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

[talbany]

Yes! It's very hard to argue with (Just the facts) Max. I tried it one time and LOST! badly

T

[Bombacaototal]

Hi Tony, is this how the MM amps were done by HAD? This is essentially how a HD130 is done I think. Doubler, with the screens tapped from the doubler. 800V to the plates, 400V to the screens/preamp. All from a single 300VAC secondary winding. Lower it to 230-250VAC and this way you'd have a hefty setup for a couple of 6550A's with 12BH7 driver in class AB2 for a SSS from hell. Oh well, I'm diverting. Again

Rootz
Here is a schematic of how Dumble configured his MM supplies in his ODS's. (Precision Power supply) As far as the voltages go Martin is correct. 700V B+ 350 scr /35V (pre amp)AC =50Vdc bias supply / 6.3V Fil /6.3V Rly
Super100_MMPSU (1).jpg


Tony

I bet...I wouldn't try to argue with Max myself.

Thanks for sharing the supply schematic. You got me very curious (almost obsessed) with making a MM amp.

I revert to this thread where you built one. In this case you seem to use 200uFx2 for B+1, 50uF for B+2 (where the choke is) and 40K (10W) / 830K (2W) followed by a non precision board with 25uF x2 (B+3, B+4) with a 10K dropping resistor. I could not find B+5...Also the rectifier board looks to have a capacitor which I cannot see on the schematic.

https://ampgarage.com/forum/viewtopic.p ... t=musicman

I think I would go for the HD130 set but use 6550 like the Alligator amp....Probably need to mismatch the OT to get primaries right as the original is designed for 6CA7/EL34.
https://www.tubeampdoctor.com/en/output ... 135w?c=292
https://www.tubeampdoctor.com/en/mains- ... 5-100/130w

Also found another thread with an example of the supply with a 44K before the premap supply and no ground reference before.
https://ampgarage.com/forum/viewtopic.p ... an#p293399

And these details from Fuchs. Are the 2x47uF (350V) are on the choke side?

Same rectification for B+, screens tied to midpoint of voltage doubler (like Music Man), only difference is a big-ass resistor (25-K 25-W I believe) feeding the preamp B+.

Make sure you use filter caps on the low level side (47/350 stacked) so they can withstand the cold start voltages.

Interesting disccussions here too https://ampgarage.com/forum/viewtopic.p ... n&start=60

[rootz]

Thanks Martin and Tony for the explanation about the PS. Taking the pi from the anodes makes perfect sense. 350vdc would be roughly 100v low for what is common in HAD’s designs.

Saw a HD-130 replacement transformer on the website of tad. 7A heater winding, so enough for 4xEL34. Makes perfect sense to use a separate transformer for the preamp tubes and add 2 100 Ohm resistors at the base of V1 in that case (and if that is what you mean).

[rootz]

Those 150/2W resistors over the first filter caps seems a bit light. Roughly 1W of continuous dissipation in either resistor. Also I think it’s safer to double on the diodes like in Tony’s schematic. It’s not exactly on the limit, but some cheap diodes to be totally safe would be a good idea in my book.

[Bombacaototal]

Thanks Martin and Tony for the explanation about the PS. Taking the pi from the anodes makes perfect sense. 350vdc would be roughly 100v low for what is common in HAD’s designs.

Saw a HD-130 replacement transformer on the website of tad. 7A heater winding, so enough for 4xEL34. Makes perfect sense to use a separate transformer for the preamp tubes and add 2 100 Ohm resistors at the base of V1 in that case (and if that is what you mean).

Yeah! I think we are on the right track. Would you get a 6.3V relay type transformer? And wire as a relay from the mains?

[rootz]

Don’t know what to make from that tad pt you posted... is that the version MM used for the amps that could switch between high and low power (voltage). Look up the HD-130 schematic. There is a switch to choose which secondary tap on the pt you use.

Also, just one heater tap. So if you want relays and preamp tubes from separate transformers, you’d need two extra transformers.

Waiting for Tony and/or Martin to provide more insights on this and how useful that tad transformer is.

[Bombacaototal]

Thanks for pointing that out about the TAD transformers. I think Mercury Magnetics also has a HD130 type.

https://www.mercurymagnetics.com/model/hd-130/

I am not 100% sure on how to go about the separate transformer for the preamp tubes.

I am also curious on how to work the bias board, how many caps and diodes, etc..

[talbany]

Hi Tony, is this how the MM amps were done by HAD? This is essentially how a HD130 is done I think. Doubler, with the screens tapped from the doubler. 800V to the plates, 400V to the screens/preamp. All from a single 300VAC secondary winding. Lower it to 230-250VAC and this way you'd have a hefty setup for a couple of 6550A's with 12BH7 driver in class AB2 for a SSS from hell. Oh well, I'm diverting. Again

Rootz
Here is a schematic of how Dumble configured his MM supplies in his ODS's. (Precision Power supply) As far as the voltages go Martin is correct. 700V B+ 350 scr /35V (pre amp)AC =50Vdc bias supply / 6.3V Fil /6.3V Rly
Super100_MMPSU (1).jpg


Tony

I bet...I wouldn't try to argue with Max myself.

Thanks for sharing the supply schematic. You got me very curious (almost obsessed) with making a MM amp.

I revert to this thread where you built one. In this case you seem to use 200uFx2 for B+1, 50uF for B+2 (where the choke is) and 40K (10W) / 830K (2W) followed by a non precision board with 25uF x2 (B+3, B+4) with a 10K dropping resistor. I could not find B+5...Also the rectifier board looks to have a capacitor which I cannot see on the schematic.

https://ampgarage.com/forum/viewtopic.p ... t=musicman

I think I would go for the HD130 set but use 6550 like the Alligator amp....Probably need to mismatch the OT to get primaries right as the original is designed for 6CA7/EL34.
https://www.tubeampdoctor.com/en/output ... 135w?c=292
https://www.tubeampdoctor.com/en/mains- ... 5-100/130w

Also found another thread with an example of the supply with a 44K before the premap supply and no ground reference before.
https://ampgarage.com/forum/viewtopic.p ... an#p293399

And these details from Fuchs. Are the 2x47uF (350V) are on the choke side?

Same rectification for B+, screens tied to midpoint of voltage doubler (like Music Man), only difference is a big-ass resistor (25-K 25-W I believe) feeding the preamp B+.

Make sure you use filter caps on the low level side (47/350 stacked) so they can withstand the cold start voltages.

Interesting disccussions here too https://ampgarage.com/forum/viewtopic.p ... n&start=60

I ended up changing the dropping string later on though (it's a long story) I landed at 30K 10w with 820k (Bleeder) also from the same point I added the Zeners that Andy recommended since mine was a 'Classic" PS and didn't have the stacked caps. Then the standard 22k and a 2k2 for V1a. I used the 50's on the screens for the 34's just to give me a bit more regulation and keep things tight. Dumble used a 20uF there so however you want to do it. I also put another string of zeners at the V1 filter (3X 150V) just to give me a layer of protection for the fet since I blew one out shortly after I got the amp working.

Long story short! For a first time build and if I were you I would do it just like the hand drawn schematic I just posted. Go with the stack caps and be done with it. If you blow through a fet then add the zeners later if you have any issues Kapish!!

Everything else you need should be in that build thread on my Tan Ultrasound amp. BTW. You may want to run the load lines on those 6550's and check the spec sheets and make sure they can handle those high voltages and as the primary impedances changes there as well. If you don't know how to do that maybe Martin can run those for you!
Keep us in the loop so we can double check things since 700V will set your house on fire or stop your heart. I get nervous recommending an amp with 700V in it on a build it yourself forum
Good Luck!

Tony

[talbany]

Thanks for pointing that out about the TAD transformers. I think Mercury Magnetics also has a HD130 type.

https://www.mercurymagnetics.com/model/hd-130/

I am not 100% sure on how to go about the separate transformer for the preamp tubes.

I am also curious on how to work the bias board, how many caps and diodes, etc..

As for the Bias supply?. There are 2 (Orange)wires for the SS preamp. 70V if you use the CT or FWB and 35 if you gnd one side. I gnd one side and went for 35 and set it up just like you would a standard Fender style this is for NO cathode follower driver!
Yes an extra filament transformer and choke would be a good idea!
Got it?

[martin manning]

I'm thinking HAD pretty much lifted the whole power section from the tube driven version of the Musicman (PT, choke, OT) with the exception of building a simpler bias supply without the bipolar part. The MM PT's filament winding could probably handle the three 12AX7's in the preamp, so the only other iron required would be the typical relay supply transformer.

Marcus' thread has really gone off track now...

[norburybrook]

and back to me.....





M

[Bombacaototal]

Thanks Tony, yes 700V makes me nervous too. It will surely take a lot of planning and to build some confidence before I attempt it, but I am up for it...Surely I will keep you guys in the loop for verifying my supply / bias section...

I am thinking of attempting the Alligator as I am usually a Reverb and Tremolo guy instead of OD. As far as the bias board, it will be slightly more complicated because of the cathode follower but I am thinking grounding one of the sides as HAD did on those type of PIs. But I will probably go for 2x 6550 with the HD130 transformers (because 150W will basically be unusable, but keeping the same transformers will give me the same character of the original).

I will try to sketch something in the coming week...

EDIT: ups sorry for keeping this off track..

[talbany]

Thanks Tony, yes 700V makes me nervous too. It will surely take a lot of planning and to build some confidence before I attempt it, but I am up for it...Surely I will keep you guys in the loop for verifying my supply / bias section...

I am thinking of attempting the Alligator as I am usually a Reverb and Tremolo guy instead of OD. As far as the bias board, it will be slightly more complicated because of the cathode follower but I am thinking grounding one of the sides as HAD did on those type of PIs. But I will probably go for 2x 6550 with the HD130 transformers (because 150W will basically be unusable, but keeping the same transformers will give me the same character of the original).

I will try to sketch something in the coming week...

EDIT: ups sorry for keeping this off track..

Yes you will need to do a completely different bias supply(-150V) if you run the CF.

See Ya!
T

[Bombacaototal]

So back at this...on the attachment, the top pic is the usual 150W (6550x4) rectifier and bias for a SSS amp.

I replicated the same approach to bias but left the MM style rectfying. Will this work?

[sluckey]

no