Good afternoon to you
Now I might be being a dick here. But this amp is causing me pain
I'm not an electronics engineer by trade, I have some knowledge
and now do this for fun, But i'm like a dog with a bone, won't let go
It came in to me with a intermittent noise issue.
I found the fault IR9 was soldered in but leg cut short it wasn't really soldered. Replaced it.
Out the job went ok
1 month later it came back distortion after a while.
I found by heating and freezing the area around IQ5 it would go away. In the end I replaced all the transistors in that area IQ1 to 7 and 14. As all very close together.
All changed like for like.
Tested the amp heat and freezer it all seemed OK.
Then it went to about 1/2 volume without touching it I wasn't heating or freezing at that time was on for 20 mins before it went
When I tested it I can see its working perfectly without distortion but low output
View attachment PM12-AMP.pdf
On checking using scope and signal gen I can see the signal in and out of pre amp is OK and higher level leaving the pre amp than the input.
I'm I being a dick question
But the signal entering the power amp is at same level as the output.!!!!
Is this possible?
Check all voltages 54v +/- and 15v +/-
Checked all the transistor /diodes
Made sure the transistors I changed are good and correct ones
At output have around 3v ac with gain /vol max
I'm not an experienced tech. Just play for fun
Any assistance would be grateful thanks in advance
Blockhead
Now I might be being a dick here. But this amp is causing me pain
I'm not an electronics engineer by trade, I have some knowledge
and now do this for fun, But i'm like a dog with a bone, won't let go
It came in to me with a intermittent noise issue.
I found the fault IR9 was soldered in but leg cut short it wasn't really soldered. Replaced it.
Out the job went ok
1 month later it came back distortion after a while.
I found by heating and freezing the area around IQ5 it would go away. In the end I replaced all the transistors in that area IQ1 to 7 and 14. As all very close together.
All changed like for like.
Tested the amp heat and freezer it all seemed OK.
Then it went to about 1/2 volume without touching it I wasn't heating or freezing at that time was on for 20 mins before it went
When I tested it I can see its working perfectly without distortion but low output
View attachment PM12-AMP.pdf
On checking using scope and signal gen I can see the signal in and out of pre amp is OK and higher level leaving the pre amp than the input.
I'm I being a dick question
But the signal entering the power amp is at same level as the output.!!!!
Is this possible?
Check all voltages 54v +/- and 15v +/-
Checked all the transistor /diodes
Made sure the transistors I changed are good and correct ones
At output have around 3v ac with gain /vol max
I'm not an experienced tech. Just play for fun
Any assistance would be grateful thanks in advance
Blockhead