Marshall JCM1H or JTM1H schematics

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Marshall JCM1H or JTM1H schematics

Postby micline » 03 Feb 2014, 19:06

Hi,

has anyone out there a JCM1H or JTM1H schematic?

Alternative some useful high resolution pictures of the pcb board(s) (from both sides)?
In connection with the Out Transformator (resistance primary and secondary)
i think we could get the whole schematic together?!

Regards,
Mike
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Re: Marshall JCM1H or JTM1H schematics

Postby micline » 03 Feb 2014, 19:58

Here is the begining (JTM1 Board):

JTM1H Board.jpg


to analyze the whole schematic we need a photo from the bottom of the board!

Informations about the TXOP00039 are also very usefull (ex. resistance of both windings).

Some components are easy to identify.

The Tubes are: 1. ECC83/12AX7 for 2 Stages and ECC82 for Power Stage (Push-Pull).
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Re: Marshall JCM1H or JTM1H schematics

Postby Thomas_H » 05 Feb 2014, 02:07

Hi,
some guys from a brazilian forum have tried some output transformers with 24.7k and 20k primary for JTM 1.

They also made a schematic for it, from photos and a youtube video.

Everthing is here:

http://www.handmades.com.br/forum/index.php?topic=5841.0

I don't think they have one to compare, but the schematic looks like the description I read in another forum (ax84 or mylespaul).

The JCM 1 has the same PI and POWER, but the preamp is more complicated. If someone has one to trace the schematic, would be nice.

If you're interested in buildin one, there are some well debugged ECC99 amp schematics online.

Hope you enjoy,

Cheers
Thomas

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Re: Marshall JCM1H or JTM1H schematics

Postby jtn191 » 13 Feb 2014, 05:49

Thanks for sharing, I've been curious about the JTM1
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Re: Marshall JCM1H or JTM1H schematics

Postby Thomas_H » 12 Mar 2014, 01:43

Are there any pictures for the jcm1 board?
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 24 May 2014, 02:11

micline wrote:Here is the begining (JTM1 Board):

JTM1H Board.jpg


to analyze the whole schematic we need a photo from the bottom of the board!

Informations about the TXOP00039 are also very usefull (ex. resistance of both windings).

Some components are easy to identify.

The Tubes are: 1. ECC83/12AX7 for 2 Stages and ECC82 for Power Stage (Push-Pull).


wow talk about not hell bent for leather, rather hell bent for cash. Do the multiple polygons really help any? why are the heater running right up the gut close to signal paths. Why not a choke at the centertap OT? Oh its a universal PCB the hell with the correct layout. JMP1 JTM1 JCM1 same board. There will be long filter cap life though, I give them credit for that though. I'll roll with the dude that came up with 60's and 80's one watters, Because man it does sound better at lower primary OT. The tube data sheet doesnt always mean everything, your ears do though. 22.5k dont sound as sweet. Feel the 12AU7 tube after about 4 min of playing. Its hotter than hell. Thats because it is mis matched quite a bit, but sounds great. The heart of these one watters are very nearly a pace maker split loader.
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 24 May 2014, 03:06

Tech28 wrote:
micline wrote:Here is the begining (JTM1 Board):

JTM1H Board.jpg


to analyze the whole schematic we need a photo from the bottom of the board!

Informations about the TXOP00039 are also very usefull (ex. resistance of both windings).

Some components are easy to identify.

The Tubes are: 1. ECC83/12AX7 for 2 Stages and ECC82 for Power Stage (Push-Pull).
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 24 May 2014, 03:37

Tech28 wrote:
micline wrote:Here is the begining (JTM1 Board):

JTM1H Board.jpg


to analyze the whole schematic we need a photo from the bottom of the board!

Informations about the TXOP00039 are also very usefull (ex. resistance of both windings).

Some components are easy to identify.

The Tubes are: 1. ECC83/12AX7 for 2 Stages and ECC82 for Power Stage (Push-Pull).


Well the 12AU7 does draw 14ma in this circuit, four over what it is meant to draw. Still I bet you cant hold your finger there for not even one second can almost lite a cigarette off it. The heart of these one watters are very nearly a vox pace maker split loader. Leo Fender Split loaders. Half Marshall and Half Fender as usual. How does copy rights come into play with that been said lol hahahaha
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 15 Jun 2014, 04:57

Thomas_H wrote:Hi,
some guys from a brazilian forum have tried some output transformers with 24.7k and 20k primary for JTM 1.

They also made a schematic for it, from photos and a youtube video.

Everthing is here:

http://www.handmades.com.br/forum/index.php?topic=5841.0

I don't think they have one to compare, but the schematic looks like the description I read in another forum (ax84 or mylespaul).

The JCM 1 has the same PI and POWER, but the preamp is more complicated. If someone has one to trace the schematic, would be nice.

If you're interested in buildin one, there are some well debugged ECC99 amp schematics online.

Hope you enjoy,

Cheers
Thomas

In the schematic....C15 is totally in the wrong place. It is supposed to be in the signal path, not on the rail lol. The way it is in this schematic you are inviting 200VDC right into the tone stack PCB. High voltage at you finger tips. Plus i see other things not correct as well, wrong values. Also the OT primary impedance is a much lower value. I know this because i have the real PCB right in front of me.
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 15 Jun 2014, 05:29

Thomas_H wrote:Are there any pictures for the jcm1 board?

You are looking at it. Its the first picture in the thread.
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Re: Marshall JCM1H or JTM1H schematics

Postby jtn191 » 15 Jun 2014, 21:09

Tech28 wrote:
Thomas_H wrote:In the schematic....C15 is totally in the wrong place. It is supposed to be in the signal path, not on the rail lol. The way it is in this schematic you are inviting 200VDC right into the tone stack PCB. High voltage at you finger tips. Plus i see other things not correct as well, wrong values. Also the OT primary impedance is a much lower value. I know this because i have the real PCB right in front of me.


You're sure of that? Is C17 also wrong? It is the same value/function...you could back it up by correcting the schematic/posting pictures...
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Re: Marshall JCM1H or JTM1H schematics

Postby Thomas_H » 18 Jun 2014, 12:37

Nice Tech28,
it took me some time to realize that the jcm and the jtm had the same board, I started to study this schematic when I posted that.
Now I know that the jmp is the one that has a different board.

If there're some errors in the schematic, please, help us solve them, the guys from the brazilian forum never had a PCB or working amp, they made all of that based on that pictures and some videos.

It's nice to see that someone that owns one of those can help to improve the schematic.

A guy at ampgarage build one of this based on that schematic:
http://ampgarage.com/forum/viewtopic.php?t=24671
and made some sound samples with the 0.1W configuration:
https://soundcloud.com/matec-br/sets

Cheers
Thomas
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Re: Marshall JCM1H or JTM1H schematics

Postby jtn191 » 18 Jun 2014, 17:36

The five caps Matec is missing are C6, C9, C19, C24, C201...if anybody has these amps, fill us in.

There also seems to be some dispute of the output transformer values...
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Re: Marshall JCM1H or JTM1H schematics

Postby Thomas_H » 18 Jun 2014, 22:04

There are some components that are only present in the JCM, maybe that's why Matec did'nt put them on the JTM schematic?
The OT impedance is something like 20k no? I read something like this at ax84, that each triode would like something like 10.5k.
Matec used a little less because of a speaker resistance mismatch.
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 18 Jun 2014, 22:57

jtn191 wrote:
Tech28 wrote:
Thomas_H wrote:In the schematic....C15 is totally in the wrong place. It is supposed to be in the signal path, not on the rail lol. The way it is in this schematic you are inviting 200VDC right into the tone stack PCB. High voltage at you finger tips. Plus i see other things not correct as well, wrong values. Also the OT primary impedance is a much lower value. I know this because i have the real PCB right in front of me.


You're sure of that? Is C17 also wrong? It is the same value/function...you could back it up by correcting the schematic/posting pictures...


I pretty much know what was going on in this circuit once i heard the Marshall designer talk a little about it. Of course i am correct. And NO C15 does not have the same function as C17. C17 is the reason there is no load on any of the filter caps once the power switch has been shut off. And yes the proof is in the putting, look at the fist picture in this thread, you see that gray cap beside the pcb mounting screw, that is C15 it is in the signal path it is not on the rail going to ground. There its been backed up look at the pic in this thread.
With common sense I mean why would you need two 100n caps on the rail going to ground it wouldnt change anything much at all. Although part of the signal is grounded by means of a 4M7 lol Besides if that 100n wasnt in the signal path would smoke all those 100v caps on the tone stack PCB and you might have a fire on your hands. Like i said its just common sense do you think Marshall would only have 1/4 watt resistors and 100v caps on the tone stack pcb when 200VDC is coming straight from the plate of the second gain stage into the tone stack pcb lol
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Re: Marshall JCM1H or JTM1H schematics

Postby jtn191 » 19 Jun 2014, 00:55

Ok, so C15 should be in the signal path...where? Also, I don't see any 4M7 resistor...
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 19 Jun 2014, 01:17

jtn191 wrote:The five caps Matec is missing are C6, C9, C19, C24, C201...if anybody has these amps, fill us in.

There also seems to be some dispute of the output transformer values...


This clone sounds a bit better than the original JCM1. An added filter stage plus a spot for a choke which im waiting on.
Plus better components a mullard on the first stage and ISKRA resistors in places which count most for best tone. I couldnt wait for
the connecters so i soldered the wires straight to the pcb's which was sort of a bitch to fit everything in all at once.
Side by side this clone sounds better than original JCM1. There is no micky mouse half ass in this its done right. You cant
see all the componenets some are on the other side of the tonestack pcb like the jube circuit. Plus i have a philips cap
in there as well with the jube circuit which adds more definition better quality components everywhere.
Thats an MG15 chassis lol. Takes a lot of work but in the end well worth it, especially when
it sounds better than the original JCM1. The one cap sounds better left out on the circuit it was only
there to filter out strong incoming radio stations. Im shielded pretty dam good up front anyway so i dont
need that 100pf cap. Its nice to have a cnc and silk screen skils lol. Black looks so kool. I might consider
selling a few kits since i just got through making 6 more pcb's with my cnc, then black with white silk screen
and yes I tinned all holes all way though double sided pcb's with same polygon ground planes scheme as original pcb's
for added shielding. Keeps things much more quiet if you know what i mean. Keeps RF and noise from getting into
signal paths.
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 19 Jun 2014, 02:01

Tech28 wrote:
jtn191 wrote:The five caps Matec is missing are C6, C9, C19, C24, C201...if anybody has these amps, fill us in.

There also seems to be some dispute of the output transformer values...
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 19 Jun 2014, 02:19

jtn191 wrote:The five caps Matec is missing are C6, C9, C19, C24, C201...if anybody has these amps, fill us in.

There also seems to be some dispute of the output transformer values...



Are you talking about the JCM1 ? If so than there is a hell of a lot more missing than only C6, C9, C19, C24, C201
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Re: Marshall JCM1H or JTM1H schematics

Postby Tech28 » 19 Jun 2014, 05:26

jtn191 wrote:Ok, so C15 should be in the signal path...where? Also, I don't see any 4M7 resistor...



Are you talking about in this schematic? Thats just it there is no 4M7 in connection with the 100n being in the correct location.
Im talking about the pcb in the thread not this schematic that someone posted. Signal comes straight from the 100nf down to the 4M7. one end of the 4M7 goes to ground. Then on the hot side of the 4M7 (same side as the 100nf) makes its way into the tonestack. The 4M7 is located all the way in the lower left hand corner of the pcb in the picture, which is right where the signal enters into tonestack via a 3 pin connecter pin#1 one. You want the correct JTM1 voltages readings through out the circuit ? well tell the dude who posted the SL5 schematic to not be scared and slide out the chassis. Then put a multi meter in high voltage DC mode. Then ground the black lead to the chassis. Then take voltage reading at HT1 which is right in between R6 and R4. Or if you cant reach R6 and R4 take voltage reading from C5N which is also HT1 . Same thing goes for HT2 which is right in between R4 and R5. Same thing for HT3 which is right in between R5 and R3. Look at the resistor labeling on PCB its easy to do. Its not the Tone stack PCB its the one with the tubes on it. Thats all i need. Now I am contributing very accurate INFO on the JTM1 so ask the SL5 dude to contribute a little on the SL5 since he has it right there with him lol. My INFO is 100% correct on every connection point for both JCM1 and JTM1. Plus i will share more that I see wrong in the JTM1 schematic but first tell dude i need those SL5 voltage readings.
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