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

[Enzo]

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.

[trip]

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.

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,

Now from the IEC connector, the neutral goes directly to J36.

the connection reads continuity,

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?

[olddawg]

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.

[Enzo]

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.

[trip]

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?

[Enzo]

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.

[g1]

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.

[Enzo]

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.

[olddawg]

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.

[trip]

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.

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.

[TimmyP1955]

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.)

[Enzo]

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.

[trip]

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.