[NJARC] Knight KX-60 Amplifier

Fri Jun 10 10:36:23 EDT 2016

Hi Bill,
Thanks for attaching the data sheet.
Looking at the schematic, your analysis sounds right on.
I did find the filter caps totally shot, which caused the power supply transformer to overheat and those transistors to fail.
I have been running it with new caps and a couple poor replacements for the 660032s, but it is stable now even though it has a hum.

Thanks,
Chuck

From: Bill Zukowski 
Sent: Friday, June 10, 2016 9:09 AM
To: Chuck ; njarc at mailman.qth.net 
Subject: Re: [NJARC] Knight KX-60 Amplifier

Chuck,

Two things are obvious from looking at the schematic: The transistor is a 2N234A; it's used as a filter amplifier.

The 2N234A is a low gain PNP Ge audio transistor that has a substitute if NTE 121, still widely available.  The only place I know of locally to pick one up is IEI on Rte. 36 in Hazlet.  Or else any mail order supply house has them.

They're used here as filter "amplifiers", one in the +23v bus and one in the -23v bus. The value of the two caps on the base of the transistor is essentially amplified, a common practice in the 60s and early 70s.

As Al said, something caused the transistor to blow.  The first thing I'd suspect are the output transistors fed by the now defunct 2N234A (TR 15, 16 or 17, 18).  I worked for Sony/Superscope in the late 60s early 70s, and the early solid state power amps were very unreliable, plus I've seen this also in other amps with germanium power transistors that I've repaired in recent years.

It doesn't look like an insurmountably problem

Thanks,

Bill

http://www.ebay.com/itm/2N234A-PNP-GERM-ALLOY-TO-3-/141579288545?hash=item20f6c87fe1:g:CPUAAOSw5ZBWIAWy

On 6/10/2016 4:40 AM, Chuck wrote:

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_________________________________________________________

  Hi Al,
  You are right --- they are PNPs.
  I do have the schematic. I attached it...
  And they are in TO-3 packages exactly like your drawing.
  I can see how it' is wired, but I never saw a transistor used as a rectifier before.

  Thanks for your help Al.

  73,
  Chuck

  From: Al Klase 
  Sent: Friday, June 10, 2016 3:32 AM
  To: njarc at mailman.qth.net 
  Subject: [NJARC] Knight KX-60 Amplifier

  Just remember
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  _________________________________________________________

  Chuck,

  660032 is probably a house number applied to transistors sold specifically to Allied (Knight).  The early Bendix products were likely PNP Germanium transistors.

  Are they in TO-3 packages similar to this drawing?

  Do you have a schematic for the amp?  I couldn't find anything on the web.  To repair this thing you'll have to reverse engineer it.  Not for beginners.  The early solid state amplifiers had all sort of problems, and most sounded terrible even when working properly.

  Good luck,
  Al
  Al Klase – N3FRQ Jersey City, NJ http://www.skywaves.ar88.net/  
  On 6/9/2016 2:55 PM, Chuck wrote:
  Just remember Reply = Poster Reply All = Everyone _________________________________________________________ 

  Does anyone know what a good equivalent replacement transistor would be for a “Bendix 660032”? 
  It’s one of those metal quarter-size transistors - circa 1973.
  I’m working on a KX-60 Allied Knight kit - 50 watt solid-state stereo amplifier and found two of them (one shorted & one open) in the power supply circuit.
  I believe they are being used as rectifiers.
  Any info would be much appreciated!

  Thanks,
  Chuck
  AC2DP

  From: RICHARD LEE 
  Sent: Tuesday, June 07, 2016 9:38 PM
  To: Reflector 
  Subject: [NJARC] June 10th Meeting at Princeton

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  Greetings Fellow Enthusiasts!  Just a reminder that the NJARC June 10th meeting will be held this Friday, at Bowen Hall, Princeton U. The agenda includes talks by V.P. Sal Brisindi...all you want to know about capacitor nomenclature.... and webmaster Dave Sica speaking on a resent break-through in CRT rebuilding...a small auction will follow.  See you all there!  Richard Lee., Pres. NJARC
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