I can read schematics, no problem figuring out how to wire this for 120VAC input, getting 375 per leg out into rectifier, 5 VAC for rectifier filament, 6.3 VAC for input tube heaters.
Question is, what to do with all the REST of the wires.
I’d like to clear out all the excess spaghetti from inside my amp build (Skunkie Designs 300b SE) and was thinking about trimming all unused wiring back into the transformer case, putting on some heat-shrink tubing and just running leads I need.
Any other ideas (that do NOT involve buying a 274BX)?
I bought this as it was on Stephe’s BOM and other folks recommended it over the EDCOR (which Stephe eventually replaced as it shorted out), now I have the upper plate of my amp drilled to fit the 374 and don’t want to spend the money/lose the money for the smaller transformer and less wiring.
Thanks in advance.
Norm
Question is, what to do with all the REST of the wires.
I’d like to clear out all the excess spaghetti from inside my amp build (Skunkie Designs 300b SE) and was thinking about trimming all unused wiring back into the transformer case, putting on some heat-shrink tubing and just running leads I need.
Any other ideas (that do NOT involve buying a 274BX)?
I bought this as it was on Stephe’s BOM and other folks recommended it over the EDCOR (which Stephe eventually replaced as it shorted out), now I have the upper plate of my amp drilled to fit the 374 and don’t want to spend the money/lose the money for the smaller transformer and less wiring.
Thanks in advance.
Norm
Yep, that should be fine...just make sure you insulate the unused wire ends properly
Well, got things going here, power supply is wired in, but I have a problem.
Question; when is Ohm's law just a suggestion?
From a SkunkieDesigns @stephe plan. I already posted this on that forum.
So power supply is wired, powered it up and I'm getting 478 +VDC at B+ on either feed.
Same voltage out of the rectifier tube + out.
In SOME schematics I've seen a 100 Ohm 10 watt resistor added there (prior to any capacitors), so I ran some numbers and came up with a dropping resistor value of 240 ohms (478 to 430 VDC drop) at a nominal 0.201 Amps (what Hammond advertises the output as at the HV red leads). Took a pair of 470 ohm resistors (close enough) in parallel and clipped one side to B+ for one channel to compare.
Nothing. No difference, same voltage output as the NON-resistor side.
It's been 40 years since physics, algebra, trig, calculus but this is simple arithmetic, not complicated derivitives or something, but NOTHING?
Should I put the resistor UPstream (at the filament B+ side of the rectifier) FIRST?
How/why should that make any difference?
Did I misread Hammond’s transformer output? Is that 0.201 Amps per SIDE of the HV portion? Like red-yellow to red is 375 vac at 0.201 Amps PLUS the other side’s output?
Thanks in advance.
Oh, BTW, that’s a “chicken stick” capacitor draining tool that used to be a ballpoint pen. Works great.
Question; when is Ohm's law just a suggestion?
From a SkunkieDesigns @stephe plan. I already posted this on that forum.
So power supply is wired, powered it up and I'm getting 478 +VDC at B+ on either feed.
Same voltage out of the rectifier tube + out.
In SOME schematics I've seen a 100 Ohm 10 watt resistor added there (prior to any capacitors), so I ran some numbers and came up with a dropping resistor value of 240 ohms (478 to 430 VDC drop) at a nominal 0.201 Amps (what Hammond advertises the output as at the HV red leads). Took a pair of 470 ohm resistors (close enough) in parallel and clipped one side to B+ for one channel to compare.
Nothing. No difference, same voltage output as the NON-resistor side.
It's been 40 years since physics, algebra, trig, calculus but this is simple arithmetic, not complicated derivitives or something, but NOTHING?
Should I put the resistor UPstream (at the filament B+ side of the rectifier) FIRST?
How/why should that make any difference?
Did I misread Hammond’s transformer output? Is that 0.201 Amps per SIDE of the HV portion? Like red-yellow to red is 375 vac at 0.201 Amps PLUS the other side’s output?
Thanks in advance.
Oh, BTW, that’s a “chicken stick” capacitor draining tool that used to be a ballpoint pen. Works great.
Attachments
+1 on Stephe's response. I use a 274BX and 5AR4. Unloaded I get about the same voltage on B+ as you have on your schematic. After loading it down with the tubes in the active circuit it dropped about 60V at the first filter cap. After my pseudo dual PS, with the chokes similar to your PS chokes, it is down to 400 to 420Vdc.
You are going to use 300B tubes? If you pull 60mA or so the voltage will come down. Then see if you are still running high then look at the dropping resistors. I am guessing your are unloaded when the voltage stayed the same adding in 470 ohms. The 470 ohm resistors should be dropping more than 30V. Just an ROM guess.
You are going to use 300B tubes? If you pull 60mA or so the voltage will come down. Then see if you are still running high then look at the dropping resistors. I am guessing your are unloaded when the voltage stayed the same adding in 470 ohms. The 470 ohm resistors should be dropping more than 30V. Just an ROM guess.
Yeah, without a load adding resistance won't change the voltage at all. With some amps you have to be careful running them at full input voltage with no load as the voltage can blow past the cap ratings!
In the immortal word of Homer Simpson, “DOH!”
Amazon just had Morgan Jones’ book on sale and I already own a copy of EJ Jurich’s book on tube amps… guess I should start READING the things.
The thought HAD occurred to me about “loading” but with no way yet of testing that and wanting to get this right step by step I thought to ask.
Thanks again.
Amazon just had Morgan Jones’ book on sale and I already own a copy of EJ Jurich’s book on tube amps… guess I should start READING the things.
The thought HAD occurred to me about “loading” but with no way yet of testing that and wanting to get this right step by step I thought to ask.
Thanks again.