Troubleshooting a Sonic Frontiers SFC 1 Integrated Tube Amp.

[MASantos]

I could use some help with a problem I have in my father's amp.

It is an integrated tube amp, Sonic Frontiers SFC-1.

The amplifier has a "direct" toggle switch, which sends the signal directly from the RCA input to the volume pot,and then has 4 inputs which go through an elna selector switch and a balance control.

When using "direct" nothing is wrong, but when using any of the other 4 inputs there is audible distortion in the music.

I went through the tubes, checked and replaced each one with some older ones and they seem to be fine, the situation continued.

I've inspected the solder joints in the rca's and the elna switch andthey seem ok. the balance control is impossible to check without removing it from the amp.

The amp is about 10 years old with an average of 1-2 hours of daily usage.

Any ideas why this is happening?

[Torpedo]

I'd say it's the Elna selector which may have some dust or rust in the contacts. I'd get the pressurized air can and spray that switch.

[spritzer]

Probably corrosion on the cotacts inside the (ELMA?) switch. Caig Deoxit is perfect for this stuff.

[MASantos]

I have a "audio" cleaning liquid from clearaudio or another known company. Would I just use the brush and clean the switch? How do I clean the inside contacts?

[spritzer]

It's best to use a can which allows you to spray into the switch and the rotate it multiple times to try and clean off the layer of oxidation.

[MASantos]

This just crossed my mind: WD 40 is very good with corrosion and oxidation. Any reason why I shouldn't use it?

[Pars]

WD-40 is mainly kerosene IIRC. I wouldn't use if for something like this. Caig DeOxit or Progold is what I would use, as already mentioned.

[MASantos]

I've used Clearaudio cleaning liquid: http://www.clearaudio.de/download/zubehoer/testbericht_clearcontact_hf.pdf

I've dropped a few drops on the elna switch, rotated quite a few times, probably more than 100 times and waited 30mins for the product to evaporate. The problem remains. guess I could try to bipass the elna with a 2 wires to see if the problem is even there. then do the same with balance control.

[spritzer]

I have a feeling that that CA stuff isn't half as good as any standard contact cleaner but then again I'm not an optimist. Shorting the switch would be a good idea and it will show you what the problem really is.