Amek M2500 thread

[glbaudio]

I REALLY DON"T LIKE THE BADGERING.........

JR

I totally agree.
And not to mention about the self-elargement about works (2 times the same pictures) clearly not about audio pro...maybe somebody can be interested, not me.
A message to all the real Amek 2500 users: feel free to contact me! I'm very busy but I always try to help nice persons.

 

[MidnightArrakis]

pictures) clearly not about audio pro

[pictures) clearly not about audio pro] -- This chassis is a "12-Channel Stereo Audio Input X 8-Channel Stereo Audio Output Digitally-Controlled Matrix Router/Switcher" used to route audio channels around as is needed:


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[glbaudio]

[pictures) clearly not about audio pro] -- This chassis is a "12-Channel Stereo Audio Input X 8-Channel Stereo Audio Output Digitally-Controlled Matrix Router/Switcher" used to route audio channels around as is needed:

View attachment 118089
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Nice! Open a new thread and share this project!

 

[MidnightArrakis]

Nice! Open a new thread and share this project!

[Open a new thread and share this project!] -- SORRY!!! NO CAN DO!!! ..... The blue chassis image I had inserted within my previous comment was a product I had designed for a previous video electronics employer I had worked at and who was bought by another larger company and put out-of-business back in 2011. So, while I performed all of the mechanical and PCB designs for all of my then-employers' products back then, not only do I not have all of the engineering documentation to even think about resurrecting this product for a DIY-project, but the general electronics circuitry behind what made this product tick is way far and beyond what is typically found on this forum. I think you will agree with me that no matter how hard you look throughout this entire forum, you won't find anything on "High-Speed Digital Matrix Routing & Switching" anywhere.

On the other hand.....something like this "Audio Switcher" -- could -- make for an interesting patchbay, NO???

/

 

[jessequin]

IIRC the tantals in the EQ module are across the rails. It´s a very good idea to replace them with electrolytics and increase their value at least x10.

jensenmann, are you selling your M2500??​

 

[gyraf]

This one? https://groupdiy.com/threads/amek-m2500-parting-out.87373/

 

[jessequin]

This one? https://groupdiy.com/threads/amek-m2500-parting-out.87373/

Yes, but it won't let me reply on that thread for some reason!

 

[JohnRoberts]

Yes, but it won't let me reply on that thread for some reason!

https://groupdiy.com/threads/private-messages-conversations-permission-update.82401/
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Black Market​

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As the BM header clearly states there are hurdles to filter out inactive members to improve security (you need more posts).

JR

 

[jensenmann]

jensenmann, are you selling your M2500??​

Yes, I´m forced to part it out. I have to move house this year and the frame won´t fit through any door or window anymore without creating serious damage and cost. Both is no option.

 

[jessequin]

Are we allowed to exchange emails/messages on here @jensenmann ?

 

[jensenmann]

pm´d

 

[xvogricx]

Hey @jensenmann i would be willing to buy the whole desk, you think there is no way to get it out whole from your house? Also what would be the price? We can talk privately if easier

 

[jensenmann]

I have a completely weird fault in a friend´s M2500. The desk blows mostly the -17V rail, sometimes the fuse (10A) is gone, sometimes the regulator card (GL48 see appendix) shuts off. I´ve replaced the socket of it´s LM338K since it was burnt and the LM338 also had a burnt pin. With the repaired regulator the desk worked shortly, then the +17V rail blew, not the fuse but it´s regulator shuts off. While searching for the fault it stopped shutting off but then the 11V logic rail showed the same behavior. I found a faulty subregulator in the master section which brings 11V down to 5V. After that repair the desk worked for 10 minutes, then again the -17V rail shuts off. I have no idea what fault could create this behavior.

When I was working on the -17V rail for the first time we started with measuring current of the -17V rail with the empty desk frame, then inserted channels and accordingly measured. The weird thing now is that all the figures made completely sense. There was no single channel drawing so much current, that it could have blown either a fuse or cause the regs to shut down. At the end of the day we had no solution and I had to leave the studio with a non working desk. Next weekend we´ll try again, but I need some ideas where to look at.

But by writing this it occurs to me that maybe the crowbar circuit could somehow be activated, but this doesn´t give me an explanation with the other rails misbehavior.
Any ideas????

 

[gyraf]

..is it a known-genuine LM338K (those are rare)?

Could you add an extra, separate and somewhat lower rated or faster, fuse between psu and desk, to verify if the problem is actual overload from desk or hysterics in PSU?

 

[jensenmann]

That´s a great idea. I can make an EP8 adapter with fuseholders for every rail. It´d make sense to add precision power resistors inline for current measurement. The -17V rail measured app 3,5A with the fully loaded desk. Matt Syson somewhere mentioned measuring a desk with full output signals drawing 20% more current than idle. That´s a good starting point for the fuses.

The new LM338K is from a reputable dealer. I hope it is genuine but don´t know it for sure.

 

[Matt Syson]

You can get a fair estimate of the current being drawn by measuring the voltages across the wirewound resistors then calculate using Ohms law. Fuses somertimes blow because they are overheated as the AC current is 1.4 (or is is 1.6?) times the DC current and heating is current SQUARED. If the little caps on the regulator board have failed (dried out) the LM338 could be oscillating at HF.

 

[jensenmann]

That´s exactly how I measured the -17V rail. The entire desk and PSU has been recapped 2 years ago and all tantalums have been replaced with electrolytics. This *should* exclude caps as failure. And since all shut downs or blown fuses happen within 10 minutes or faster I tend to believe that overheating is not a problem. I´ll order parts for an adapter like Jakob suggested with fuses und measuring resistors inline. The owner agreed to invest that money since he has a large tracking session coming up in a few days, so he wants his desk to work reliably.

 

[jensenmann]

The desk is working again, thanks good people for your input!

I made the adaptor suggested by Jakob and measured currents through 0,1Ohm precision power resistors thermally-glued to a heatsink. Each rail had an external fuse using car-fuse holders. After fiddling with the right fuse values (underrated compared to the PSU rail fuses) we found out that the problem is inside the PSU. Ether the PSU-internal higher rated fuses blew or the regulator shut down, while the external, lower rated, fuses of the adapter kept working. Hence the problem had to be inside the PSU. In the picture you can see the current measurement of the three problematic rails. We did a video of what happened when the PSU was crapping out and found either the +17V or -17V rail to be the first to shut down. It then turned out that the crowbar circuit on these two rails had defective thyristors as well as their according driver transistor were dead. Why the +11V rail also occasionally crapped out in that process is beyond my understanding, though. It´s crowbar circuit was ok.

Just for the record, the +17V rail is pulling 6A and the -17V rail is pulling 5,3A current in a 36 channel desk with app 12 channels of upgraded chips (TLE2074 instead of TL074). The 11V rail is pulling 2,2A. All values idle.