Kenwood 600

vuntruong

Active Member
So I was finally able to get my 600 up and running. See PIcs. I replace the 4 burnt output transistors (Sanken 2sa747A 2sc1116A), and a few other transistors, and diode. During the process, I notice that the preamplifier board number (x08-1560-10) is not the same as the board number as stated on the service manuel (X08-1470-01). Anyone have the same board number? any diff in sounds as the board is a little diff. Furthermore, after the amp has been running for an hour, the power amp section burnt a resistors. I think current bias setting is off from 25mv. Any suggestions on how to set current bias setting on the kenny 600 without burning the power amp board?
album.php
 
The manual explains it pretty well. Is there a problem following that procedure?
 
Kind of, Maybe i am doing something wrong. So when I got the amp, it was in pretty bad shape. I worked hard fixing the regulated psu (changed diodes, transistors etc..) and fixed the preamp section. Now the preamp is working really nice. The power amp section had one burnt channel (a few transistors and the output transistors Sanken, etc..). I've change all those transistors with NTE replacement transistors. Hook everything up, adjusted the bias and DC offset. After playing music for 30 mins or so, or when i turn the volume up to about halfway, the power amp section would burn a couple of resistors, really odd. Do you think it is the cheap NTE transistors? or maybe when i installed the transistors, i might have mixed up the emite/collector leads? hmm. ohh well, i am going to change the bias trim pot today, and see what happens.
Thanks EW,
hope i don't blow up the amp
 
Just to be clear...

Are you currently having troubles with one channel only?

Are you still using all of the original transistors ( and other components ) in the good channel?

I'd be wanting to verify that no other faulty components in the troublesome circuit have been overlooked, but I'm also very sceptical about the generic NTE replacement transistors you have used.

One of AK's resident SS amp gurus should be along with some excellent advice very shortly.
 
Oh hey,
So as of right now. PSU, Preamp, and one good channel is all functioning well, ( PSU, preamp, and good channel got new Caps and diodes only). When I got the Amp, the bad channel seems like it had been worked on before. I noticed one of the transistors (Q10) was cracked in half, Output transistors Sanken 2sa747a, 2sc1116 burnt, and Transistors Q11, Q12 (NECD381, and NEC B536) was also not working. So I changed the output transistors ( I used NTE bs it was readily available at local frys store, will change to original when I get the amp up and running properly) and I also change Q11 and Q12. When I replace Q10, I decided to replace Q8, Q6, and Q7 because I bought all those transistors as matching pair. I also decided to replace Q3, Q4, and Q6. So now the Kenny has just transformed into NTE  . I hook everything up, checked the current bias and Dc offset quickly (maybe too quick), and tested the amp out bypassing the preamp section. It made music for 30 mins or so. Then resistors R32, R22, R23, and and R13 started to smoke. OWWEEE, pretty exciting stuff. So I change those resistors and check the bias carefully this time. Hook everything up, and now only resistors 22, 23 and 13 smoke instantly when I power the amp on. Now I am confused, I just ordered the trim pot, and resistors. I want to fix this bad boy, but really don’t know where to start now. Attached is a couple pics of this little fire starter for your amusement. If anybody else want to see more detailed pics of what is inside a kenny 600, email me.

Any suggestions would be appreciated EW. Once i get this amp going, and it is stable, then i'll swap in better components.
 

Attachments

  • DSC_0104.jpg
    DSC_0104.jpg
    65 KB · Views: 66
  • DSC_0134.jpg
    DSC_0134.jpg
    105 KB · Views: 73
  • DSC_0138.jpg
    DSC_0138.jpg
    70 KB · Views: 74
Anytime this amp blows, Q7, Q8, Q9, and Q10 need to be replaced. Just an FYI.

If the resistors you're talking about burn up, you have shorted driver transistors (Qe11, Qe12). Qe4, 5, and 6 might not be so healthy after this happens, and you need to check the thermistor (TH1) to make sure it isn't open.
 
Thanks EW,

sorry, this might be a stupid questions. Thermistor? is this on the power amp board? I am not too familiar with this component
 
TH1 on the amp schematic. It is remote-mounted on the heatsink, and connected to pins 1 and 2 of the driver board. It must be functional, and must be connected when the amp is powered on.
 
In my amplifier I have one 2sc1116a which has to be replaced. It has the "60r" below the name "2sc1116a".
Can I replace this transistor with "2sc1116a" which has "480" below its name?
 
Back
Top Bottom