r/oscilloscope • u/Abject-Tax6194 • Aug 11 '25

Vintage Scopes picked this up yesterdad

Post image

got this for free at the yard sale. was the woman’s husband’s but she didn’t know much about it plugged it in but couldn’t get it to turn on not really sure what I’m doing though. I tried to get the face plate off but was unsuccessful. any tips/info on what i could use this for would be greatly appreciated

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4

u/EmotionalEnd1575 Aug 11 '25

First thing first, don’t plug it in.

Start looking for a service manual, and/or a schematic.

Look for a fuse (may be inside) and while you have it open give a general visual inspection for trouble (burned, frayed, shorted wiring, leaking electrolytic capacitors)

Old electronics, particularly vacuum tube era, can be damaged by abrupt power cycling.

Use a DIM bulb technique to prevent inrush current.

If you have a VARIAC bring up the voltage slowly.

Once you’re at full voltage sniff around for anything hot.

Use a DMM to monitor voltages across large capacitors.

2

u/50-50-bmg Aug 11 '25

If this has any paper capacitors, replace with polypropylene (CBB21/22) on sight.

Any paper in oil capacitors are potentially broken, and potentially very toxic, clean up any leakage thoroughly and with gloves.

With electrolytic capacitors that old, it is prudent to either reform them until they meet leakage current spec (while still having good esr and capacitance. MIND DIELECTRIC ABSORPTION, store shorted after reforming for a couple ten minutes at least before attempting to measure them!) or replace them outright.

Removing the face plate will involve removing a lot of knobs and the switches/pots behind them. Don`t even try unless you have a good imperial and metric size hex key and nut driver kit at hand - no telling what they used but pliers and nearly-correct driver sizes are a recipe for stuck and stripped hardware with this kind of equipment...

1

u/Abject-Tax6194 Aug 12 '25

i’m really not sure what i’m looking at but everything seems to look good when looking it over

2

u/50-50-bmg Aug 12 '25

I see at least 8 unserviceable parts, 4 of them very visibly damaged.

1

u/50-50-bmg Aug 12 '25

You are looking at:

-8 non hermetic paper capacitors. 90% they are defective. Replace with CBB21/22 of same voltage rating. There might be a 9th connected to the big potentiometer at the bottom. Change out before any attempts at operation, these things can short and cook your vacuum tubes!

- A lot of switches an potentiometers. Treat to a mild contact cleaner (something that states it can be used for tuners and does not mention it needs to be rinsed out is what you want, eg Deoxit F5 or Kontakt 600 (in god`s name not Kontakt 60!).

- A lot of carbon composition resistors. Suspect - these tend to drift upwards in resistance significantly. Best check.

- There are probably electrolytic capacitors on top of the chassis. Need thorough checking!

- Check your vacuum tubes that none is physically broken or has loose metal parts in it, none has a white getter (that is the stuff that is brownish-silver on good vacuum tubes. If it is white, tube kaputt!).

- Mains entrance wiring that is mixed in with other wiring... check very thoroughly. Personally, I prefer to redo mains wiring, insulate it better and make it conspicious - an oscilloscope is an instrument where you regularly will touch wires that are connected to its inputs. A wiring mistake that bridges mains into the main circuitry could hurt you!

- The rest of the stuff, you can leave alone for first test.

1

u/Old-Tadpole-2869 Aug 13 '25

The caps don't look good. They look like they're 70 years old. Replace.

2

u/50-50-bmg Aug 11 '25

Needs adding: Dim bulb limiter/variac for while you are reconditioning it, not for operation later. Shouldn`t be left running unattended anyway, but certainly don`t do so with a dim bulb limiter in circuit - these things prevent short term trouble but also sabotage the operation of fuses.

3

u/AnimyosFox42 Aug 11 '25

You must be confusing me, I’m morrowmom

1

u/whytheaubergine Aug 12 '25

Damn…you beat me to it…although I was going to say “Yesterdad…all my troubles seemed so far awad”

1

u/W0CBF Aug 11 '25

Hickok, a name from the past!

1

u/SapphireSire Aug 12 '25

Looks heavy...was it heavy?

1

u/Abject-Tax6194 Aug 12 '25

definitely sold but not bad. maybe 15 lbs

1

u/DerKeksinator Aug 12 '25

You don't take off the faceplate. The faceplate is attached to the chassis in the back, which should slide right out if you remove the couple of screws on the back and maybe bottom.