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Old 20th July 2009, 05:44 PM   #811
udailey is online now udailey  United States
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I think what he thinks. I think try the dmm and check resistance from sink to tab of LM3886 and from sink to ground and from tab to ground. Do this with no power to the amp. Check sink and tab to signal ground as well. Its in there somewhere.
Ri
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Old 21st July 2009, 01:56 AM   #812
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I have a question about wiring an AnTek AN-2225 toroidal transformer to the Rev C board. (toroid wiring attached)

I am using a filtered IEC C14 connector. I have the two red input wires from each toroid (4 wires total) attached to the 125V hot and the two black input wires from each (4 total) attached to the 125V negative. I have a separate green wire to the power ground.

I measured continuity on the secondaries on each transformer and combined a non-connected green and blue pair to PGND. I then have the other green attached to AC1 and the other blue attached to AC2. AC1 and AC2 now measure as continuous through the combined PGND.

Is this the correct wiring? I plugged my input, switch and toroids into my dim bulb tester sans boads and the 15 watt bulb glowed dimly. I measure 22V on each toroid between what I have labeled AC1 & PGND and AC2 & PGND.

Thanks,

Martin
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Old 21st July 2009, 01:58 AM   #813
jERiCOh is offline jERiCOh  Canada
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Quote:
Originally posted by udailey
I think what he thinks. I think try the dmm and check resistance from sink to tab of LM3886 and from sink to ground and from tab to ground. Do this with no power to the amp. Check sink and tab to signal ground as well. Its in there somewhere.
Ri
After testing everything up there, I finally found something. Tab of the LM3886 is seeing the Input ground, 457ohm to be precise. There is no other short.
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Old 21st July 2009, 02:11 AM   #814
jERiCOh is offline jERiCOh  Canada
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Quote:
Originally posted by mhconley
I have a question about wiring an AnTek AN-2225 toroidal transformer to the Rev C board. (toroid wiring attached)

I am using a filtered IEC C14 connector. I have the two red input wires from each toroid (4 wires total) attached to the 125V hot and the two black input wires from each (4 total) attached to the 125V negative. I have a separate green wire to the power ground.

I measured continuity on the secondaries on each transformer and combined a non-connected green and blue pair to PGND. I then have the other green attached to AC1 and the other blue attached to AC2. AC1 and AC2 now measure as continuous through the combined PGND.

Is this the correct wiring? I plugged my input, switch and toroids into my dim bulb tester sans boads and the 15 watt bulb glowed dimly. I measure 22V on each toroid between what I have labeled AC1 & PGND and AC2 & PGND.

Thanks,

Martin
Red+Red------0000------Green
.................. 00000-----Blue+Green
Black+Black---0000------Blue
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Old 21st July 2009, 02:38 AM   #815
udailey is online now udailey  United States
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So, your signal ground comes into the board right there near the sink. If it is touching the sink somehow then thats bad plus that means that your LM3886 is not insulated from the sink. The problem that will develope rather quickly when you put it in a chassis will be that the LM3886 will see ground through the sink and it will fry on the spot. If your chassis is grounded which wont get by our AndrewT, I guarantee it
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Old 21st July 2009, 02:43 AM   #816
jERiCOh is offline jERiCOh  Canada
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Well actually what is amazing about that is that the LM3886 is perfectly insulated from the sink and the DMM is proving it. I unscrewed the sink just to make sure. The problem might come directly from a faulty chip or a short.
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Old 21st July 2009, 02:54 AM   #817
udailey is online now udailey  United States
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If you have to replace the chip you can get them from Digikey and make sure to get the TF package. I think thats all I will buy from now on. Fully insulated package. I have burnt to many of the chip amps from letting a sink touch something grounded.
Well, I am off to bed.
Uriah
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Old 21st July 2009, 02:55 AM   #818
troystg is online now troystg  United States
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Quote:
Originally posted by mhconley
........................
Thanks,

Martin.................
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Old 21st July 2009, 03:52 AM   #819
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OK - I have it wired correctly. Thanks Jericoh & Troy.

Should the 15 watt bulb in my dim bulb tester be glowing when only the transformers are hooked up? (Power leads are not plugged into the boards.) It is lit very dimly.

Martin
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Old 21st July 2009, 08:39 AM   #820
AndrewT is online now AndrewT  Scotland
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I have never used as low as 15W. 40W never glows with just the transformer wired up.
Sometimes the 40W does not even flash when plugging in the transformer. That is down to when it is connected.
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