Pignose grounding noise

[angelodp]

Hi Guys, longtime.... Trying to help a pal that has an old Pignose 7-100. It has quite a bit of ground static noise. Thought it me be the pot so I opened things up and cleaned the pot but still getting the crackle and sandpaper.
if anyone has experience with these little guy and can suggest a route? I think it a grounding issue as when i lifted the signal i still had the noise.

best Ange

[surfsup]

I beilieve crackle is usually caused by a bad/cold solder joint...?

[angelodp]

Thanks Taylor I'll run through all the joints.

A

[angelodp]

I reflowed all the solder, still crackling....must be a bad transistor.

A

[Structo]

So this is the little battery powered Pignose?

If it was a tube amp I would say that it's probably carbon comp plate resistors causing the static.

But on a solid state amp, not sure what it would be other than checking the solder joints and grounds.

So can you get guitar noise out of it or is it all noise?

Any hum?

If you do get a guitar through it then you may have a duff transistor.

[angelodp]

Yes, I am getting the guitar thru and the noise also persists without the guitar in circuit. I took the pot apart but its fine. I think its down to the transistors. Looking now for replacement for this germanium Japanese type.

A

[ampdoc1]

Take a can of "coolent" spray and hit each of the transistors one at a time. I'll bet you find the culprit in minutes.

a'doc

[angelodp]

Ok so how does that work exactly. Spray each transistor with the coolant ( where do you get that RS? ), and see if it gets worse/better.

[ampdoc1]

Yeah! Just a small shot on each component 1 at a time. This also works well to find noise in resistors and caps.

You can buy freeze spray at most electronics shops. but a cheaper alternative is to buy a can of computer "duster" spray. Turm the can upside down when you spray, and you get only the propellant which is generally a freon type component.

a'doc

[angelodp]

Thanks amigo

[angelodp]

A-doc, you nailed it. I had some info form Pignose that the transistors in the heat shield are the first to go and so I procured two replacements. Turns out they were not at fault, by then I had posted here and tried the coolant trick which did produce the culprit. It was one of the power transistors and luckily the other transistors that I had pulled were close enough in spec to drop in. Hey this a cool little amp and sounds pretty good. Scratchy weirdness, gone and its back to its old self.

Thanks for the help, as always this place is the best.

Ange.