Anderton '64 reissue JTM145 - any info?

[Matec]

Hello jazzkramer

Great work.

This connection pin 9, the cathodes of V3, it was a good observation yours. Once you finish your check, I will update schemes.

Thank you

Matec

[Matec]

Jazzkramer. I need another test.

In your photo, the R9 resistor seems to have 56K, and not the value of 560k, as it seemed to me in other pictures. Could you please measure the value of this component?

Thank you!

Edit:

There was a coincidence, in every picture I could on the internet. In none of them I could see C1 on the board, to the point of never included in my schemes. Now I see clearly that he was there all the time. Anyway ... will be included in the next update.




Matec

[epis]

Jazzkramer. I need another test.

In your photo, the R9 resistor seems to have 56K, and not the value of 560k, as it seemed to me in other pictures.

Hi Matec, it looked to me more like 5K6, so I did try it in my amp.
Works very well It sounds a lot more like a real JTM.

[jazbo8]

Jazzkramer. I need another test.

In your photo, the R9 resistor seems to have 56K, and not the value of 560k, as it seemed to me in other pictures.

Hi Matec, it looked to me more like 5K6, so I did try it in my amp.
Works very well It sounds a lot more like a real JTM.

5.6k is way too much attentuation... Green, Blue, Black, Red, Brown = 56k, 1% as Matec suggested.

[epis]

Jazzkramer. I need another test.

In your photo, the R9 resistor seems to have 56K, and not the value of 560k, as it seemed to me in other pictures.

Hi Matec, it looked to me more like 5K6, so I did try it in my amp.
Works very well It sounds a lot more like a real JTM.

5.6k is way too much attentuation... Green, Blue, Black, Red, Brown = 56k, 1% as Matec suggested.

Well at first I thought the same, comparing to 470k what I got there before, I did try 56K as well, sound didn't change a lot.
Compare the red you see to red on R8. Not even close. Looks as brown to me.

P.S.
Even if I'm not right about the color, different monitors-different look , I would suggest to everybody to try it out, it is big change to better, at least to me.
At high volume amp doesn't sound compressed as before.
Cheers, Damir

[jazzkramer]

Hi Matec, hi guys, I confirm R9 is by tester 56,2 Kohm.
This night I probably have no time to go on checking the schema, but I will finish it in the next days, we need it!

Bye, jazzkramer.

[epis]

Hi Matec, hi guys, I confirm R9 is by tester 56,2 Kohm.

I was wrong , my apologies to jazbo8

P.S.

Anyway 5K6 stays in my amp

[Matec]

Hey epis

It is a good suggestion, I'll try here.


==========================================


So, knowing the scheme that jazzkramer are using to compare is already out of date and full of small mistakes, I'll send the most "recent".
I hope this one is closer to reality.

Cheers

[img625]http://s26.postimg.cc/k4sll6lft/JTM1_28_08_2014_B.png[/img]
(To see the full size image, click on the link above and open in new tab.)

(Corrected, 03/09/2014.)
MATEC

[Littlewyan]

There are so many modifications to try on my amp now, but unfortunately I have to wait until tomorrow night .

Matec - R3, R5 and R6 are 100R on your schem. I think they're meant to be 100K.

[Littlewyan]

We really do appreciate you doing this Matec. Without you our amps wouldn't exist! And without Jazzkramer and build we wouldn't be able to have a 100% correct schematic. I'm sure Marshall will hate us when they find out

[Colossal]

Great job here guys. I've been reading everything with interest regarding this amp.

[Matec]

Littlewyan

One thing I suspect, Marshall never got poorer, to have their amps with the schemes disclosed, was not only richer.

This week was laborious. So I did not have time to create a topic about the miniamps. Now we have much more to discuss and testing. We will certainly go a long way in this matter.

Maybe next week.

Matec

[epis]

Hi guys, just an update, after playing more with values of R9, actually I put resistor 5k6 in series with 100k pot, I have found I was wrong (again).
56K is way to go, what looked to my ears great at volume set at 10 with 5k6 is almost same as volume at 6 with 56k resistor.

[Matec]

Hey epis.

You like to experience?

What if we measured the primary impedance of the output transformer?

You do that?

Matec

[epis]

Sure, what do you need ? Just ask.

If you wanted to ask how to measure impedance, it's easy, but conjuctiv filter C9+R12 needs to be unsoldered at one end and center tap of primary ( going to B+) as well.
Small AC voltage should be applied to secondary.
Primary voltage should be measured at pins 1 and 6 of the socket V3.
Output power switch must be at 1W.
That's gonna be complicated, probably transformer needs to get out of board
It would be nice to know even DC resistance and inductance of primary.
These measurements are kind of primitive, but could give an idea how OT was done.
I assume there is no complicated interleaving schema, these amps were build cheap (my opinion)
Probably to much headache for jazzkramer.
Cheers, Damir
P.S.
I would like to know the size of transformer core too.