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Hi to all usual suspects here.
You will maybe remember you helped me resurect my 7704A from decades of non working neglect. Thanks!
Here is for me a new challenge. I did a large leap in time from the 7704A and just bought a TDS520.
At boot:
All ok except:
FAIL++Acquisition
FAIL++ Attn/Acq interface
As soon as I knew it will be coming I read here all I could about it so I know that Artek has the documents.
Btw I want to praise Artek a bit here. I bought them the service manual for my two HP8640B I just bought too (yes, two is gluttony, I know but they were cheap and defective of course, so how to resist?)
Anyway Artek gives a really good service. The manuals are of upmost quality. I got them instantly and the charge is very reasonable.
I posted the boot to "TDS520 in Brittany" /g/TekScopes/album?id=291619
Also the 1993 rom: A11U1331 ver 1.5

There's a 7 segments inside at the back which only blinks alternately his two right segments.
Apart for the fails the scope is in perfect shape and was only very dusty inside. I disinserted all flat cables I could find and re-inserted them. I also removed the dust with hope this will change the fail boot (not really!) It did not.

All advices will be received gratefully.

I repaired a TDS520 with exactly same error screen after repairing a (literally) burned power supply. In my case leaking electrolytic caps damaged a trace to U900 on acquisition board.
Ozan

First thing, replace all the SMD electrolytic capacitors throughout the unit, on the processor board, acquisition board, and front panel (maybe the firmface board if fitted and caps are there too? I'm not sure on that model)

I would suggest making note of values, then removing them all, then putting the bare processor board and acquisition boards through the dishwasher.
Washing by hand is fine too if no dishwasher is available.

Repair any damage caused by the leaked electrolyte and install new caps.
If you need a replacement VCO board (the little PCB sticking up off the acquisition board) I made a replacement design, and may have a few spare blank PCB's laying around if you need.




The two segments alternately flashing on the 7-seg display on the processor board indicate that the processor has sucesfully booted and is running, so I'd concentrate efforts on the acquisition board, besides any electrolyte corrosion damage as previously mentioned.

That ROM chip you took a photo of is the boot ROM (basically equivalent to the BIOS in a standard PC), and can be ignored as working as the unit boots ok.


Jared

Thanks to you both. Yes my intention was to:
Buy the manual
Measure the psus
Desolder and take notes of caps data.
Clean the boards. I will indeed put them in the dishwasher Jared. I would not have dared but now I will. How long that will take to dry I wonder?
Look with a magnifier at the traces.
Recap with Nichicon 105 deg low z caps. Good price when ordered by hundreds!

I understand the rom is a bios and I documented it in case the firmware was any use.
What is the frequency covering of the vco? From the L101 I'd guess GHz.
What makes you think I will have to replace it Jared?
Thanks,

Don't bother buying a manual, head to Tekwiki where I've uploaded everything I can find for these scopes.



You'll only need to replace the VCO board if the two capacitors on the board have leaked a lot and damaged it. I have done one replacement, but other scopes didn't have enough leakage to need it. A visual inspection is enough, if you see corrosion of the traces, it's a small board so better safe than sorry IMO.

I leave the boards in to dry from the heater in the dishwasher, then blow out any remaining water from under the chips etc with canned air or an air compressor with the pressure turned down to avoid parts flying off the board.
Give it a few days and a blast with a hairdryer to be safe and you'll be fine.

Don't put the input hybrids through the dishwasher though! They are delicate and never need it anyway.



Jared

Thanks Jared. Duly noted.
Yesterday I measured on J1400:
+15: +15.06
+5: +4.69
-5.1: -4.93
-15: -15.08
Ripple is less than 5mV.
I cleaned the boards prudently (ipa, brush & comp air). The PSU is something! My guess is it is outsourced by Tek?

I wanted to order caps with Mouser but was surprised to see they charge 20€ p&p. Last time I ordered with them there was free shipping for orders above 50€ ex vat.
Renaud

Hi,
Sorry for this old story but there's some news about my TDS520.
Due to real life it waited since december 2023 for my attention. Last week only took it from its shelf, opened it and I removed the nearly 50 chemical caps on the acq board (A10).
Then A10 went in a friend's dishwasher. I then recapped with Nichicon and put it back. Remember it booted in 2023 and only failed on Acquisition & Attn/Acq interface. Now no boot.
I measured on the new caps and found one supposed +5V to be -0.6V. To make it short there's a through hole just near C1584 and of course it juiced there and now no more continuity. I soldered a small piece of wire and got back that 5V.
But still no boot and no 1kHz on the probe comp signal.
I followed the troubleshooting procedure which told me to "Change A12". Well, thanks but no. That procedure had me disconnect some connectors though and once reconnected the scope booted.
-Fail processor (pass in 2023)
-Pass acquisition (fail in 2023)
-Fail Attn/acq (as in 2023)

There I got myself a little snack away from the darn thing. Came back two hours later and rebooted
Now Fail processor and all the rest pass.
And : "Consult service manual for fault isolation. Press CLEAR MENU to continue" which I did but not with much hope.
I was wrong. I put a probe on CH1 and got the probe comp signal on screen.
I did not proceed recapping A11 (processor) because it booted and I wanted to test A10 first. Now I will.
Also I should "Consult service manual for fault isolation" ! There's still that Fail processor.

Here I am and, as usual, all criticism, comments or advices welcome.
Best
Renaud