My Harman Kardon 730 blows the power supply fuse only on the left channel. I recap the whole unit except the tuner board. I check the output transistors, they look OK but I replace all anyway with MJ21193G/94 and still have the problem. When turn the unit on, without hooking up the speaker, DC is almost zero on both channels and pass the DBT. Attach 8 ohm, 50W resistor to the Right channel and adjust the idling to 30 mV OK. Then I attach the 8 Ohm resistor to the Left channel speaker terminal, it blows the fuses. I replace the fuse and put it under DBT and within 2-3 seconds, the DBT gets brighter so I shut it down right away before blowing the fuse. As you could see on the pictures, all new transistors. I did my A 402 before so this 730 is identical with A402. I also replace some resistors and diote but it does not help to resolve this issue. I check the voltage of both power supplies and they are consistent so I don't think the problem at the power supply. I don't think I short the circuit neither since it turns on OK under DTB without speaker attached to LC speaker terminal.
Harman Kardon 730 issues
- Thread starter N_Soph
- Start date
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Since you appear to have one channel working and one that is not, might try first to check components on the working channel and compare with non-working. Especially check orientation and values of any replaced parts. And if outputs are okay, check driver transistors also. (advice from an amateur, so take with a grain of salt
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Don't overlook an issue with cable / speaker, a short there would give you a problem. Ohm test the left speaker at the cable.