How to identify part values....

[mmrxcsr01]

...specifically, paper electrolytics. I have an old, old amp, no schematic, and the cardboard tube is just completely unreadable. I have searched every way I can think of online, it's not in Doug's files....any suggestions? TIA....

[acheld]

Is it a commercially built amp?  Pictures?   

[mmrxcsr01]

It's 1949 Silvertone, model 1304, 5u4, a pair of 6l6's....12sj7, 12sn7, 7c7. Field coil 12". Passes signal, but with a bad hum. Sorry, no pix....from what I've been able find from a few searches, this was a transition model, only produced for 6 months...

[sluckey]

This model 1303 looks like a close match. I'd use these cap values...

     https://el34world.com/charts/Schematics/files/Silvertone/Silvertone_1303.pdf

[mmrxcsr01]

Thanks Slucky...so 8mfd at 450vdc should about cover it....Merry Christmas.

[PRR]

Silvertone wudda used whatever they could get (post-war shortages).

Yes, a fist full of 8uFd seems likely.

The field-coil speaker was already going out of style. But so were large parlor radios, and maybe Silvertone had a 6-month supply to use-up.

[mmrxcsr01]

Thanks PRR, that thought hadn't occurred to me...here's a pic, from online...

[sluckey]

Three of those caps are filter caps and should be rated about 450v. The fourth cap is a cathode bypass and only needs to be rated for 50V.

You can buy all four caps for under $10 at AES is you use MOD brand.

[mmrxcsr01]

Sluckey, what about the pot for the trem? It's missing, and a weird 650k value. It controls the speed; do you think a 500k would suffice?

[sluckey]

I would use a 1M pot. Bigger values can give you a slower speed and still give the same fast speed as a smaller pot.

[mmrxcsr01]

Thanks again all, much appreciated. Merry Christmas....