EVH 5150iii filament supply

[telejames23]

Fender EVH 5150iii heater supply issue. Don't have a schematic for this, but after running for 20 mins ac filament heater goes dead. Ironically V1 and V4 are getting dc filament voltage. Is there a separate trans winding for the rectified dc filament? I can pull the ac secondary heater supply leads off the board and ac voltage is present, once i re-attach voltage dies (but v1+4 still stay lit with dc).can anyone shed some light here?

[Enzo]

V1 and V4 are series wired heaters across the +16v and -16v. That is 32vDC for to 12v heaters. The difference is made up with a few resistors. SO unrelated to the AC heaters. These are th same 16v rails used for the ICs, LEDs, etc

DO ALL the 6vAC heaters go dark? IN all manner of amps, a common enough issue is burnt up connections. The high current of the heater supply hats connections and the solder fails or the connector fails. Also, the fuse clips tend to be heat damaged for same reason. Does just pressing on the heater fuse restore action?

You say the voltage is present on the wires when hanging in air. Put the wires on the pins on the board, now measure the voltage right on those pins, not at the tube sockets. Does it go away there? If it remains on those pins, but goes no further, you have a connection issue or solder/trace issues. If the voltage even there fails, then pull the transformer wires back off, and with power off, measure for continuity THROUGH the winding.

Remember the transformer wires with 6v come to the power supply board, through a fuse and back out of that board over to the other boards. Each of those points is potential failure node.

[Jon Snell]

Bad connection on F4, it is a 7Amp fuse. Gets too hot and goes open circuit on the board when hot.

Or P15/16 bad connection.

[Enzo]

Wow, my schematic is very different.

Fender EVH 5150-III head.pdf

[Jon Snell]

Wow, my schematic is very different.

[ATTACH]n945363[/ATTACH]

It is. My schematic uses DC heaters for the 12AX*s Would be nice if they made sure we all knew there were different versions.

Ah, mine is the 50W version.

[drewl]

Well there are several versions of this amp now, Peavey, Fender, etc.

[Enzo]

In fairness, Peavey never made an EVH5150III.

[telejames23]

So I reconnected the ac heater leads to the power board, 6volts still there. Will pull the board and reflow anything that looks cold/cracked. Still not sure which leads break out to the main board, are they the black and white? Not measuring anything there.

[Enzo]

I think black and white, it says on the schematic. You got 6v into the power board. it goes through the fuse and back out, so is there 6v on the coming out end? Measure end to end of the fuse holder. Do not push on it, just poke at the solder. A good fuse will have zero volts across, right? If you measure 6v end to end on the fuse, it is open...or not making contact with the clips. If it doesn't leave the power board, there is no point looking for it at the tube sockets.

[telejames23]

So I removed the power board, redid all solder points and still no luck. There are 4 black/white leads, 2 go to the 6 preamp tubes, another 2 to the 4 power tubes. V1 and 4, the dc filaments ok. This is a dual layer (front n back) board. I ended up pulling all 6 leads, put in an inline fuse and crimped everything. Working now. Again, no visible cold or broken solder joints, reflowing did not work. Thanks all for all the insight, have a great Thanksgiving, you folks are great!

[Enzo]

I am glad you got it going, but consider that the suggestion was to trace the voltage along to find where it went missing.