"Pooh Bear" wrote in message
...

JustMe wrote:

Greetings,

I know there are a few here who are very well qualified with hifi (and
particularly amplifier) electronic design. Can you help?

I have an Alchemist Nexus amplifier which, when turned above a certain
volume, screeches loudly through the speaker output.

I believe that the amp is outputting DC - does that sound right?

No.


I have removed two burnt out resistors - identical on each channel on
the
PCB - and I had already replaced two 4 amp output fuses before testing
produced the results described and before I removed the burnt resistors.

Can anyone confirm my translation of the resistor colour codes (gathered
from an identical amp as those in the faulty amp were badly burnt):

1st digit: Brown: 1
2nd digit Black: 0
Multiplier: Black: 0
Quality: Brown: 1

I make this 10 ohms of a high-tolerance 1%/1000 hour anticipated
failure?

Resistors don't have " 1000 hour anticipated failure " bands !

I believe that they have a failure rating which is a percentage after 1000
hours, hence 1% per 1000 hours - 1% anticipated failure after 1000 hours. Is
this wrong?

I want to be certain as, while I am confident that my soldering skills
are
up to the task (the components are not surface mount), I have not
carried
out such a repair before without the aid of a manufacturer's service
manual
before.

I have created a small rollover image at
http://www.alchemisthifi.info/fault/resistor.htm which allows you to
compare
the damage on the bad amp with the good amp.

The manufacturer (Alchemist) is no longer in business and there are no
circuit diagrams about.

Beyond the resistor confirmation, any constructive advice you can offer
about my approach would be appreciated.

If you don't know how to troubleshoot - give up or give it to someone who
does.

That's very helpful - I'll learn a lot like that - thanks.

Graham