Denon PMA-735R

[diif]

My friend has killed another of his amps and i am hoping someone can help me to understand what is going on. It went off after playing two 12" subs.
The amp powers up. the led comes on, i hear the relays click but there is no sound. There is 90v going into the hot circuit of the transformers but nothing coming out.
If there was a short on the main board would that stop the transformers outputting or is it the transformers that are dead ?

Apologies for the poor photos i smashed my S3.

[stj]

Re: Denon PMA-735R

check the power transistors for shorts before you do anything else.

[diif]

Re: Denon PMA-735R

I have unsoldered them from the board and tested each in turn, no shorts found.

[budm]

Re: Denon PMA-735R

Do you get any DC voltage on those two main power supply filter caps (C103, 104)?
There are 3 relays, one (on a small board with small transformer T101) for powering up the two power transformer, the other two are for the speakers protection. Do you know if the speaker relays come on?
All the fuses are tested OK?

[momaka]

Re: Denon PMA-735R

My friend has killed another of his amps and i am hoping someone can help me to understand what is going on. It went off after playing two 12" subs.

Perhaps his 12" subs are rated for 4 Ohms and the amp is rated for 8 Ohms?

The amp powers up. the led comes on, i hear the relays click but there is no sound. There is 90v going into the hot circuit of the transformers but nothing coming out.

I know this may sound stupid, but did you set you meter to measure AC voltage instead of DC? That 90V on the input seems a bit odd. Check the rectifying diodes that are connected to the output of the transformers (with the power off, of course) - i.e. see if any of them are shorted. I presume that would be the devices attached to the smaller heatsinks next to those large caps. If the diodes are okay, turn ON the amp and carefully measure the DC voltage across the two big caps. If none, the transformers may have a fuse inside them that has blown. If not, do you hear any harsh buzzing coming from the transformers when you power ON the amp?