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CR1020 Main C board TR608 blows after recap

J

jplewicki

New Member
I am recapping my CR1020 which was working until recently when I lost output on one channel. As well as recapping the main amp R and L boards I confirmed that the fuses were blown on the R board, TR613 and TR614 were shorted. I replaced 13 and 14 with MJ21193G and MJ21194G’s and replaced TR607 and TR608 with KSA1015 and KSC1845’s.

The fuses hold when I power on, speaker protect stays in protect and my KSA1015 TR607 blew its head off after about 2 seconds. See picture

With fuses removed from both amp boards the speaker protect relay will come out of protect and I measure normal voltages from B+, B-, b-

I diode tested TR’s 11 and 12, checked for any obvious resistors that were open or shorted but can’t find anything glaring.

Any thoughts on where I might have gone wrong?
 

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mrk229 said:
Did you check the driver transistors? Also check FR 601.
Click to expand...
Thanks for the reply, much appreciated! I checked the driver transistors and they seem out ok with a multimeter diode check at least. Fuse resistor is not shorted or open either and gives me 68ohms. R601 is reading 100Kohm in line with diagram. I can try replacing the driver transistors and will go over the whole board again to look for shorts/bad joints but right now still struggling to see what made it fail.
 
Look for silly stuff like pinched wires. Transistor pin out, bad solder blob, lifted traces, missed solder joint.

I did a ca-620 and lost the left channel. After hours of effort I grabbed a wooden stick and poked every connection until I found one I missed. As soon as I touched it the channel came back.

Stuff happens. Good luck.
 
jplewicki said:
I am recapping my CR1020 which was working until recently when I lost output on one channel. As well as recapping the main amp R and L boards I confirmed that the fuses were blown on the R board, TR613 and TR614 were shorted. I replaced 13 and 14 with MJ21193G and MJ21194G’s and replaced TR607 and TR608 with KSA1015 and KSC1845’s.

The fuses hold when I power on, speaker protect stays in protect and my KSA1015 TR607 blew its head off after about 2 seconds. See picture

With fuses removed from both amp boards the speaker protect relay will come out of protect and I measure normal voltages from B+, B-, b-

I diode tested TR’s 11 and 12, checked for any obvious resistors that were open or shorted but can’t find anything glaring.

Any thoughts on where I might have gone wrong?
Click to expand...
Check that you replacement transistors have the correct pin-out orientation. Some part numbers are available with different pin-outs
 
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