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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 1st August 2020, 02:28 AM   #271
yardbird is offline yardbird
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Thanks Jeremy!
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Old 24th August 2020, 02:23 AM   #272
yardbird is offline yardbird
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Getting close to finishing. Both PS rails are at ~70v. The photo voltaic voltage is a little under 8v. No continuity between the chips and the heat sinks. I have a question about PS grounding.

Is it acceptable t float the PS ground or should I attach or the star ground vis a cl-60 (the green loose wire attaches to the ground of the PS). I did something similar with a Pass F-6. Not sure if applicable here.

Thanks!!!
Jeff
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Old 24th August 2020, 11:46 AM   #273
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retry the link to the photo
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Old 24th August 2020, 03:17 PM   #274
Destroyer OS is offline Destroyer OS  United States
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
You can connect to chassis from PG on the power supply board.
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Old 8th September 2020, 11:08 PM   #275
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I made some stupid mistakes and trashed my amp. Now to repair....

One (yes, one) of my errors was omitting the diode on both sides. After adding the diode, I get ~.5 volts at the binding posts (on one side). The offset adjust barely changes things at all. Did not hookup speakers, etc. Ran the amp at full voltage for just a bit w/o the diode. Per Jeremy's directions supposed to be <.5mv Am guessing i smoked this side of the amp (even though no "smoke" appeared). Can someone please provide some guidance. Sadly, it gets worse...

On the other channel I had 2 errors- No diode and i carelessly screwed the polarity on the power from the PS. Smoked the center cap on the light board before figuring out my error. Replaced the cap and then smoked the amplifier chips at ~70v (variac). I have removed the amp chips and the transistors and will replace those. perhaps that is what i need to do on both boards?

Nothing other than the amp chips (resistors or caps) appears damaged on the worse board. Do you recommend changing anything other than chips and transistors prior to trying again? i could get new boards and start fresh. hate to replace the hard to get caps. hopefully, no other stupid mistakes are lurking. Move slowly, be careful (advice to myself).

Jeff
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Old 9th September 2020, 03:07 AM   #276
Destroyer OS is offline Destroyer OS  United States
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
Always feel free to email pictures before turn on, to be reviewed by us.

PM sent on your amp Jeff.
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Old 11th September 2020, 10:39 PM   #277
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This is the board that I omitted the diode (next to the 3 resistors) AND screwed up the polarity at the input. I blew the center cap on the light board before figuring out my bonehead move. It was after replacing the blown cap that I smoked the amps (assuming because of the omitted diode).

Anyway. I replaced the 3 caps and the regulator on the LED board. I replaced all the caps on the main board except the large, green cap; the small, red cap (1nf?) and the silver, pricey ones. I replaced the transistors and the amp chips. i installed the diode next to the 3 resistors. i did not replace the offset pot or any resistors.

Planning to try again with the variac tomorrow. Will double check cap orientation, diode orientation, wiring polarity and isolation of the chips. Sure hope to not see any smoke.

Was thinking it would be prudent to desolder the amp bridge and check the light voltage before proceeding.

Any other things i should do before trying again? Thanks for any help!
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Old 12th September 2020, 05:53 AM   #278
Destroyer OS is offline Destroyer OS  United States
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
Do those chips sit pretty flush?
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Old 12th September 2020, 07:32 PM   #279
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Yes, they are sitting nicely flush.

Installed the new board (right). Checked everything over a few times and nervously turned the variac up. No smoke, sparks or fire. Very happy for that. Let it cook for a few minutes. measured offset and got it adjusted to .0001 volt.

The other channel (left) still measures 0.3v. The regulator on the light board is measuring much hotter than the right channel ( 145 vs 95 degrees F). the caps appear to be a bit warmer as well. Was thinking or ordering a new regulator for the left LED board and replacing the caps. I will order new amp chips as well. I already have the transistors. I'll change the Clarity cap to the Rifa as well.

Thanks for the help! Any thoughts or advice is welcome.

Jeff
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Old 12th September 2020, 07:54 PM   #280
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Folsom EC7293: PVI Powered Frontend, 60/120w 8/4ohm
You should be able to read 24v across the big red resistors on PVI board, can you check?

If that's too hard to measure the voltage across the LED board pins behind the regulator should be 24v below the input voltage to the PVI board.

Last edited by Destroyer OS; 12th September 2020 at 08:01 PM.
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