The Amp Garage

RPM... bit type and feed pressure, and depth setting. I'd try a faster speed... gentler feed and a fresh bit. The other thing that happens is that its easy to make assumptions about securing the work on the machine bed. the bit can pull the work up... and the bit can cup... with repeated work a hole...

Ohh jeeez. Still surprised its not a cockup and works and sounds nice despite how rough the appearance. The problem has become how to get the two channels to play nicely together. I found examples resistance mixing in very early fenders. The volume pot. is turned around with input on the control wip...

Fender Bassman modded to Marshall JCM lead master volume.
Point to point on tag strip. It works well much to my surprise.
Some bit still to finish. The amp came to me half cooked and
Half modded... Bias wacky with cooked tubes and screen grid resistors.

Wouldn't be using it on hi volts... To observe ac signal. A blocking cap can be used to view ac ripple on a dc supply. About the same as using a software scope on a computer. I got lucky and inherited a Tektronix 2232 after cooking a B&C on hi V thinking it was within its ratings... I proceed with b...

I was looking up scopes thinking of the tools
that would need for a series of beginners
circuits and found this.

www.adafruit.com

Vert cute.

thought this might fascinate

http://www.americanradiohistory.com/Rad ... _Guide.htm

Im always digging, its the oldest resources that provide practical solutions.

Un-expected resolution... The problem was heater hum. I like old octal base NOS tube types. But these come with a strong likelihood of heater cathode leakage. So the focus became the heater... Floating the 6.3 fil., hum dinger, And DC heater supply... Etc... Nothing worked, which was a surprise... E...

Oky... Reworked the pre towards recommend layout considerations. Attention to wire placement and high impedance stray capacitances.... For example, one of the grids of a 6sl7 is adjacent to the heater on the socket. Use the other one.... Much quieter and better perfoming amp. Now I can very clearly ...

Yes, but its been remarkably stubborn. Trying to use old tubes In as old of a way as possible. Its just the first half of the pre tube. If dc heaters dont help ill be looking very closely at layout. Very very finicky. Im useing 6sl7 6j5.. Amp is nearly silent Other wise. Im assuming the junction of ...

Looking for a quick stupid simple DC solution for one tube. I'm noodling with a 6sl7 zero bias stage,.. grounded cathode. Great tone but very prone to hum. I can get away with running the entire pre series at 12 v, less current, but a solution that takes less space than a voltage double'r and filter...

Your not wrong of course. This is most certainly a ballpark method that can not really give you a valid trans-conductance figure. But it can give you a practical circuit measurement under static conditions, a quick double check with a measurable observation. I think it works in this case because of ...

So... I'm working a rig an goin to her for hum an buzz. Its a 50 w P-P with 6l6 and one of my goals was to explore the early designs that have the screen grids tied together. No screen grid resistors. I was swaping power tubes going thru the bench spares. I noticed that one pair 6l6 had alot of hum ...

Picked an old JAN UHF receiver.

The output driver is 6aq5 SE with a 4k / 600ct. Opt.

I was thinking a tube pre and line driver, it just too clean not to use.

Any thoughts ?

That's a red coil bobbin on the input assembly.
And, a yellow coil bobbin on the output assembly.

Im looking to source an "FC" tank other than the more common "FB".
"F", is input impedance... 1475/1926 ohms.
"C" is output impedance... 10k/12k ohms.
Type "4" or type "9" respectively.

Cheers