CR600 - 2SC458 subs in power amp

david winter

Classical music lover.
Hi,

I recaped the power amp section of a CR600 to make some first tests.
The amp worked fine but started to develop some static, which by experience I believe to be from those 2SC458.

Has anybody replaced them by KSC1845 ?

I uploaded the service manual here on a temp folder of my server (I'll remove it as soon as I get an answer).

Also, if anyone knows a good sub for the many 2SC454 and 2SC460 on the tuner board that would be helpful just in case they also develop the same noise issues as the 2SC458.


Thanks,

David
 
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Obvious mistake for the KSC1845 (not 1892...) which I have used many times without trouble.
I never (or almost never) used the KSC945C and don't know which would be of higher quality.

Other question: why a tuner board equiped with some 20 transistors would use two different types (2SC454 / 460) ? What's the difference to explain this choice ? C/E capacitance more suitable in IF circuits ? Can I use the 1845 instead (I must have 150+ in stock) or would the 992 be more suitable ?

I'll have to work on the power amp first, the relay no longer clicks. Either the 1845 will fix it, or there's another problem. But so far the four outputs show no shorts and both fuse resistors are ok (should they be replaced by fixed resistors by the way ?).
 
I forgot one important point: would the KSC1845 also replace the two 2SC458 on the heatsink (output transistors) ? I'm talking about "thermal compatibility" to make sure the bias circuit will work fine with the KSC1845 unless something else should be used. Thanks !
 
I forgot one important point: would the KSC1845 also replace the two 2SC458 on the heatsink (output transistors) ? I'm talking about "thermal compatibility" to make sure the bias circuit will work fine with the KSC1845 unless something else should be used. Thanks !

Yes.
 
Can I use the 1845 instead (I must have 150+ in stock) or would the 992 be more suitable ?
The KSC1845 (NPN) and KSA992 (PNP) are complementary to each other, you can't use one instead of other...

For the 2SC454 (NPN) you can use the KSC1845, which is low noise and is rated 500mW (Pd).

-------------------------------------

P.S.: beat by avionic at 04:05 PM
 
Yet another typo. I know the 2SA/2SB are PNP and 2SC/2SD NPN. Just used the wrong reference.
I replaced all 2SC458 by KSC1845.
One channel has both outputs C-E shorted.
After removing its outputs, the relay clicks and the other channel works fine.

What I'll do is start another thread to rebuild the output stage using subs, I'm sure this will be useful for others and this will be easier to find with a more relevant topic.

Thanks for your help !:

David
 
Am I reading this thread correctly, that the 2SC458's aren't the only transistors I should be replacing?

I was getting lined up to swap out the little outhouses in my CR800...
 
I opened another thread with suggested transistor replacements:
http://www.audiokarma.org/forums/showthread.php?t=665718

All 2SC458 must be replaced by KSC1845. They are often noisy and can cause all sorts of troubles in the power section. In the CR600 you also have two of these on the power board which is under the tuner chassis, so you need to remove the four red screws in order to flip the tuner chassis to access the power section.

As for the rest: I put KSA992 in the differential, and used MJ 21193/21194 for the outputs. So far the amp works great except for a minor DC output which I need to investigate (nothing serious, it's a matter of slowly reaching 10mV or so (didn't test longer to see if it goes any further).
 
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