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Myarc cards for sale/repair tips

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For reference, I am guessing those caps were replaced by Don as part of his attempts to resurrect cards or by me in the late 90s for the same reason. Either way, they are more than likely 20+ years old. I would recommend replacing all electrolytic caps if you have the ability to do so.

Understood, ability yes, desire, not so much, if they work well. Many kinds of projects and so little time to do them ;)

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We are facing a last centuary computer, its capacitors are between 20 and 30 years old. They are very important because they ensure smooth operation, stability of the board. Changing all of them cost so few so no need to take risks.

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Yes of course, both you and Tim, make a good point. I am just looking at the damage caused by someone who removed the regulators and seriously damaged the traces and pads in those areas. Don't want to tear up anymore, though I do know how to remove solder. :)

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The Geneve 9640 is a fragile computer but it is not made out of crystal :-)
I think that if people like to use very old computers, they must have a minimal tools set to make a bare minimum in maintenance or repairs. This set must at least contain a good soldering iron, desoldering pump, desoldering wick and multimeter. Without spending a lot of money, we find good quality item. Then, it is necessery to learn the good maner for using them. Learning is not difficult.
Because, we have to accept that all these old materials have, and since a long time, exceeded their life time envisaged by their manufacturer. They are 30 years old or more. To keep them alive, to continue to use them, that must include a good maintenance.

In addition, a hurried work, avoiding a preventive maintenance could permit to quickly enjoy of the material but it never offers a lasting usage. Old computers are a fantastic hobby, they offer so many nostalgic pleasures. There is no rush, we must take our time :-)

Edited by fabrice montupet
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I imagine the scene (laughing!) Fortunately all the Geneve PCB aren't like this.
I wonder which manufacturer produced the PCB.
To desolder without damage this fragile PCB, it is absolutely vital to have a a steady hand and respect a good desoldering and time temperature : about 3s at 360°C/400°C.

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Fabrice, I was going to use sockets, either trimmed down from chip sockets, or machined sockets, that would accept the 7805 regulators, and epoxy them to the board for strength. Then I was going to run wires to the various places that the pads and traces would have routed to. But you mentioned via repair, or in my terminology, through holes, so my question is do you have a method to repair the actual pads and connections through the hole, to the various layers? I am not an electrical engineer, just a hobbyist, that has soldered over the years, so if there is a better way, I would desire to learn. BTW, I did replace the capacitors, except one, I ran out of the correct ones, will need to reorder some more, and in the process did have some pad issues. Thanks

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Here is what I was alluding to, on placing sockets and then adding the regs. these are not set in stone(epoxy) yet. Though this is the direction I am traveling, unless I can get a better solution. I saw a couple of videos on repairing holes, but the kits were out of my range in price, till I get a better job. And I did replace the capacitors, in the power circuit, except the one in the upper right(orange colored).

 

post-41593-0-47044400-1532955894_thumb.jpg

Edited by RickyDean

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Depending on which through-holes are damaged, it may be as simple as a single wire between the regulator and the card's supply or output. The capacitors tie into the input/output leads, so you might find contiunity to other components through those adjacent connections. Unfortunately, the regulator leads are often not cylindrical and when desoldered (and pulled) they can destroy the cores and pads, particularly if the Geneve is one of those "brittle" cards I refer to periodically.

 

I know one person who used a small drill/dremel to clean out the through-holds on his card, not realizing that doing so destroyed the connections between the pads and the middle board layer. Now that was a hard card to restore....

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Tim,

Do you know if these cards where generated CAD/CAM or hand drawn?

Can you give us a rough guess of number of versions?

Was there any talk in the Cecure Electronics day of reproducing the Myarc cards, or was keeping the broken ones going more than could be handled?

thanks,

d.

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Sorry, I don't know the specifics regarding how the cards were manufactured or created. Where there were corrections made to the traces, those certainly appeared to be hand-drawn.

 

I know of at least one early version of the Geneve that did not have a gate array and if I recall correctly, was not as robust a card. The Geneve we know today had had at least two iterations if we include the trace corrections. I don't know how many board runs were made though if I were to guess I would say at least three based on the color of the mask, the trace correction, and the brittle nature of some cards. Eric Bray is one person who might know the answers to some of these questions, as he knew/knows Lou. (As an aside, there are at least two runs of HFDCC cards, notable by the colors of the board, the quality of the traces, and the QIC-02 circuit differences)

 

As for Cecure reproducing cards I recall discussions but little came of it. The TI-CARES deal gave Cecure a shot in the arm, However, while both the TI and Myarc business kept Cecure busy it certainly was not a sustainable, long-term model. It was always my impression that more money was spent supporting the TI community than came into the business, whether through long hours of phone tech support via their 800 number or trying to drum up new business from a dwindling group of people who demanded more service for less money. Other non-TI efforts to make money to keep the TI business afloat took time and resources away from the very TI business that was slowly dissolving as people left for other computers. By the time I took ownership of Myarc repairs, the situation was pretty rocky. The rest is, well, history.

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so my question is do you have a method to repair the actual pads and connections through the hole, to the various layers?

 

For this Geneve card, I used this method:

 

I remove all the copper off the damaged through-hole.

I remove the coating off the trace(s) that are linked to the damaged pad.

I slide very thin wires (one ou two max.) through the hole keeping enough space for the component leg to slide too.

I place the component taking care that the thin wires have not moved.

I apply soldering flux into the area to solder.

I solder the leg to the hrough-hole (thus also the added wires)

I cut the extra lenght of the wire that permits me to make the continuity between the layers keeping enough lenght to go to the trace(s) to link.

I bend the wires against these traces

I solder the wires to the traces.

I verify the continuity of traces with a multimeter

 

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Sounds good, I will probably do that for the sockets, but will still use the method shown in my picture, it should make replacing the regulators in the future, easier. The kit I saw was like 200+ dollars, and at the moment that's a little out of my reach, as I have other things standing in the way. Thanks sir, appreciate your knowledge and dedication.

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Well I've still been working on the card I got from Tim and still haven't gotten it fired up yet, will try to work on it some this weekend. I have however been cleaning up the scanned images from 1987, using Photoshop and have cleaner images to follow traces and such, a lot on man hours over Labor day weekend.

But in the process I did have a chance to examine my PFM+ machine, last night and found that the wire circled was not attached to the chip leg, but just laying very near it. When I soldered it back and plugged the Genny into the PEB she came up with the boot screen, The third time in 20 years, I was a happy camper.

Tim are there any schematics, drawings or other info as to the blacked out chips and wire paths for the PFM+ and I believe 384mb mod, maybe wrong there though?

post-41593-0-33686400-1536321676_thumb.jpg

post-41593-0-56902600-1536321696_thumb.jpg

Edited by RickyDean
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Here is an example of a cleaned scan. Keep in mind this is several hours work zooming in close and enclosing the speckled areas, to remove the specks and other ugly areas. Still not absolutely done with this one. I did about 5 of these types this week including labor day.

post-41593-0-45700500-1536323030_thumb.jpg

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Nice! Is someone getting ready to etch new boards?

Not thought about doing it recently, But the thought has crossed my mind. I have no experience with an electric CAD program, but have ACAD experience in machining, so I have tinkered with the idea of recreating the board, somewhat as Stuart has done, with 9995 Cortex boards, using other logic for the gate array, as they are not produced any more. Just an idea though.

The above is just to get clean copies and to be able to visualize how the traces run, though the various layers of the Geneve. That helped last night when I was looking for the issue on the above mentioned Genny (my girl).

Edited by RickyDean

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Even if someone etched a new board, there are a very limited number of Gate arrays. The big issue would be reproducing the gate array. Also not sure how easily available the 9938 chips are? Are new chips available, or is it pretty much an old but limited inventory out there?

Beery

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I know when the original M.E.S.S. emulation was done up, Raphael did not have the gate array logic. He was just given what the various CRU bits did and what the memory layout was that toggled everything in the architecture. I remember digging around that M.E.S.S. source code back in the 2003-2004 (or therabouts) timeframe.

 

As far as what has transpired since with the incorporation into MAME, I doubt that aspect changed. I could be wrong, but to my knowledge I have never heard anyone say they had the details to ever reproduce the gate array.

 

The closest anyone came to ever understanding the gate array was Ron Walters when he developed the MEMEX and GenMod. I never heard him say Myarc/Lou provided the details of the array either. He accomplished what he did on his own.

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The prototype machines didn't have the gate array though, so the circuitry that simulates it on them should also be somewhat informative (although not necessarily complete). I do have one of those prototypes, and I know of another one in Germany. . .

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Well I've still been working on the card I got from Tim and still haven't gotten it fired up yet, will try to work on it some this weekend. I have however been cleaning up the scanned images from 1987, using Photoshop and have cleaner images to follow traces and such, a lot on man hours over Labor day weekend.

But in the process I did have a chance to examine my PFM+ machine, last night and found that the wire circled was not attached to the chip leg, but just laying very near it. When I soldered it back and plugged the Genny into the PEB she came up with the boot screen, The third time in 20 years, I was a happy camper.

Tim are there any schematics, drawings or other info as to the blacked out chips and wire paths for the PFM+ and I believe 384mb mod, maybe wrong there though?

Is that a PFM or PFM512? If the latter, you can update it with the files on the MDOS 6.50 distribution disk.

 

Fabrice created nice, updated instructions for the 384K mod based on some of my original documentation.

 

I have not released any of the PFM modification documentation into the wild. My notes are hand-written and not really adequate to step-wise reproduce the installations. There are also some 'protections', including at least one undocumented trace cut that I would need to pull out of my deep storage brain cells. The only other person who currently has some of the PFM information is Swim.

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Is that a PFM or PFM512? If the latter, you can update it with the files on the MDOS 6.50 distribution disk.

 

 

I always thought it was called the PFM +, but the year you see in the picture is 1994, was the PFM512 available then? Thanks for your good work on this system though.

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I always thought it was called the PFM +, but the year you see in the picture is 1994, was the PFM512 available then?

PFM+ is a stack of two 128K chips whereas the PFM512 is a single 512k chip. I couldn't see the number on my phone screen; I see now it is the double stack. Your Geneve is atypical in that the identification information was usually obscured or removed from the chips.

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