caps for a silvertone

[genewiseman]

I am new here and need some advice. I have an old silvertone amp that sounds pretty good as a harmonica amp but it is time to replace the caps. I have it in storage right now so I can't tell you the model but it has one el34 output tube ( I think) and a ten inch speaker. The power output should be comparable to a princton. Can y'all give me some advice on where to get caps and what type and brands you like. I plan on replacing all of them and not just the filter caps.
Thanks a lot,
Gene

[Chuck H]

It partly depends on the year, but replacing the signal chain capacitors should be unnecessary unless any test bad. Old "paper in oil" caps are the oldest and seem most prone to failure. Dry film caps might last several lifetimes so replacing them arbitrarily isn't practical. IMHE whenever a novice starts fixing things that aren't broken it invites more trouble than improvement. JM2C on that.

Electrolytic caps DO suffer degradation with age so it makes sense to replace them in an amp that age as a matter of maintenance. This would be the power supply capacitors and any preamp tube cathode bypass capacitors. In a two power tube amp there are sometimes a couple more electrolytics used for a bias supply. You're amp probably won't have a bias supply.

If your amp uses a multi section can type capacitor for the power supply I've had good luck with JJ capacitors. I like the value options they offer and I've used them a few times with good results. Admittedly, I haven't tried any others because I haven't had to. If your amp uses individual axial lead capacitors F&T are popular, but I can't speak from experience since I stopped using axials when the brand I was using stopped working for me.

With an older amp like that you may have a two prong AC cord. For safety reasons this should be changed to a proper three prong grounded cord. I'm not being a fuddy duddy! You're holding a metal mic in your hand connected to the amp. A lack of safety ground in this case is not cool, it's just careless and more than a little dangerous. Especially if you play dives where God knows who has serviced the electrical.

Many of the older single ended (one power tube) amps make wonderful harp amps. The best thing you can do to make it a reality is service it properly. Clean all the jacks, switches, pots and tube pin sockets. Replace the electrolytic caps. Retrofit an AC cord with a proper ground.

[genewiseman]

Thanks Chuck. To tell you the truth, I haven't actually looked inside the amp. I just figured that they used a lot of paper capacitors like old radios did. I see your point about not replacing the film caps. I will replace the cord too. The wiring in my house is probably just as questionable as any dive. lol. Where do you buy your caps?
Thanks again,
Gene

[patlaw]

Welcome, Gene. Feel free to post before and after pictures, if you like. We like pictures. Once you open it up, if you have specific questions, it's helpful for you to post a link to the schematic, if you have one. If you don't have one, this group may be able to help. You've come to the right place.

[Silvertone Jockey]

Is it this amp?

[genewiseman]

Thanks patlaw.
Silvertone jockey, mine just has a volume and tone control if I remember correctly. I need to get it out of storage and see for sure. I probably am going to need to get a schematic when I get the model number anyway.

[genewiseman]

OK, I just got the amp back home. It is a Silvertone 10XL. It has four knobs: volume, tone, tremolo strength, and tremolo speed. It has four tubes: a 6x4 rectifier, a 7025 for the tremolo, a 7025 preamp tube, and a 7189 output tube. From what I understand, a 7189 is an American EL84 ? It plays and really don't sound bad for harmonica but it does have some hum to it. I opened it up and it all looks to be original and pretty clean. Other than the filter caps in the "can" it has one other cap that I figure will need replaced. It says 600 volts on it but that is all I could read because of it's placement. Where would I go for a schematic? Any help would be greatly appreciated.
Thanks a lot,
Gene

[The Dude]

Amp: http://rudn.nodevice.com/preview/big/373/373272-1.jpg

Power Supply: http://rudn.nodevice.com/preview/big/373/373272-2.jpg

If this is the right schematic, you'll want to clip out C11.

[genewiseman]

Thanks a lot Dude. I think that is exactly what I needed. This is probably a stupid question but, why clip out the capacitor ?

[The Dude]

If the cap were to short and the AC in was not grounded, the chassis would be hot and you would have smoke coming out of the top of your head. If the amp has a grounded AC cord as shown in the schematic, the cap is not necessary and is a safety hazard.

[Chuck H]

To add to what The Dude sed... The clipping of the cap is generally done when installing a proper three prong AC mains cord that earths the chassis.

[genewiseman]

Thanks for the info Chuck and Dude. I will eliminate that cap and put a three prong plug on the amp. I am thinking that that is the other cap that I was going to have to replace anyway. I don't think there would be a need for a 600v capacitor anywhere else. I just need to order the filter caps now. Where is a good place to get filter caps?
Thanks again,
Gene

[Chuck H]

I think Angela electronics carries the JJ can caps. I work with them whenever they have what I need. The price is usually comparable or better and the service is good.

[genewiseman]

I ordered the caps last night. Thanks again Chuck.