-
Categories
-
Platforms
-
Content
What is the resistance?
It doesn't agree with the:
"2 reads 48.5 ohms with Amp off, ground probe on ground speaker terminal, meter set to 200 ohms." from #54 .
All this points should be close to zero (2.5 in this dmm and probes you use),
Can you confirm this?
O.K.
can you "play and move " the S1 connector and repeat the resistance test between S1-2 and the black speaker terminal.
Does it change the reading?
O.k
Let's continue with cutting the wire going to pin-5.
and see if the amp goes into protect as before (no speakers).
Rick,
you should check the presence of DCV on all speakers terminals before you connect them .
Since we disabled that protection mechanism.
There probably isn't any, but still do check it without the speakers.
So,
Is the amp working fine now ?
High volume and clear sound?
We should continue testing.
Rick have you got a variable DCV power supply?
Or any potentiometer on hand?
Checking with the small ones is fine.
We can continue tomorrow.
Sleep well.
Yes,
We just need to find out which one
It would be best to find the faulty component and fully repair the amp.
As thing are now ,the amp is working with the output DCV protection disabled.
Since you checked that there is no DCV on all outputs you can play the amp as it is(with the wire cut).
There is future risk of blowing a speaker :
If for some reason, the amp will develop a fault that will create DCV on an output .
The speaker connected to that output may be blown.
With power disconnected.
Check the resistance of R2 and R3 (DMM in ohm 200K range).
Take two measurements on each ("flipping" the probes ,4 measurements).
Repeat the test in Diode Test mode on the DMM.(another 4 measurements)
What do we get?
Have you got any resistors on hand?
View attachment 26967
O.K
Lets test the diodes D8-D11 ,
DMM in diode test mode and flipping the probes on each diode.
Have you got a 4.7K or about resistor?
How are your soldering skills(on PCB,any experience with that)?
View attachment 26968
Looks like we found our bandit...D8.
Please confirm it's measurement's (comparing to the other diodes).
If they confirm you should cut a single leg of D8 (in the middle as shown,so that if needed it would be easy to solder it back),
lift the leg a bit and recheck D8.
I hope your cutter is fine enough for that job.
View attachment 26969
Please check on the PCB pads of D8(with the diode leg lifted as in #78).