Harman Kardon 330C blowing fuses

[petehall347]

Q414 E -20.77vdc C -22.01vdc B -21.44vdc
Q416 E -20.19vdc C 22.62vdc B-19.50vdc
Q418 E 20.60vdc C 22.68vdc B-20.23
Q420 E -22.74vdc C -19.80vdc B -21.16

Q413 E 20.99vdc C -22.23vdc B 20.33vdc
Q415 E 21.93vdc C 22.93vdc B 22.55vdc
Q417 E -21.83 C 22.91vdc B 20.33vdc
Q419 E -22.93vdc C 21.15vdc B 20.33vdc

 

[petehall347]

check r419 and around there first .

 

[pcrosewood]

I've checked all the resistors on the whole board and they're all good. I pulled all the transistors one at a time, and they all test good. I soldered the transistors back being careful the BCE was arranged properly. I've replaced the electrolytic capacitors with nichicon caps checking the schematic to make sure they're in correctly. I re-soldered the whole board making sure all traces and solder joints were good. Still get the same results.

 

[petehall347]

see what voltages each side r419 .

 

[pcrosewood]

each side of r419: -22.95vdc and -22.38vdc

 

[petehall347]

next need to find why that negative voltage isnt reaching q419 base and q413 collector .

 

[pcrosewood]

Checked and the Q419 base ,r419, and q413 collector all read -22.57vdc

 

[petehall347]

best get all these voltages again then .
Q413 E 20.99vdc C -22.23vdc B 20.33vdc
Q415 E 21.93vdc C 22.93vdc B 22.55vdc
Q417 E -21.83 C 22.91vdc B 20.33vdc
Q419 E -22.93vdc C 21.15vdc B 20.33vdc

 

[pcrosewood]

Q413 E 21.27vdc C -22.55vdc B -20.73vdc
Q415 E 22.00vdc C 23.04vdc B 22.60vdc
Q417 E 21.33vdc C 23.13vdc B 22.11vdc
Q419 E -23.16vdc C 21.32vdc B -22.55vdc

 

[petehall347]

Q414 E -20.77vdc C -22.01vdc B -21.44vdc
Q416 E -20.19vdc C 22.62vdc B-19.50vdc
Q418 E 20.60vdc C 22.68vdc B-20.23
Q420 E -22.74vdc C -19.80vdc B -21.16

Q413 E 21.27vdc C -22.55vdc B -20.73vdc
Q415 E 22.00vdc C 23.04vdc B 22.60vdc
Q417 E 21.33vdc C 23.13vdc B 22.11vdc
Q419 E -23.16vdc C 21.32vdc B -22.55vdc

 

[Binkman]

readings probably within % of readings both posters. seems like the neg base at -22v Q-419 or reversed the reading on the test leads? the 32vdc on Q417 might hint at a resistor.

 

[petehall347]

i am struggling with this one .

 

[pcrosewood]

32vdc on Q417?

 

[Goldie99]

Struggling to follow this one as well - if I understand the service manual correctly (hifiengine version), most of the schematic voltages are listed on page 21.
If so, quite a few values are still wrong / not making sense to me.

Not sure if it'll help, but could you maybe check & report a new set of voltages for Q405, Q407, Q409, and Q421 as well ? A list of which transistor replacements you've used might help, even if only to eliminate possibilities.

 

[petehall347]

Struggling to follow this one as well - if I understand the service manual correctly (hifiengine version), most of the schematic voltages are listed on page 21.
If so, quite a few values are still wrong / not making sense to me.

Not sure if it'll help, but could you maybe check & report a new set of voltages for Q405, Q407, Q409, and Q421 as well ? A list of which transistor replacements you've used might help, even if only to eliminate possibilities.

no main amp voltages apart from b+ b- on the one i have here .
edit ... i found them in another manual i have here .. damn thing wont let me copy them ... might have to screenshot or something ...

 

[petehall347]

B E C is the order of above voltages
Q414 E -20.77vdc C -22.01vdc B -21.44vdc
Q416 E -20.19vdc C 22.62vdc B-19.50vdc
Q418 E 20.60vdc C 22.68vdc B-20.23
Q420 E -22.74vdc C -19.80vdc B -21.16

Q413 E 21.27vdc C -22.55vdc B -20.73vdc
Q415 E 22.00vdc C 23.04vdc B 22.60vdc
Q417 E 21.33vdc C 23.13vdc B 22.11vdc
Q419 E -23.16vdc C 21.32vdc B -22.55vdc

 

[petehall347]

ok as suspected both channels are wacked out .. i was led to believe left side was working fine ... something strange here ....

 

[pcrosewood]

Left channel was working when we started but now when I engage the speakers, ir blows the fuses. So I haven't done that for a while.

 

[petehall347]

yes something has gone bad .. need to regroup ..
some pics of both sides of the board might shed some light on this .
i didn't think the voltages were correct but was being thrown by the way the circuit is with it not being the classic circuit .
we will get to the bottom of it ...

 

[pcrosewood]

Sorry for the confusion.So I'll make an attempt at photos.