Blown fuse on KA-6100 upon power up.

[beer_me]

NTE85

 

[beer_me]

It tested out fine actually, but I replaced it anyway since I had already removed it. I happen to have a 1N4006. It’s an 800v, 1A. I’ll put the original SA945 back in and see what happens.

 

[beer_me]

Same results...

 

[beer_me]

It is being very stubborn. I'm going to be away for about a week. I'll get back to it when I get back.

 

[beer_me]

Well, here I am am again, back at the seemingly endless troubleshooting. Can anyone tell me if RM138 should be letting 44v through the side that goes to dm15? My problem has to be around here.
And whats the correct voltage that should close the relay?

and please forgive my rudimentary drawing haha

 

[petehall347]

you should be seeing about 600mv across dm15

 

[petehall347]

qm28
qm31
voltages ?

 

[beer_me]

So should rm138 be limiting dm15 voltage to 600mv?
Qm28-
E=44v
C=0v
B=0v

Qm31-
E=0v
C=44v
B=.18v

 

[petehall347]

qm31 needs to be on hard ..1.2v at its base . this should give qm28 600mv to turn on and ground the relay
qm27 voltages will help next ..it needs to be turned off ..
if qm27 base is 0v . we need to look at more stuff .. if above 0v like in the volts range we need to see which channels dc offset is high .

 

[beer_me]

Just figured out that if I short qm28 that that grounds the relay...oops haha. Don’t worry, no smoke, still tests the same as before.
Qm27
E=3.9mv
C=.65v
B=0v
So. I need to check bias current? That’s all the 6100 does

 

[petehall347]

qm27 might be shorted . or cm82 ... rm316

 

[beer_me]

Bias current adjusted on vrm5 from 38mv to 20.1mv. Vrm6 from 42mv to 20mv.

 

[petehall347]

dont see over-current protect . been trying to figure this out .

 

[petehall347]

pull qm27 . if no click check rm136 rm137 .

 

[beer_me]

Pulled qm27. Got a relay click!

 

[petehall347]

test qm27 . plus now you have relay clicking on check voltages at speaker terminals

 

[beer_me]

I’ll check it here soon as well as voltages at the speaker terminals. Gotta go get some dinner. Thanks very much for your help thus far Pete. I’ll post my test results soon.

 

[beer_me]

Well, I tested the speaker output without qm27. I hooked up an old pair of 50w per channel speakers and read 3.9ohms before relay kicked in but once the relay closed it dropped to 0. After that test...
Put in a new (&tested) NTE47 on hand and put that in qm27. Still have same results as before on qm27...
E=.18mv
C=.64v
B=0v

 

[petehall347]

volts not ohms ..better not to connect speakers for now.

 

[beer_me]

Eureka!
Pete, you got me thinking that since the relay closed without qm27. It got me thinking about the pinout for some reason. Glad I checked because I found that
that the original sc1681 had a pinout of B,C,E. The NTE47 that I replaced it with had a pinout of E,B,C.
Now I have solid test results at qm27, qm28, qm31, Dm15...a very satisfactory relay click...and most importantly, MUSIC.