I couldn't tell you what I was working on once upon a time, I just remember that out of frustration, I banged my fist on the workbench and the circuit popped, as in the trouble revealed itself. Bad solder joint. Couldn't see the problem right in front of me.
Fair enough, we're going to have get more technical. Measure the voltages @BSST and we'll see if anything stands out there.
hi guys.
today i had no time and tomorrow i am on a trip.
so i will do it this weekend and update here.
hopefully i can close the case soon.
today i had no time and tomorrow i am on a trip.
so i will do it this weekend and update here.
hopefully i can close the case soon.
hi guys.
big update.
i replaced TR6 and TR8.
They measured fine when removed.
but i put in some new ones and now the amp is playing fine.
No DC-offset no disortion!
maybe the values were too close?
I don´t know.
THANK YOU EVERYBODY FOR YOUR BIG SUPPORT!
this forum is awesome.
greetings from vienna.
big update.
i replaced TR6 and TR8.
They measured fine when removed.
but i put in some new ones and now the amp is playing fine.
No DC-offset no disortion!
maybe the values were too close?
I don´t know.
THANK YOU EVERYBODY FOR YOUR BIG SUPPORT!
this forum is awesome.
greetings from vienna.
That's good 🙂
Could there have been a break in the print around the pads on the board that had a crack and no continuity? That is not so uncommon.
Could there have been a break in the print around the pads on the board that had a crack and no continuity? That is not so uncommon.
can be.
I have no clue.
but now everything is assembled and playing 1h straight. no issues at all.
it gets veeery hot.
😳
I have no clue.
but now everything is assembled and playing 1h straight. no issues at all.
it gets veeery hot.
😳
That is why they break down, they get too hot. Imagine them being installed in closed audio racks or not as highest device in a stack.
I would inspect the PCB tracks very carefully and inspect for tiny cracks. This was already suggested but the pattern is that no reply follows.
I would inspect the PCB tracks very carefully and inspect for tiny cracks. This was already suggested but the pattern is that no reply follows.
Last edited:
Probably.
This is a thermal cut-off, soldered in series with the AC live wire, after the fuse and before the front panel ac switch. It is fixed, with screws and thermal paste, to the aluminium U-channel that joins the output transistors and the heatsink.
It is very useful for the output transistors and I think that you can find something like this in the market.
This is a thermal cut-off, soldered in series with the AC live wire, after the fuse and before the front panel ac switch. It is fixed, with screws and thermal paste, to the aluminium U-channel that joins the output transistors and the heatsink.
It is very useful for the output transistors and I think that you can find something like this in the market.
this image was taken from the internet.
also no thermal switch inside.
i think they added them in the later versions.
also no thermal switch inside.
i think they added them in the later versions.
Hi friends , bought once mf a1 newer rev,
the same distortion problem in one channel ,everything visually looks and tested fine,
sometimes the bad channel works fine for a while ,
after checking everything i tried to to run the amp with open case connected dvm to bad channel out
,and when the amp still cold and on.
tried with small low power heat-gun to heat some semis, and find the culprit.
one of the input transistors bc560 or 550 was defective, when heated with the heat gun dc offset in the bad channel jumps up quick.
i replaced the bad part and that's it.
hope this helps for someone in the future.
the same distortion problem in one channel ,everything visually looks and tested fine,
sometimes the bad channel works fine for a while ,
after checking everything i tried to to run the amp with open case connected dvm to bad channel out
,and when the amp still cold and on.
tried with small low power heat-gun to heat some semis, and find the culprit.
one of the input transistors bc560 or 550 was defective, when heated with the heat gun dc offset in the bad channel jumps up quick.
i replaced the bad part and that's it.
hope this helps for someone in the future.
@eldad : good info, thanks.
@ fencki : I don't know from what version this installed, but from the color of the PCB, these are very early versions of A1, this explains the missing diodes that you have add later on the circuit.
Mine was manufactured on 1992, 10th Anniversary, but and the Hennessey A1 that was simple version of A1, this cut-off sensor exists.
@ fencki : I don't know from what version this installed, but from the color of the PCB, these are very early versions of A1, this explains the missing diodes that you have add later on the circuit.
Mine was manufactured on 1992, 10th Anniversary, but and the Hennessey A1 that was simple version of A1, this cut-off sensor exists.