silvertone 1482 hum and hiss

[gitaar0]

Hi,

I have a Sivertone 1482 that I restored and rehoused (There was no cabinet with the amp when I bought it.

Amp was working perfectly and was dead quiet untill last week.

I connected a preamp with an effectprocessor (just to test that) that suddenly started to oscillate. Not too loud and I have turned it down asap.
Ever since I have a hum and hiss in the silvertone.

There is a slight hum with the volume down. It gets louder when I turn the volume up and a hiss is added. It is the same on both channels.
- changing the preamp tubes does not make any difference. I have used a couple of different tubes.
- changing the power tubes does not make any difference.
- I have checked the voltages in the amp and they about what they where and in the area of what the schematic indicates.
- no change in the hum when moving parts and wiring with a chopstick.
- I am feeding the am on a 220-110 convertor as I am in Europe. I have done this eversince I have the amp. The problem was not there before.
- No dc reading after the caps in the amp.
- caps are original. I know that would be one of the first to change but I happen to like the sound of the originals.
- can capacitor is not original but is possibly from that era. I have chnaged it before with a weber can cap but I did not like that sound. Too harsh.
But I did not have this problem before and I was using the "original" can cap at that time.

The question is?
Could the hiss and hum come from that oscillating effectprocessor? Could that have damaged something?
Where could I be looking too solve this?

Thanks, Marc

[capnjuan]

Hi Marc; sorry about your amp. There are two 68K and one 1 meg at the input; I'd hot check those first; if ok, I'd move on to the preamp plate and cathode resistors. I don't think your processor damaged the amp ... I think it's just a coincidence. Good luck! CJ

[gitaar0]

Hi Marc; sorry about your amp. There are two 68K and one 1 meg at the input; I'd hot check those first; if ok, I'd move on to the preamp plate and cathode resistors. I don't think your processor damaged the amp ... I think it's just a coincidence. Good luck! CJ

Hi capnjuan,

Thanks for replying. Yes I also think that the damaged processor and this problem are just a coincidence.

I came to the conclusion that the hum might come from the powerfiltercaps. As I explained I was hesitative to change those as I had already done that once before but did not like the sound as well as the old cap can.
But, as I had a new cap can anyway I thought I might as well replace it and see what happens.
Hum is gone now.

While I was working at it I also replaced the bias resistor and now it is pretty much as quiet as it was before. The sound is a bit brighter then it was, but I guess I will have to live with that. The amp is dark by itself anyway.

So basically that problem is solved. I hope this info might help others some other time.

I am now working on the tremelo circuit. It is different from what it was.
Now end then it sounds as if only half of the tremelo cycle is audible. It also seems to be slower then it was even at max speed.
I have no idea were that comes from.

I am open to suggestions.

Thanks, Marc

[capnjuan]

Hi Marc; my experience has been that most trem problems can be cleaned up by replacing the several caps in the circuit. That circuit is 'hot' whether the trem is switched on or not. Over time, those caps just wear out. Just a suggestion ... everyone feels differently about how much replacing should get done. The trem circuit is a 'worker bee' ... nothing to do directly with the audio chain ... anyway, that's what I'd do ... do you have a fresh 6AU6 to work with? John

[gitaar0]

Hi Marc; my experience has been that most trem problems can be cleaned up by replacing the several caps in the circuit. That circuit is 'hot' whether the trem is switched on or not. Over time, those caps just wear out. Just a suggestion ... everyone feels differently about how much replacing should get done. The trem circuit is a 'worker bee' ... nothing to do directly with the audio chain ... anyway, that's what I'd do ... do you have a fresh 6AU6 to work with? John

Hi John,

I have done some searches on this problem and found the same suggestion as you are giving. I will have to dive into that. In the meantime I reflowed the solder joints and that helped to bring back the tremelo to how it was. So that leaves me with the rather slow "fastest" speed. I will have to get some other caps to experiment and another 6AU6. (that is a good suggestion as well).

For now it works and I am very pleased that it is back to how it was.

Thanks for thinking with me.

Marc

[pontiacpete]

I'm working on a 1482 now and it has a big hissing problem, and an ac hum.
Someone had taken out all the input jacks and left one. I changed 90% of the caps, not the can, yet. Put in a 250ohm bias resistor, no change. Changed 2 sockets, the 6au6 and 1 of the 12ax7...
the latter one had some popping noises coming from it when moving the tube around. Still hisses, though.
I think the can has to come out.

[gitaar0]

I'm working on a 1482 now and it has a big hissing problem, and an ac hum.
Someone had taken out all the input jacks and left one. I changed 90% of the caps, not the can, yet. Put in a 250ohm bias resistor, no change. Changed 2 sockets, the 6au6 and 1 of the 12ax7...
the latter one had some popping noises coming from it when moving the tube around. Still hisses, though.
I think the can has to come out.

Hi Pete,

Sounds a bit like the same problem. I did not replace any of what you describe. I am in general hesitative replacing parts if they might still be working fine. To me they are part of the original sound of the amp.

It sounds as if the hum might come from the cap can going bad.
If you have one around to replace, as I had, it is an easy fix. (watch the voltages though!) I understand you can also bridge every section of the cap can with a capacitor of the same value of that section. If that reduces the hum you know that that section has gone bad.
The hiss might not have to do anything with the caps but could be the resitors.
Before you start replecing everything I would first determine in wich part of the amp the hiss is located. Pull the preamp tubes one by one. If it goes away it is in that section or after that. Have you done that already?

Marc

[pontiacpete]

I tried a new set of filter caps to replace the can, jumpered them in and still no change. Put the can back in. The problem with this amp was that one channel had been removed. Clipped out the second triode connections of the first pre amp tube.
Got it going with one input / one channel , one volume and tone control.
THe owner didn't seem to care about restoring it to its original configuration, so I gave it back.