JTM45 GZ34 Diode Rectifier Schematic Anywhere?

[pete_g]

I'm looking to make a solid state diode rectifier for my JTM45 head, as I like the attack of the SLP amps, rather than the sag you get from a valve one. I talked to Tim Lovell and he said it does make a difference as well in how the valve uses the voltage in the input signal. Has anyone made one? Just want to know what diodes to use, in what direction on what pins of the tube socket, and if any resistors are involved. I don't wanna pay $60 for one already made

[brett]

Hi.  From memory my JTM60 (silicon rectifier, high voltage version of a JTM45) had 4 x 1N4007s in a standard bridge rectifier arrangement, elevated about 5mm above the pcb (60s had pcbs).  Presumably, that was for heat dissipation, though with only 0.7 V drop and tiny current (100mA max) it seems unnecessary.
So you could just use 2 x 1N4007s. Just point them from transformer to the rest of the power supply.
Although it seems wrong to go for a solid state rectifier then add resistance, it might save you from nasty problems.
Let's imagine a speaker burning out.  It goes to low impedance, then the power tubes are driving low impedance.  The tubes and or the output transformer will fail very quickly if the fuse doesn't blow very fast.  With 100 ohms of resistance in the power supply, it'll all go wrong slower. 
A 1W, 100 ohm resistor might save things in these amps.  One way that valves fail is to short from screen to cathode (EL34s do it regularly).  They'll draw 150mA and generate 75-100W of heat.   A 100 ohm, 1W resistor will either reduce the current enough to a prevent a worse failure, or it'll overheat and blow, saving other components.
One of my EL34  amps failed this way recently, to be saved by the cathode resistor and PS resistor.

[pete_g]

Is there any schematics anywhere?

[antonis]

[matt_garman]

It might be worth taking a look at the schematic for the Traynor YBA-1 (or YBA-4) amps.  (Not the "a" version.)  It looks like the YBA-1 is essentially a Bassman/JTM-45, but it is solid state rectified.  (The YBA-4 is the combo version, YBA-1 head-only.)

[pete_g]

I've heard people say to put resistors in there, others just diodes. because I'm not experienced in amplifier technology, I was hoping a simple diagram showing which diodes (and/or resistors) to put across which pins of a valve rectifier base, and follow that. I've made plenty of pedals, and did a Friedman fat cap mod and made the soldano hot mod with a 6K11 tube.  I thought I'd attempt a diode mod for my JTM45, as I prefer that direct, harsher attack of it, rather than the sag and spongy sound of a JTM45. hopefully it'll be clear, as I wanna be sure I'm getting the correct version of what's needed. Forgive my lack of knowledge