Music Man Power Supply [was Re: #102 died yesterday :( how,why]

[Bombacaototal]

I’d like to see more of those blurry pictures. Can you post a zip here?

There you go...this is where I got the close ups from

[talbany]

Here is everything I have on the Pentode. You should be able to match the numbers on the parts in the Jpeg's and cross them into the parts list and figure everything out.
BTW.If you take and use this info I want a complete layout posted here when you are finished. Kapish

Tony

[talbany]

More

[talbany]

Let me know if you need anything else?

[talbany]

Just the Facts Max.

To complete the picture I'll add some remarks concerning the "Pentode Amp".

This amp is in many aspects a "very special" variant of a Dumbleland for guitar:

It had (when I met it) a wonderful clean sound but one very different from the DL/SSS sounds you are familar with from (e.g.) SRV live-recordings. The really "clean" sounds had much of the mellow but silvery highs of a good steel string acoustic. This "clean" sound was very elegant with a less pronounced attack. It was in no way spectacular or flashy like a SSS can sound, but more of an airy, refined and cultivated kind.

To get an idea, how the cleansounds of this amps are with tremolo and a bit of reverb listen to Ry Cooders "Crossroads" track 8, "Feelin' Bad Blues". This kind of "acoustic" sound I could easily get with the Pentode amp using a maple neck strat with usual strat single coils, jazz on, bright switch on, deep switch on (? not sure, maybe off) volume around 4 or 5, treble 9, middle 7, bass around 7 (not sure, maybe around 4), presence around 7, bit of reverb, slow tremolo.

And if you turned the input "volume" past 6 (Humbucker) or 9 (single coil) and engaged the PB you had great crunch and blues sounds with just the right amount of distortion for many kinds of blues styles.

But this is for sure not the amp for someone who is a fan of the signature SRV DL/SSS sounds. But if you like the guitar sound of this "Crossroads" take, you will not find an amp better suited. Great, great blues amp it was/is.

So if one wants to clone a Dumbleland or SSS to get SRV sounds I would stay away from using the schematics Electron has posted, that I suspect anyway as not beeing very trustworthy. As far as I know, Electron never met the "Pentode amp" in real life, but derived the preamp-schematic by own conclusions from some pictures he got from someone that show the boards. And a tech, who did service to this amp, once told that this posted schematic is wrong, after what he saw with his own eyes in the real amp. So I would be cautious in regard of this schematic (as with, as far as I know, many Dumble schematics you find in www).

From a technical point of view I can add that the "Pentode Dumbleland" did not have those giant PTs and OTs you find in other Dumblelands but smaller ones that look far more usual.

Tubes and their function after what I remember what this tech told me concerning this: 2xEF (input, recovery after EQ), 7247 (reverb mix), 7025 (reverb return), 12AX7 (tremolo), 5751 (reverb send), 7025 (phase inverter), 7025 (driver), 4 x 6550A.

It did put out around 140 Watts without any distortion and had an unusual high plate voltage (output tubes) for a Dumbleland.

Nice weekend to all!

[Bombacaototal]

Thank you vey much Tony for the generosity. I had been asked by an esteemed member not so share, so I was trying to construct the information making links to the public information available. I am adding a couple of files which seem to be missing from your collection. You had a couple files which I did not have.

Let's get this one out in the world.

[Bombacaototal]

So based on the parts list this is where I am at as far as the power section and supply board. Still unsure why there are 2x 40K (5w) and also why there is no cap for the PI Driver

EDIT: schematic updated further down the thread

[Bombacaototal]

And this is my trace of the amp. I will add the power supply once it has been confirmed. I had a different approach than W. Dunham on the buffer tube. I think his might be correct, but mine as is attached

And to answer Rootz, yes the PT and OT are confirmed. You can find their part numbers on my schematic.

I am still unsure on the bias network at the PI as I am still missing 2x47K. There seems to be 2 resistors more than a SVT power section

I am also missing 1M on the tremolo


EDIT: schematic updated further down the thread

[rootz]

Did you say trace of the amp? Have you been in the original so you could trace it? In that case this schematic seems like a candidate for the files section.

[Bombacaototal]

Did you say trace of the amp? Have you been in the original so you could trace it? In that case this schematic seems like a candidate for the files section.

Hi Rootz, no I haven’t been in the amp, by tracing I mean I used the parts list and the scan gut shots, whereby some parts were mapped and tried to make sense of the circuit. With that I put the schematic together. But note the difference in interpretation of the “buffer tube” between my schematic and the one by Bill. Maybe his is correct? I do not know.

[talbany]

Thank you vey much Tony for the generosity. I had been asked by an esteemed member not so share, so I was trying to construct the information making links to the public information available. I am adding a couple of files which seem to be missing from your collection. You had a couple files which I did not have.

Let's get this one out in the world.

Yeah Well now you have everything you need and it's all out in the open so? So much for keeping the Pentode secret. That's generally how it works around here. Once it's out in the open it's all fair game. I've had this info about 10 years that's long enough for those that want to profit from it can Time to get some of this stuff out there so everyone can enjoy it. Eventually and in good time more stuff will flow out.
Looking forward to your layout.

BTW. Bills is correct!

Tony

[Bombacaototal]

Thank you vey much Tony for the generosity. I had been asked by an esteemed member not so share, so I was trying to construct the information making links to the public information available. I am adding a couple of files which seem to be missing from your collection. You had a couple files which I did not have.

Let's get this one out in the world.

Yeah Well now you have everything you need and it's all out in the open so? So much for keeping the Pentode secret. That's generally how it works around here. Once it's out in the open it's all fair game. I've had this info about 10 years that's long enough for those that want to profit from it can Time to get some of this stuff out there so everyone can enjoy it. Eventually and in good time more stuff will flow out.
Looking forward to your layout.

BTW. Bills is correct!

Tony

That is Brilliant Tony, I am glad you jumped in and made it open to all! I am bound by my word and hence the previous approach but this makes it much better and also more fun!

Thanks for the advice on Bills schematic. I will amend mine accordingly tomorrow. I haven’t started the layout but as soon as schematic is good this is my next task.

The diodes are old RCA SK9010 3-Amp 1000Volt. I got 7 of them! Will go all in this one!

Questions pending:
1) bias network on the PI, are my 2x10K, 2x30k correct? Where should the 47K go?
2) where should the extra 1M go on the tremolo
3) on the pentode is the .1uF going to cathode or ground on the original
4) on the supply there are 6x470k, so the 2x47uF (350V) are indeed stacked. Does my current schematic look good? Any ideas on the 2x 40K (5W) and how to go about the PI driver (which doesn’t have a dropping resistor listed and also is missing a cap supply)
5) the lnfb on the reverb, is the 10k inside or outside? I’ve seen amps taking both approaches

[talbany]

Got to head out of town right now so I don't have the time to look it over. I"ll try to take a look at it in the next day or two. In the interim if someone else wants to help and knows by all means

Get back ASAP.

Tony

[martin manning]

Thanks for adding that info to the pile, Tony!

Raphael, if you are posting schematics, please sign and date them, so people know the source, and I'm sure there will be revisions.

Is the "Bill" schematic posted somewhere for comparison?

Maybe the title of this thread should be changed, now that it has morphed into documenting a specific model?

And, why would you want to use old rectifiers?

[talbany]

Thanks for adding that info to the pile, Tony!

Raphael, if you are posting schematics, please sign and date them, so people know the source, and I'm sure there will be revisions.

Is the "Bill" schematic posted somewhere for comparison?

Maybe the title of this thread should be changed, now that it has morphed into documenting a specific model?

And, why would you want to use old rectifiers?

Martin
No the Bill schematic was taken from all the parts info and we did it together and it is accurate AFAIK. The other one was done by someone else and according to Max is not accurate as he mentions this in my last thread.
I don't have the time right now to help the man out so feel free to look add correct whatever to get this thing done if you don't mind. Out of town and will check back in when I can

Good Luck
Tony