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Test Equipment Anonymous (TEA) group therapy thread

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tautech:

--- Quote from: bd139 on May 24, 2018, 04:59:16 pm ---Well 20 minutes into the D83 and the power supply board is out of the good one and it is in a right state. Genuinely surprised it even powered up. I'm going to swap the entire bottom half of the dead scope into the good one. That has IEC sockets, a board which isn't totalled and some healthier looking parts on it. I've got replacement caps so will re-cap, rebuild the power supply and backplane. Fun fun fun! Will temporarily jump the mains switch to bring the power supply up on its own.

This is quite difficult to work on this one. Everything is soldered individual wires. Fortunately it's "solder by numbers" so easy enough to put back together after.  I'm happy for once. No 10 minute easy fix here!

Some pictures:

Gunky cap vomit, courtesy of another British quality manufacturer (not): ITT.

PCB-eep! This might have survived if it wasn't for the massive bodge wires helping electrolyte puke capillary action.

Now for some engineering fun that my mother warned me about. The reason those big black wires are on there is a quality control fail. The board exposure was done badly and had gaps in the ground trace. It likely got all the way through assembly like this and then some poor fucker had to debug it and just jumped the duff traces with bodge wire  :palm:  :palm:  :palm:  :palm:

Other board is in much better state so will just sub that in.

--- End quote ---
Interestingly the D83 I had didn't have a mask on the PCB, they were just bare FR4. Really early one I guess.  :-//
IIRC there were bodge wires on mine too and I'm sure I traced them out and found there was no other way to get the connectivity in that layout style. Unless I missed something.  :-// Was a good few years back when I was still fairly green.

mnementh:

--- Quote from: bd139 on May 24, 2018, 04:59:16 pm ---Well 20 minutes into the D83 and the power supply board is out of the good one and it is in a right state. Genuinely surprised it even powered up. I'm going to swap the entire bottom half of the dead scope into the good one. That has IEC sockets, a board which isn't totalled and some healthier looking parts on it. I've got replacement caps so will re-cap, rebuild the power supply and backplane. Fun fun fun! Will temporarily jump the mains switch to bring the power supply up on its own.
(SNIP)

Other board is in much better state so will just sub that in.

--- End quote ---

So... forty-something years it worked amazing with that bodge wire from the factory, and NOW it needs to be "fixed"?  :-DD

I've always believed you should love your old iron "warts & all"; besides, you're going to be rebuilding that board anyways, when you decide to have a go at the basket case that came as a side order.  :P

Yes, I get it... you want to make this example as good as it can be; but there's a better than even chance that other mainboard has all sorts of OTHER crap wrong with it not related to the bodge wire or cap vomit.

mnem
Hopefully I'm wrong.  ;D

GerryBags:
Thank the stars for dopey Ebay sellers (sometimes)!

My 3455A was sold as not working because it wasn't reading on the resistance ranges (apparently), I have just tested it after first checking the line voltage selectors, and because I remembered to RTFM, the line frequency selector.... which was set to 60 Hz, not 50. I didn't think that on its own would be the issue, but apparently it must have been as once powered up, and self-test run (not even warm) it was telling me a Vishay .01% 110k resistor was 100.009 - 100.010.

Then I had to turn it off because I thought I smelled magic smoke. I opened it up though, and I can't see any signs.... just really clean, gold-plated loveliness. I didn't find any evidence of smoke release, but I did find a dry solder joint on one of the EL caps inside the shield. I gave it a wiggle and you can feel both too much movement and a vary faint click as the joint opens and closes. Bummer.

Does anyone have a hi-res scan of the service manual? Most of the schematics in the one I found are just too low to see component IDs. I've got an original Operating Instructions manual on order, but I'm not sure that has the full schematics in.

Whichever way I cut it, it looks like a real bargain: Best £100 I ever spent  :-+

Neomys Sapiens:

--- Quote from: GerryBags on May 24, 2018, 03:21:26 am ---
--- Quote from: Mr. Scram on May 24, 2018, 02:51:38 am ---German tank maintenance? Do you have a Tiger in your lab you're not telling us about?

--- End quote ---

I wish I did! I've spent the last ten years making scale models of armour, Tigers included, and I'm a stickler for accuracy. I suppose it's unsurprising that once I got into electronics I'd gravitate to TEA in short order. Weirdly, both Silicon Valley and the British tech industry owe their existence to WW2, so having a handle on the history of that period has helped me get my head around the story of how things have developed since then. My understanding is up to about the early eighties at best, I reckon, I'm trying to give myself a better grounding in the basics before diving into MCU's and more complicated stuff.

--- End quote ---
My granddad served with a PzInst, first in Africa, later in Russia. So my early youth (when he was still around) was filled with stories about how to salvage a Tiger with three 18ton-halftracks, how the material suffered from the eastern cold and how they improvised vehicles (specially in africa), like scabbing a british PaK onto a salvaged italian tank and so on.
It took a long time for me to come back to armoured vehicles, but when I did, it was in the veritable house of Krauss-Maffei Wegmann. Had a lot of fun and interesting work there. As it is the home of the Leopard2, it was always very funny when you had someone at the telephone and they always were a bit shocked when a driver in the yard opened the throttle a bit. Lovely sound!

Specmaster:
 Are there any Hacker radio fans out there in TEA land? I like to repair and restore radios and Hackers and HMV Diplomats especially and today I couldn't believe my eyes at the price this old Hacker sold for on Ebay today https://www.ebay.co.uk/itm/HACKER-SUPER-SOVEREIGN-RADIO-MODEL-NO-RP-75-MB-WELL-OVER-40-YEARS-OLD/163052588190?hash=item25f6b10c9e:g:2U4AAOSwkcFa~dc5

Just wish it was one of mine and it sold for that kind of money, could reinvest in some TEA as well then  :-DD

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