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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
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Old 12th September 2020, 08:41 PM   #281
yardbird is offline yardbird
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Here tis-
L- 69.3v at PS, 7.52v at PVI, 23.95 at the resistor, DC OS- 0.0002v
R- 69.2v at PS, 7.47v at PVI, 23.95 at the resistor, DC OS- 0.299v

Couldn't get a solid measurement across the LED pins on either board. The R seemed to be making good contact but would not settle down.

Not sure why the regulator on the R is getting hotter (140 vs 98F). I'll reseat the heat sink.
JG

Last edited by yardbird; 12th September 2020 at 08:43 PM.
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Old 14th September 2020, 04:12 AM   #282
Destroyer OS is offline Destroyer OS  United States
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
Are the negative and positive voltages the same?
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Old 14th September 2020, 07:57 PM   #283
Destroyer OS is offline Destroyer OS  United States
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
(to PG)
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Old 15th September 2020, 04:21 PM   #284
yardbird is offline yardbird
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I got 35.3 to negative and 35.5 to positive on both channels.
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Old 16th September 2020, 03:55 AM   #285
Destroyer OS is offline Destroyer OS  United States
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
Any hot caps on either regulator board?

Carefully look for any burnt traces as well please.

Last edited by Destroyer OS; 16th September 2020 at 04:15 AM.
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Old 16th September 2020, 04:21 AM   #286
Destroyer OS is offline Destroyer OS  United States
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
If you touch the input wires/connections on RCA, do you get AC on output? (hum)

As for offset, measure voltage to ground after the input cap, at pins 2 and 3 of first chip, and at the top ends of the 3,3k resistors above the dc trim pot.

Last edited by Destroyer OS; 16th September 2020 at 04:28 AM.
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Old 27th September 2020, 03:32 PM   #287
yardbird is offline yardbird
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Reworked the light board and things are looking mostly better. While reworking he lightboard i also changed the amp chips, transistors and most of the smaller caps (not the aluminum ones).

Both channels are functioning. The light board regulator on L channel is about (130 F). Confirmed the heat diffuser was not resting on the light contacts. There also continues to be about .295 v at the speaker output on the L. The Right terminals are at 0.0001v. I measured DC offset after the input capacitor and it is 0002v. The three resistors next to the diode that I initially omitted are also warmer than the other channel (124 F vs 85 F) There are 2 little caps (can't remember value)next to the diode and 3 resistors. The one closer to the resistors is also warmer. I have the resistors and can swap those I don't have a spare cap. This was not one of the caps I changed (it was backordered. argh!). Should have ordered a similar product but NO!

Thanks Jeremy for your above and beyond assistance. Getting closer.
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Old 27th September 2020, 03:54 PM   #288
Destroyer OS is offline Destroyer OS  United States
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
My primary thought is checking resistor values because if you're using RN dales they are easier to mix up than other types.

You got the extra PVI board, right?
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Old 27th September 2020, 04:31 PM   #289
mctavish is offline mctavish  Austria
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Hey guys, just wanted to see if anyone else has not received the boards?

I am in Austria so maybe it takes a bit longer but they were shipped a while ago or?

Im itching to get started with this build!

Thanks!
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Old 27th September 2020, 07:06 PM   #290
yardbird is offline yardbird
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Yes, I got the board. Big thanks to you.

I replaced those resistors and one of the caps. Had some 10 Ohm (?) caps from the other board and measured them to see if they were in spec. Seemed to be. The resistors I changed are now running cooler. The regulator is not (130-140 F). Was fastidious (for me) to confirm the values of the 3 resistors. The two larger Dale resistors next to the larger (green on my board) cap are running warm (next to the ceramic cap). Might change those as well. The amp is running in now.

DC offset is still goofy. More likely, my measurement of the offset is goofy. Thought i had one board on target but it is now off. I am measuring at the side of the input cap near the PVI test points, right. negative to ground. The goofy board is still 0.295v. perhaps the potentiometer if fried? I have one of those as well.
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