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Music Man serial numbers demystified

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Ingo Raven (ingo)
Username: ingo

Registered: 07-2007
Posted on Monday, July 23, 2007 - 11:05 pm:   

Hello,

this is my first message in this great forum.

I didn't find any explanation here on the serial numbers, only the assumption that they are random numbers. I believed that they must contain some information, so I collected serial numbers here from this forum and from ebay to draw my own conclusions.

This is what I found out so far:

The serial numbers have a form like C004235, BN05663, DP05491, etc.

They have 7 digits.

The first digit (A, B, C, D, or E) is the chassis size (width):
A: small size e.g. 65 watts bass head
B: two channel amps, left channel without bright switch and middle control, e.g. 112-65, 410HD-130
C: the big two channel amp like the 212HD-130 or 212-65
D: the RD or RP series with 65 or 100 watts
E: the small RD with 50 watts


The second letter (N,O,P) denotes the output power (we should read 0 as Oh here and not as zero):
N: normal(??) = 65/75 watts, or 50 watts on the small RD, generally "little power")
O: 130/150 watts
P: 100 watts

The following numbers seem to be chronological *for each series*. It seems there were more B models like C models, so a 78 B-model has a higher number than a 78 C-model.

What I didn't find out is what exactly happened when they changed to new models (75/150 watts). It seems they kept the first two letters and possibly started the numbering with 0000 again. Here I need more data.

Generally this means it IS to some extend possible to identify the model according on only the serial number. Also the numbers have to do with the year of production, but only indirectly. We need to find out which number range corresponds to which year *for each series (A - E).

greeting from Germany,

Ingo
Giorgio (giorgio)
Username: giorgio

Registered: 07-2007
Posted on Tuesday, July 24, 2007 - 03:16 pm:   

Well done Ingo!

I give you two S/Ns (both from Germany ;) I bought them on ebay):

HD One-thirty 2100-130 EX A001627
Sixty-five 2100-65 EX AN01950

As soon as possible I'll give you the S/N of a RD112-65 that is from 1980 (year written inside the amp).

Bye!
Ingo Raven (ingo)
Username: ingo

Registered: 07-2007
Posted on Wednesday, July 25, 2007 - 12:03 am:   

Both of your amps are A series. Do they in fact have the same chassis width, or should I modify something of my theory?
According to the rather low numbers they both should have the driver tube. Am I right?
Giorgio (giorgio)
Username: giorgio

Registered: 07-2007
Posted on Thursday, July 26, 2007 - 09:49 am:   

They have the same chassis an follow the rules of your theory.

From the model chart found in this site it seems that the HD130 never have transistor phase inverter.

The sixty-five has transistor paraphase inverter, so I think it's a 1978/79.

There is a difference between their knobs: numbers on the knobs in the HD130 are bold-like respect the sixty-five's ones. I'm quite sure that HD130 is older than the sixty-five.

I compared the components inside the amps but I haven't found any differences.
Giorgio (giorgio)
Username: giorgio

Registered: 07-2007
Posted on Thursday, July 26, 2007 - 01:36 pm:   

Some news about the sixty-five head. It's a kind of hybrid (!) It has a preamp board rev BB-1 B, with LM307H opamps (metal can package), and the "filter circuit" (as mentioned in the schematic) BUT has no 12AX7, so the bias circuit in preamp board is unused and the two EL34 are biased by transistors. If you look the schematics of 2100-65 chassis , in the matter of fact, none of them is correct for this head.

This makes me think that has been produced in the period of migration from tube PI to opamp PI.

NOTE: In the previous post when I wrote about component differences I was referring to preamp board.
Ingo Raven (ingo)
Username: ingo

Registered: 07-2007
Posted on Friday, July 27, 2007 - 12:40 am:   

Hi Giorgio,

thanks for your table with the data you sent me.

The numbers on the transformers (and also on all potis) also have some information about the date of manufacture, e.g. 606-740 means 606: manufacturer code, 7: 1977 (or 67 or 87), 40th week

So the 65 can't be built before end of 77, while the 130 is from early 77 or later.
The change from tube inverter to SS inverter was to my knowledge in 77 (not in 76). However, many amps that came with a tube were called back and were equipped with the SS driver board - this was a free service by MM.

For this reason you might find SS drivers on 75 or 76 amps as well. On the other hand, the latest tube driver we find should mean that all amps up to that date were originally made with the tube - until now this seems to be early 77 (but I need more data).

The schematics with the SS board were from a later version, without choke and with the stand-bye switch at the front. My 1980 HD130 is one of these.

Ingo
waltergrund

amp# 137 or 132...?

Hi,

I tried to date my amp and for now I found out, it must have been built in 68, 78 or 88.
Here's some infos:

Serial# C006336
Transformer# EIA-606-718
Transformer# EIA-606-823
small Transformer# EIA606-740
Cassis NO 2475-130

I'd appreciate any help!
Walter

mm210
mm210's picture

I'd say 78.

I'd say 78.

lmv

Sounds right

In another thread you say either 68, 78 or 88. In this context, it is very simple: Music Man amps were only produced from 74 into 83 or 84.

Cheers,
Lars Verholt

Wenbil

Dating a 412GS cab

I have an old 412GS straight cabinet that I'm trying to find a date on...I pulled a speaker which is dated 1976...is there a serial number, stamps or anything that will help
Thanks, Bill

335

early 130 head

B0002XX serial

Used it briefly, because a tube red plated shortly after receiving it, and there was smoke. It was sounding good.

Tbh, I never plug in amps anymore. I think it would be good to get all them
serviced by a person who knows these models. A few of them sound good, a few don’t. I run a little electricity through them all every few years or so.

My interest in the mentioned head is due to an anomaly. The feet on the base are small round rubber donuts, probably secured by a screw. IIRC they seemed not out of place, and there were no footprints or signs that any other pads were mounted there. Every MM head I have seen or owned has the big rubber pads. Since this is a very early serial number, I am asking if anyone else has seen such a head?

Another question would be is there anything to the rumor being circulated here and there about there existing some early 65 130 style HD models which had a genuine tube pre-amp? This is being mentioned on some guitar forums and I thought that this place would have the lowdown. The story being put forth, by a person or two who seem to know these amps well, and who are apparently familiar with both the tube and transistor designed PI SS front ends, is that there do exist some first run amps which use true tube preamplification. And that they are rare, so don’t expect to see one. Does anyone have the last word on this rumor?

eta: I just searched the forum and saw that Steve did answer this part of my question for a guy who was asking about the PI tube in regard to 150s vs 130s and are there any true tube preamp MM amps etc.... This subject probably gets beat to death.
It persists in my head because of the supposed MM amp awareness the person putting the story out seems to have, and that he stated the ‘very early/very rare’ mantra. There is nothing ‘rare’ about a tube phase splitter in 65s and 130s...not even a little bit rare. idk.

BTW the new board looks great. I have checked in from time to time and it seemed the board was shut down for a while, not sure. This is my first visit in years. Thanks, Steve, and all involved.

mm210
mm210's picture

I sold MM's in the 70's and I

I sold MM's in the 70's and I never saw a tube front end in any of them but that was around 77 though. Mike.

Jackguitar
Jackguitar's picture

Music man amp serial numbers

I have a 1970s 212 music man amp.. serial number CN 00283 output 65 Watts RMS

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