies white the error message stays on the screen and it has a good response to pushing the buttons but NO output can be detected.

[Andy Watson]

This error indicates that the cross-isolation interface

At least hang a scope on the isolation optos (U304-A and U305-A) and check that they are attempting to communicate.

[free_electron]

it's dead jim ...

the fpga is loaded through a serial link from the main flash memory. so swapping it is not a problem.

i had one of these with a similar fault. the negative rail would sag after like 1 or 2 seconds after power up.
if i remember correctly there are 0 ohm resistors in all the supply rails. or they were big filter coils from coilcraft. they sit in the centre of the board , kind of alone ..
simply remove the ones going to the +15 and -15 rail. and start up.
if you get a comms error the fpga is dead.
there is a dpak regulator right next to the fpga . that one should be running very hot...

the fpga draws way more current than normal and pulls down the power supplies.

[plesa]

The last try check following in menu:
1 Turn on the menu. A: MOD MENU
2 Move across to the PHASE MENU choice on this level. G:PHASE MENU
3 Move down a level and then across to the UNLOCK ERR command.4:UNLOCK ERR
4 Move down a level and disable the unlock error. DISABLE
5 Save the change and turn off the menu.
The unlock error setting is stored in non-volatile memory, and does not change when power has been off or after a remote-interface reset

I found this in option menu manual, so give a try.

[Quarlo Klobrigney]

U501 1822-1342 1 IC PLD FPGA-SRAM UNPRGMD CMOS 240-PQFP 12880  EP1C6Q240C8
from the parts list, however it looks like you have a different part there...

I also wondered that also, even with a config EEPROM you still have to do up the FPGA.

[HighVoltage]

The last try check following in menu:
1 Turn on the menu. A: MOD MENU
2 Move across to the PHASE MENU choice on this level. G:PHASE MENU
3 Move down a level and then across to the UNLOCK ERR command.4:UNLOCK ERR
4 Move down a level and disable the unlock error. DISABLE
5 Save the change and turn off the menu.
The unlock error setting is stored in non-volatile memory, and does not change when power has been off or after a remote-interface reset

I found this in option menu manual, so give a try.

I think you are mixing this up with the older Agilent 33120A that had the vacuum fluorescent display (VFD)
This one is the 33220A with LCD and graphics display that does not have this menu
Or I am mistaken?

[HighVoltage]

The generator is now sold

https://www.eevblog.com/forum/buysellwanted/agilent-33220a-arbitrary-waveform-generator-%28needs-repair%29/

May be we will hear from the buyer, how he fixed this instrument.

[plesa]

The last try check following in menu:
1 Turn on the menu. A: MOD MENU
2 Move across to the PHASE MENU choice on this level. G:PHASE MENU
3 Move down a level and then across to the UNLOCK ERR command.4:UNLOCK ERR
4 Move down a level and disable the unlock error. DISABLE
5 Save the change and turn off the menu.
The unlock error setting is stored in non-volatile memory, and does not change when power has been off or after a remote-interface reset

I found this in option menu manual, so give a try.

I think you are mixing this up with the older Agilent 33120A that had the vacuum fluorescent display (VFD)
This one is the 33220A with LCD and graphics display that does not have this menu
Or I am mistaken?

You are right, so if this menu is not available you can try it by SCPI.
It is not fix, but can be used like bypass to enable output.

PHASe:UNLock:ERRor:STATe {OFF|ON}
PHASe:UNLock:ERRor:STATe?
Disable or enable the function generator from generating an error if
the phase-lock is ever lost. The default is OFF. If the phase-lock is lost
and the error is enabled, a “Reference phase-locked loop is unlocked”
error is generated. The unlock error setting is not stored in non-volatile
memory. That is, the setting will be lost when the power is cycled. The
:STAT? query returns “0” (OFF) or “1” (ON)

Reference phase-locked loop is unlocked
The PHAS:UNL:ERR:STAT has been enabled (“on”) and the internal
phase-locked loop that controls the frequency is currently unlocked.
This error is most likely to occur when the external reference is out of
lock range.

[Andy Watson]

May be we will hear from the buyer, how he fixed this instrument.

May be! But don't hold your breath I like a challenge but I think I might have bitten-off more than I can chew with this one. The board shown in your original photo appears to be an early version. If it is the FPGA at fault, as  free_electron confirms, it might be beyond economic repair. It looks as if HP/Agilent re-spun the design because the 20k200 FPGA became obsolete. The only sources I've found for the original FPGA are asking silly prices.

[Quarlo Klobrigney]

Well good luck to whomever has possession of the unit, hopefully all will be repaired in due course.

[MadTux]

May be we will hear from the buyer, how he fixed this instrument.

May be! But don't hold your breath I like a challenge but I think I might have bitten-off more than I can chew with this one. The board shown in your original photo appears to be an early version. If it is the FPGA at fault, as  free_electron confirms, it might be beyond economic repair. It looks as if HP/Agilent re-spun the design because the 20k200 FPGA became obsolete. The only sources I've found for the original FPGA are asking silly prices.

Why that, I found one that seems to fit for $32 on ebay. Might be worth a try,since that box is probably worth more than $250 when working.
http://www.ebay.com/itm/Brand-New-FPGA-IC-Chip-Altera-EP20K200RC240-3-Field-Programmable-Gate-Array-/331326657509?hash=item4d249b93e5

It's a faster version, but other than that I don't see why it woiuldn't work