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Thread: Help - BV120H - Nothing, no power, nada, zilch, ideas?

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    Help - BV120H - Nothing, no power, nada, zilch, ideas?

    Hey Guys,

    Hoping anyone can give some insight on this, if it's a common failure or if any one has seen it before, I know Enzo is on here and he knows all so hoping I can get some guidance.

    Quick background, amateur at this stuff, I think it's fun to pick up broken tube amps and fix them. I would love to learn everything there is to know but I'm not at that level yet. I've fixed a handful, less than 10. I know enough for safety, but my troubleshooting practices are limited, most problems have been visual or obvious so far.

    Grabbed a BV-120H for cheapp, I know there's a lot of bad talk on this series but for 70 bucks with 8 new tubes you can't go wrong.

    Low and behold I get NOTHING with power up. No indicator light, nothing reaching the tubes, basically dead. The 5a slow fuse right in front of the power is good, the 10 amp is good, there's 4 .25 amp fuses, they all test good although one looks a bit bronze, is it possible that one of these .25 amp fuses would cause nothing to work? Seems a bit far down the electrical path.

    I also see other pics on the internet where I see 2 blue wires coming from the OT but mine only seems to have 1, from what I read I'm pretty sure that's only used for wiring to something other than 110 but I'm not 100%, I don't know if this one wire could be the cause.

    Visually this thing seems really clean, nothing looks burnt or out of place.

    It's just dead and I'm not 100% on where I should be looking but I want to figure it out.

    Anyway, best advice on how to start trouble shooting this issue? What/where should I be using my meter to follow and find this issue? I'm really into this stuff and passionate about learning, and would appreciate any help.

    Attached is a crappy picture pointing out where I'm not seeing the blue wire since I'm not around it atm. Will update with better later.

    Any insight on this? Is it a common issue with the older bvs? I'm hoping/thinking it's an easy fix, this thing looks great inside to my amateur self at least.

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    Old Timer Leo_Gnardo's Avatar
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    First of all, let us know what the hellza BV .... oh Crate Blue Voodoo, now some folks might know about those.

    No power getting anywhere? Check line fuse. Check power switch. Check AC cable. We hope the power transformer hasn't failed. That's a possibility but DO check the easy cheap-to-fix things first. Wouldn't it be nice if you found a solution there, sure would relieve a lot of panic.

    Further in, you'll notice the Blue Voodoo has an unusual feature, the circuit board holding output tube sockets is attached to the rest of the world thru multipin connectors at each end. These are a source of problems, not to say your BV has 'em. Heat and corrosion do their dirty work here, and in some cases I've found output tubes getting no filament power because the multipin connectors handling filament current are roasted. In those cases I've run separate wires from the tube sockets to appropriate connections on the main circuit board.

    In spite of their hassles, Blue Voodoos are good sounding amps when they're running right.

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    Supporting Member The Dude's Avatar
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    Yes, do all of those things Leo suggested. Also, check the AC voltage across the white and black PT wires (primary). Post here. Then check (with power switch on and unit unplugged) resistance across the blades of the AC cord. Post here. Don't worry about "common issues". We just want to troubleshoot it like anything else. Also don't worry about the OT just yet. We need to find power first.

    Schematics here:

    http://music-electronics-forum.com/a...37-105xxh1.pdf

    http://music-electronics-forum.com/a...0-29512h0_.pdf

    http://music-electronics-forum.com/a...16-105xxp2.pdf

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    Appreciate the help guys.

    Unfortunately I don't have an area where I can leave my stuff out anymore so it might take another few days to get back to it (don't want to come home to stuff more broken than before)

    The line fuse is new, the 10a is also new, all 4 .25s seem to test out good too, might replace one of those 4, the d plug is verified working too.

    I'll definitely check the voltage across the PT mains and post here afterwards, kinda hoping it reads out normal so it's a simple fix (would suck to buy a new PT for more than the I got the whole enchilada for haha) Hoping this one will teach me a lot more about diagnosing, everything before has been mostly aided by visually broken components. Everything pretty much looks flawless in here to me, I could be wrong but idk if the blue LEDs are stock for these original ones, nothing on the board looks modified but I also didn't take it fully out of the chassis yet to look at the other side (knobs amr?)


    Quick question, what is the proper way to test the power / stand-by switch?

    Will report back after testing the voltage through the pt primary. I should be aiming to see the standard 120 ac right? (Alligator clips and one hand in the pocket!)

    Thanks guys!

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    Alright so I checked for ac volts across the white and black pt wires and I got absolutely 0, plugged it in turned it on and nada. I also took the resistance across the blades of the ac chord and it looks ∞... what else can I do to be sure it's the PT?



    Quote Originally Posted by The Dude View Post
    Yes, do all of those things Leo suggested. Also, check the AC voltage across the white and black PT wires (primary). Post here. Then check (with power switch on and unit unplugged) resistance across the blades of the AC cord. Post here. Don't worry about "common issues". We just want to troubleshoot it like anything else. Also don't worry about the OT just yet. We need to find power first.

    Schematics here:

    http://music-electronics-forum.com/a...37-105xxh1.pdf

    http://music-electronics-forum.com/a...0-29512h0_.pdf

    http://music-electronics-forum.com/a...16-105xxp2.pdf

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    Old Timer Leo_Gnardo's Avatar
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    Quote Originally Posted by trip View Post
    Alright so I checked for ac volts across the white and black pt wires and I got absolutely 0,
    That tells us power is not reaching the power transformer primary.

    plugged it in turned it on and nada. I also took the resistance across the blades of the ac chord and it looks ∞...
    Still leaves AC cable, fuse, fuseholder as suspects.

    what else can I do to be sure it's the PT?
    Break out your ohm meter. Measure the PT black & white leads. If you get continuity, maybe a couple of ohms then your PT is probably good and the problem elsewhere.

    Measure AC cable blades to AC cable connections inside amp. And measure across the fuse holder. Might be all you need is a new plug on your power cable, that sure would be better than replacing the power transformer and finding you didn't need to do that, right? Internal breaks in power cable also commonly happen a within a couple inches of the chassis.

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    hmm I get 1.2 ohm between the black and white leads w just resistance (still hooked up to the board)
    from the blades to the internal plug i'm getting .1 on all 3
    about 1 ohm reading w conintuity between the b & w leads

    i'm getting continuity between the black and white, plug leads, fuse holder

    although i'm not getting continuity on the diode bridge D6 7 8 & 9 ,
    i am on D 11 12 13 and 14.. but not 6 7 8 & 9.

    getting it across the stand by switch between j26 and j44, beeps on off as i flick the switch, same with power switch between j31 and 33 so those seem to working,

    but from end to end on any of those d6 d7 d8 or d9 diods i don't read continuity, they don't look burnt but is this leading me to think that bridge failed? (had this exact issue happen in a second hand 65605+112 but they did look slightly tinged)

    am getting 121 ac between the ac plug so it's getting there


    Quote Originally Posted by Leo_Gnardo View Post
    That tells us power is not reaching the power transformer primary.



    Still leaves AC cable, fuse, fuseholder as suspects.



    Break out your ohm meter. Measure the PT black & white leads. If you get continuity, maybe a couple of ohms then your PT is probably good and the problem elsewhere.

    Measure AC cable blades to AC cable connections inside amp. And measure across the fuse holder. Might be all you need is a new plug on your power cable, that sure would be better than replacing the power transformer and finding you didn't need to do that, right? Internal breaks in power cable also commonly happen a within a couple inches of the chassis.

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    Old Timer Leo_Gnardo's Avatar
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    Crikeys, one of those cases where it looks like "all systems go" but it's not. You said no pilot lights either. Sometimes the ones inside switches fail so we can't count on them as reliable indicators of "power's on."

    Let's see if power really is getting to the PT primary, set your meter for AC volts, clip your test leads to the power transformer's primary leads. Plug in, switch on, 120 VAC shows up or no? If yes then check voltages on the secondary taps, one set at a time.

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    Stray Cap DrGonz78's Avatar
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    What about testing continuity from, I think it's the hot blade, AC hot input on amp to the fuse holder. It's the side that has ICL1 between power input and the fuse holder. I think ICL1 is a thyristor that limits inrush current on turn on. Perhaps that component is open or the solder connections have failed.

    Quote Originally Posted by trip View Post
    i'm getting continuity between the black and white, plug leads, fuse holder
    Perhaps this statement needs better understanding on my part but reading it confuses me a bit.

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    Supporting Member The Dude's Avatar
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    What Gonz said. I can't remember for sure. Is this one of the amps with a little circuit board where the IEC connector solders in? If so, pull that board and check all of the solder joints. Often, the input AC connections crack loose. There's also a thermistor there that comes loose. Sometimes, they even fall out and are rolling around in the chassis.

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    Lifetime Member Enzo's Avatar
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    If you don't get 120vAC right at the primary wires, then nothing on the rectifier side is going to matter.

    You have continuity through the primary, but not through the mains wiring. SO go back and check the switch, the fuse/holder, any thermistor, and the wiring. And as Dude said, check for broken solder on the IEC connector.

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    ---Let's see if power really is getting to the PT primary, set your meter for AC volts, clip your test leads to the power transformer's primary leads. Plug in, switch on, 120 VAC shows up or no? If yes then check voltages on the secondary taps, one set at a time.

    Nada, if I hook the leads up to the white and black while connected to the board and turn it on I get nothing, should I be doing these readings with the PT disconnected from the board? if i clip and read from one side of the ac plug and the other end on pretty much any component I get ac wall v but not up by the removable board the power tubes sit in,

    better even, I don't even see this thermister there, I can't find the best pics online of other guts but I'm pretty sure it's not there, though I don't see a placement on the board for it, and I
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    Old Timer olddawg's Avatar
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    Quote Originally Posted by trip View Post
    ---Let's see if power really is getting to the PT primary, set your meter for AC volts, clip your test leads to the power transformer's primary leads. Plug in, switch on, 120 VAC shows up or no? If yes then check voltages on the secondary taps, one set at a time.

    Nada, if I hook the leads up to the white and black while connected to the board and turn it on I get nothing, should I be doing these readings with the PT disconnected from the board? if i clip and read from one side of the ac plug and the other end on pretty much any component I get ac wall v but not up by the removable board the power tubes sit in,

    better even, I don't even see this thermister there, I can't find the best pics online of other guts but I'm pretty sure it's not there, though I don't see a placement on the board for it, and I
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    What he said. There is another old tried and true test bench tech test that I'm hesitant to tell you to do. We used to call it a suicide cord. It's an AC cord (preferably with the high side fused) that you either clip or temporarily solder to the PT primary. It bypasses everything up to the primary and allows you to see if there are additional problems. I used to have several of them with different valued circuit breakers. The advantage is as a bench tech it saves you time if a unit has multiple problems or is missing it's weird detachable AC cord.

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    Lifetime Member Enzo's Avatar
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    He doesn't need a suicide cord, though it would work here.

    The IEC connector for the mains cord has exposed terminals in back. Have you tried a different power cord by the way? Plug the amp in, is ther 120vAC at the two main terminals on the rear of the IEC connector? When you turn on the main power switch, does it light up?

    Look at the schematic, the mains circuit is simple. The black and white transformer wires plug onto the board at push-ons J35, J36. Do they in fact connect to those two? Now from the IEC connector, the neutral goes directly to J36. The hot goes through a thermistor, which is right beside the fuse holder. Though your board appears not to have had one, in which case the hot mains lead runs to the fuse holder and out its other end to J31 for one end of the power switch. The other end of the switch is wired to J33, which is a direct shot to J35.

    I hope you have a good mains fuse in there and of the proper value. But a good fuse is no guarantee the fuse HOLDER is OK.

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    Stray Cap DrGonz78's Avatar
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    I am thinking this might be the thermistor but it is hard to see in the pic.
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    Lifetime Member Enzo's Avatar
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    The blue thing would be C41 or C42, the thermistor would be directly beside the fuse holder, basically touching. I could believe an early revision board might not have it. They burn out a few too many power switches, they add one in a later reverison.

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    Quote Originally Posted by Enzo View Post
    The IEC connector for the mains cord has exposed terminals in back. Have you tried a different power cord by the way? Plug the amp in, is ther 120vAC at the two main terminals on the rear of the IEC connector? When you turn on the main power switch, does it light up?
    yeah, diff d-plugs same thing. If I measure across the two main terminals on the back of the IEC I do see the 120v, absolutely nothing lights up.

    Quote Originally Posted by Enzo View Post
    Look at the schematic, the mains circuit is simple. The black and white transformer wires plug onto the board at push-ons J35, J36. Do they in fact connect to those two?
    Confirmed,

    Quote Originally Posted by Enzo View Post
    Now from the IEC connector, the neutral goes directly to J36.
    the connection reads continuity,

    Quote Originally Posted by Enzo View Post
    The hot goes through a thermistor, which is right beside the fuse holder. Though your board appears not to have had one, in which case the hot mains lead runs to the fuse holder and out its other end to J31 for one end of the power switch.

    The other end of the switch is wired to J33, which is a direct shot to J35.

    I hope you have a good mains fuse in there and of the proper value. But a good fuse is no guarantee the fuse HOLDER is OK.
    The schem does seem simple and I'm hoping it's just the fuse holder since the fuse is good, but what's my next step to be sure?

    I feel like I should be seeing continuity between the two blades of the iec but I don't so something within there has gotta be stopping it, no?

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    Old Timer olddawg's Avatar
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    Quote Originally Posted by Enzo View Post
    He doesn't need a suicide cord, though it would work here.
    True... he doesn't need to but it would tell him in 2 minutes if the PT was good and the amp worked. To me it's really simple. Connect an ohm meter across the AC input. Power switch off = open circuit. Power switch on = very low resistance. If you don't have the low resistance follow the circuit with an ohm meter until you do. The last place it was open will be your fault. If it's a fuse block jump it with a pigtail fuse. If it's the receptacle use a suicide cord. Temporarily of course. Replace with the correct parts eventually.

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    Lifetime Member Enzo's Avatar
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    Yes, and I have a couple suicide cords right by the bench here too. Indeed they often are used to plug a ??? transformer into my variac. But that two minutes is all it takes to go down the row of fuse switch thermistor looking for where the 120 goes away too. he has power at the IEC, and not at the primary.


    yes, something stops it, you have an open in between the IEC and the primary.

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    Quote Originally Posted by Enzo View Post
    Yes, and I have a couple suicide cords right by the bench here too. Indeed they often are used to plug a ??? transformer into my variac. But that two minutes is all it takes to go down the row of fuse switch thermistor looking for where the 120 goes away too. he has power at the IEC, and not at the primary.


    yes, something stops it, you have an open in between the IEC and the primary.
    so I get continuity from the hot blade to the end of the fuse holder and beyond, but I don't seem to be getting voltage between the hot blade of the iec and the only end of the fuse I can see. I'll go grab another fuse to be safe (this one tests fine but who knows) but worse comes to worst wouldn't it be narrowed down to the fuse or the fuse holder at this point if I'm not seeing the 120 there?

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    Lifetime Member Enzo's Avatar
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    OK, do it this way, plug a cord into the IEC, but not into the wall. Meter on resistance. Clip one meter probe to the hot blade of hte plug. Verify continuity to the fuse holder. We are testing one half of hte power cord so far, now with power switch set to on - but still not plugged into the wall - Do we have continuity from the hot blade to the power switch? The other side of the power switch? and finally all the way to the primary wire, J35. COntinuity all the way? If not, where did we lose it? If you still have continuity from the hot blade all teh way to J35, move the probe to J36, still have continuity (Including the resistance of the winding)? Now check continuity at the netral pin connection on the back of the IEC. Still continuity? Then you should also have it at the remaining blade of the power plug.

    Or clip one probe to the neutral blade of the power plug and trace it step by step for continuity up through the back of the IEC, to J36, to J35, to the switch, to the fuse golder, to the back of the IECC, etc. Just the same thing we did, but from the other direction.

    Have you had the board out? I think we mentioned early on that cracked solder under the IEC terminals is all it takes to leave the amp dead.

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    Don't forget the joker g1's Avatar
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    Quote Originally Posted by Enzo View Post
    Have you had the board out? I think we mentioned early on that cracked solder under the IEC terminals is all it takes to leave the amp dead.
    Or a bad solder connection on the board mounted fuse holder.

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    Lifetime Member Enzo's Avatar
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    Exactly, and that is the point of testing through teh circuits as I described rather than just checking the parts. The IEC or hte Fuse holder might be perfectly fine parts, but what matters is that they are well connected into the circuit. A cracked solder joint is the same to the amop as the part not being there.

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    Old Timer olddawg's Avatar
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    Quote Originally Posted by g1 View Post
    Or a bad solder connection on the board mounted fuse holder.
    Or the holder is not "gripping" the fuse. Or it's the wrong diameter fuse. In any event something is open. I've removed a lot of fuse holders and replaced them with a soldered in pigtail fuses in my time.

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    OK, do it this way, plug a cord into the IEC, but not into the wall. Meter on resistance. Clip one meter probe to the hot blade of hte plug. Verify continuity to the fuse holder. We are testing one half of hte power cord so far, now with power switch set to on - but still not plugged into the wall - Do we have continuity from the hot blade to the power switch? Yes The other side of the power switch? Yes and finally all the way to the primary wire, J35.Yes COntinuity all the way? If not, where did we lose it? If you still have continuity from the hot blade all teh way to J35, Yes move the probe to J36, still have continuity (Including the resistance of the winding)? Yes, about 5 ohm from the wire coming out of the transformer to j36 Now check continuity at the netral pin connection on the back of the IEC. Still continuity? No Then you should also have it at the remaining blade of the power plug.

    Or clip one probe to the neutral blade of the power plug and trace it step by step for continuity up through the back of the IEC, Yes to J36, no to J35, No to the switch, to the fuse golder, No to the back of the IECC, etc. Just the same thing we did, but from the other direction.

    Have you had the board out? Not yet, thats the next step I think we mentioned early on that cracked solder under the IEC terminals is all it takes to leave the amp dead.

    Quote Originally Posted by Enzo View Post
    OK, do it this way, plug a cord into the IEC, but not into the wall. Meter on resistance. Clip one meter probe to the hot blade of hte plug. Verify continuity to the fuse holder. We are testing one half of hte power cord so far, now with power switch set to on - but still not plugged into the wall - Do we have continuity from the hot blade to the power switch? Yes The other side of the power switch? Yes and finally all the way to the primary wire, J35.Yes COntinuity all the way? If not, where did we lose it? If you still have continuity from the hot blade all teh way to J35, Yes move the probe to J36, still have continuity (Including the resistance of the winding)? Yes, about 5 ohm from the wire coming out of the transformer Now check continuity at the netral pin connection on the back of the IEC. Still continuity? No Then you should also have it at the remaining blade of the power plug.

    Or clip one probe to the neutral blade of the power plug and trace it step by step for continuity up through the back of the IEC, Yes to J36, no to J35, No to the switch, to the fuse golder, No to the back of the IECC, etc. Just the same thing we did, but from the other direction.

    Have you had the board out? Not yet, thats the next step I think we mentioned early on that cracked solder under the IEC terminals is all it takes to leave the amp dead.

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  26. #26
    Senior Member TimmyP1955's Avatar
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    Any time there's a mains issue and there's a PC mounted mains IEC, its solder connections are the first thing you check after the fuses have been confirmed good. (And it's a good idea to check them even if everything works - I've seen several that we on their way to failure.)

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    Lifetime Member Enzo's Avatar
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    You have continuity from the hot power blade all the way through the transformer to J36. You have a break in continuity between the neutral IEC pin and J36. Again, MOST LIKELY bad solder on the IEC connector.

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    Education is what you're left with after you have forgotten what you have learned.

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    Quote Originally Posted by Enzo View Post
    You have continuity from the hot power blade all the way through the transformer to J36. You have a break in continuity between the neutral IEC pin and J36. Again, MOST LIKELY bad solder on the IEC connector.
    hey guys just wanted to give you all an update. finally got the board out, saw there was indeed a cracked solder joint where the iec goes to the board, reflowed that and another 2 that looked questionable.

    Boots up and sounds awesome! Didn't really check the bias yet (even though i shouldve) kinda got caught up in it actually working but the thing sounds mean, played it for about 2 hours fine and dandy. No burning smells or hot transformers, no redplating, extremely quiet even maxing the gain this thing is a beast.

    Only strange thing is the yellow LED light doesn't want to stay on the ryhtm side, it blinks/goes back to the red lead LED, but it definitely changes channels just fine. I was thinking of runnin this with just 2 of the 6l6s too, should be fine I would imagine as it's a push pull, but I'm also not sure what to look for when a push pull system wouldn't be fine to remove 2 and half the ohms.

    Thanks for all your help everyone , & you are indeed an all-knowing wizard, Enzo, you knew exactly what it was.

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