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Harman Kardon 330C blowing fuses

bingo i hope ...
q421 B -22.16vdc E -22.85vdc C-21.05vdc
q413 B +20.85

q421 emitter connects to q413 base so should be same voltage ...
look for a break on the board .
 
Frustrating. When I checked q421, I actually tested q422. The numbers on the board are a mistake. On the board,what is numbered q422 is actually q421 and vice versa. The numbers are printed wrong on the board. I tested the actual q421 and E+22.90vdc and q413 B +20.85vdc.
 
which transistors did you replace ?
and when you removed transistors for testing did you remove replace one at a time ?
am wondering whether you could have the transistors fitted in the wrong places .
 
I tested and replaced them one at a time. The only one I replaced was q601 and that was early on. The original q601 tested good but one of the legs broke off when I was adjusting it to fit back in the board.
 
q421 q422 should really have all the same voltages .
all even numbers are left channel .all odd numbers the right channel .
 
q401 B .080vdc E 1.61vdc C 21.77vdc
q403 B 2.21vdc E 1.56vdc C 21.19vdc
q405 B -21.31vdc E -22.12vdc C -6.23vdc
q407 B -22.10vdc E -22.71vdc C 20.58vdc
q409 B 21.90vdc E 22.72vdc C 22.68vdc
q421 B -22.16vdc E -22.85vdc C-21.05vdc

q405 collector should be same as q401 q403 emitters .
mistake in reading or break in circuit
 
Which type of transistor did you use as replacement for the Q601 ? and did you check that it had the same pinout ?

I'd suggest to check voltages on both sides of D602 - it might help to see why Q601 is apparently not working. C601 & C602 could be an issue - I'd just change them if you have replacements, being careful of the orientation.
 
For a replacement for q601 I used an NTE129, the only replacement available locally. I did check the pinout and they're the same. When I checked, C602 was in backwards. Don't understand as C602 was an original cap and untouched by me. I replaced C601 and C602. The measurements across D602 are now neg -1.6vdc and pos -4.00vdc
The measurements now for transistors q405 C -4.62vdc q401 E 1.75vdc q403 E 1.75vdc. Will check for break in circuit today.
 
Need to look at this - in the mean time, why do you say C602 was in backwards ? if it's original and untouched, then it's worked like that for 40 years.......

If you're going by the pcb markings, then maybe the marking is wrong ? check it vs. the circuit, and make sure your replacements for both are correct.

Once that's done, and you've checked everything around Q405 (circuit breaks, bad solder joints, etc.), a new set of BEC voltages for Q601, Q405, Q407 would be useful.
 
c602 ....
thing is if you put this in the wrong way round it would stop q601 working properly .. it would act like a short circuit .
please make sure the + positive side goes to ground and the - negative side goes to r605 r603 d602 .
yes i know the + going to ground might not make sense to you but it so happens the negative side connects to a negative voltage .
i have a strong suspicion when you get it in the right way round things might behave quite differently .
 
I put C602 in the same way it shows in the service manual from vinylengine. I'll check and make sure + is to ground. Still experiencing the same problem, fuses blow, not at startup, but when speakers engaged.
 
petehall347, on checking c602, if you are right on the orientation, the orientation in the vinylengine drawing is incorrect. I followed your advice and reversed c602. Now the neg side of c602 reads -1.63vdc as do r605, r603, and d602.
 
On the underside of the receiver, there is a resistor bridged between q405 collector and q401 emitter. The same for q406 collector and q402 emitter. They have a black shielding over them and you can see them in the photos. Both these resistor test at 5.52ohms. I don't see a break in the board.

q405 C -4.61vdc q401 E +3.26vdc q403 E +3.26vdc
q406 C -8.11vdc q402 E -.730vdc q404 E -.730vdc

Could you check and tell me what C601 orientation should be. I'm not sure if I should go by the orientation provided in service manual. Thanks.
 
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C601 orientation is +ve lead goes to ground, the same as C602

I have no idea what the extra resistors are. They don't appear on the schematics, or pcb drawings anywhere that I can see.... when you say there's no break in the board, could you confirm that there's a continuous trace from Q403(E) to Q401(E) to Q405(C) ? (that's what's shown in the pcb drawing shown on manual pg. 24), and that the resistor is soldered to 2 points along the same trace ?

How did you measure the resistances, in situ ? or did you lift one end ?
 
lift one end of the thing in tubing under the board and measure its resistance again ..i just looked at pics and one looks fuse shaped from the way the covering has shrunk .also see if the board trace has been cut or if it looks like the trace was never there .
 
I thought someone may have added those bridges but there is a repair video of a HK330C online and the bridges are visible in the video.
 
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