Hi, I am new to this forum. Came across this forum, while I was searching on some details on how to fix my old Denon PMA 737 Amp. There is another thread which I came across in this forum on the same amp, but the problem on mine looks different.
Here is the problem : The power LED lights up, and I hear no Final Relay click, and so no sound from speakers.
How did it get into this state : Well, I played it loud the other day with loudness button on for 10 mins! I heard a 'pop' from the speakers, and then a relay click. And the next song didn't had sound. Tried turning it off and on, and it seems like something is wrong which doesn't let the relay click.
What have I done so far : I 'assumed' the power transistors got fried up, so replaced the 'Sankens'. On checking the old ones for broken junctions (http://www.instructables.com/id/HOW-TO-TEST-YOUR-TRANSISTORS-WITH-YOUR-MULTIMETERS/) they looked fine.
Can anybody let me know what else could be a possible reason? What should I first start looking into?
Appreciate any help.. Thanks in advance
Here is the problem : The power LED lights up, and I hear no Final Relay click, and so no sound from speakers.
How did it get into this state : Well, I played it loud the other day with loudness button on for 10 mins! I heard a 'pop' from the speakers, and then a relay click. And the next song didn't had sound. Tried turning it off and on, and it seems like something is wrong which doesn't let the relay click.
What have I done so far : I 'assumed' the power transistors got fried up, so replaced the 'Sankens'. On checking the old ones for broken junctions (http://www.instructables.com/id/HOW-TO-TEST-YOUR-TRANSISTORS-WITH-YOUR-MULTIMETERS/) they looked fine.
Can anybody let me know what else could be a possible reason? What should I first start looking into?
Appreciate any help.. Thanks in advance
Hi, first of all you need to get a schematic or service manual (with schematic).
Not sure about PMA 737 particularly, but there is the one for PMA 730 >HERE< Must be very close to 737.
Then you need to take a DMM and measure the voltages, starting from the power supply, in order to understand why protection does not let the amp to switch on (most likely some rail voltages will be missing).
Hope this helps
Cheers,
Valery
Not sure about PMA 737 particularly, but there is the one for PMA 730 >HERE< Must be very close to 737.
Then you need to take a DMM and measure the voltages, starting from the power supply, in order to understand why protection does not let the amp to switch on (most likely some rail voltages will be missing).
Hope this helps
Cheers,
Valery
This DENON PMA 730 sound very dull, harsh, at any price it is not a bargain to have it. The sound is very "tarnsistor" like, no treble, no bass, no stereo effect, just horrible middle.
They claim in that amplifier NO NFB of course it is a lie. look carefuly the NFB network in the schematic diagram they "have forget" to draw the 1K resistor of the NFB network of course this resistor does exist in this amplifier
They claim in that amplifier NO NFB of course it is a lie. look carefuly the NFB network in the schematic diagram they "have forget" to draw the 1K resistor of the NFB network of course this resistor does exist in this amplifier
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