Amiga 600 right sound channel does not work

01 July 2018, 18:02

Amiga 600 right sound channel does not work
After recapping my Amiga 600 rev 1.5, the right sound channel is gone. As a part of the troubleshooting, I desoldered all the capacitors and measured the capacitance before soldering them in again. I did not find any broken capacitors. When measuring the voltage on the circuit, the values on the right port is high (10,8 v) and U15 gets glowing hot. The red values on the schematic is the voltages. Have replaced U15, C332, R333 and R337, but no change. Any ideas where to look next?

ajk · 01 July 2018, 18:36

Is the power supply verified good? Otherwise I'd suspect something is shorting the supply and one output of U15.

supaduper · 01 July 2018, 20:22

yes U15 is a chip that can go bad ,so change it

ajk · 01 July 2018, 20:29

But if he's already changed it once, there must be something in the other circuitry causing it to short out like that.

supaduper · 01 July 2018, 21:49

Quote:

Originally Posted by ajk

But if he's already changed it once, there must be something in the other circuitry causing it to short out like that.

Sorry did not read it fullY

Shatterhand · 01 July 2018, 21:51

I have a similar problem with my A600, which has been related here:

http://eab.abime.net/showthread.php?t=78344

I have tested it with 2 different power supplies, though I wouldn't be surprised if both are troublesome, since they are 25+ years old ny now.

How do I test my PSU? I never opened an Amiga PSU before.. I do have a voltimeter and kinda know how to use it

(And it has been recapped

)

Daedalus · 02 July 2018, 09:53

For audio issues, check the power available at the U15 chip itself against ground. Pin 4 should be +12V, pin 11 should be -12V. This power is supplied through two small resistors, so if you don't have the right readings there, check R301 and R302 which are nearby. But if one channel is working fine, it's not the PSU.

As for the original fault, it sounds like there could be a short or something nearby the op-amp, perhaps solder from the recap contacting a via, or a trace that's close to a pad and has had its soldermask removed.

02 July 2018, 21:14

Thanks for the input.
The power on pin 4 are 12,3 and on pin 11 it is -11,4. So I do not think it is the power either. I will look for a short again must have missed it on the first redo....

01 July 2018, 18:02	#1
DetFedeSvin Posts: n/a	Amiga 600 right sound channel does not work Amiga 600 right sound channel does not work After recapping my Amiga 600 rev 1.5, the right sound channel is gone. As a part of the troubleshooting, I desoldered all the capacitors and measured the capacitance before soldering them in again. I did not find any broken capacitors. When measuring the voltage on the circuit, the values on the right port is high (10,8 v) and U15 gets glowing hot. The red values on the schematic is the voltages. Have replaced U15, C332, R333 and R337, but no change. Any ideas where to look next? Attached Thumbnails

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01 July 2018, 18:36	#2
ajk Registered User Join Date: May 2010 Location: Helsinki, Finland Posts: 1,341	Is the power supply verified good? Otherwise I'd suspect something is shorting the supply and one output of U15.

01 July 2018, 20:22	#3
supaduper Registered User Join Date: Oct 2012 Location: Krypton Posts: 1,224	yes U15 is a chip that can go bad ,so change it

01 July 2018, 20:29	#4
ajk Registered User Join Date: May 2010 Location: Helsinki, Finland Posts: 1,341	But if he's already changed it once, there must be something in the other circuitry causing it to short out like that.

01 July 2018, 21:51	#6
Shatterhand Warhasneverbeensomuchfun Join Date: Jun 2001 Location: Rio de Janeiro / Brazil Age: 41 Posts: 3,450	I have a similar problem with my A600, which has been related here: http://eab.abime.net/showthread.php?t=78344 I have tested it with 2 different power supplies, though I wouldn't be surprised if both are troublesome, since they are 25+ years old ny now. How do I test my PSU? I never opened an Amiga PSU before.. I do have a voltimeter and kinda know how to use it (And it has been recapped )

02 July 2018, 09:53	#7
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,380	For audio issues, check the power available at the U15 chip itself against ground. Pin 4 should be +12V, pin 11 should be -12V. This power is supplied through two small resistors, so if you don't have the right readings there, check R301 and R302 which are nearby. But if one channel is working fine, it's not the PSU. As for the original fault, it sounds like there could be a short or something nearby the op-amp, perhaps solder from the recap contacting a via, or a trace that's close to a pad and has had its soldermask removed.

02 July 2018, 21:14	#8
DetFedeSvin Posts: n/a	Thanks for the input. The power on pin 4 are 12,3 and on pin 11 it is -11,4. So I do not think it is the power either. I will look for a short again must have missed it on the first redo....

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