Hi friends , ive bought sec hand para hca-1500a for cheap as untestesed ,the seller said its maybe fuses.
inside one fuses of the r channel was blown and replaced with correct one.
Anyway ive plugged it with light
bulb limiter for precaution ,the amp work normal ,dc offset ok 0mv ,bias ok (15 mv) without light bulb limiter.
The amp playing normal and stable but ive notice by ear some distortion , and then connected to amp to my test bench with 8r 100w dummy load both channels and to rta on pc.
Then i saw the problem . R channel distorted
L channel clean.
after all the tests i cleaned the amp , checked and cleaned all the fuses and their holders,repalced the protection relay ,dexoit pots ,resolder joints and wash the pcb ,tested all the semic' for shorts checked the bias again on both channels and the problem not solved.
Still got distorted r channel.
Thanks
Eldad.
Im adding pics in pdf files.
inside one fuses of the r channel was blown and replaced with correct one.
Anyway ive plugged it with light
bulb limiter for precaution ,the amp work normal ,dc offset ok 0mv ,bias ok (15 mv) without light bulb limiter.
The amp playing normal and stable but ive notice by ear some distortion , and then connected to amp to my test bench with 8r 100w dummy load both channels and to rta on pc.
Then i saw the problem . R channel distorted
L channel clean.
after all the tests i cleaned the amp , checked and cleaned all the fuses and their holders,repalced the protection relay ,dexoit pots ,resolder joints and wash the pcb ,tested all the semic' for shorts checked the bias again on both channels and the problem not solved.
Still got distorted r channel.
Thanks
Eldad.
Im adding pics in pdf files.
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Can you post either a sine or a triangle waveform at a few watts output?
Is the rear panel "bridge" switch set to stereo? If not, turn amp off and then reset it.
Is the rear panel "bridge" switch set to stereo? If not, turn amp off and then reset it.
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Is the positive peak clipping prematurely? Seems so.
Post the triangle waveform with twice the output level.
It may be necessary to measure DC voltages in the bad channel, and compare
them with the good channel.
Post the triangle waveform with twice the output level.
It may be necessary to measure DC voltages in the bad channel, and compare
them with the good channel.
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The voltages on the 4 big caps 76.1v, 75.9v ,76.1 v75,9v. dropping to 73v on 40vpp 8r- triangle ouptut both channels load.
adding pdf waveforms
Thanks
;Eldad.
e.g.; the 4 big caps nichicon "great supply" 80v 15000uf tested good on esr meter both capacity ,loss,esr.
adding pdf waveforms
Thanks
;Eldad.
e.g.; the 4 big caps nichicon "great supply" 80v 15000uf tested good on esr meter both capacity ,loss,esr.
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No obvious problems there, but the previously posted spectrum seems bad.
Does the good channel has a better spectrum?
Have you checked the driver transistors, Q111 and Q116?
Maybe JC will offer some suggestions.
Does the good channel has a better spectrum?
Have you checked the driver transistors, Q111 and Q116?
Maybe JC will offer some suggestions.
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Thanks rayma, the good channel has very good spectrum. Im adding pics.
Ive tested all transistors in circuit but for shorts etc, i need to resolder drivers and test them on transistor tester. Thats my next step ,just want second opinion before.
Pdf with channel R vs channel L spectrums.
Ive tested all transistors in circuit but for shorts etc, i need to resolder drivers and test them on transistor tester. Thats my next step ,just want second opinion before.
Pdf with channel R vs channel L spectrums.
Thanks allot rayma, ive suspect the drives is the culprits from the begining , i let you know after test them outside.
Maybe JC shed some light?
Maybe JC shed some light?
Hi rayma ,in the schematics the drivers q116 =j162 ,q111=k1058, in my specific amp ive found j200 q=116 ,k1529=q111, on both channels .
They interchangble?
Ive found new 2 pairs of j162 &k1058 renesas in my spare parts...
They interchangble?
Ive found new 2 pairs of j162 &k1058 renesas in my spare parts...
There you go, make sure the associated gate and source resistors are still ok.
The amp should work fine now.
The amp should work fine now.
Just need to 2 get j200 toshiba ,in the schematics wrote ; j162 =q116 ,k1058 =q111 and 4 pairs of 2sc4029 &2sa1553, in my amp has MJL21193 and MJL21194 motorola 4 pairs and sj200 & sk1529 toshiba it seems original in both sides no repairs made before ,maybe my amp newer rev ?
On the four big ps caps stamp date 9730 , week 30 1997 ,= july 97' if the capacitors made in july 1997 the amp must be newer.
Anyway i need advice about substitute drivers i afriad j162& k1058 thats wrote in schematics wont work because diffrent output pairs,the schemtic and my amp not 100% the same..
Anyway i need advice about substitute drivers i afriad j162& k1058 thats wrote in schematics wont work because diffrent output pairs,the schemtic and my amp not 100% the same..