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Myarc cards for sale/repair tips

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It was the same when I got the TI Professional from a local seller; when we powered it up, black smoke came out of the case. It's impressive how dense and black such smoke may be, and still the computer is running. But it was enough to get it for €200 instead of €250, as he planned.

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In slo-mo

 

The electrolytic caps are no fun when they explode and fill the whole room with fuzz either. ;)

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The electrolytic caps are no fun when they explode and fill the whole room with fuzz either. ;)

 

 

The YouTube rabbit hole stuck again... it thought I'd enjoy to watch this video (gotta admit, it's really neat:  https://www.youtube.com/watch?v=EoWMF3VkI6U)

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Thanks, Acadiel, you really know how to motivate me to get back in the saddle.  lol

 

Today I formatted one of my remaining two "good" MFM hard drives using an HFDC for the first time in years.  Two of the four drives were completely seized up.  I was able to get one of them to rotate but it sounded like a garbage disposal.   MY miniscribe spun up but the rotator arm was very tight.  Even after some work it spins but the drive light just blinks and error message.  :(  Fortunately, my ST-251 is functioning and just finished formatting all 820 cylinders without any errors.  Whether it holds data or not is another story..

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I have a hard drive (I'll have to look for it) that you can have, Tim. Don't know if it works. If not you can use it for a door stop. I actually found two ST-251s if you are interested (or if anyone else is interested in one or both of them).

Edited by atrax27407

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Thanks guys. For now I'll stick with the drive that I have, as I might not keep but one HFDC.  If I do keep it, I will probably go the same route Beery took.  I do like the functionality the HFDC brings to the TI and Geneve systems. Of course, as Swim and I were discussing the other night, there is something nostalgic and almost comforting about a big ol' MFM drive putting in the background ;)

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For someone truly interested and capable of repair work, I have another Geneve up for grabs.  This one does work but it has a bad connection somewhere. I think it may be in the video RAM area as the screen periodically garbles and then the Geneve freezes; could be some data or address line issue as well. I replaced the caps and regulators at some point during the past few years but I have no recollection of work done beyond what I can see I did.  It has the 192K VRAM and 64K ram updates, so it will load MDOS 6.50.  0.98 swan EPROM.  No clamshell. It is possible that with a clamshell the card will not flex and will be stable but someone needs to go through the sockets and look for corrosion or bad solder points.   $225 as-is.  PM me if interested. As with the other Geneves, neither Swim nor I will entertain repairing them. 

 

Edit:  Card has been purchased.

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I spent the evening working on one of my last remaining problematic Geneves.  The card works just fine with exception of the clock.  If a clock chip is plugged into the socket, the Geneve just hangs.  I've replaced the transistor and traced everything more than once to no avail. 

 

I grabbed some dinner and then it occurred to me to check the parts and placements one last time.  I yanked my development geneve out of its case to perform a stare and compare.   It was then that I noticed one of the resistors was wrong - instead of 100K it was 10M.  Inspecting the circuit, I find that the 10M resistor is tied to the transistor that controls whether the clock chip's pin 8 acts as ground (when -18 to -24v is applied to the transistor) or battery (when 0 volts is applied to the transistor).  I pulled clock chip pin 8 and tied it to ground to test my theory; the Geneve powered up successfully. 

 

I measured the voltage at pin 8 and found that on the good Geneve there is 0v when running; the bad Geneve had 2.6v AND at R251, there was +2.5v where -2.0 was expected.

 

For those of you who are still working on the Geneve you purchased be sure to confirm the right components were installed.

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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. ;)

I thought about this today as I worked on the exploding-capacitor HFDC. :)

 

I was able to read the EPROM and the powerup seemed to be happening but there was no drive activity.  Considering how many of the recent problems I've found were simple (i.e., wrong resistor, low voltage) I tested the regulator output and sure enough, one of the 5v regulators was bad.  So I took the card to the woodshed, removed the extra capacitors that were installed in the 90s (!!!) and replaced all three regulators, also installed in the late 90s.   Resistance across the outputs looked good so I donned my imaginary vest and powered it up. Powerup worked and it loaded MDM5.  There is still some testing to be done but it looks like the card is back among the living and I might use this card as another test case for the switching regulators. ;)

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

 

Puny humans and your weak flesh.

 

[attachment=633215:DRom9b_VAAAqgdV.jpg]

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I thought about this today as I worked on the exploding-capacitor HFDC. :)

 

I was able to read the EPROM and the powerup seemed to be happening but there was no drive activity.  Considering how many of the recent problems I've found were simple (i.e., wrong resistor, low voltage) I tested the regulator output and sure enough, one of the 5v regulators was bad.  So I took the card to the woodshed, removed the extra capacitors that were installed in the 90s (!!!) and replaced all three regulators, also installed in the late 90s.   Resistance across the outputs looked good so I donned my imaginary vest and powered it up. Powerup worked and it loaded MDM5.  There is still some testing to be done but it looks like the card is back among the living and I might use this card as another test case for the switching regulators. ;)

 

You're on a nice repair roll of late. Don't stop, keep going until the bench is clear. :)

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You're on a nice repair roll of late. Don't stop, keep going until the bench is clear. :)

That's my goal!  The next 'phase' will be to refresh some of my own equipment so that I can turn my hobby attention to some software.  Alas, there just aren't enough hobby clock cycles in the day to multitask effectively, if at all.

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The exploding capacitor must have damaged one of the controller chips.  I was getting corrupted data on the floppy and hard drive. Temporarily swapped out the chip and the card now seems to work normally.

 

At Swim's suggestion I hunted down a few DS1000 chips on ebay.  First one I popped into a card worked.  Whew.  Bought them from Syracuse Semiconductors  http://myworld.ebay.com/syracusesemiconductors after conversing with the seller about whether or not the stock was genuine/original. 

 

Oh.. and for the easy yet head-scratching win of the night, one of the Geneves I have left to repair had a joystick port that sensed the UP position intermittently.  The resistor for the UP direction is next to the V9938 crystal. 

 

When ohming out the resistor it registered 10k as expected.  However, over time the protective jacket on the resistor had worn in one tiny spot, just enough to make contact with the crystal cases' pressed edge.  The Myarc case exerted just enough pressure on the resistor to eventually short the two together, dropping resistance to 30 ohms!

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I've bought from Syracuse Electronics for the last 20 years or so, directly from their website and from eBay listings. They are one of my go-to parts sources, along with Unicorn Electronics.

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I installed a switching regulator and appropriate caps into one of my Myarc FDCs this afternoon. The linear regulator w/heat sink was running at 165 degrees F (74C) after 20 minutes.  The switching regulator is holding at 81F (27C) after the same amount of time.  The controller chip is warmer than the regulator. I'll snap a picture or two later today.

 

However... I realized that I don't have a comprehensive test program to exercise the controller and put it through its paces. I have used a copy/compare method in the past but I want to really 'stress' the card a bit.  Any ideas?

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Use the comprehensive test routines in the standard Disk Manager module from TI. You can set those to run in really long testing loops. Use the destructive tests, as that runs through everything. . .

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Good idea.  I'll give that a whirl. I just finished replacing the linear regulators on a 2nd Geneve so that I can eventually send the Heatwave card back to its owner, now that it's had a 6+ month burn-in.  The newly updated Geneve and FDC are in the same PEB playing nicely together.  I'll hunt down my DM2 cartridge dump so I can run both cards run for a while.

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Myarc Hard& Floppy controllers are notorious for having too much play on the MFM 34-pin edge connector, allowing the cable to slide half of a pin width (or more!) up and down the connector.  The inevitable result is the owner shorts one or more of the signal lines, leading to corruption or damaged logic chips including the LS240 and LS374 near the card's neck.

 

Alas, Myarc didn't manufacture the card with a slot. It is therefore imperative to carefully look at the mating when you slide the cable on the connector.  If you have a steady hand and the right tool, there is another way to make the connector nearly foolproof. 

 

At Cecure we used a thin hacksaw style blade to slowly and carefully cut out the proper slot. The trick was to very, VERY carefully start the cut on both sides and then slide the blade outward from the top side of the card. The blade must be parallel to the fingers and perpendicular to the cutting plane.  Failure to do so will result in a misaligned slot and/or cutting into the metal contacts.  (Fortunately, since the back of the connector is all grounded pins, cutting into one of them by accident isn't the end of the world.).  A fine file can be used to take away any rough edges and smooth the slot.

 

I recently repaired a card for someone and took a picture of the slot for reference.

[attachment=634662:CCA856B7-3019-4E9E-940D-15C15B8B6752.jpeg]

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Myarc Hard& Floppy controllers are notorious for having too much play on the MFM 34-pin edge connector, allowing the cable to slide half of a pin width (or more!) up and down the connector.  The inevitable result is the owner shorts one or more of the signal lines, leading to corruption or damaged logic chips including the LS240 and LS374 near the card's neck.

 

Alas, Myarc didn't manufacture the card with a slot. It is therefore imperative to carefully look at the mating when you slide the cable on the connector.  If you have a steady hand and the right tool, there is another way to make the connector nearly foolproof. 

 

At Cecure we used a thin hacksaw style blade to slowly and carefully cut out the proper slot. The trick was to very, VERY carefully start the cut on both sides and then slide the blade outward from the top side of the card. The blade must be parallel to the fingers and perpendicular to the cutting plane.  Failure to do so will result in a misaligned slot and/or cutting into the metal contacts.  (Fortunately, since the back of the connector is all grounded pins, cutting into one of them by accident isn't the end of the world.).  A fine file can be used to take away any rough edges and smooth the slot.

 

I recently repaired a card for someone and took a picture of the slot for reference.

attachicon.gifCCA856B7-3019-4E9E-940D-15C15B8B6752.jpeg

Well, I did not know this. I believe I modified one of my HFDC's like this in the 90's, maybe both, will have to look, when I worked at my Dad's machine shop, but it was for different reasons.

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Quick and dirty mouse/joystick/sound test program for the Geneve circa 1994

 

Used this during days at Cecure to verify the 9901 and 9938 connections and resistors were all good. 

 

MODE 80 to restore text mode when complete. Usually turned off the system after this test so I didn't restore the environment ;)

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Myarc Hard& Floppy controllers are notorious for having too much play on the MFM 34-pin edge connector, allowing the cable to slide half of a pin width (or more!) up and down the connector.  The inevitable result is the owner shorts one or more of the signal lines, leading to corruption or damaged logic chips including the LS240 and LS374 near the card's neck.

 

Alas, Myarc didn't manufacture the card with a slot. It is therefore imperative to carefully look at the mating when you slide the cable on the connector.  If you have a steady hand and the right tool, there is another way to make the connector nearly foolproof. 

 

At Cecure we used a thin hacksaw style blade to slowly and carefully cut out the proper slot. The trick was to very, VERY carefully start the cut on both sides and then slide the blade outward from the top side of the card. The blade must be parallel to the fingers and perpendicular to the cutting plane.  Failure to do so will result in a misaligned slot and/or cutting into the metal contacts.  (Fortunately, since the back of the connector is all grounded pins, cutting into one of them by accident isn't the end of the world.).  A fine file can be used to take away any rough edges and smooth the slot.

 

I recently repaired a card for someone and took a picture of the slot for reference.

attachicon.gifCCA856B7-3019-4E9E-940D-15C15B8B6752.jpeg

 

always bothered me that this wasn't well labeled as to where the hell pin1 is..  I assume its on the bottom based on this photo.. since I just moved (and again neglected to take pictures before unplugging) just confirming that..and where pin1 on the index cable is

 

Greg

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