[NJARC] Knight KX-60 Amplifier

[Mike Feher]

Chuck -

I do not think the IRF240's are doing you much good in that circuit as they
are N channel FETs. If the amp now works, you could even try it by not using
any transistors at all in the PS, however, possibly replacing the caps to
about 10,000 microfarads at 25 volts. Even just one in the positive and one
in the negative should do it. As those transistors were C multipliers
anyway, as I said before, you can get away without using them. A scope may
help also, but, I would definitely take out the FETs. Also check for other
defective caps within the amp itself. 73 - Mike  

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 


-----Original Message-----
From: Chuck [mailto:cpaci1 at verizon.net] 
Sent: Friday, June 10, 2016 10:26 AM
To: Mike Feher; 'Al Klase'; njarc at mailman.qth.net
Subject: Re: [NJARC] Knight KX-60 Amplifier

You are spot on Mike...
Both filter caps were totally dried up and causing the power transformer to
cook.
I am sure that also caused one of those transistors to open and the other to
short.
I re-stuffed the filter caps then replaced the Bendix 660032s with a couple
of Motorola IRF-240s I had in the shop.
The amp came to life after that, but not quite fixed yet.
Those transistors have built-in diodes and do not seem to be quite right,
since they introduced a hum.

Thanks again,
Chuck

-----Original Message-----
From: Mike Feher
Sent: Friday, June 10, 2016 7:44 AM
To: 'Chuck' ; 'Al Klase' ; njarc at mailman.qth.net
Subject: RE: [NJARC] Knight KX-60 Amplifier

Chuck -

BTW, something caused those transistors to fail, and, you should try and
find out what that is prior to just replacing them. I also believe that it
is much earlier than the 1073 that you mention. By that time most amps were
using Silicon NPN transistors. In 1973 I bought a Pioneer SA9100 amp that I
still have and use. 73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960


-----Original Message-----
From: NJARC [mailto:njarc-bounces at mailman.qth.net] On Behalf Of Chuck
Sent: Friday, June 10, 2016 4:40 AM
To: Al Klase; njarc at mailman.qth.net
Subject: Re: [NJARC] Knight KX-60 Amplifier

Just remember
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