Denon 4308CI NO AUDIO

[ngen33r]

I picked up a Denon 4308CI cheap and the unit powers on fine but I have no audio output. I tore the unit down and found on the audio unit board a bad cap and a blown transistor. C507 100uF 50V and TR501 KTA1268. The KTA1268 is not available so I need to find something equivalent.

https://cdn.badcaps-static.com/pdfs/...fffd426395.pdf

This one is close but not exact.


Any recomendations?

[budm]

Re: Denon 4308CI NO AUDIO

992 is only rated at 50mA Ic, 1268 is rated at 100mA.

[ngen33r]

Re: Denon 4308CI NO AUDIO

I cannot find an exact match at digikey or mouser.

I can go 1/2 the rated voltage


or

Higher voltage and less gain


Or I can try my chances on eBay transistors which are probably fake.

[tibimakai]

Re: Denon 4308CI NO AUDIO

You could also contact Digikey, and they may suggest something.

[ngen33r]

Re: Denon 4308CI NO AUDIO

You could also contact Digikey, and they may suggest something.

Never thought to do that. Thank You

[ngen33r]

Re: Denon 4308CI NO AUDIO

They recommended these:

https://www.digikey.com/product-deta...X795A-ND/92573

Parts ordered let's see what happens. I am replacing all of the caps in that section as one of them ruptured, which most likely killed the transistor with noise the other parts seem to test ok.

[ngen33r]

Re: Denon 4308CI NO AUDIO

I recapped that section of the board and replaced the PNP with

The transistor blew again when powered on so another problem exists.

[ngen33r]

Re: Denon 4308CI NO AUDIO

Any ideas on this one because these look like the muting circuits they shouldn't have excessive current flowing through them.

[R_J]

Re: Denon 4308CI NO AUDIO

Hard to tell without the service manual. The partial schematic you posted does'nt even show C507.

[R_J]

Re: Denon 4308CI NO AUDIO

I found a schematic, I take it the transistor shorted? if you remove it, what voltage do you get on TR501 collector (C503) it should be around -7 volts. also check the base voltage (d511 anode)
What was wrong with C507? You should check the voltage on each side of C507, you should have -12v on the negative and possibly +5v on the positive lead.

(Page169)

[ngen33r]

Re: Denon 4308CI NO AUDIO

C507 was blistered and leaking, could be an un-related problem. I checked the voltage rails and everything seems to be good there.

I will test the things you listed tomorrow.

[ngen33r]

Re: Denon 4308CI NO AUDIO

More problems found:
B - 34V
C - 10V
E - 61V

I unplugged CW155 & CW068
B - 100mV
C - -3.88V
E - 475mV

More checking shows both transistors (TR630 TR631) on the 5V supply are shorted and I have a blown audio output. IC301 is also fried. My guess is the blown output is the cause. I am not sure that I can find a replacement for the outputs. IC301 might also be impossible to source. I am not sure if I trust eBay parts but that may be my only option. I have the service manual but it is too large to post.

[ngen33r]

Re: Denon 4308CI NO AUDIO

Must have been a big boom.

[ngen33r]

Re: Denon 4308CI NO AUDIO

Trace Repaired:

[Häiriö]

Re: Denon 4308CI NO AUDIO

Have you checked the main amplifier transistors? Usually when they short they take some smaller transistors also.

[tibimakai]

Re: Denon 4308CI NO AUDIO

http://pacificsemi.com/search.php
SAP15N

[ngen33r]

Re: Denon 4308CI NO AUDIO

Mains were blown. I also found a bad diode.
https://www.digikey.com/product-deta...03P-ND/3661836