Amek M2500 thread

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Spaceyjb

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Oct 9, 2016
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18
Great!
I finally got back to GroupDIY and found this thread. I have bought M2500a for about 7 years ago and was quite lost, becouse of lack of any inforamtion. So i am really happy to find this thread.
I love the desk. We fully recapped it and rebuild PSU. We used different fuses than original has as + rail burned quite often and we found out we cannot find originals ones.
I use the desk everyday since - mostly for recording. I have tried to mix on it, which turned ok, but there are some problems there, as my desk was unfortunately modified to bring 72 channels to the mixbuss. As i do not have much time for finishing repair of the desk I postponed work on this.
I think i probably ask some question about that later, but for now i'd like to ask about main input module channel PCB. My plan was to get rid of the modification and put it into original state. For that i do need new main PCB boards. Have you made them new and where?
Next: i thought to turn some of the preamps to trasformer ones. It seems it is easy "swap the board" option. I did not find anybody having PCB board layout of those.
If anybody needs i have full original schematics and schematics for my modification (if someone is interested). I will post more about my desk later.
Thanks
Jan
 
Last edited:

jensenmann

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Oct 10, 2004
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Hi Jan, welcome aboard!

I doubt that anyone has a complete layout of the M2500A main PCB. You´d better try to bring the modules you have back to original state.

The transformer preamp uses a different gain pot than the transformerless preamp which means the boards cannot be interchanged without replacing the pots. I made a layout for the transformerless preamp card because a friend needed these for his desk. But I don´t have a layout for the transformer preamp as my desk is fully fitted with these anyway. I´m not sure if it´d even make sense to do a 1:1 layout as Sowter, who made the original transformers for these boards, changed owner and seems to not make as many custom jobs as they used to. Add ROHS on top of that and it´s pretty unlikely that these trannies will be available at all. From a technical POV they are 1k:5k 1:2,25 mic input transformers (PRO AUDIO TRANSFORMERS ARCHIVE look for 4057). They could be replaced with other brands, e.g. Lundahl LL1528. But as the circuit in general is nothing special I don´t see any advantage in swapping transformerless to transformer preamp cards.
 

Spaceyjb

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Oct 9, 2016
Messages
18
Hi Jan, welcome aboard!

I doubt that anyone has a complete layout of the M2500A main PCB. You´d better try to bring the modules you have back to original state.
Hi Jensenmann.
Thanks a million for opening this thread and for your great tips ragrding buss amp and bypass capacitors. I will definitelly try them out.
Regarding bringing my desk to original state: Unfortunatelly it seems the modification was too aggresive - including backplane and adding summing amps - so i am quite scared to do it, using old PCBs. Lots of significant czech albums were recorded and mixed on this desk, so it should be well thought of. As soon as i get to documentation i will post the schematics of the modification. Maybe someone will find it interesting.
Thanks for explaining tranny pres. I thought it could be interesting to have that option, but if there is no significant sonical advantage and it requires gain pot change - i won’t do it. As i said i am scared to solder to main PCBs more than necessary, as they feel quite sensitive.
Jan
 

jensenmann

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You are right, the PCBs are "home-etched style" and very sensitive to mechanical stress. Any work on the PCB needs to be done very careful in order to not lift or break traces.

Keep us updated with the modifications. It´d be very interesting, at least for me, what the previous owner changed.
 

glbaudio

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Joined
Nov 15, 2008
Messages
56
I've made with Eagle the re-draw of the Schematics and PCBs of M2000A modules, submodules and power supply, as I'm an M2000/2500 owner.
I've also made a substitution for the Hamlin reed relay.
 

Attachments

  • AMEK M2000A SCHEM.pdf
    1.6 MB · Views: 47
  • AMEK M2000A PCB.pdf
    1.2 MB · Views: 30
  • DL144 MicAmp Sub.pdf
    189.7 KB · Views: 33
  • GL121 LineAmp Sub.pdf
    109.2 KB · Views: 24
  • GL123 VCA Allison Sub.pdf
    138.8 KB · Views: 20
  • GL124C EQ (2500).pdf
    390.7 KB · Views: 25
  • GL131 Vca DBX.pdf
    159.7 KB · Views: 20
  • GL48 PCB.png
    GL48 PCB.png
    44 KB · Views: 33
  • GL48 Power Supply 1 leg.png
    GL48 Power Supply 1 leg.png
    212.7 KB · Views: 30
  • GL179 Phantom Power.png
    GL179 Phantom Power.png
    18.9 KB · Views: 30
  • IMG_2824.jpg
    IMG_2824.jpg
    55.4 KB · Views: 29

glbaudio

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Joined
Nov 15, 2008
Messages
56
Hi glbaudio
you have redraw all the PCBs?
Mostly. Input channel, All the sub-boards in various versions (eq A and C, VCA Allison and DBX, ...), all rails of power supply. And the reed relays adapter.
Still missing the other modules (Aux module, C/R, and Studio monitor), no time to do it!
I have all the scans, but to search a problem, the redraw is really useful.
 

MidnightArrakis

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Sep 25, 2015
Messages
307
I've made with Eagle the re-draw of the Schematics and PCBs of M2000A modules, submodules and power supply, as I'm an M2000/2500 owner.
I've also made a substitution for the Hamlin reed relay.
Send me all of your EAGLE files, BOM's and the dimensions of the PCB's and I will take a look at them and see if I can help you guys out here!!! Include any information that details modifications and upgrades that either has already been implemented or that you wish to have implemented. Then, I can include those wishes into new layouts. Attached are some PDF files of my previous PCB designs for your review.

In addition, I can also offer you assistance with any mechanical designs as well. Just sayin'.....

/
 

Attachments

  • JBW-Designed -- Various PCB Designs - 2D & 3D.pdf
    2.5 MB · Views: 17
  • JBW-Designed -- RSIII Rear-Panel PCB (Close-up).pdf
    1.5 MB · Views: 3
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    944.5 KB · Views: 3
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    501.1 KB · Views: 2
  • JBW-Designed - CADENCE-OrCAD PCB's.pdf
    633.2 KB · Views: 6
  • JBW-Designed - 256X256 Video Matrix Output PCB.pdf
    1.2 MB · Views: 4
  • JBW-Designed -- SolidWorks mini-Portfolio+FAA Projects+Camera_2108.pdf
    4 MB · Views: 11

58Glammer

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Feb 14, 2022
Messages
63
Location
Germany
Hi, great thread!
Could someone post pics of the different sections of the channelstrip? I just saw pics of the complete board, where you can´t see that much details :)
Also I would be interested how you all proceeded with your boards. These posts are from 2021
I have some PM01 modules in a frame I just recently recapped. But as I read through this thread, I saw it´s recommended to exchange the tantal through electrolytics. Superb!
 

glbaudio

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Joined
Nov 15, 2008
Messages
56
Hi, great thread!
Could someone post pics of the different sections of the channelstrip? I just saw pics of the complete board, where you can´t see that much details :)
Also I would be interested how you all proceeded with your boards. These posts are from 2021
I have some PM01 modules in a frame I just recently recapped. But as I read through this thread, I saw it´s recommended to exchange the tantal through electrolytics. Superb!
next time i will go in my town (where I have the console) I will do it!
 
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