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Old 14th August 2011, 12:01 PM   #1221
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hi all I have a problem with my dc-b1 in that the relay isn't clicking in. I am using a 12v g6h2 relay and measure 12v at the wire jumper. Reg voltages are a stable +11.5 -11v. Are there any other checks I can do?
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Old 14th August 2011, 12:03 PM   #1222
AndrewT is offline AndrewT  Scotland
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Check the voltage across the relay diode.
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regards Andrew T.
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Old 14th August 2011, 01:27 PM   #1223
Salas is offline Salas  Greece
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Quote:
Originally Posted by cersepn View Post
Ah, i was looking around every part of the PCB to make sure i didn't miss out anything. Turns out one of the transformer wire wasn't secured properly to the terminal and it was loose.

The whistle/high frequency hash is gone - but the hum's back.

I've tried every conceivable way of wiring up the GND but i can't just get rid of the hum; the hum gets louder as i turn up the attenuator volume. This is even without any source plugged in.

Is it possible that i overheated any of the parts during soldering? Are the FETs particularly susceptible to overheating? But if that were the case, then wouldn't my measured values of the voltage, offset etc be weird/wrong?
The whistle has gone is positive. Does it get warm on all sinks the same now also? Fets are sensitive, but they would just cease if soldered too hot, just getting to hum bcs of that is quite unlikely. Do you have an alternative system to check it out also, even very small one, to see if there is hum there too? Any other source than the computer card? Even an Ipod, whatever.
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Old 14th August 2011, 01:38 PM   #1224
cersepn is offline cersepn  United States
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Quote:
Originally Posted by Salas View Post
The whistle has gone is positive. Does it get warm on all sinks the same now also? Fets are sensitive, but they would just cease if soldered too hot, just getting to hum bcs of that is quite unlikely. Do you have an alternative system to check it out also, even very small one, to see if there is hum there too? Any other source than the computer card? Even an Ipod, whatever.
Yea the sinks are all equally warm. You're absolutely right - it was the wind draft that caused some to be cooler than the rest.

Actually the strange thing is i've been testing the dcb1 out with a cd player all this while and the hum's there. But when i tested it with the computer sound card, it was dead quiet despite the lack of attention to wiring detail. Because of the nasty sudden hum that triggered out of the blue, i stopped testing it using the PC.
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Old 14th August 2011, 01:48 PM   #1225
Salas is offline Salas  Greece
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Are all relevant equipment powered from same mains outlet off a strip on same ground?
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Old 14th August 2011, 01:57 PM   #1226
cersepn is offline cersepn  United States
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Yea, same power strip
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Old 14th August 2011, 02:06 PM   #1227
Salas is offline Salas  Greece
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Where does the middle (mains earth) pin of your IEC receptacle goes connecting, talking about the one on that wooden board build.
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Old 14th August 2011, 02:10 PM   #1228
cersepn is offline cersepn  United States
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it's not connected anywhere, will that be a problem other than safety?

btw, i tried connecting the CDP directly to the speakers without the dcb1 and the hum is much much louder than with the dcb1. Can i say then, that it's the cd player with the problem? It's an el cheapo dvd player
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Old 14th August 2011, 02:29 PM   #1229
Salas is offline Salas  Greece
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It looks like a system grounding thing relative to the actives. You probably got no problematic component per se. Two things to try are: 1. Link the mains earth IEC prong to DCB1 earth (middle transformer wire screw terminal will do, or whatever handy near there point on same line). 2. Wire the DVD's chassis to DCB1 earth. See if one of those actions, or both, can help.
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Old 15th August 2011, 02:50 AM   #1230
cersepn is offline cersepn  United States
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Doh! After all that work.. it was really my mistake - the rca plugs were not properly inserted at the CDP, somehow causing the hum and weird noise.

The preamp is whisper quiet now. Zero hum/buzz at all Thank you for all your help!

Now i will get to mounting it inside a proper chassis. Fingers crossed it will be as quiet as it was when mounted on the wood panel
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