Simpson O-Scope & Signal Generator

[Findm-Keepm]

You should probably scan the manuals and submit them to a freebie manuals site - I try to do that with any/all odd manuals. The BAMA site along with eService and Electrotanya have helped me greatly, so I try to reciprocate.

[MadMan]

Originally Posted by Findm-Keepm

You should probably scan the manuals and submit them to a freebie manuals site - I try to do that with any/all odd manuals. The BAMA site along with eService and Electrotanya have helped me greatly, so I try to reciprocate.

Working on it!



So, ok. I recapped both thingies. The signal generator, I haven't really tested it, but it turns on and doesn't catch on fire, so I consider that a win! The scope, on the other hand, had a whole lot more caps to replace, I finally got it done and went to turn it on. It started sparking at the crt base, a small fizzling spark like you'd get from a cracked solder joint. The base is broken (it was like that) and I had resoldered the pins years ago (they were all loose). I figured I must've done a shit job, so I redid it, twice, but I just couldn't get it to stop sparking there. Because the base is broken, and I don't feel like repairing it until I know all is working, I didn't want to totally unsolder it and redo it completely. So, I just so happen to have a nos crt to use. The scope has a 5UP1, but my new one is 5DEP1. From the info sheets, I can't see anything majorly different, but maybe you know something I don't?

Anyway, I tried the new crt, and when I turned it on, it immediately started sparking violently from the V4 socket (5Y3GT). I didn't risk leaving it on to pinpoint the location. I went through and retested all the tubes, checking especially for shorts, but all was ship-shape.

->Schematic<-

Coincidentally, that resistor I suspected missing is directly off of V4. It's R19, and I did indeed confirm it was there once upon a time. Unsoldering the capacitors there revealed two tiny sections of resistor leads. I have replaced it.

Before:


After:


It's also worth noting that it's pretty clear this scope was either an in-house experimental unit, or grandad and/or his coworker (the previous owner) did some hot-rodding.

Oddity notes:
C3A (near V1) was 50uf. It's now 100uf again.
C6 (near V2) is missing, still.
V2 pin 2 has a resistor to ground, still.

I don't think any of those things would cause it to spark violently at V4. As I turned it off within seconds, it didn't burn anything, so no evidence. The kicker is: the tiny little bitty sparking from the crt base was nowhere near the very loud snapping, obviously-high-voltage arcing from the bottom of V4. Also, I have not touched any of pins on the V4 tube socket. Unless the really bad sparking is simply because I tried the wrong CRT?



I didn't break it! Sadly, it's held to the chassis by a hose clamp, someone probably overtightened it. I was going to remake this with epoxy glue. Pretty sure it'll turn out fine, been practicing on other things. The leads are not touching each other, and I checked to make sure the base was properly aligned to the leads (by following the ones to the filament [also I had marked the No. 1 pin on the glass with marker]).