Tube Amp Archive

I'm interested how you like your CF mod. To be clear, anything drawn by me is more of a report for my own learning purposes, not anything to be trusted. I'm serious. I am only a student here. Make sure you get advice from more experienced builders. That said, plate resistor values are only meaningf...

I did the Trem-O-Nator mod. Works great. Thanks Sluckey. The mod freed up 1/2 an 12AX7 so I could do the CF mod. I also finished the CF mod that Viperdoc drew out. I used the attached schematic. Some of the plate resistors are 200k instead of 100k. How can I test it to make sure it's working? I don'...

Adding the Layout with the Trem-O-Nator mod for the DR.
Ignore the edits on the right side. I started the mod to add the CF

First step in the mod is to do the Trem-O-Nator Mod to the DR to free up 1/2 of a 12AX7 to use as the Cathode Follower.
Of course I need to change to the Vactrol VTL5C1

I've edited the Weber schematic for the DR. See any problems?
I'll add the layout mod when I finish it.

I'll probably give it a shot too.

Fixed--errant .0022 cap, incorrect tone slope resistor value. Might need new glasses. AB763 LEAD CH 3.0.pdf Did you ever add this to your DR? Results? I may try this with the FET just to see how well it works. Looks like I need to rewire to get input--> gain-->volume-->gain--> CF -->TS -->PI Afterw...

Good news to hear! When I do the Trem kill mod in silver face Fenders with a master volume I disconnect the gain boost on that master volume and use that switch section for the Trem mod. I then use that shelled cable removed to replace the non shielded feed from both channels to the 220k mixers. I ...

That Weber switched pot is rubbish, at least mine was, the switch failed after a few uses. It did me a favour really, the trem off tone / boost was too much. I was much happier with a 100k lin trem intensity pot. That provided a couple of dB boost compared to a 50k pot, but without being excessive....

I isolated the channels one at a time and the problem is still present in both channels. I isolated each channel at the junction of the mod. Something else I noticed. I switched the trem on and then off again to get the boost. After about 30 seconds, the output dropped back out. This hasn't happened...

Stevem wrote: ↑Thu May 06, 2021 9:31 pm If you uncouple either channel one at a time does the issue still manifest itself?

That's what I plan on doing later today. Thanks

Mod schematic- There is another 220k between C15 and the same node

Switch closeup

Weber schematic
EDIT: Sorry, had the wrong schematic

The mod can be found here:

https://robrobinette.com/AB763_Modifica ... Reverb_Mod

What tube are you referring to that isn't conducting? The preamp tube?

This picture was taken before the amp was finished.

Mod pic:

First real post. I built a DR from a Weber kit a year or so ago but I didn't notice this problem until recently. I included the mod for trem and reverb on both channels from robinette's website. (0.047uF cap and 220k resistor to isolate each channel) This Weber kit includes a built in switch on the ...