View Single Post
  #28   Report Post  
Old January 19th 16, 02:00 AM posted to sci.electronics.repair
Phil Allison[_3_] Phil Allison[_3_] is online now
external usenet poster
 
First recorded activity by DIYBanter: Aug 2014
Posts: 1,095
Default Peavey Classic 60 questions

John Heath wrote:


I have a digital AC power meter on my bench to monitor AC power
consumption. It has many uses that I did not think of when buying
it. It is useful for eyeballing idling current to see if it is
creeping up into thermal runaway. I found it can also be used to
set idling current. Adjust the bias pot until ac power starts to
change. Then back it off to match the idling power for that type of
amp. This saves a lot of time trying to measure the voltage drop
across output emitter resisters.


** I guess your meter reads in 1 watt increments ?

I have been doing the same jobs with a 3.5 digit LED current meter that reads in 1mA or 10mA increments with a maximum display of 20amps in two ranges. It couples to the AC line via a Hall effect sensor that also provides a waveform output for a scope.

It gets used with every repair job and is indispensable when working on valve or solid state amps. Makes it possible to diagnose some faults using only the readings and scope display - like high ESR main filter electros.

There is also a safety bonus, a glance at the meter tells you if the AC power is really switched off.


..... Phil