Vintage JTM-50 - S/11295 - 1968 - what it it worth? How to rennovate (if at all)

StuC

Active Member
Joined
Feb 12, 2014
Messages
120
Reaction score
157
Where did you see those pics!!!
Yes def Partridge

looks like TG9624?
Do you know where they were used Stu? Not one I recognise.

My eyes aren't that good, I can't make it out.
 
Last edited:

redfish

Member
Joined
Dec 14, 2011
Messages
35
Reaction score
17
I posted my thoughts on the old Plexi Palace forum. This is only what I came up with after looking at dozens of amps of different makes, so it's by no means definitive, but it seems to fit.

Usually, there's a part number and a batch number. It seems to me that the part number follows the pattern T(X)(1234) where T presumably stands for transformer, X is a letter denoting the decade when the part was designed and 1234 is a four digit number.

The second number takes the form (X)(1)(234) where again X is the decade, but this time the decade in which the transformer was made. The first digit appears to be the year in that decade and the last three digits a batch or job number.

The relevant decade letters are G for the '60s and H for the '70s. Prior to 1967, it's rare to see any codes on the transformers. '67 and '68 codes are usually hand written with a paint marker, later ones are stamped.

So for example, TG5479 H1422 would point to a '60s designed part produced in 1971.
wow thats cool ... great detective work
 

redfish

Member
Joined
Dec 14, 2011
Messages
35
Reaction score
17
I might have to take it out again to get a good pic ... but this seems to show TG9624 athough the 'G' is a bit too blurry to tell for sure on this pic
 

Ned B

Well-Known Member
Joined
Nov 19, 2012
Messages
347
Reaction score
429
I posted my thoughts on the old Plexi Palace forum. This is only what I came up with after looking at dozens of amps of different makes, so it's by no means definitive, but it seems to fit.

Usually, there's a part number and a batch number. It seems to me that the part number follows the pattern T(X)(1234) where T presumably stands for transformer, X is a letter denoting the decade when the part was designed and 1234 is a four digit number.

The second number takes the form (X)(1)(234) where again X is the decade, but this time the decade in which the transformer was made. The first digit appears to be the year in that decade and the last three digits a batch or job number.

The relevant decade letters are G for the '60s and H for the '70s. Prior to 1967, it's rare to see any codes on the transformers. '67 and '68 codes are usually hand written with a paint marker, later ones are stamped.

So for example, TG5479 H1422 would point to a '60s designed part produced in 1971.


Thanks! I actually remember that post as I was an avid PP member. These are pictures of my SA212 transformers. Are the TG numbers the model and the H numbers the date code? Sorry, Redfish...not intending to hijack your tread!
 

Attachments

  • 063-4782-09 Hiwatt SA212 50W Combo 1973.JPG
    063-4782-09 Hiwatt SA212 50W Combo 1973.JPG
    341.7 KB · Views: 14
  • 063-4782-10 Hiwatt SA212 50W Combo 1973.JPG
    063-4782-10 Hiwatt SA212 50W Combo 1973.JPG
    208.1 KB · Views: 13
  • 063-4782-11 Hiwatt SA212 50W Combo 1973.JPG
    063-4782-11 Hiwatt SA212 50W Combo 1973.JPG
    255.4 KB · Views: 11

StuC

Active Member
Joined
Feb 12, 2014
Messages
120
Reaction score
157
Yes, H2 would be 1972 if I figured it out correctly. Don't see many 50s with the original PT, does it run hot?
 

alpha al

Active Member
Joined
Oct 19, 2017
Messages
101
Reaction score
146
Location
Gastonia, NC
Well I would certainly remove that death cap, it is call that because if it leaks and if in some situation you would be the ground, through your guitar or a microphone, well it could kill you..
Not possible if it's "Earthed" (grounded) properly.
 
Last edited:

Seanxk

Well-Known Member
Joined
May 14, 2018
Messages
958
Reaction score
884
Not possible if it's "Earthed" (grounded) properly.

And it is.....:D

Red, can you read off any letter codes on the Brown cap please, they will be capitols XXX.
I have a curious finding, will post later.
 

redfish

Member
Joined
Dec 14, 2011
Messages
35
Reaction score
17
The .05uf 1000v Hunts cap next to the Bulgin and P/T :)
I cant read it on any of my pics or video - would have to open her up again - will post what I find when I get round to opening up again
 
Last edited:

TAZIN

Well-Known Member
Joined
Mar 18, 2013
Messages
722
Reaction score
436
And it is.....:D

Red, can you read off any letter codes on the Brown cap please, they will be capitols XXX.
I have a curious finding, will post later.

Hunts
A74 (series)
0.05uF 1000v
DC Wkg
H Y? (date code)
 

Ivan H

Active Member
Joined
Jan 17, 2021
Messages
98
Reaction score
180
Hunts
A74 (series)
0.05uF 1000v
DC Wkg
H Y? (date code)
I could be way off base here, but through using modern 1,000V (& greater) capacitors, my understanding is that an X rated capacitor will fail closed, or "short" while a Y rated capacitor will fail open. Not at all sure when these designations came into use, but is it possible the H Y designation has something to do with this?
My JMP50 has this same 1,000V Hunts capacitor mounted between the HT fuse holder & ground. Cheers
 

TAZIN

Well-Known Member
Joined
Mar 18, 2013
Messages
722
Reaction score
436
I could be way off base here, but through using modern 1,000V (& greater) capacitors, my understanding is that an X rated capacitor will fail closed, or "short" while a Y rated capacitor will fail open. Not at all sure when these designations came into use, but is it possible the H Y designation has something to do with this?
My JMP50 has this same 1,000V Hunts capacitor mounted between the HT fuse holder & ground. Cheers

I believe the three letter sequence to be a manufacture date code. A similar type date code was used on their electrolytic capacitors. So, if true then I'd expect the code to be either 'H YN' or 'H YD'.
 

StingRay85

Well-Known Member
Joined
Aug 18, 2019
Messages
2,094
Reaction score
1,809
I posted my thoughts on the old Plexi Palace forum. This is only what I came up with after looking at dozens of amps of different makes, so it's by no means definitive, but it seems to fit.

Usually, there's a part number and a batch number. It seems to me that the part number follows the pattern T(X)(1234) where T presumably stands for transformer, X is a letter denoting the decade when the part was designed and 1234 is a four digit number.

The second number takes the form (X)(1)(234) where again X is the decade, but this time the decade in which the transformer was made. The first digit appears to be the year in that decade and the last three digits a batch or job number.

The relevant decade letters are G for the '60s and H for the '70s. Prior to 1967, it's rare to see any codes on the transformers. '67 and '68 codes are usually hand written with a paint marker, later ones are stamped.

So for example, TG5479 H1422 would point to a '60s designed part produced in 1971.

Great info. Now I need to check my own Partridge codes
 

StuC

Active Member
Joined
Feb 12, 2014
Messages
120
Reaction score
157
I could be way off base here, but through using modern 1,000V (& greater) capacitors, my understanding is that an X rated capacitor will fail closed, or "short" while a Y rated capacitor will fail open. Not at all sure when these designations came into use, but is it possible the H Y designation has something to do with this?
My JMP50 has this same 1,000V Hunts capacitor mounted between the HT fuse holder & ground. Cheers

As TAZIN said, it's a date code. I checked the one in my JTM50 as it's out of the cabinet and it's H TU.
 
Last edited:

Seanxk

Well-Known Member
Joined
May 14, 2018
Messages
958
Reaction score
884
As TAZIN said, it's a date code. I checked the one in my JTM50 as it's out of the cabinet and it's H TU.

Yes it's a date code, Stu is it a Hunts or an Erie, is there a type space between those letters or are they equi spaced.
 

StuC

Active Member
Joined
Feb 12, 2014
Messages
120
Reaction score
157
Hunts. It's spaced like that: H TU, so tempting to see the H as the year, which would make it week 46 of 1962. It could be week 24 of 1966... I haven't yet found one with a middle digit that would confirm which way around to read these. I've only come across H and Y as the first letter in Marshalls.
 

Seanxk

Well-Known Member
Joined
May 14, 2018
Messages
958
Reaction score
884
Interesting, yes the spacing makes it confusing, but 62 could be from the first batch ( they probably didn't use that many) or more likely 66 I think, let's see what others come up with.
 

Latest posts



Top