Silvertone 1482 Questions

[otgordin]

Hi, I have a 1960s silvertone 1482 that I got at a garage sale 6 years ago. I've been abroad the past 4 years and it spent that time in my parents' basement. Now, when I turn it on, the jewel light comes on. However, the amp pops and cracks and does not respond to any change in what i do to the inputs (guitar1 guitar2, mic) or knobs on the front. To the best of my knowledge, the amp worked fine when I put it down there. I have a degree in engineering with some circuits/microcontroller experience and am decent with a soldering iron, but have never worked on tubes. Any help troubleshooting this old gem of an amp would be very much appreciated.

-Vadim

[soapbarstrat]

Hmm, worked 4 years ago, then after sitting 4 years, doesn't work. I know little about amps, but I have to say if that thing still has original filter capacitors, I bet that's the problem.

[RFR]

Hmm, worked 4 years ago, then after sitting 4 years, doesn't work. I know little about amps, but I have to say if that thing still has original filter capacitors, I bet that's the problem.

+ 1

That is the first thing I would check.

Roman

[otgordin]

hmmm.... I'll have to find myself a decent multimeter and check it out then. What's a ballpark figure for the cost to replace the caps in one of these? [a guess is all i'm looking for] Thanks.

-Vadim

[ansil]

hmmm.... I'll have to find myself a decent multimeter and check it out then. What's a ballpark figure for the cost to replace the caps in one of these? [a guess is all i'm looking for] Thanks.

-Vadim

depending on the size of them not much i would say. most of the amps back in those days had 50c5's or similar line operated tubes. so its usually less than 200 volts dc.

although a bit extreme in a pinch i have used the disposable camera capacitors in a pinch. that was way over kill on the capacaitance level.

alot of the older amps will pass some voltage on the caps. some like to say this is vintage and if its a few volts to leave it be. i am from the school of a cap blocks dc if it doesn't tis broken.

i am downloading a schematic for this which is avialable many places such as http://www.freeinfosociety.com/electronics...vertone1482.pdf

k i was wrong on which amp i thought this was. it would cosst under 20usd if you have a ce account. or you can use their sister site. this will give you the can you need.

ed

[otgordin]

CE account? Would any ole capacitors from Digikey work?

[otgordin]

with matched values of course.

[soapbarstrat]

According to this web page you've got one of those old "multi can caps" (aluminum cylinder on the same side of the chassis where the tubes are). I think it's pretty standard to forget about replacing with an identical type of can cap, so then you have to "jerry rig" some seperate new caps inside the chassis. You can see how that guy did that. He even had to use glue to help secure the caps.

What I would highly consider (if possible), is to remove the rivets holding the can cap, which would leave me two holes for screws, which terminal strips could be bolted to. But, pretty tight space, so I don't know if that would be better than what that guy had to do. The import caps you can buy from various places (Mouser, etc) are smaller than the trusty Sprague blue atoms, so at least the import caps have that advantage. (Illinois brand was a popular import cap 10 years ago when I was experimenting with amp modding. have not kept up with what's out there and what is good/bad).

I think you need to take this to the next level by going to a more specialized amp forum. This forum just barely scratches the surface on amps. There's some hard-core dudes on those amp forums who should steer you in the right direction. They can sometimes be harsh to beginners (I know from experience), but I guess that's what breathing a lot of solder fumes can do (lol)

[Geo]

Replacing the caps should cost you almost nothing. Try one of these places.

https://taweber.powweb.com/store/capord.htm

http://tubesandmore.com/

Also, you can sometimes find 200v power supply caps in computer power supplies or in old monitors. The value doesn't matter much in this kind of amp, anything from say 8uf-50uf will probably work. I'm sure that amp isn't hifi/doesn't have good bass, so it doesn't really matter what value you use.

Note, however: even if your filter caps were dying and your signal caps were leaking DC, you should still hear SOMETHING when you play the guitar. So there may be another problem somewhere. Take some voltage readings, check for broken connections, etc. Also, new tubes is always the first thing you try when an amp is sick. So, when you buy your caps, you should probly buy some tubes too.

Here's a trick... you say you can hear crackling and popping in the speaker. So something is getting through the power amp. Assume for the moment that the power amp is good. Take a probe on your multimeter and touch it to points in the signal chain before the power amp. You should hear a pop. If you don't, you know that something in that stage is wrong and killing the signal.

Some pics of the exposed chassis would be interesting, perhaps helpful.

These guys can answer any question you have.

http://www.el34world.com/Forum/yabb2/YaBB.pl

[otgordin]

no, there is NO guitar signal making its way through. When I get the chance I'll disassemble the chassis and take some pics. Any particular precautions I should take when checking the connections?

[Geo]

"Any particular precautions I should take when checking the connections?"

Yeah. Look at the schematic and take note of where there are high voltages. UNPLUG THE AMP, but as I'm sure you know, the power supply can still hold its DC charge and zap you. If the power supply has more than ~20VDC on it, discharge it with a resistor (say 10k-220k) clipped between any node and ground.

If you're testing the amp while it's running, with the chassis open, you have to be extra careful.

If there's absolutely no signal getting through, then there may be a more serious problem. If a power supply cap blew, it could have taken out other more expensive components. It's hard to say what's going on without more info, pictures, etc.

[ward]

If there's absolutely no signal getting through, then there may be a more serious problem. If a power supply cap blew, it could have taken out other more expensive components. It's hard to say what's going on without more info, pictures, etc.

I agree.

Unplug the mains,

go have a beer or coffee.

First check all electrolytics for remaining dc.

I there is, read a book.

If not:

Check if there's a good connection from the output transformer to the speakers.

The speaker should pop when you touch the terminals with your multi meter.

Remove all your tubes, except the rectifier tube 6x4.

Plug it in,

If you know you can do it safely,

measure your voltages at the tube sockets.

then report those over here.

[Geo]

However, the amp pops and cracks and does not respond to any change in what i do to the inputs (guitar1 guitar2, mic) or knobs on the front.

This almost sounds like there's DC on the speaker. If you put a 9v battery on a speaker (to get several speakers in phase when wiring up multi-speaker cab), you hear a pop. You could test this by setting your meter to DC (say 20v range) and measuring the speaker. If there's DC on the speaker, something is seriously wrong with your output transformer.

Just another thought. Perhaps if there was DC there, it would have already blown the speaker, so this may be beside the point. And if you're hearing more than one noise, the DC would have to be changing, which seems unlikely, but I'm just throwing it out there... your OT may be bad.