Tektronix AWG2020 No Output - SOLVED

[RPP]

I picked up a clean AWG2020 a while ago and finally found some time to take a look at it.  It booted up fine and all the functions appear to work despite a SETUP CH2 error code (620) but I get no output on either channel (it has option 2 installed).  I went through it and replaced 62 - 22uF/35V SMD caps since some appeared to be leaking and checked PCB traces in the areas where the caps leaked after cleaning the boards. The caps under the RF cages appear to be nearly impossilble to remove without damaging the boards so I left them alone, but those look OK.  Unfortunately, I still get no output.  The lights for output on the front panel for each channel come one when I select the channel, so the front panel appears to function normally . . .  strange that it's happening to both channels. 

I'm planning to check voltages, although the AWG2021 service manual has limited info, then pull the A3 & A23 boards to check the output relays and start tracing backwards from the output connector but any suggestions would be appreciated. 

Rich

[Kean]

Have you seen this?  https://www.jvgavila.com/awg-2020.htm

I don't have one, but as is common it looks like old leaky capacitors can eat through some fine PCB traces and you need to carefully inspect for damage.

[gianrisa]

Hey hi,

what does the selftest reports ? Any error ?

trace back the signal out on the dac pin 17/18 of the chip under the shield in the board A21. There should be the output, if yes then te problem is the amplifier attenuators.

Have a look  at my post https://www.eevblog.com/forum/repair/awg2021-troubleshooting/msg5192367/#msg5192367 there is a bit of description about the debug process I use.

Let me know I can try to help.

Cheers Gian

[RPP]

Thanks for the help.  I found some time yesterday to troubleshoot the issues.  I was able to follow the FG signal up to the output relays - K228 & K230 but they weren't energizing when the front panel switch was pushed.  I followed the thin traces from the relay coils to the underside of the board where they connect to U360 (an LB1265) but they lost continuity along the way, so I ran jumpers from the relays to the IC on both boards.   I remember checking all the traces in the vicinity of the leaking caps when I replaced them, but I must have missed the these or damaged them as I was cleaning. 

 

The SETUP CH2 error 620 appears to have been caused by a failed relay on the A23 board - K215.  The normally open contacts remained open when the relay was engaged, so I have a replacement on order.  Once that arrives, I'll put it all back together and expect that it will be back to fully operational.

While I was troubleshooting, i also discovered yet another of those insidious 22uF/35V SMD caps on the front panel board that was, of course, leaking. 

I'll report back when I get it back together. 

Thanks again.

Rich

[coppercone2]

damn I should probobly service the AWG2020 but holy hell I have that tektronix oscilloscope to do as well. I guess that is the price. 

[nctnico]

The SETUP CH2 error 620 appears to have been caused by a failed relay on the A23 board - K215.  The normally open contacts remained open when the relay was engaged, so I have a replacement on order.  Once that arrives, I'll put it all back together and expect that it will be back to fully operational.

Don't rule out the problem is caused by a damaged PCB trace or via. A long time ago I restored a TDS544 which also had major damage from electrolyte. I even had to resolder some chips because the electrolyte had 'eaten' the solder joints away.

[RPP]

Don't rule out the problem is caused by a damaged PCB trace or via. A long time ago I restored a TDS544 which also had major damage from electrolyte. I even had to resolder some chips because the electrolyte had 'eaten' the solder joints away.

Point well taken.  I rechecked every area with electrolyte damage on all the boards again, but if the relay doesn't resolve the error code, I'll have a good idea where to look now.

Rich

[nctnico]

Taking the relay out gives a good chance to look under it. Don't be surprised if it turns out the pins of the relay are gone. In the TDS544 I restored, the pins on some of the encoders on the front panel where dissolved completely.

[RPP]

Quick update - I got the K215 relay today and soldered in into the A23 board.  Reassembled everything and it works perfectly.  The SETUP CH2 620 error is gone and both the outputs switch on and off as expected.  Woo Hoo!  Now i just have to learn how to use this thing . . . the function generator section is simple, of course, but the AWG features will be a learning curve.  I downloaded the 'sample waveform library' and will install the files on a disk at some point.  Hopefully the FDD works.  Another addition to a growing collection. 

Don't procrastinate on replacing those leaking SMD caps in your 1990's Tek equipment!  the damage just keeps getting worse with time.

Rich

[coppercone2]

do you have a list of the caps you need to replace for likely buying quantity and values?

[RPP]

It's a short list:

62 x 22uF/35V SMD caps replaced with 62 x 22uF/50V Nichicon UHE radial caps 

EDIT: 63 x 22uF/35V - I found another one on the front panel board when I was troubleshooting . . .

My unit has Option 2 installed so there are 2 extra boards to support the 2nd channel output.  Example of a radial cap replacing an SMD cap:

[nctnico]

Why not replace with SMD capacitors? Preserve the originality 

[RPP]

Radials are easier to retrofit, IMHO.  The original caps leaked and destroyed parts of the boards . . . don't want to keep that part of the originality, just the function,  lol.

Rich

[coppercone2]

imo good call on the THT parts being used instead of more SMT. Bet they will last longer because its isolated from the heat.


Hah, I wonder how much life you can get from a cap if you use heatsink clips on it during assembly.

I need to do a TDS 1992ish~ 4 channel tektronix oscilloscope with all caps and the AWG2020. year of the capacitor it looks like