Continued: Static on amp, not volume related

[Dean]

Anyway, to answer the questions:

It is a solid state amplifier.


Most components are soldered directly to the board or have flying
leads.

Tweetldee:
The components in the power supply are definately thermistors, at
least, according to the circuit diagram I have (could be -ve slope
though as you say)

I disconnected the preamp stage inside and the noise persisted. i then
tapped components along the circuit path to see if any affected the
noise (very scientific I know but I have no equipment beyond a
soldering iron!). A couple of electrolytics seemed to make the noise
worse/better when tapped them so I figure I'll replace these first.
They are feed through capacitors on the small driving (before the
power) transistors.

The problem is farnel/RS don't stock these value of cap. Can I replace
these with 2 or more caps in series/parallel to make up the value i
want?

Cheers

Dean

 

[El Meda]

Anyway, to answer the questions:

It is a solid state amplifier.


Most components are soldered directly to the board or have flying
leads.

Tweetldee:
The components in the power supply are definately thermistors, at
least, according to the circuit diagram I have (could be -ve slope
though as you say)

I disconnected the preamp stage inside and the noise persisted. i then
tapped components along the circuit path to see if any affected the
noise (very scientific I know but I have no equipment beyond a
soldering iron!). A couple of electrolytics seemed to make the noise
worse/better when tapped them so I figure I'll replace these first.
They are feed through capacitors on the small driving (before the
power) transistors.

The problem is farnel/RS don't stock these value of cap. Can I replace
these with 2 or more caps in series/parallel to make up the value i
want?

Yes, you can.

In the event that one transistor is making the noise, you can test one
by one by heating them momentarily with the tip of your soldering
iron. The noise will be louder when you find the one responsible.

Check the smaller ones first.