Onkyo M-504 problem seek

[Netlist]

Looking at the M-508 block diagram which could be similar to the M-504:
djk is right, if the power amp is fried, RL781 should be open and the meters will peg due to a faulty protection or meter drive circuit.
I agree with others. This is not an amp to tackle without experience. Stripping it is an option but it would be a shame to dump a nice amp like that.

/Hugo

 

[Revenoor]

Working on my M-504 as well

Not to hijack your thread but I am starting work on one of my 3 M-504s today (I hope), I have the service manual if you need info. My problem is different in that on power up the left channel fails with no output. I noticed when I powered up that that amp didn't go thru it's protection check routine, meters went immediately to green. So far I've just done a check for DC at the speaker terminals (good at 17mV) and then I noticed that while one channel diodes are glowing the other side is not. Let me know if you need something from the manual.

BTW, if anyone wants to take a crack at my issue, it would be appreciated.

 

[tvi]

Meter circuit M-504

 

[tvi]

Power supply

The 2 smaller transformers (T003, T004) are the Real Phase™ transformer Onkyo touted in thier products back then, if one side of these goes open you will lose a rail.

I have the full service manual if anyones interested?

Regards
James

 

[saabracer23]

Well my amp has one small transformers and two larger ones (I am talking physical size). So is my idea a bad one as far as the two larger transformers "sharing" the larger one and the smaller one being bad? That is why both meters are pegging, from what I read I have a classic case of the amp going into protection as soon as I turn it on. That is why I have no relay, and no servo light. Does anyone think the transformer could be my problem? I think the power supply is fine because I looked at it closer and the meters are pegging and when I push the power button to turn the amp off they slowly go back to zero after a few seconds. Would that be the capacitors discharging?

Thanks again for all of the help
Dan

 

[djk]

The probability of one of those common-mode chokes going open is slim-to-none.

Measure the rail voltages on the outputs to confirm.

Where the 21.5V supplies come from:

An externally hosted image should be here but it was not working when we last tested it.

 

[saabracer23]

Ok this shouldn't be that hard. Can I measure the rail voltage with a common 50 dollar radio shack multimeter? Where exactly would I measure the rail voltages? I would obviously measure this with the amp on? Man I bet I sound like a rookie! I am with amps but not too much with the speaker end of things. Here are some pictures of the innards so you can get a closer look. The board is a single board but looks like it is divided down the middle and one side is mirrored of the other. One pic shows the three transformers and the small bottom one says inphase transformer. One pic shows where the wires from the transformers meet up ans distribute.

Thanks
Dan

 

[saabracer23]

another

 

[saabracer23]

and another, sorry I can't get all of the images on one post

Thanks
Dan

 

[Revenoor]

Re: Working on my M-504 as well

Not to hijack your thread but I am starting work on one of my 3 M-504s today (I hope), I have the service manual if you need info. My problem is different in that on power up the left channel fails with no output. I noticed when I powered up that that amp didn't go thru it's protection check routine, meters went immediately to green. So far I've just done a DC bias check (9 and 17 mV). Has 3 glowing diode; D411, 412 and 418). Let me know if you need something from the manual.

BTW, if anyone wants to take a crack at my issue, it would be appreciated.

I have started a new thread so as not to side track yours, my apologies.

 

[saabracer23]

No worries, no need to apologize. Who knows maybe be have a similar problem and you can help me later lol

Dan

 

[Revenoor]

I haven't listened to another amp since 1982 when I got my 5060R and 506RS. Now I have three 504s, one 508 and the original 5060R. I got the 508 last week in the box mint from 1998 for $550.00 Use them for my home theater now, not much 2 channel now these years with the kids. If I can help let me know.

 

[tvi]

In yor pic of the RB60s you can see the wire at the bottom of the board (RED, BLUE, GREY) if you measure between the with your multimeter set to DC volts you shoild get the following voltages.
+B1 (RED) to ET (GREY) 68.1V
-B1 (BLUE) to ET (GREY) 66.7V

Be careful

The 1 smaller transformer I think is actually 2 back to back?

Regards
James

 

[saabracer23]

Ok, so yes the bottom small one is actually has a twin, it is two.

From red to grey I got 67.0V
From blue to grey I got 71.0V

I assume that there is no reason to check the other side (red, blue, black) at this point. So does it look ok? Where do I go next since both amps are being effected?

Thanks
Dan

 

[Burnedfingers]

Take it to the dumpster open lid and insert the Onkyo. Sure, you will be out $10 but that is far better than spending $$$$ on what is clearly a piece of junk.

 

[saabracer23]

ummm no

Dan

 

[saabracer23]

Ok so I was able to get a better connection today since I wasn't so nervous lol.

blue to grey I got 71.8V
on the red to grey I got a Negative 67.0V

does the negative number mean anything?

Dan

 

[rmarkn]

Meter problems with onkyo m504

Hey guys,

I have a similar problem, I need help with.

I bought my 504 this weekend and it worked fine - that is until I took the covers off to clean them. And I cleaned the heat sinks.

Now, the meters go negative on power up and really peg on the negative side when the speaker relay kicks in. The amp still works fine.

Any ideas? I am sure I wiggled a wire or two while cleaning, but didn't unplug anything.

Thanks,

Mark

 

[saabracer23]

any help with the numbers from my transformers, one of the numbers being negative.

Thanks,
Dan

 

[djk]

It's supposed to be negative.

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