Dual Rec no filaments on V1 and V2

[LarBal]

100W 3 channel dual rectifier came in, owner hasn't used it in 10 years , said it was "dead" when he put it away.

Rectifiers are fine, both SS and 5u4gb, replaced power tubes and installed bias pot, and are pulling 36mA each with 430 on plates. All volatges look good except on V1, V2

No sound coming out of speaker however, so I started pulling preamp tubes and noticed there's no filament voltages on V1 and V2.
Now if just V1 was the issue, I'd be looking at that circuit(which honestly I don't fully understand, but it looks like DC filaments on V1), but V2 also has nothing between pins 4/5 and 9, and it's on the same rail as V3,V4,etc. all the way through the 6L6s.
I reflowed the PCB pads for all heater connects V1,V2,V3.
What other possibility could there be besides a busted trace between V3 and V2 filaments??

All other filaments on V3 through V9 have 6.7VAC between pins 4/5 and 9( and 2 and7)

Also, none of the channel lights on the front panel work, which appear to need the same 3V, -3V supply that V1 needs.

Also, I'm not sure which schematic to be looking at, I've found 2 that are slightly different with this low V supply . I'll attach both.

Also, I'm getting 4VDC on V1 and V2 from pins 4 to ground , and pin 9 to ground. I'm not even sure if this matters.

Any ideas? Maybe I've got an amp this id running DC heaters on V1 and V2??

[Enzo]

You post schematics for a Dual Rectifier and a Dual Rectifier Solo. Which do you have? There are small differences between the two on that power supply, but not different enough to worry about. In either one V1 gets the rectified heater supply and V2 doesn't.

What other possibilities? Well, why couldn't it be a broken trace? Check that out.

Also, I'm getting 4VDC on V1 and V2 from pins 4 to ground , and pin 9 to ground. I'm not even sure if this matters.

Pull V1 and measure again at the empty socket. I bet pins 4/5 and 9 no longer read the same 4v.

[LarBal]

It's a "Dual Rectifier Solo Head 100".

As for the traces, there is continuity on pins 9 on v3, v4, v5 (and also 4/5). There is no continuity there between v3 and v2, but there IS continuity on pins 9 (and 4/5) between v1 and v2, leading me to believe this amp has dc heaters on v1 and v2

[Enzo]

Pull the tubes to do these tests. The heaters have very low resistance and can fool you.

[LarBal]

Yes, all preamp tubes were pulled before the last tests. Also, with tubes pulled, I have +3.5 or +4.0VDC (depending on spongy/bold switch) to ground for pins 4,5,9.
Pretty sure one side should be negative. It also should by 3VDC not 3.5VDC.
I've put new preamp tubes in after these tests and filaments aren't lighting

[LarBal]

So it's gotta be the diodes in the +/-3 V circuit. I will replace those in the morn.
Also, I found a thread that confirms V1 and V2 are DC filaments , https://music-electronics-forum.com/...-with-solution

[drewl]

That's a common problem I've seen after years of use.

A clue is burn marks in the pc board around the filament diodes.
Mount the new ones off the board to prevent further board damage

[Jon Snell]

Do the relays pull in?
V1 uses DC for its heaters. The DC is commoned with the relay supply.
There may be your clue; check the bridge rectifier.

[LarBal]

Ok well I pulled the diodes on the bridge, figured out what was what, and was getting continuity(even with the main filament supply from transformer lifted) in places I shouldn't . I replaced all the diodes correctly anyway, and got nothing but rapidfire clicking.
Also lifted a trace from the top right diode in the process. Shit. . It's still connected to it's pad and to wherever it goes(3 or -3 VDC supply), just kinda stickin up in the air, still connected ;(

So I made a bridge rectifier on a piece of fiberboard, floated it over the board, and tapped the AC filament supplies from V5, then ran the rectified parts of the bridge, both + and - 3VDC to their respective spots on V1(pins 4/5 and 9). Ok great so now the amp works and produces sound, but only through channel 3 I believe. No lights working, and channels won't switch. I don't have a layout but obviously the channel switch low voltage is coming off the area where the bridge was on the board, which is not there anymore.

So I need to figure out where to put that - and + 3VDC into the switching circuit, and hope that there isn't something shorted back at wherever it was supposed to come from.

Any suggestions?

[LarBal]

Actually, now I've found -3VDC on 6426-4 transistor so now I'm looking for the +3VDC supply for the switching circuit. Maybe something else is going on with the switching circuit?

[g1]

Is this double sided board? Did a thru-hole maybe get disconnected when you removed the original diodes?

[LarBal]

Yes, It's double-sided, in the sense that one can solder on both sides. I'm not sure what you mean exactly by a through hole getting disconnected. On the top side of the board, I did accidentally lifft a solder pad of one of the diode, on the top side, and when it came out it also pulled up(but not off) a trace that goes somewhere still TBD. So the top side of the board is not connected to the bottom side of the board, where the pad is. Is that what you mean? I figured it didn't matter, in the sense that the trace was still connected. Also, when I soldered to that pad, I soldered it to the lifted pad, that was just floating, so there was indeed no connection with the bottom of the board, for that diode. I hope that makes sense!

[LarBal]

Ok getting closer.... So i found the 470r that feeds the channel 3 LED, where +3V feeds the switching circuit. its NEGative 3VDC instead of positive. However I definitely have +3V on pin 9 of V1, that technically should feed the 470r with +3vDC

[g1]

Yes, It's double-sided, in the sense that one can solder on both sides. I'm not sure what you mean exactly by a through hole getting disconnected. On the top side of the board, I did accidentally lifft a solder pad of one of the diode, on the top side, and when it came out it also pulled up(but not off) a trace that goes somewhere still TBD. So the top side of the board is not connected to the bottom side of the board, where the pad is. Is that what you mean?

If there are traces connected to the pads on both sides of the board (for that leg of said diode), you must restore the connection. If the pad on top or bottom does not connect to anything, then it doesn't matter, the lifted trace is the only thing that needs to connect.
Thru-hole means there are little 'pipes' that connect top and bottom traces where components go through. They are also called 'vias'. If you didn't have them, you would have to solder both sides everywhere a leg goes through when there are traces connected on top and bottom sides. Hope that makes sense.

[LarBal]

Yes that makes good sense. Thank you for the explanation.

So to recap:

-After floating a bridge rectifier above the board(and removing the original ones off the board), tapping the filament voltage of the main 6.3VAC line, and connecting the + and - 3VDC(it's actually like 2.8VDC) directly to pins 4/5 and 9 of V1, I've got filaments working in V1 and V2, and amp is producing sound, but only through channel 3. That channel and the rest of the amp is working perfectly . No front panel channel lights or switching(from the back channel selector switch) is working at all.

-I've come to the conclusion that the reason the switching circuit isn't working is bc where +3VDC is supposed to be, I've got -3VDC, at the 470r resistor, before the LED. However I DO have the correct +3VDC at pin 9 of V1, which technically should be connected to the 470r.

-What could cause this incongruity ? The only thing inbetween those two points circuit wise (I think?) is a 39r resistor and 1n760 diode.

-I've attached a picture to illustrate

-the only other clue I can find is that there is a loop selector switch on the back, and when in Loop Bypass mode, it hums loudly

_The only other thing I can think is that after having removing the diodes from the original board, and floating the bridge circuit as I explained above, that certain connections are not being made.