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212 #1 is on its way to being fixed. I thought it was cool enough that when I found a 212 on the Facebook marketplace that looked very clean, complete, included the original case, and owner's manual, I bought it long distance without the opportunity to test it. I figured it was worth it even as only a parts scope. So I now have 212 #2, s/n B103611.

So it arrived, and it was very clean and complete. But when I plugged in it was dead, so I opened it up and found the dreaded leaky NiCad batteries.

The amplifier board and power supply board both have damage, although all the other components look like they are good enough that they only need contact cleaner.

I will detail the two damaged boards and follow-on posts. It looks like the easy way to fix this would be just acquire a new amplifier board and a new power supply board. I don't know how available these are, but with the propensity of the NiCads in these mini scopes to leak that at least the power supply board may just be plain unavailable.

But this is such a clean and complete scope I really want to fix it, although this one may be a candidate for a lithium conversion.

Here is a picture of the power supply board:


Question: Is it even worth trying to fix this board? I am worried about damage than may not be visible. I don't want to put a lot of work into a board that just isn't worth fixing.

T250: This transformer looks good, there was no corrosion evident on it. Hoping for the best.

L257: This inductor was encrusted with corrosion. I don't trust it. Per the service manual it is described as COIL, RF, 2.2 MH.

Question: Can any 2.2 micro Henry inductor work here, or is it necessary to use a Tek part?

CR261: This component is splitting on one end and it don't trust it. CR 262 through CR 268 are all the identical parts and appear to be in better condition. They are described as SEMICOND DEVICE: SILICON, 400V, 400MA.

Question: Will any diode with suitable voltage and current ratings work here?

Question: Are any power supply boards available?

Here is a picture of the amplifier board:


This board seem to have cleaned up pretty well with the following three exceptions.

L108 and L111: Both we're encrusted with corrosion, and at least one of them has a broken wire. They both need to be replaced. Both are described as COIL, RF, 1.8 MH.

Question: Can any RF rated 1.8 micro Henry inductor work in this application, or does it have to be the tech part?

U105: This appears to be a Tek custom IC. All 16 pins appear to be encrusted with green corrosion around where they enter the socket on the board. I am not sure the best way to remove this corrosion without causing problems, although I will see if DeOxIt will dissolve it.

Question: Any better ideas for removing the corrosion around the IC pins/sockets?

I would think these amplifier boards are somewhat more common than the power supply boards because they are above the battery and corrosion is less likely to attack them.

Question: Are these amplifier boards reasonably available?

Hi

You're still confusing milli and micro. You'll want to straighten that out sooner than later.

1.8 MH is 1.8mH is 1.8 millihenries

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070

The Tek 212 service manual is capitals only in the parts lists. I assumed that MH meant micro Henries in this case.

In that case, they would have used a capital U as the closest match to a mu. That's the sort of thing that was common in the ASCII monofont days of yore.

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070

L257 is not critical, you can get a higher value if you want - not lower. Make sure the current is equal or higher than original.
CR261-268 can be replaced with 1N4937. These are 600V 1A very fast switching, low capacitance and reverse leakage.
See if you can repair L108/L111. These are wound on a resistor.

Mark