Ensoniq eps16 + main board issue

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Hyde
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Ensoniq eps16 + main board issue

Post by Hyde » Sun Oct 09, 2016 7:18 pm

I picked up an eps16+ that is in screen self test mode. I've downloaded the service manual & deducted that it's an issue on the main board. That's where the manual stops. I'm happy to change out the main board but, I can't find one available. So I'm wondering if there are any other diagnostics I can do to narrow it down to a component? I've reset all of the cables & there is nothing visually that raises any flags. I'd love to have this unit operational!
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Re: Ensoniq eps16 + main board issue

Post by blueknob » Sun Oct 09, 2016 9:14 pm

"downloaded the service manual" - I bought mine from Syntaur, it does give a lot of useful clues and from memory some test codes. To my frustration it talks of a diagnostic floppy disk which I've never seen, but naturally would like.
I've had an EPS16+ main board fail on me, took a while to find the fault, was indeed a chip.

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Re: Ensoniq eps16 + main board issue

Post by Hyde » Sun Oct 09, 2016 9:36 pm

blueknob wrote:"downloaded the service manual" - I bought mine from Syntaur, it does give a lot of useful clues and from memory some test codes. To my frustration it talks of a diagnostic floppy disk which I've never seen, but naturally would like.
I've had an EPS16+ main board fail on me, took a while to find the fault, was indeed a chip.
Any pointers would be appreciated. It looks like some of the chips on the board are remove able w/o soldering? Any tricks for this? Do you remember which chip was bad in yours? How did you figure this out? Thanks, Hyde
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Re: Ensoniq eps16 + main board issue

Post by madtheory » Sun Oct 09, 2016 11:35 pm

Use a chip removal tool, or gain experience with levering out chips with a flathead screwdriver on some device you don't care about.

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Re: Ensoniq eps16 + main board issue

Post by Hyde » Mon Oct 10, 2016 2:11 am

madtheory wrote:Use a chip removal tool, or gain experience with levering out chips with a flathead screwdriver on some device you don't care about.
Any way to test said chips? Or is it a replace & see what happens s scenario?
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Re: Ensoniq eps16 + main board issue

Post by blueknob » Mon Oct 10, 2016 7:54 am

In my view there is no easy way to fault find the board, I think a lot comes from experience. Look at page 25 of the Service Manual and check page 8 then page 10 those are your starting points. At a more basic level, make sure your boot floppy is good. And also those ribbon cable connectors are reeeealy stuck on tight.

If anyone knows of that diagnostic floppy disk from Ensoniq - let us have it!!

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Re: Ensoniq eps16 + main board issue

Post by Hyde » Mon Oct 10, 2016 8:04 am

blueknob wrote:In my view there is no easy way to fault find the board, I think a lot comes from experience. From memory the only chips in sockets are the 2 OS EPROMs, the 68000 and the 68k series I/O controller. Look at page 25 of the Service Manual and check page 8 then page 10 those are your starting points. At a more basic level, make sure your boot floppy is good. And also those ribbon cable connectors are reeeealy stuck on tight.
So far the drive isn't in the equation. The unit goes straight into "screen self test mode". Will do. Thank you.
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Re: Ensoniq eps16 + main board issue

Post by rhino » Mon Oct 10, 2016 5:31 pm

As in all vintage Ensoniq boards, clean every removable connector. They have a well-known problem with powdery corrosion.

Remanufactured main board MAY be available from
http://WWW.TheSoniq.com

Not, cheap, but have gotten several mainboards from him and saved another Ensonic.
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Re: Ensoniq eps16 + main board issue

Post by Hyde » Mon Oct 10, 2016 5:53 pm

rhino wrote:As in all vintage Ensoniq boards, clean every removable connector. They have a well-known problem with powdery corrosion.

Remanufactured main board MAY be available from
http://WWW.TheSoniq.com

Not, cheap, but have gotten several mainboards from him and saved another Ensonic.
Thanks for the link. Wasn't familiar with this source. Yes, I reset the cables & disconnected on the keyboard end. That gave me the results consistent with a keyboard cable fail. Seems pretty certain that cables are ok & the issue is in the main board. I'll try to pull this chips this week & reset them. Maybe that'll provide some further success.
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Re: Ensoniq eps16 + main board issue

Post by Rasputin » Tue Oct 11, 2016 4:27 am

Tracking it down is going to be pretty tricky without either luck or experience on your side, but if reseating any socketed chips / ribbon cables, etc. and looking for anything visually wrong (broken traces, etc.) doesn't get you anywhere then pick up a logic probe. They're cheaper than you'd assume.

Assuming you've already checked to make sure you've got a solid +5V digital rail on the mainboard, if you've got a logic probe then check the reset activity on the CPU.

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Re: Ensoniq eps16 + main board issue

Post by Hyde » Tue Oct 11, 2016 7:47 am

Rasputin wrote:Tracking it down is going to be pretty tricky without either luck or experience on your side, but if reseating any socketed chips / ribbon cables, etc. and looking for anything visually wrong (broken traces, etc.) doesn't get you anywhere then pick up a logic probe. They're cheaper than you'd assume.

Assuming you've already checked to make sure you've got a solid +5V digital rail on the mainboard, if you've got a logic probe then check the reset activity on the CPU.
Thanks for the advice. I'll try to pull it tomorrow & get a better look at things. We'll see what I find & report back. Maybe I get lucky & find the problem... We'll see
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Re: Ensoniq eps16 + main board issue

Post by Jabberwalky » Tue Oct 11, 2016 8:53 pm

I can't remember if mine was stuck in self test mode (I recall it just displaying things when pressing the instrument buttons), but it wouldn't boot and 2 of my ribbon connectors were shot. I ended up just cutting the ends off, and moving them down the cable.

You could check continuity on the ribbons.

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Re: Ensoniq eps16 + main board issue

Post by Hyde » Tue Oct 11, 2016 9:17 pm

Jabberwalky wrote:I can't remember if mine was stuck in self test mode (I recall it just displaying things when pressing the instrument buttons), but it wouldn't boot and 2 of my ribbon connectors were shot. I ended up just cutting the ends off, and moving them down the cable.

You could check continuity on the ribbons.
Thanks. I'll check that too
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Re: Ensoniq eps16 + main board issue

Post by Hyde » Wed Oct 12, 2016 6:40 am

work in progress here. Pulled the ribbon cables to the keyboard & floppy. tested them. both have continuity. bought two chip removal tools & reset all the chips. put it all back together & IT still comes up in "screen self test mode".
i pulled the main board & took a closer look. nothing seems odd. its really pretty clean for it's age.

so, as a reiteration, i get no action at power up. the disk drive green light is on & i get the yellow button lights but, no insert boot disk prompt
, or any main screen info, until i start hitting buttons.
all the buttons display properly across the screen. according to the service manual, this tells me it is a main board issue. but, what issue exactly, is a mystery because, i can't get it out of screen self test mode. any thoughts?
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Re: Ensoniq eps16 + main board issue

Post by Jabberwalky » Wed Oct 12, 2016 9:05 pm

If the floppy light is on, wouldn't that indicate that it's attempting to read from it, and possibly not going any further? Are you certain the floppy works? Also, I'm pretty sure the synth won't boot if there is an issue with the keyboard, since it runs through that before the main board. I'm just going off memory here.

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