Punch 500a2 messed up channel - Page 5

brandes.cm · 6th April 2012, 02:45 AM

Hmm, wonder if I should check the .1ohm resistors. Hey looky there, 3 are open and the other 3 read high. Man I wasted everyone's time.

brandes.cm · 6th April 2012, 02:07 PM

I guess that wasn't the whole issue, since bias won't adjust unless I lift D104. I also have a full sinewave with it lifted. Something is still tripping the protect circuit. Q116-118, R162 and D105 have been replaced.

Perry Babin · 6th April 2012, 03:58 PM

Will the amp produce a clean rail to rail sine wave with a load with D104 lifted?

brandes.cm · 6th April 2012, 04:08 PM

Yes all looks good when D104 is lifted.

Perry Babin · 7th April 2012, 06:41 AM

Reinstall D104. Remove and then replace the following transistors, one at a time in the order listed. Which one is the first to allow the amp to play when it's out of the circuit.

Q118, Q117, D116

brandes.cm · 12:58 PM

Q118 showed a sawtooth waveform, not a nice sine.

Q117 allowed full sinewave.

sent from an IRFZ48N

Perry Babin · 9th April 2012, 08:51 AM

Reinstall all of those parts and remove R157. Does that allow the amp to produce clean audio?

brandes.cm · 9th April 2012, 11:50 AM

With R157 removed I have a sinewave.

Perry Babin · 9th April 2012, 10:41 PM

It appears that the fault is in the DC offset protection circuit.

Check the following and confirm that you have the ±14 on the diodes.

D103
D105
R127
R129
R130
R147
R156

brandes.cm · 10th April 2012, 12:10 AM

All check ok, diodes show correct voltage.

With a signal being input and a 3 ohm load Q113 gets hot in a short period of time(about 30 seconds).

6th April 2012, 02:45 AM	#41
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	Hmm, wonder if I should check the .1ohm resistors. Hey looky there, 3 are open and the other 3 read high. Man I wasted everyone's time. __________________ BK 1544 40Mhz scope.....Pyramid PS-26KX supply.....Tenma 72-380 Func. Generator

6th April 2012, 02:07 PM	#42
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	I guess that wasn't the whole issue, since bias won't adjust unless I lift D104. I also have a full sinewave with it lifted. Something is still tripping the protect circuit. Q116-118, R162 and D105 have been replaced. __________________ BK 1544 40Mhz scope.....Pyramid PS-26KX supply.....Tenma 72-380 Func. Generator

6th April 2012, 03:58 PM	#43
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Will the amp produce a clean rail to rail sine wave with a load with D104 lifted? __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

6th April 2012, 04:08 PM	#44
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	Yes all looks good when D104 is lifted. __________________ BK 1544 40Mhz scope.....Pyramid PS-26KX supply.....Tenma 72-380 Func. Generator

7th April 2012, 06:41 AM	#45
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Reinstall D104. Remove and then replace the following transistors, one at a time in the order listed. Which one is the first to allow the amp to play when it's out of the circuit. Q118, Q117, D116 __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links


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7th April 2012, 12:38 PM	#46
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	Q118 showed a sawtooth waveform, not a nice sine. Q117 allowed full sinewave. sent from an IRFZ48N __________________ BK 1544 40Mhz scope.....Pyramid PS-26KX supply.....Tenma 72-380 Func. Generator Last edited by brandes.cm; 7th April 2012 at 12:58 PM. Reason: added Q118 comment

9th April 2012, 08:51 AM	#47
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Reinstall all of those parts and remove R157. Does that allow the amp to produce clean audio? __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

9th April 2012, 11:50 AM	#48
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	With R157 removed I have a sinewave. __________________ BK 1544 40Mhz scope.....Pyramid PS-26KX supply.....Tenma 72-380 Func. Generator

9th April 2012, 10:41 PM	#49
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	It appears that the fault is in the DC offset protection circuit. Check the following and confirm that you have the ±14 on the diodes. D103 D105 R127 R129 R130 R147 R156 __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

10th April 2012, 12:10 AM	#50
brandes.cm diyAudio Member Join Date: Sep 2009 Location: Wisconsin	All check ok, diodes show correct voltage. With a signal being input and a 3 ohm load Q113 gets hot in a short period of time(about 30 seconds). __________________ BK 1544 40Mhz scope.....Pyramid PS-26KX supply.....Tenma 72-380 Func. Generator

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