Tube Amp Archive

Hey everybody! I replaced the power transformer with a Classictone 40-18005, replaced all the components on the rectifier board, and some of the resisters that were far off spec, and it's working great. I'm using the taps to ground as opposed to the 100ohm resister thing. I also created a ground hub...

`ok, so i'm going to replace the PT, and while i'm at it, i want to rebuild the bias/rectifier board and replace the bias pot. the only thing that isn't listed on the schematics, is the diode type. I've seen some blackface twin reverb clones that use a 1A 1000V diode, but I can't find anything refer...

ampgeek wrote:That applies ONLY to the filament CT connection.

The HV CT should remain connected to ground.

Good luck,
Dave O.

OK, so they cut two wires off, but only should have removed the filament CT?

the resiter on the bias board is brand new (470-2W) specs only call for 1W. All of the diodes have been tested and are functioning correctly. I may just go out out on a limb and drop the $$ for a new transformer. Seems like it's a pretty strong limb at this point. Does anyone have opinions about the...

I'd like to see a couple of shots of the PT end of the amp showing all the PT leads and where they go. The bias supply looks odd: where there should be a reversed diode, there appears to be a 1/2W resistor (and a toasted one at that). The PT wire going to the 1W 470R (I think) looks red/yellow to m...

Firestorm wrote:I see something scary. There's a metal washer on the left-most screw for the circuit board that looks like it's about 1mm away from the HT connection. That's going to want to arc.

Thanks, I will locate a smaller washer!

no, i have not changed anything.

oops, tried to attach aif

Well, it was working without the CT before, so I'm not sure. I understand if you all want to shoot me by now, but if you feel like it, I'm attaching some audio of the bad noise and what happens when power is switched off. BTW I just finished my vibrolux clone build, and it's amazing. I think I have ...

attaching some pics[/img]

let me know if there is something you would like to see better.


I'm going to post a recording next

That's interesting about the tap, thanks. I'm going to post some pics tomorrow.

If you're measuring 715V between the reds, but nothing from either red to chassis, I would suspect the center tap is not connected to the chassis. This is true. It appears that someone before me cut off the center taps. I'm guessing this was done when the power cord was changed to 3 prong. Seriousl...

yes. on the 200v AC setting on my meter, using alligator clips on the leads and chassis.

that was just across the leads

leads to ground looks strange:

Red #1 = .5

Red #2 = .2

bias tap = 0

yes, sorry - bias tap

thanks for bearing with me!