Jump to content
InsaneMultitasker

Myarc cards for sale/repair tips

Recommended Posts

After I get the aspect ratio to come up properly on my images(does so In Photoshop, when I tell it to) I will have the cleaned up scans for the 4 layers of the Geneve PCB and the two for the HFDC ready to be released here to the wild. FYI, maybe tomorrow, if all goes well, here is a sample

Share this post


Link to post
Share on other sites

Is anyone making available the boot eprom chip for the Geneve that removes the swan and allows booting from mutliple devices?

 

 

It is definitely on my todo list, just to remind you.

 

(However, I also plan that my boot ROM has some Swan on the title screen, but maybe much smaller. I don't like boot EPROMs without the Swan. :-) )

Share this post


Link to post
Share on other sites

Well, I finally got it down to fit on a single page from most image programs, So here, with the caveat that they probably not perfect, and though I tried to make sure I only removed clutter or enhanced areas that were not clear, are the resulting pictures. They ave been scaled down from the ones that I was originally editing and may have lost some detail (though they look pretty good to me. If you see something missing like the end of a trace, first before reporting it find Paul's originals on ftp.whtech.com and compare them. I know of at least two traces that didn't have an end point. Enjoy!!

Share this post


Link to post
Share on other sites

Well I got my standard Geneve up and running again, a couple of weeks ago I had an issue with the card when I turned the P-box on of the swan coming up with squiggly lines running vertically up and down the screen. This weekend I replaced the vram chips and it worked for a few turn ons then started another strange activity, the screen with the swan was full of artifacts. I thought that I had blown those dram chips too, but decided first to remove the 9938 and swap it. Now this 9938 is the one I bought from China, when I first blew the card up, some months back. I had started working on the Geneve that I got from Insane Multitasker and used the old chip on there after making sure it was working on mine. I believe the video chip is faulty, and of the first vram chips, one of those tested bad. Don't know if the 9938 blew the ram or vice versa, but the ram was purchase from either Jameco or Mouser, so I don't think they were bad. The second set is fine and I can go into mdos and do thing:)

 

I would say at the moment, beware where you get you chips.

Share this post


Link to post
Share on other sites

For the past year or so, Swim and I have been talking about using switching regulators in place of the linear 7805s.  The primary benefits are reduced heat output and increased efficiency.  The suggestion originally came from ckoba,a past AtariAge member. 

 

  1. Before starting any work I did some baseline heat scans.  After 15 minutes, the three primary 5 volt, 1.5A regulators had reached a temperature of 170F degrees (approx 78C).  The memory chips directly above the regulators were being warmed to 120-140F (50-60C). 
  2. I first replaced all of the old electrolytic capacitors with newer, higher rated components.  A resistance check confirmed no shorts were introduced by my efforts.   I then removed the three primary 5v regulators and the associated input/output capacitors.
  3. Next I installed ceramic capacitors per the application notes.  This consisted of a 10uF capacitor on the input side and a  22uF capacitor on the output side. For this exercise, Swim recommended adding a 0.1uF ceramic capacitor in parallel with the 22uF on the output side.
  4. I reviewed my solder work, tested continuity again for any mistakes, checked for input/output orientation.
  5. Next - the smoke test.  I removed all cards from the PEB and inserted the Geneve.  I turned on the PEB and was greeted with the standard bootup swan.  Next, I added a floppy controller and proceeded to boot the OS.  I left the system running for an hour.  There were no visible signs that the switching regulators were causing any problems. 
  6. A heat scan showed the temperature of the regulators holding below 90F (32C).  I then scanned the chips and found that most were close to the same temperature with exception of the V9938. It was running at about 120F (48C).  I expect this is normal as I did not check its temp before the regulator change.

There are a few more things I want to update, such as removal of the 12v regulator (no need for it in my opinion) and testing whether or not the case will still close properly with the slightly higher regulator form factor. 

 

For a longer burn-in I may replace the heatwave Geneve with this modified Geneve.  Doing so will help me to confirm whether there is a noticeable difference in heat and operation between a PEB power supply and a PC ATX power supply (with 12v tied to the 5v line).  I suppose I should pull out my KillaWatt to compare power draw, to see if there is any difference in power use with the more efficient regulators.

 

Swim and I still need to do some more testing before feeling comfortable with this modification. However, early results are positive.  Here is a copy of the regulator data sheet. We'd be happy for anyone to look things over to make sure there aren't any "gotchas" that we haven't considered.   I've included pictures of the updated Geneve for reference.

 

[attachment=601702:v78xx-1500.pdf]
[attachment=601699:IMG_1113.JPG]

[attachment=601700:IMG_1114.JPG]

[attachment=601701:IMG_1115.JPG]

Share this post


Link to post
Share on other sites

Fascinating stuff!

Great job Tim and Richard for figuring out this mod, it's pretty easy to see the heat damage that has already occurred...

What's the 12V regulator for?

Other things I don't know, whats the voltage on RGB signals?

Does anyone on here remember which chips on the Geneve need to be changed for use with Ron Walters Memex card?

    I vaguely remember some chips needed to be swapped from LS to HCT?

   This page offers a pretty good explanation of logic families and incompatibilities....

     https://www.avrfreaks.net/forum/compatibility-between-chip-families-ls-hc-hct-etc

 

d.

Share this post


Link to post
Share on other sites

What's the 12V regulator for?

The 12v regulator provides power to the video connector.  It's dangerous having it out there, especially with some of the RCA to 5-pin DIN cables people use for composite video.  I think it also powers one of the chips used for composite video so before I do any further surgery I still need to trace the connections.  A jumper to enable/disable the 12v output on the connector would have been a nice "feature".   (I disabled the 12v output on my TI for safety reasons).

Share this post


Link to post
Share on other sites

Confirmed that the new regulators work well with the Myarc case. They will no work as-is with a TI or corcomp case, as the body of the regulator partially covers the threaded holes used to keep the case together.  It might be possible to bend the leads a bit to provide sufficient clearance.  Some different varieties of dc-to-dc switching regulator may provide the 'traditional' through-hole.

Share this post


Link to post
Share on other sites

I had a chance to take Heatwave offline this afternoon.  I have temporarily swapped the Heatwave BBS Geneve with this newly updated card.  I'll let it run for a few days to see how well it operates. I hope to find time to refresh the BBS card while it is out of service. :)

 

On a related note:  although the Myarc cases look like plastic they are conductive.  With the test leads in close proximity, I registered 1.5K; at a distance of 1 inch it was aproximately 3.4K.  I suspect case composition varies. A few of the dc-to-dc converter leads needed to be clipped to avoid contact.

Edited by InsaneMultitasker

Share this post


Link to post
Share on other sites

The Geneve schematic incorrectly depicts u55 in two places.  I seem to recall this was brought up some time ago.  Looks like my repair notes propagated this error.  Such is life.

  • The 12v regulator (u55) supplies voltage to the MC1733CP video amplifier and the video port.
  • The 5v regulator (u56) supplies voltage to the V9938.  It may be appropriate to refresh this regulator or replace it with a more efficient dc-to-dc part as wileyc mentions in another thread. 
  • I somehow missed replacing the capacitors associated with these two regulators when I changed the caps.  :dunce:

The modified Geneve has been running for 8 hours with no issues.  I'll let it run for the weekend. 

Share this post


Link to post
Share on other sites

I had a chance to take Heatwave offline this afternoon.  I have temporarily swapped the Heatwave BBS Geneve with this newly updated card.  I'll let it run for a few days to see how well it operates. I hope to find time to refresh the BBS card while it is out of service. :)

 

Been running a week without any problems.  I may take the system offline this weekend to swap cards and do some more work with the new regs. 

Share this post


Link to post
Share on other sites

too cold out in the garage to do any work on the Geneve. I did take the system down briefly to replace the boot EPROM with Gazoo's version 1.00.  I also completed quick heat scan.  The two dc-to-dc converters on the LED side of the board were running between 95-100F.  The converter on the V9938 side was running just under 110F.  The 9938 was running at 135F and most other chips were in the 100-120F range.  For reference, this is with +12v supplied to the 5v rail via a PC power supply.

Share this post


Link to post
Share on other sites

Hmmm, good question.  I didn't bother to check the outputs.  I'll find my extender card and measure them for you the next time I work on the Geneve.

5.02 volts on the one I measured this weekend. Sorry it took so long.  I'm hoping the cold weather moves out in time for this weekend so I can finish modifying a second Geneve and maybe an HFDC or Myarc FDC. 

Share this post


Link to post
Share on other sites

Not too long ago I purchased a new 450 watt power supply to replace the very aged supply in the Heatwave BBS geneve system.  While reading up on using ATX supplies for bench use (e.g., for repair testing) and low current draws (since I am installing switching regulators in some of my cards) I came across some references to newer supplies needing a higher load to activate and properly regulate power.  I have not figured out what this means for my supply but it is certainly information to tuck away for later.

 

I inspected my new power supply and realized that the manufacturer used black wires for everything. There is no color coding!  Argh.  Not wanting to chop the connector without a way to test the pinouts (and validate my work without blowing something up in the process) I poked around for a visual solution.  I first came across some bench conversion kits.  They sounded nice but the comments and manufacturing origin made me skeptical of the quaility.  I then happened across a color-coded extender cable that looks like it might do the trick:

 

https://www.ebay.com/i/331518241847?chn=ps

 

I purchased two of these cables.  My plan is to cut the proper end, tie the ground, +5, and +12 together, and then connect the +5, +12, -12, ground wires to the TI PEB backplane.  This should allow me to easily swap out power supplies in the future, if needed. 

 

The only thing that isn't clear to me right now is what happens if the power supply has more than one 12v or 5v rail. Do all of the 20/24 pin connector voltages come from the same rail and does it even matter?  Anyway, I hope to receive the cables by the end of the week so that I can start updating my system.

Share this post


Link to post
Share on other sites

About 19 years ago I replaced a generic ATX PS in a 486DX4 server system(performed similarly to a desktop Pentium at the time) with a proprietary ATX from a DELL I think... the wire colors were almost all different... I managed to get the server back up with about five or six wires(that got laughs) and maybe one lucky guess.

...as I recall internally one of the supplies had many different and similar +5v regulator sections, whose outputs all joined together...
...the other PS had a completely different looking design... but most of the motherboard's seem to link them together(solder) at the connector.

If the similar voltages source from the same rail... then the resistance between those lines should be zero.

Edited by HOME AUTOMATION

Share this post


Link to post
Share on other sites

I have an Antec 700W and it states it has 4 +12V 30A rails, 1 +5V 18A and 1 -12V rail.

 

I looked at a Thermaltake 1500W and it has 1 +12V rail at 150A.

 

Guess it all depends on what brand and wattage you have and how much you need in the PEB.

Share this post


Link to post
Share on other sites

Today I was triaging some of my remaining Myarc cards.  While testing a floppy controller, my favorite monitor whined, popped, and quit working before my eyes. 

 

Fast-forward and hour or so later.  I was testing my first Myarc HFDC when I started to smell something acrid; seems the AT power supply I was using was overheating or pushing itself toward failure.  I quickly shut things down and disconnected the power supply.  I don't know if it was dust, a component, or both but I don't want to take any chances.   I tested a second HFDC and that worked just fine. 

 

I cracked the case of another HFDC and inspected the card. Sometimes the regulators are jumpered and since I haven't looked at these cards in a while, old habits set in. Everything looked fine.  I put the case back on and inserted the card into the PEB.  I powered the card up and immediately saw a flash of light and a LOUD bang.  Nearly scared me to death!  The PEB was still running (!) so I quickly powered everything down and waited for my heart to slow down a bit.  Meanwhile, the room filled with a bit of smoke, so I had to open a window.

 

I pulled the card and carefully opened the case.  It is fortunate that the case was in place and that I wasn't testing the card with a PEB extender.  I suspect I would have been right in the cross-hairs of capacitor shrapnel.

 

I guess these things come in threes.  Might be time for me to take a break for the day :-o

 

Share this post


Link to post
Share on other sites

Ouch!  I'm glad you had that case on too, Tim! Capacitor shrapnel is bad for biological creatures. . .

 

Maybe we should take up a collection and get the insane one a military grade vest to wear while testing/repairing/upgrading TI/Geneve hardware. ;)

Share this post


Link to post
Share on other sites

Ouch!  I'm glad you had that case on too, Tim! Capacitor shrapnel is bad for biological creatures. . .

Indeed! Oddly enough, no matter how I tried I could not get the camera to focus on that capacitor.  It was almost as if it was taunting me after the fact. 

Share this post


Link to post
Share on other sites

Today I was triaging some of my remaining Myarc cards.  While testing a floppy controller, my favorite monitor whined, popped, and quit working before my eyes. 

 

Fast-forward and hour or so later.  I was testing my first Myarc HFDC when I started to smell something acrid; seems the AT power supply I was using was overheating or pushing itself toward failure.  I quickly shut things down and disconnected the power supply.  I don't know if it was dust, a component, or both but I don't want to take any chances.   I tested a second HFDC and that worked just fine. 

 

I cracked the case of another HFDC and inspected the card. Sometimes the regulators are jumpered and since I haven't looked at these cards in a while, old habits set in. Everything looked fine.  I put the case back on and inserted the card into the PEB.  I powered the card up and immediately saw a flash of light and a LOUD bang.  Nearly scared me to death!  The PEB was still running (!) so I quickly powered everything down and waited for my heart to slow down a bit.  Meanwhile, the room filled with a bit of smoke, so I had to open a window.

 

I pulled the card and carefully opened the case.  It is fortunate that the case was in place and that I wasn't testing the card with a PEB extender.  I suspect I would have been right in the cross-hairs of capacitor shrapnel.

 

I guess these things come in threes.  Might be time for me to take a break for the day :-o

 

Yes, last year I placed a Horizon into the PEB that had not been fired up for 17+ years and it popped loudly too. It was a cap that wasn't happy to be powered up, got lazy I guess.  :-D

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...