The Amp Garage

martin manning wrote: ↑Sat May 18, 2024 5:43 pm No slight intended, I just thought it made an interesting plot.

Cool.

When the voltage drop across the MOSFET is larger, the voltage on the tube plate is smaller. When the voltage on the tube plate is smaller, the tube draws less current. So when the drain-to-source voltage increases, the drain-to-source current decreases. Let's graph that: MOSFET Dissipation 1.JPG T...

I will remove that fuse. There is already a fuse in circuit. I am also going to move the green wires back to the indicator lamp. It is a clear look and that less things to fail. I already bought a replacement power cord. I found the attached diagram to install a 3 prong power cord. I would like to ...

Kagliostro wrote: ↑Thu May 16, 2024 7:22 pm p.s.: Do you mean that also power is divided in two parts so if one Mosfet is subject to 10W dissipation having two mosfet each one is subject to 5W dissipation ? ( 5W + 5W = 10W)

Yes.

Should I leave the thermal fuse ... I would think that you, as a loyal, patriotic, flag-waving, queen-loving Canadien, would want to be in compliance with your CSA. I mean...I mean...Those fine people have fought tooth and nail to prevent lousy, stinking, bottom feeding corporations from incinerati...

I had heard (and I don't fully understand why) that the Mosfets actually produce the most heat around the middle of the reduction area. They had said it was actually easier for them closer to full voltage as well as the more extreme bottom 1/3 voltage setting. Can someone verify or explain this? Wh...

akabek wrote: ↑Thu May 16, 2024 3:22 am I pulled the post with the white wires to get a better pic. I am not sure if it a resistor on there.

That's a thermal fuse. Fender put those in there for amps sold in Canada.

Those MOSFET's have wild variation in their Gate Threshold Voltage. If a parallel pair were not well matched, I could see one conducting most of the current while the other is barely turning on. To make matters worse, the Gate Threshold Voltage decreases as the temperature rises making the conductin...

load line is tangent to the 100% Pa max curve ? Help me see that. You're going to have a hard time seeing that because the JJ curve is actually for 12W instead of the 14W label. With 450V and 12W, R comes out to 16.875k so that 4.219k would be used for the class B load line. The line will run from ...

Here is a straightened-out Concert Series schematic. There isn't really a Concert II, but everybody uses that designation because all of the other ones are "II's".

... but what the hell are those boxes with the little plus sign? Those are VTL5C1 light dependent resistors (LDR). They have an LED and a photocell inside them. When the light from the LED hits the photocell, the resistance of the photocell plummets. VTL5C1-5C4 PerkinElmer.pdf Fender Deluxe Reverb ...

Hello, I'm in the planning stage of building an amp with the foundation being the 5F6-A. I've got a great power transformer that I'm going to use, however it doesn't have a bias supply tap. I have Merlin's book on both preamps and power supplies, but I'm still struggling to understand the precise s...

The bias is connected to the oscilator circuit. Just trying to understand what is happening here and why. Sometimes the neon lamp in the LDR unit will remain lit when the LFO stops unless you put the LDR driver tube into cut-off. If the neon lamp remains lit, the Intensity control acts like a volum...

So I built the thing and got an open loop gain of 1.824 with no regard for significant figures. Using this in the closed loop equation above, I calculated a closed loop gain of 1.766. The observed closed loop gain was 1.774, pretty close. The observed gain reduction was 1.774/1.824 = 0.973 = 0.24dB....

I'm not really following much of that, so I took off in my own direction. The cathodyne already has 50% NFB, 30.2dB of gain reduction, before the 3.3M local NFB thing. CF 11 PNG.png So I used the gain without the 3.3M local NFB as the open loop gain. I used this cheat sheet for the closed loop gain....