My guess is that your intrepid modifier added that open frame relay to switch the power instead of the front panel switch, which often burns its contacts over time.
Follow the wiring to it, and you'll probably see that the sparking contacts are in line between the mains and the power transformer and the coil connects to the front panel switch. As long as there aren't any shorts and you are aware that it has 120VAC on it, it should be OK. Make sure any wiring to/from it is away from signal leads.
Follow the wiring to it, and you'll probably see that the sparking contacts are in line between the mains and the power transformer and the coil connects to the front panel switch. As long as there aren't any shorts and you are aware that it has 120VAC on it, it should be OK. Make sure any wiring to/from it is away from signal leads.
I added some more pictures of that specific area of the amp. Maybe you could tell me if he wired it okay away from signal leads? New pics at the bottom of the album. There's a few of the thermal sensors under the amp module too. It looks like the previous owner left those alone.
*new pics added - ImageShack Album - 23 images
The fan control switch looks like its wired in on top of what's already there. Does it look like I could just unsolder the wires that come from the switch?
*new pics added - ImageShack Album - 23 images
The fan control switch looks like its wired in on top of what's already there. Does it look like I could just unsolder the wires that come from the switch?
Your DH500 looks like the earliest version.
Since it is, there is a 0R5 resistor (green, black, silver, gold) on the left and right PC boards right next to the big blue cap in the middle of the PC board that connects input ground with speaker ground.
With the amplifier un-plugged, check for continuity from the input ground to the speaker grounds.
Since it is, there is a 0R5 resistor (green, black, silver, gold) on the left and right PC boards right next to the big blue cap in the middle of the PC board that connects input ground with speaker ground.
With the amplifier un-plugged, check for continuity from the input ground to the speaker grounds.
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I just saw some of the thumbnails and wanted to mention that if this unit was run much in pro duty and you haven't taken it out and ran a hose over it before shooting the pics, it sure hasn't seen many dive bars. The fan is probably fine. You'd get further making sure the sink area inside the cage is clean.
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Yeah, mine's dustier than that and it's just been in my living room. 
Not sure what to do about the fan switch. If it just runs in parallel with the temperature switches there's no problem leaving it in, set for low speed operation. If the temperature rises (unlikely in home use) the temp switch should activate the fan to a higher speed. otherwise restore it to the connections in the manual if you can.
Not sure what to do about the fan switch. If it just runs in parallel with the temperature switches there's no problem leaving it in, set for low speed operation. If the temperature rises (unlikely in home use) the temp switch should activate the fan to a higher speed. otherwise restore it to the connections in the manual if you can.
Yeah, mine's dustier than that and it's just been in my living room.
Yeah, she is pretty clean for what he said it was used for. The thing is, he's gotta be over 50 years old and still "DJ's," just not sure what he means by that. Lol. But, he did say that he has 3 of these and this was the least used. He must have had it stored inside because I didn't do anything to the amp before taking pics. The heatsink doesn't have any dust on it at all.
I'm not sure if one position allows normal function of the speed control or not. I'll have to get it up and running with some speakers before I know that. I know the switch has "on/off/on" positions, and in the middle (off) position, the fan still runs at it's lowest speed.
I didn't mean nothing by it Bob...without you experienced guys out there, I wouldn't have come to learn half as much about this hobby as I do now. 
I hang out with some guru's twice my age and still enjoy the same music and atmosphere. I just meant that older guys seem to take care of their stuff.
Cory
I hang out with some guru's twice my age and still enjoy the same music and atmosphere. I just meant that older guys seem to take care of their stuff. Cory
Just one channel humming doesn't seem like a cap issue.
Is the hum 60 Hz or 120 Hz? How many volts of hum do you get?
What do you have connected to the inputs? Try with nothing connected but the inputs grounded. Still have hum?
Remove the left channel rail fuses. Power up just the right channel. Hum?
Is the hum 60 Hz or 120 Hz? How many volts of hum do you get?
What do you have connected to the inputs? Try with nothing connected but the inputs grounded. Still have hum?
Remove the left channel rail fuses. Power up just the right channel. Hum?
Don't know if it's 60 or 120 Hz...do I check at the binding posts just like I was doing? Where do I measure hum voltage from?
I powered it up first with nothing connected to the signal inputs, just speakers from the outputs. I'm at a friends and he's wiring up the RCA's where the 1/4" jacks were. We're wiring it just the the pictoral diagram.
Once they're wired up, I'll do some more tests.
I powered it up first with nothing connected to the signal inputs, just speakers from the outputs. I'm at a friends and he's wiring up the RCA's where the 1/4" jacks were. We're wiring it just the the pictoral diagram.
Once they're wired up, I'll do some more tests.
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