capacitor brands & power transistor trouble on hk amp

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capacitor brands & power transistor trouble on hk amp

capacitor brands,

im working on a harman kardon amplifier, seems one of the componenets faulty is a "Koshin" 63v 470uk capacitor, well my question is would i need to replace with the same brand? would i need to get another koshin capacitor? can you use a diffrent brand? would it make a diffrence?

whats happerning is, i kept blowing the main fuse, i replaced the output power transiator, and after 5 mins it is getting red hot to the touch, and then blowing again, and then blowing the fuse, any ideas? or suggestions?

also trying to source a a harman kardon vr 507 or harman kardon avr 4550, service manual, no luck,


thanks
 
brands...

Brands of components sound different, but to my uncertain knowledge 'koshin' is not one of the known 'great' sounding capacitors. So if you can't get koshin easily, I'd go with any of the known good brands, nichicon, panasonic.

If you can't get an exact match you must have the same or greater voltage, and if necessary go to the next larger value.

If applicable, you may want to replace the same device in the other channel, whatever difference it makes will then at least be the same side to side...

Good luck

Stuart
 
Re: capacitor brands & power transistor trouble on hk amp

mrlennon said:
capacitor brands,

whats happerning is, i kept blowing the main fuse, i replaced the output power transiator, and after 5 mins it is getting red hot to the touch, and then blowing again, and then blowing the fuse, any ideas? or suggestions?
thanks


Transistors getting red hot? Like literally red hot? :hot:

If marginally hot, I suspect either an overbiased output stage, bad VBE circuit (no thermal compensation) or the amp's oscillating.

Perhaps you have checked those already?
 
yes i too have a h/k and in for repair after 2 mins or so after powerup with a new power transistor is getting red hot, so hot if you did try and touch it it would burn your finger,

i used a genuine Sanken transistor too. there must be a overload someware on the channel, im still trying to track my fault, had no luck yet,

must be common on these units.
 
well on the one im working on, im not 100% sure where the driver transistors are located, as theres quite a few on the channel, about 11 transitors on board.
im still trying to get hold of a avr 507 and cant get the scematic or service manual anyware, ive heard this model is very close to the harman kardon avr 330 but i cant even get hold of that.
 
I think changing brands of the component does'nt have a great impact on the problem. Maybe you have no proper heat sink of your component causing it really hot. It is normal in power stages to become very hot. To avoid damage of your component, put a heatsink on it. Or, maybe you have a short circuit on your output side causing the component to become really hot and bursting your fuse.
 
K-amps said:
Why would there now be a need for a heatsink all of a sudden? You dont put heatsinks on components that get overly warm (unless by design), you trace the source of the problem and fix it...;)

If the transistor is used as an amplifier then it will need a heat sink to absorb the heat it produces. But if not, then, I think there's a short circuit or simply your transistor cannot handle such current. Look for other transistor with higher power/ current capacity.

If you have a copy of the schematic, pls post it so that we can take a look and help identify the problem.
 
K-amps said:
Why would there now be a need for a heatsink all of a sudden? You dont put heatsinks on components that get overly warm (unless by design), you trace the source of the problem and fix it...;)

If the transistor is used as an amplifier then it will need a heat sink to absorb the heat it produces. But if not, then, I think there's a short circuit or simply your transistor cannot handle such current. Look for other transistor with higher power/ current capacity.

If you have a copy of the schematic, pls post it so that we can take a look and help identify the problem.
 
buloi123 said:


If the transistor is used as an amplifier then it will need a heat sink to absorb the heat it produces. But if not, then, I think there's a short circuit or simply your transistor cannot handle such current. Look for other transistor with higher power/ current capacity.

If you have a copy of the schematic, pls post it so that we can take a look and help identify the problem.


You missed the point....;)
 
ok heres a scematic of the channel in question,

also any ideas which one is the driver?

also what else to check as the power transistor is getting red hot after 5 mins.
 

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