The Amp Garage

Math in public

I meant to write 1.41 x 2 = 2.8, shouldn't it be 3 x 1.41 = 4.2?

[EDIT: I changed my error of 2.14 to 1.41] Since we are on the topic of equivalent feedback, my understanding is when moving the feedback tap from the 2 ohm tap to the 4 ohm tap to keep the feedback the same you would increase the feedback resistor value by 1.41 (sqrt of 2), and do it again from 4 t...

Cool, glad you got it working. Nice catch bcook.

Ok so I disconnected the 100k slope resistor of the tone stack and the 250pf tone stack cap from the 100k resistor feeding the tube plate and just as you say, the amp is still playing signal. No, your pots are most likely ok, you have a major wiring mistake. The two 220k resistors just before the p...

If it's not the external ground wires then your pots' must be bad. I'd test them and replace them. The pots are variable voltage dividers and they're not functioning as dividers at all--no signal is being shunted to ground.

Take a look at the schematic. Since the signal is getting through the tone stack and volume pot it MUST be their grounds. Take an alligator clip and clip it from the chassis to the volume pot #1 ground pin and give that a try. [img:2058:1568]http://www.thevintagesound.com/ffg/schem/deluxe_reverb_ab7...

Check the ground connection(s) to the volume and tone pots. Lift the ground and they will be ineffective. If you are using a ground bus make sure and get your bus wire hot before you start to solder a wire to it. If the grounds look good I'd still re-flow the connections as the symptoms are perfect ...

The 5F6A Modification web page is complete with graphics now: https://robrobinette.com/5F6A_Modifications.htm Here's a sampling of some of the mods' diagrams: Negative Feedback Switch [IMG:450:803]https://robrobinette.com/images/Guitar/Bassman/Bassman_Feedback_Switch.png[/img] Adjustable Bias [IMG:6...

Looks like the amp was on a desk with tubes horizontal so heat would not rise into the chassis?

Yes. The shot is vertically downward into the chassis. I had to stand on a bar stool to get the camera high enough to get the whole chassis.

Are the power tube plates really hotter or is what you seeing really just the larger plate structure of the those tubes?. Ocassionally, when burning in a build I will use my Fluke IR gun to measure the temps of the OT tubes. I'm just going by the larger and whiter white (hot) spots on the power tub...

I have a Seek Thermal Imaging camera for my Android phone so I thought I'd take a pic of the 5F6A '59 Bassman chassis at idle temperature so we can see what's hot and what's not. I was surprised to see the power tubes are hotter than the rectifier tube. [IMG:831:430]https://robrobinette.com/images/G...

Here's a short sound clip of Deluxe Micro #3 using a Tele's neck pickup and 12" Tester speaker:

https://www.youtube.com/watch?v=aD42Z26Ua3A

Tele neck pickup playing through a Tester 8 inch speaker in a completely open back cab.

We finally have our first clip of the Deluxe Micro (hopefully more to follow). Keep in mind it was recorded using an iPhone but it still sounds really good. This is from Deluxe Micro #3's builder:

https://www.youtube.com/watch?v=aD42Z26 ... e=youtu.be

sliberty wrote:Have you posted clips of any of the Micro builds?

Not yet but a guy that built a Deluxe Micro says he'll post some clips shortly, hopefully today.