Took a chance... MM content.. package arrived

[Bob-I]

I saw this on ebay

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWNX:IT

Music Man 2475 disassembled but he claims all the parts are good and listed with money back guarantee so I bid $100. Looks like chassis and iron for my next build.

Hints and suggestions are welcome. I've read all the threads on MM iron and I plan to use the high B+ and low screen PS with a precision PS for the rest.

I'm debating the generation to build. I have several great HRM and high plate amps (thx to dogears tweaking my Bluesmaster couldn't sound better) so I'm wondering how MM voltages will work with low plate non-HRM.

This is a small chassis so I'm thinking I'll build a 1x12 combo with either an EVM12L or Celestion 12-65

[Structo]

I hope you get your money's worth Bob.
Kind of blurry pictures, hard to see what's what.

[Bob-I]

Yea, but I figure is I get a chassis and iron out of it I'm ahead of the game. I don't care about the boards and other components.

Like I said in the title, I took a chance.

[ToneMerc]

Bob, I was watching that one as well for MM#2 build. I passed on because the "high tap" on the 65 model doesn't have a high enough voltage and it's a lil light on the filament for 4 OT tubes.

Specs of the Music Man 100-65 transformer are:

0-120 Blk-Red/Blk
Red/Yel-Red=180v high tap Red-Brn= 90V low tap @300mA
31-0-31 62VCT Org-yel-Org @375mA
G-G/Yel 6.3 @3.5A


MM 100-65 Type2

Music Man 100-65-120-2 Power Transformer

primary
Black-0
blk/yel-80
blk/red-90
white-120


secondary
red-red =176v @ 1.16 Amp
orange-orange=24v @ 120mA
green-green = 5v @ 3Amp



MM 200-130, heres the one that Dumble used and what I used in my build as recommended by my Music Man PS mentor Tony.

0-100-120 blk-blk/yel-blk/red
268V-89V @1Amp brn-red/yel
62VCT @150mA org-yel-org
6.3v @ 6A grn-grn

Using the 268V high tap provided around 756V; while loaded around 725V plates/350V on the screens.

TM

[Bob-I]

Bob, I was watching that one as well for MM#2 build. I passed on because the "high tap" on the 65 model doesn't have a high enough voltage and it's a lil light on the filament for 4 OT tubes.

Specs of the Music Man 100-65 transformer are:

0-120 Blk-Red/Blk
Red/Yel-Red=180v high tap Red-Brn= 90V low tap @300mA
31-0-31 62VCT Org-yel-Org @375mA
G-G/Yel 6.3 @3.5A

Hmmm... little light on the filaments, but for the price I was mostly looking for the chassis and OT.

That said this PT looks usable for 6L6's and 3 12AX7s. Add a filament xformer and it should handle EL-34s.

Thx for the info.

[Bob-I]

Ok, now I'm confused...

I looked up the schematic on the 2475-65 and it shows 700V on the plates

http://www.music-man.com/techinfo/old_a ... 275-65.pdf

I guess the proof will be in the voltmeter.

[ToneMerc]

My next one will be an HRM, Heyboer trannies again.

I was confused too, verify that it has a brown tap. The brown tap is the one that you want to use to get 700V.

For the bias supply, I went straight MM design tapping the negative supply side. The next time I might use a parasitic feed from the HV.

TM

[Bob-I]

My next one will be an HRM, Heyboer trannies again.

I was confused too, verify that it has a brown tap. The brown tap is the one that you want to use to get 700V.

Thx, will check when it arrives.

For the bias supply, I went straight MM design tapping the negative supply side. The next time I might use a parasitic feed from the HV.

TM

The MM design was enough? It looks to me like the max is -32V. I was going to use the low HV feed (red)

[talbany]

Bob
It would be nice to confirm the # on the PT if it's a 100-65 type 1 or 2

Tony

[ToneMerc]

My next one will be an HRM, Heyboer trannies again.

I was confused too, verify that it has a brown tap. The brown tap is the one that you want to use to get 700V.

Thx, will check when it arrives.

For the bias supply, I went straight MM design tapping the negative supply side. The next time I might use a parasitic feed from the HV.

TM

The MM design was enough? It looks to me like the max is -32V. I was going to use the low HV feed (red)

Plenty for EL34s at 70% dissipation, using the 62Vct(31) bias tap. I had 45/-45V at the zeners. With the SED EL34's my bias range is from -23 to around -32V, IIRC. I'll have to check but I think I last set bias at 24.5.

70*25W= 17.5, then 17.5/725V = 24.14

For the next build, if I use the same style of supply I may go back and tweak the values to get the range a tad more positive, so that I get down into -19V or so range.

.



TM

[Bob-I]

Bob
It would be nice to confirm the # on the PT if it's a 100-65 type 1 or 2

Tony

Live and learn, I didn't know there was 2 versions. No biggie, PT's are pretty inexpensive, I just hope the OT is good, there's just something about old OT's.

[FUCHSAUDIO]

The MM design was enough? It looks to me like the max is -32V. I was going to use the low HV feed (red)

With the 700 plates and 350 screens, you need very little bias (25 volts or so) to keep things properly biased (25 ma max per tube 20 even better).

[Bob-I]

Well. I'm very dissapointed.

The add said chassis, panels and showed pic of them, plus the main board and a second small chassis. I only received the small chassis, no MM chassis, panels, main board. Plus I paid $30 for shipping and she sent in a $15 flat rate box. I can only surmise that a second box has not been received yet. I sent a message to the seller, waiting for a reply.

I can't quite match up the xformer leads to any of the diagrams I've seen yet but I'm very colorblind. The numbers are 1-65 and EIA606 737 which I also can't locate. I could hook it up but I won't disconnect anything until I hear from the seller or receive the rest of the parts.

Any help is appreciated.

[FUCHSAUDIO]

Gotta love sleazebay.
a

[Bob-I]

Gotta love sleazebay.
a

Well, the buyer listed as a money back in 7 days so I need to 1) See if I get the remaining parts and B) Decide if I can use this iron.

Any information on this part number will be helpful, otherwise I'll need to desolder it and test the voltages.

I got a reply from the seller, there is a second box, dummy post office didn't deliver them together.