DCP going south??

roccus

roccus

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#181
Billboard said:
Sounds like your DCP is working fine, I wouldn't remove it.

I am sure you will figure it out, once you get the 8 ohm dummy load see if you can duplicate the shutdown at will. Run the amp at different frequencies from the tone generator from your PC, and also at different levels.

Stick with it you will get it.
Click to expand...
yes something somewhere is leaking out DC now and then.. it shut down again I turned the volume down and plugged a TT into the preamp and click had to turn off to reset it
 
WOPL Sniffer

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roccus said:
yes something somewhere is leaking out DC now and then.. it shut down again I turned the volume down and plugged a TT into the preamp and click had to turn off to reset it
Click to expand...
DC is Leaking out NOW AND THEN?? Send that amp out and let somebody look at it.

Sounds like an intermittent short.
 
roccus

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WOPL Sniffer said:
DC is Leaking out NOW AND THEN?? Send that amp out and let somebody look at it.

Sounds like an intermittent short.
Click to expand...
Don't look like much of anything will happen soon I will be pretty much shutting the shop down for the winter will probably just toss the wopl in a box and store it on a shelf maybe deal with it next year or get rid of it....
 
wattsabundant

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My guess is the amp really is putting out a subsonic signal. The first thing is to make sure the input signal does not have a DC component. I would then try lifting one channel to the relay board and driving the other channel. If it doesn't trip then reverse the procedure. If one channel is the culprit then attack it. A hair dryer operating on the low setting from a distance of a foot or more may be helpful. you don't melt the driver board, just raise it's temperature. Likely suspects are the front end differential amplifiers. Outputs and drivers are less likely. Asymmetrical clipping could be detected as a DC offset.
 
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roccus said:
yes something somewhere is leaking out DC now and then.. it shut down again I turned the volume down and plugged a TT into the preamp and click had to turn off to reset it
Click to expand...


Plugging components into a preamp can often cause a voltage spike or a temporary buzz.....bad idea. I'm not surprised the DCP tripped here...

You have a scope and signal generator now correct?? Don has some good advice there, but also monitor the output at 20 and 200 hz to see if you can catch the clip or DC transient...
 
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Another trick is to lift one end of D9 or D10 to isolate the driver board protection circuit....
 
roccus

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laatsch55 said:
Plugging components into a preamp can often cause a voltage spike or a temporary buzz.....bad idea. I'm not surprised the DCP tripped here...

You have a scope and signal generator now correct?? Don has some good advice there, but also monitor the output at 20 and 200 hz to see if you can catch the clip or DC transient...
Click to expand...
Yea I know I was bad plugging my TT in without powering everything down I kept getting interrupted and wanted to test a cartridge out before I ended the day .... I don't think it is the preamp as it does it on 2 different preamps... the real problem I am having here is it can runs for days at different volume levels and not trip so I can't get it to trip on command I even tried a drop test raising the amp 3 inches off the bench and dropping it while it is running but nope just kept purring along it is running wide open right now and has been for 3 days without tripping... I think I will replace C7 on the DCP board with a 120uF cap and see what happens then
 
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Chill Nav, they're good for a couple foot drop........depending on impact angle!!!!!!!!!!!!!!!!!
 
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NavLinear said:
OH MY!!!!!!!!!!!!
Click to expand...
I only picked the front of the up up and let it drop not the transformer I would bet PL's back when they were used on the road took a heck of a lot more beating than that... also believe it of not but it is actually an acceptable procedure on some electronics
 
wattsabundant

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roccus said:
... I think I will replace C7 on the DCP board with a 120uF cap and see what happens then
Click to expand...
I'm not very fond of just throwing parts at a problem. The most likely thing to happen by changing C7 is the board gets damaged. If anything verify it is the correct value. R3,4,5 should be 56K.
 
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wattsabundant said:
I'm not very fond of just throwing parts at a problem. The most likely thing to happen by changing C7 is the board gets damaged. If anything verify it is the correct value. R3,4,5 should be 56K.
Click to expand...
OK I will have a look at those... it has now been running for 3 days at all volumes and has not shut down so out of 100+ hours of running over the past few weeks it it has only shut down 2 times and when it did it was not cranking it was at moderate volume one last thing I will try when my load resistors get here is load the crap out of it as some here have suggested and see if I can get it to trip and maybe find a pattern that trips it then maybe I can get to the bottom of it
 
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