Monkeymatic Tamalpais - build in progress

[xtian]

This build was inspired by a trip to the flea market. I've made friends with Bill, a crusty old engineer who sells bullets among other things. He's got binders full of hand-drawn schematics, and he's more than willing to talk your ear off. But he doesn't internet, which is a shame. He's got a lot to share.

Anyway, he's sitting on a huge cache of vintage parts. House full. Storage space full. Last week he brought me an unused Woodward-Schumacher OT, 6k for about 40 watts. Said he has 100 more. There followed a discussion of the stupid high voltages Fender puts on the plates in their modern amps, and how sweet a pair of cathode-biased 6L6 sound at 350v. Thus, this build.

As with all of my for-me builds, using parts on-hand and already paid for is the word. So my PT is a Hammond 272JX, which will put about 420 on the plates, but I'm going to implement the MOSFET B+ reducer we're talking about over here.

A first draft (and unfinished) layout is attached. Princeton style Treble/Bass tone stack (it's my favorite), volume, presence.

The 5v winding (yellow) is connected to a voltage doubler (already breadboarded and tested) that will provide 12v for a string of RGB LEDs ($16 for a five-meter string with IR remote!).

First question: A full-wave recto with capacitor input will give about 420v B+. But a choke input will drop the B+ to 270. What about a CLC (cap, choke, cap) input? Same as cap input, 420?

[Phil_S]

100 WS 40W OT's? I smell a business deal here.

Really, for cathode biased 6L6, don't you have a 5B6 yet? Everyone needs one of these.

Sorry, your CLC question is beyond my expertise. I suspect it is going to be less than 420. I suggest Duncan's PSU will answer your question. It requires some info you didn't provide. Just a note on this software. For years I was baffled by it until I found the sample files. The samples are models that have enough variety including tube rectifiers, chokes and whatnot. You've got to find the right sample when you start a design.

[Invertiguy]

A CLC is still a capacitor input supply, since the choke is after the filter cap in the power chain, so the output voltage would be 1.4x the RMS input voltage.

[naciketas]

+1 for above and maybe you could find usefull the following link:
http://www.hammondmfg.com/pdf/5c007.pdf
for future reference.

[xtian]

+1 for above and maybe you could find usefull the following link:
http://www.hammondmfg.com/pdf/5c007.pdf
for future reference.

Thanks. I refer to that often. But didn't explicitly answer my question.

[Phil_S]

I'm not certain I did this correctly with Duncan's PSU. At the first filter cap (4x 47u parallel/series = 47u) B+ is:
CLC 393
LC 273.
The LC simulation is spot-on to the rule of thumb, in this case 600/2.2.
CLC is close to Phil's rule of thumb, in this case 300*1.4*96% = 403. 96% is the estimate of loss at 4%.
Conclusion: CLC is a cap input circuit.

[xtian]

I'm not certain I did this correctly with Duncan's PSU. At the first filter cap (4x 47u parallel/series = 47u) B+ is:
CLC 393
LC 273.
The LC simulation is spot-on to the rule of thumb, in this case 600/2.2.
CLC is close to Phil's rule of thumb, in this case 300*1.4*96% = 403. 96% is the estimate of loss at 4%.
Conclusion: CLC is a cap input circuit.

Agree. Another user said, same as cap input, except choke will drop DC when it draws current, based on its DCR.

Thanks!

[Phil_S]

...choke will drop DC when it draws current, based on its DCR.

I guess that accounts for the other 10 volts. I accepted the default DCR in the PSU, so yours may differ.

[matt h]

(deleted)

[xtian]

Updated schetchy. Ordering parts.

[xtian]

Board build and populated.

[Dr-Joned]

Your tools look like mine. Lindstrom and Xcelite dikes. I started using the Lindstrom back in the 80's and those are some of the smoothest, finely crafted cutters around.

[xtian]

The Lindstrom nippers are brand-new. I tried using the three dollar tools at Harbor freight but they actually do suck. And I couldn't imagine spending 50 or $60 on a single pair of clippers. The Lindstrom's were just right at about 30 bucks, and they feel great.

[xtian]

I built the MOSFET B+ dropper. The Zener that sets the drop is in a socket for easy swapping (27v Zener in there now).

[xtian]

Need comments on my proposed grounding scheme. See attached.

I have only one connection to the chassis, near the input jack. Heaviest black line will be a heavy copper bus wire.

Best place to ground HT CT after it runs thru my B+ reducer?