The Amp Garage

I worked on a Holland "Lil Jimi" several years ago. The pots weren't making good contact with the oxidized aluminum chassis! Same as you! So I roughed -up the metal and applied some non-ox pastes. What a difference it made!

Hi Folks, I am so comfortable with Fender Blackface style clean tones, have built them, and used them for years. For those of you you who like Dumble-style clean tones (i.e., amp overdrive not engaged), I would be very curious to hear which of the architectures of which you enjoy the clean tone, and...

A fuse is a better defined protection device - use a fast blow fuse (as there is no normal in-rush or short-duration high current condition above max tube current draw). Adding a 150V 5W zener across the fuse is an additional measure that can save the tube when the fuse has blown for other reasons ...

A fuse is a better defined protection device - use a fast blow fuse (as there is no normal in-rush or short-duration high current condition above max tube current draw). Adding a 150V 5W zener across the fuse is an additional measure that can save the tube when the fuse has blown for other reasons ...

labb wrote:The Crate Blue Voodoo fuses the cathode. Take a look a BV-60 schematic for the power tubes

Ah...indeed it does...thanks P.

Signal grid and suppressor grid* first, then cathode (but could be plate as well, although that is not likely to cause meltdown), depending on how the screen grid (and the screen grid support rods) start to melt and flex inside the electrode cage. * or beam plate (in a tetrode) Seems like a cathode...

Hi Steve, thanks for your input.
I guess what I am trying to first understand is exactly what happens when there is a screen short. Where is the screen shorting-to?

I like the idea of cathode fuses since the voltages are low there.

Is the screen grid shorting to the cathode? Seems like it must be. If it was shorting to the grid, then the grid leakage resistors are large enough in value to limit the current to a degree that the screen grid resistors would not fry. So then, my feeling is that fusing in between the power tube cat...

the inner conductor of this coax is way thinner than 22 AWG. I am concerned about reliability in terms of mechanical reliability, not current limits.

the inner conductor of this coax is way thinner than 22 AWG. I am concerned about reliability in terms of mechanical reliability, not current limits.

I have a batch of RG 187...the inner conductor is SO thin...makes me worried about long term reliability. What are you folks using for Coax that has a reasonably low capacitance per foot, but also has an inner conductor that is robust. I had some RG 187 from Apex Jr..loved it.. Then I got another ba...

Mercury magnetics makes a clone of an old Jim Kelley 4x6V6 OT.
I think it's called the: JIMK-O

The amp I played it in was a Fargen Blackface style amplifier and I thought it sounded very good.

good luck!

P.

Yep, 2K resistance solder joint to one sockets pin-7

Customer brought his 100W JCM 2000 into the shop. One of the power tubes isn't heating. I swap tubes, the problem stays with the one socket of interest ( "V6"). I take out the tube from that socket, stick my multimeter probes into pins 2 and 7 of the socket and measure 7V RMS AC. Looks about right. ...