Hello everyone. First post here.
At my place of work we have several old pieces of equipment. I found an RCA WV-98C, opened it up, and found some very bad battery corrosion inside. I’ve currently got the metal platform soaking in some vinegar, and if I get far enough with it I may take it to a local place for a sandblast and re-galvanizing.
The internal part I think I’m most concerned about is the transformer. It may just be surface corrosion, I was able to clean the majority of it off, but I have yet to see if it works as it should.
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Hi, because you had published pictures and/or links for the first time here they have been automatically erased due to some sort of “anti-spam algorithm” that is running on this site but if you re-post them then they will most likely show this time around. It has happened to everyone (who posted links) on their first post.
My mistake :^)
Here it is again:
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You’ll need to try posting your link again. The system puts new accounts through review and won’t allow new users upload any links to prevent spam.
-Mr Carlson’s Lab Admin
@wrapscallion Welcome, that transformer looks like it should work just fine. Could be much worse I’d say, should clean up pretty nice!
Radios + Tubes + Scopes + Cars= Nothing better!
I’ve been working on restoring the VTVM! As far as I can tell the transformer does indeed work.
So, I only have the WG-289 high voltage probe for this VTVM. I haven’t been able to locate the WG-299D or any of its variants in the storage where I found the meter.
I was thinking of replacing the front jack with a BNC to use modern leads, but I’m unsure of the safety ratings that I should be looking for when replacing the leads, since this meter goes to 1500 volts. The only ready-made leads that I’ve found on the Internet are the Fluke TL175-HV, which are rated for CAT III 1500 volts.
Additionally the original probe has a 1 meg resistor that is switched in line for DC measurements. I would lose that with a modern probe, unless I want to always clip my probe to one before I make DC measurements?
I’m just looking for some guidance on either modern replacements, sourcing the original probe, or if this sounds like a DIY project.
@wrapscallion For the probe situation, I highly recommend Kent Craft LLC on ebay. I have several of his probes and they are top notch! If you don’t find something that will work with your meter, message him and he will make it happen. Honestly, any voltage over 1kv should be using a HV probe in my opinion. Although, a real fluke lead set even rated at 1kv should have no problem at 1.5kv.
https://www.ebay.com/str/kk4hxj
Radios + Tubes + Scopes + Cars= Nothing better!
Thanks for directing me to him! It looks like he has exactly the stuff that I need. Personally I was hoping to avoid the directly attached common cable as I would have liked to have a removeable cable, but I can accept it.
Whoever assembled this unit the first time definitely must have assembled it from a kit, because there was such a mix of different wire colors inside. And I believe there was a snipped wire off of the ground lug. I’ve elected to rewire the whole thing because of the battery corrosion and the confusing wiring mess. I’m a novice so it’s been quite a learning process, and I’m confident that I’ll finish it.
I’m currently in the calibration process, but I’m feeling pretty foolish because it occurred to me that I replaced the two tubular ceramic capacitors without understanding the importance of their temperature stability. The 56 picofarad cap (C9) is measuring at about 66, and I have to double-check the 24 picofarad cap (C3).
My hand-picked replacements are about as close to their nominal values as I could get.
Turns out that the capacitor that I replaced cap C3 with is an NP0. I forgot that I had chosen that. But I’m looking into some 56 pF NP0 ceramic caps for C9.
Oof. Well, I feel foolish again. I didn’t understand temperature coefficients.
C9, the 56 pF cap, has markings indicating a N330 temperature coefficient. I’m not sure how much this matters in the circuit. But I suppose I should either consider putting the old capacitor back in, or… I’m not sure yet.
I’m having trouble getting the .5 volt range to calibrate. I’m not yet sure what’s going on. I replaced the electrolytic cap again because for some reason the brand new one decided to fail. Switched to a Rubycon.
Additionally I seem to be getting only -0.7 volts on pin 7 of the 6AL5. I did buy two of each tube from ebay in case I end up needing to replace them.
Well… I made the mistake of trying to get into the meter to fix some sticking that was occurring, and ended up breaking the circular spring, I think a clock spring? So I guess I’m going to be looking for parts units to replace the meter.