Late 1970s Sprauge Capacitor Markings

[Compgeke]

Good Evening,

I'm working at getting a capacitor list together for my Tektronix 650A monitor but a few of the caps I'm iffy on whether I've decoded the value correctly or not. I'm not too familiar with the old school Sprague or even Tektronix in house markings - not generally my specialty. That's normally old Mac computers .

I've gotten everything else figured out. Absolutely beautiful build quality as one would expect with a Tektronix .


Anyway, the caps.

Here's #1: 50v 1uf? "1-150DC"


#2: 25v 1uf non polarized? "1.0-25 VNP"


#3: 6v 330uf? "330-6 DC"

[stj]

Re: Late 1970s Sprauge Capacitor Markings

i would look for a service manual or schematic - your more likely to find it than the cap data.
specially considering that the last cap may not be electrolytic.

[momaka]

Re: Late 1970s Sprauge Capacitor Markings

Well, I'm no expert in old gear like that either. However, I did acquire an old HP adjustable lab PSU a while back from the same or similar era (either 60's or 70's) and have gone through the service manual several times (and unfortunately still not fully fixed it... but that's a different topic.)

With that said, I think you pretty much did get those values right. Only the first one I think is different.

Here's #1: 50v 1uf? "1-150DC"
https://i.imgur.com/34ymEtp.jpg

I think that should be a 1 uF, 150V cap.

#2 and #3 should be right, though.

Oh and 500D is the series, IIRC. (Good luck finding a spec sheet, though.)

That said, do you have an ESR/capacitance meter, just to double-check them? On my HP bench PSU, believe it or not, most of those old caps tested OK to Good. Only a few smaller ones had slightly higher ESR or too low of a capacitance. I think these old caps have really good seals and also really thick aluminum plates, which is probably why they seem to have lasted so many years. Not all old caps are build like that, of course. But I think these particular Spragues were.

Anyways, I'm curious to see what some of the more knowledgeable folks here think / will suggest.

[budm]

Re: Late 1970s Sprauge Capacitor Markings

500D series cap
https://cdn.badcaps-static.com/pdfs/...9a1d34ec44.pdf

[redwire]

Re: Late 1970s Sprauge Capacitor Markings

The 330uF 6V part looks like solid-electrolyte tantalum, I can't see the series number but maybe 150D or military version M39003 note glass seal and there is no crimp on the barrel.
Sometimes their low leakage current 7.5-10uA was specifically used by Tek for LF sweep oscillator, or their tighter tolerance (than electrolytic) or high ripple current ability.
I would check how they are used in the circuit and decide what's best to replace it with. Tek would have just plopped in a 330uF electrolytic - but not good enough here so something is special.

I think those IC/transistor sockets oxidize and give a poor connection, so they need some wiggling or Deoxit or something, if you find the monitor has intermittent problems.

[Compgeke]

Re: Late 1970s Sprauge Capacitor Markings

I do have a tester, but it also needs work. Was going to do a restoration on it, until I got to the controls where someone greased them and it turned to glue. Kind of threw it on the back burner at that point, degunking the controls is a headache in and of itself.

For now I'll just replace the caps I know are electrolytic for sure. The 25v 22ufs are already leaking so they're the first to go.



What's prompting the repairs anyway?


I already know the vertical adjustment is whack, but the control for that just needs some cleaning. The actual screwy image is the horizontal board being covered in capacitor goo though. You go to check to see what caps it has to replace and find goo everywhere, that's usually how it goes.

As for schematics, the service manual for the 650A and 650HR are surprisingly difficult to find. I've got one of each and man, I'd love to find them but they seem to not exist. If someone has one of either, that'd be amazing.