The UniWreck Lives!!!

[sliberty]

The UniWreck Lives!!!

I just discovered that my TW, completed last night at about 12:30am, works! I love it when a plan comes together.

I have only played through it for 2 minutes so far, so I won't comment on tone just yet. I found that a couple of switches are wired backwards (power and bright), and there are some noises that I'll have to deal with, so I still have a few tasks ahead of me before I really give it a work out. But, I do have a few issues to resolve right away.

1. I powered it up through a current limiter like the one that Gerald Weber describes in his books and his video. Its a 100 watt light bulb in series with the amp. When the amp first turns on, the light starts out bright, and then gets very dim. I think that's the way it should behave, but would love it if someone would confirm that for me.

2. My power indicator is a 120V lamp (salvaged from the Univox I started with). While connected to the current limiter, the lamp dims when I play, and glows normally when I don't. Whats up with that? When I am not connected to the current limiter, the power indicater doesn't dim when I play.

3. I was innitially red-plating (although oddly, on only one of the two EL34's. I set the bias supply to -33 VDC like the schematic shows, and the red-plating seems to have stopped. I do have rear panel bias probe jacks and a rear panel trimmer, but for some reason, my meter is not measuring anything at those probe points (on the order of .003 VDC) Any ideas? Bad meter? Wiring error???

4. There are noises (some hum and buzz which change based upon the tone control settings), but I'll get to those after dealing with the more immediate problems.

I am thrilled that the amp fired up, but a little frustrated with the remaining issues since I have so much to learn in order to fix them. I'll post some voltage readings soon (they may be a bit low), and some other findings for your opinions and help.

Thanks all,
Steve

[Buschman]

Yes the 100 watt bulb should be brighter at power on. That is when your amp is drawing more current. It dims after warmup-after the caps get a good charge on them. You want a dim bulb at idle.

[Elcabong]

2. My power indicator is a 120V lamp (salvaged from the Univox I started with). While connected to the current limiter, the lamp dims when I play, and glows normally when I don't. Whats up with that? When I am not connected to the current limiter, the power indicater doesn't dim when I play.

It is normal; since you are limiting the current, you are effectively "starving" the amp. It cannot get all the current it needs.

3. I was innitially red-plating (although oddly, on only one of the two EL34's. I set the bias supply to -33 VDC like the schematic shows, and the red-plating seems to have stopped. I do have rear panel bias probe jacks and a rear panel trimmer, but for some reason, my meter is not measuring anything at those probe points (on the order of .003 VDC) Any ideas? Bad meter? Wiring error???

Your probe jacks should connect your meter across the 1 ohm resistor that goes from pin 1&8 and ground. Be sure your meter is set on range suitable for DC millivolt reading.