Eden WT-300 Heater problems

[rf7]

I'm going crazy trying to figure this one out. The tube filament does not light up and is sitting around -2Vdc. Initially I found that D10 and D11 were shorted. I replaced them and I have low heater voltage. With the tube pulled, everything sits where it is supposed to be. There is -26Vdc coming onto the preamp PCB, which gets split down to -12Vdc. As soon as I plug a tube in there, the voltage drops way down.

I used an external DC supply to feed -26V onto the board and the heater voltage held up, pulling 130mA, which seems reasonable. So that points me back to the power supply, and there's not much there to look at, just a diode and a resistor. I've got all the other connectors unplugged, so it's only running the preamp PCB. I replaced that power supply diode, but nothing changed. I even pulled the secondary of the PT and fed the amp from my variac and the heater voltage still dropped.

Any ideas?

Thanks in advance!

[nosaj]

heater issues

Check this out

http://music-electronics-forum.com/t16561/

Make sure if you replaced the fuse that you didn't put it in upside down. By that I mean some fuse holders are wired for 110v or 220v and by flipping the fuse holder around it makes contact with a different winding.

jason

[Enzo]

One of those diodes was a zener, did you use the right one?

Note the power supply doesn;t just hit the tube, according to the schematic I see, there is a TIP32 transistor handling current into the heaters. The didoes just establish a voltage reference point for the base of that transistor. If the voltage across the tube collapses as soon as the tube is inserted, then it sounds like the supply cannot provide the current. SO either the supply has failed or the transistor is not conducting.

A bad transistor maybe. Monitor raw supply. Is the volotage across C35 holding up or collaapsing? If holding up, try a new transistor. If it collapses, then perhaps ther is a basic issue with the raw supply.

[rf7]

Check this out

http://music-electronics-forum.com/t16561/

Make sure if you replaced the fuse that you didn't put it in upside down. By that I mean some fuse holders are wired for 110v or 220v and by flipping the fuse holder around it makes contact with a different winding.

jason

That was the problem. The fuse was put in upside down. Oh well.

[nosaj]

Actually that's great if you didn't spend any money on it. Sometimes it's so simple you just can't believe it. Anyways that was figureed out with a google search I by no means am a tech yet, just have a good handle on how to use my resources and filter out a lot of junk. Sometimes I hit sometimes I don't but that's waht experience is making lots of mistakes.

jason