Myarc cards for sale/repair tips

[+Ksarul]

Nice troubleshooting. . .

[+InsaneMultitasker]

2 hours ago, Ksarul said:

Nice troubleshooting. . .

Thanks Jim.  I shut everything down after attempting to format the hard drive which ended in failure.  What bugged me is that my floppy was corrupted at the same time. So a few minutes ago I fired up the system and tried to write to the hard drive and floppy -- and corrupted both drives.  On a hunch I replaced my test bench 9234 with the owner's 9234 - and it now works!  Seems that my test chip bit the dust since the last time I used it.  I just finished formatting a MFM hard drive and a SS/SD floppy successfully.  To cover the bases I need to verify that the bad chip is indeed bad, since there could be a poor socket connection or some other flakey chip/solder joint that is the culprit.  (That has happened more times than I wish to count yet it is a lesson I sometimes must re-learn).

 

EDIT: Confirmed, sadly, my test bench 9234 will read data but cannot write without corruption &  locks on cylinder 0 during a format operation.  

[+InsaneMultitasker]

Sometimes the 'third time is the charm'.  Last weekend I replaced my defective test bench 9234 with the owner's 9234.  Everything seemed to work fine until I noticed that occasionally the HFDC would not load MDM5. I put this down as a fluke until I realized the problem was not limited to the hard drive.  The strange thing is that it only happened after I turned the PEB off for a few minutes.  When I turned on the PEB and tried to catalog a drive, the card would go out to the hard drive and lock.  Turning the console off and on resolved the issue.  I was able to repeat the process with similar failures; sometimes the hard drive light came on and locked the system, other times it would blink and go out to spin the floppy, then lock.  Tonight I checked the components for any obvious issues.  This card had been modified for 9+ heads (I reverted it back to <9 for use with my MFM drives) so I first thought one of the head-related chips was affected. 

 

I then remembered something from my earlier tests:  when my bad 9234 was in the system, I didn't experience these initial powerup lockups.  I replaced the owners 9234 with another chip and so far, so good.  I'm a bit skeptical this is the fix so my next step will be to tempt fate (and on a Chicago TI Faire weekend!) by testing the two suspect 9234s in one of my own cards. I may still opt to replace the some of the common circuitry to be safe, depending on the results.

[+InsaneMultitasker]

Skepticism is good.

 

I tested the bench 9234 (the one that corrupted my mfm and floppy drives during writes) in my HFDC.  To my surprise, the chip did not corrupt the drives.  I then tested the customer's chip in my HFDC; it did not lock up during the first access.  Just to be sure I wasn't dreaming I installed the 'bad' 9234 into the customer card, wrote to the hard drive, and the card immediately corrupted the drive. Two chips common to the floppy and mfm drives are U9 and U11.  I desoldered them and tested both in my HFDC with success.  I socketed the customer card and installed new chips - no change. I figured it was time to mull over the problem so I walked away for a while.  I then remembered that early in the repair effort I had not experienced the first access lockup scenario so I brought the card back to the woodshed workbench to take one last look at my work.

 

When removing the QIC-02 circuit chips and socket (U22, U23, U24, U32) the final step is to add a jumper on the back of the card, in the vicinity of the 8Mhz xtal. I had prepped the two through holes for a jumper and was about to install it when I got called away for a short while.  When I returned, I completed the rest of the work but failed to realize the jumper was missing. 

 

I initially dismissed the missing jumper as the cause of the 9234 problems. I could not fathom why three 9234s act differently in the same card. So I traced the two connections back to the gate array and 9234.  The two traces tie the  9234 Chip Select pin 16 to the gate array.  The 9234 datasheet states:  

 

It isn't clear to me if this means the CS signal can be derived separately using either source.  Regardless, if pin 16 isn't tied to the gate array strange things can happen.  In my case, three different 9234 chips presented three different outcomes during testing:  corrupted writes, lockup on first access, and no problem .   As soon as I installed the jumper the card functioned normally with all three 9234 chips. 

 

I inspected a Rev 'C' HFDC card for the jumper and found a trace had been added to U32, between pins 9 and 12.  This is much safer and easier than installing it behind the xtal.  It also matches the Rev C board. 

 

The card tested fine with both a TI and Geneve system; CRC stress test showed no read/write errors.  I slotted the edge connector and now finally consider this card fit for return.

 

 

 

[+InsaneMultitasker]

I spent the rest of the afternoon working on what will be my new Geneve workhorse so that I can strip down my 20+ year always-on primary system.  

 

Before my 'break' I installed  DC-to-DC converters in place of the three 5v regulators. Today I only got so far as replacing the caps and some prep for the 192K video update because I decided it was time to try removing the 12v regulator and composite video chip from the card.  I have wanted to reduce the power load and eliminate the 12v at the video port.

 

Unfortunately removing the chip and regulator result in a black screen and no analog RGB.  I couldn't tell from the schematic WHY this was the case and since I really wasn't interested in messing around further I re-installed the regulator and chip, now the card is working as expected.   Next weekend I will add the 384K SRAM to the card by following Fabrice's and my instructions and prep the card to play with some Winbond chips Atrax sent me for the PFM512 modification. 

[+InsaneMultitasker]

A little off0-topic except for the use of repair equipment for 'medical' needs

 

Family member had fever this morning but alas, the battery in the thermometer died between then and this evening.  With stores closed and very limited options (including an instant-read thermometer with little accuracy and a high probability of skewering the patient)  I found a AA battery holder in my 80s parts box, grabbed ye olde solder and solder iron, and made do with what I had at hand.     My family member roller her eyes profusely just before using the contraption. 

 

[+Ksarul]

It worked--and that's what counts here! 

[+chue]

Macgyver saves the day

[globeron]

On 7/11/2018 at 3:32 AM, fabrice montupet said:

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.

 

(Myarc Repair tips  (not selling))

First of all @Shift838 / Chris with his great support, I am trying to get my Geneve 9640 working.  Until this weekend I came finally to a result I can work with the item (with a lot of troubleshooting cabling in between)

I connect it via the GBS8200 v5 (repeat v5),  the two v4 I got somehow I could not get a stable sync. (and the screen was kind of split in 4 parts and/or jumping all over)

 

Situation:

*  Now I can get the screen, but it is still not stable (letters are moving)...I can live with it

 

* but I still loose once in a while the signal

   (I start to doubt it is the cabling, especially the HS-Sync, I can do it one more time, but done so many times, that I think this is not the problem)

   Connectors, all seem to be okay.

   * is it the LCD-TV (VGA), I do not think so (I have tried 3x different type of TV screens)

   * is it the GB8200 v5?  (maybe)

 

    * but can it be something someone experienced which is Geneve Card related? 

       @fabrice montupet  (I was actually expecting that after 20-30 years everything works in perfect condition like my TI-99/4As ?  but I have no clue

       about capacitors (and how many),  I also read about a PAL-chip or so?

 

     * is it maybe better to test with the other jumper setting (to change from RGB to Composite ?  and bypassing the GB8200 v5 device) ? 

 

* For the rest what I can see is the Geneve9640 working  (with a normal TI FDC I can read disks  MDOS 6.5 and load GPL and the TI)

    (I have not tried anything graphically)

     * TI FDC is working (floppy is 720k)

 

     * but I also tried the other FDC for DS/DD -- the BWG controller,  Myarc gives an error

       and I tried the Corcomp FDC  DS/DD same issue it does not work

  

     * and I have a Corcomp 512K ramdisk (but no powersupply, so need to fix this first to see if that load, it seems that Myarc sees it)

        (I have not tried the Horizon3000/Rambo Ramdisk, but I have some issues with that in my normal TI setup).  Not sure which one

       I prefer yet in which box.

 

 

[globeron]

1 hour ago, globeron said:

 

(Myarc Repair tips  (not selling))

First of all @Shift838 / Chris with his great support, I am trying to get my Geneve 9640 working.  Until this weekend I came finally to a result I can work with the item (with a lot of troubleshooting cabling in between)

I connect it via the GBS8200 v5 (repeat v5),  the two v4 I got somehow I could not get a stable sync. (and the screen was kind of split in 4 parts and/or jumping all over)

 

Situation:

*  Now I can get the screen, but it is still not stable (letters are moving)...I can live with it

 

* but I still loose once in a while the signal

   (I start to doubt it is the cabling, especially the HS-Sync, I can do it one more time, but done so many times, that I think this is not the problem)

   Connectors, all seem to be okay.

   * is it the LCD-TV (VGA), I do not think so (I have tried 3x different type of TV screens)

   * is it the GB8200 v5?  (maybe)

 

    * but can it be something someone experienced which is Geneve Card related? 

       @fabrice montupet  (I was actually expecting that after 20-30 years everything works in perfect condition like my TI-99/4As ?  but I have no clue

       about capacitors (and how many),  I also read about a PAL-chip or so?

 

     * is it maybe better to test with the other jumper setting (to change from RGB to Composite ?  and bypassing the GB8200 v5 device) ? 

 

* For the rest what I can see is the Geneve9640 working  (with a normal TI FDC I can read disks  MDOS 6.5 and load GPL and the TI)

    (I have not tried anything graphically)

     * TI FDC is working (floppy is 720k)

 

     * but I also tried the other FDC for DS/DD -- the BWG controller,  Myarc gives an error

       and I tried the Corcomp FDC  DS/DD same issue it does not work

  

     * and I have a Corcomp 512K ramdisk (but no powersupply, so need to fix this first to see if that load, it seems that Myarc sees it)

        (I have not tried the Horizon3000/Rambo Ramdisk, but I have some issues with that in my normal TI setup).  Not sure which one

       I prefer yet in which box.

 

 

 

The  Corcomp floppy diskcontroller is working now with Myarc. for DS/DD disks.

 

 

 

[globeron]

This "no signal" is still a problem

 

[+arcadeshopper]

This "no signal" is still a problem
 

Seems like your monitor is having trouble when the video mode changes

Sent from my LM-G820 using Tapatalk

[globeron]

10 hours ago, arcadeshopper said:

Seems like your monitor is having trouble when the video mode changes

Sent from my LM-G820 using Tapatalk
 

 

I tried several TVs, but same thing happens (also when not changing video mode,

like leaving it on for a while it also looses the signal). I think it is the Geneve, but not sure.

 

[Shift838]

On 5/17/2020 at 6:33 AM, globeron said:

 

(Myarc Repair tips  (not selling))

First of all @Shift838 / Chris with his great support, I am trying to get my Geneve 9640 working.  Until this weekend I came finally to a result I can work with the item (with a lot of troubleshooting cabling in between)

I connect it via the GBS8200 v5 (repeat v5),  the two v4 I got somehow I could not get a stable sync. (and the screen was kind of split in 4 parts and/or jumping all over)

 I have sent back 3 GBS8200 v4 for the exact same reason.  divided into 4 equal parts!

[+jedimatt42]

On 11/3/2019 at 5:35 PM, InsaneMultitasker said:

I spent the rest of the afternoon working on what will be my new Geneve workhorse so that I can strip down my 20+ year always-on primary system.  

 

Before my 'break' I installed  DC-to-DC converters in place of the three 5v regulators. Today I only got so far as replacing the caps and some prep for the 192K video update because I decided it was time to try removing the 12v regulator and composite video chip from the card.  I have wanted to reduce the power load and eliminate the 12v at the video port.

 

Unfortunately removing the chip and regulator result in a black screen and no analog RGB.  I couldn't tell from the schematic WHY this was the case and since I really wasn't interested in messing around further I re-installed the regulator and chip, now the card is working as expected.   Next weekend I will add the 384K SRAM to the card by following Fabrice's and my instructions and prep the card to play with some Winbond chips Atrax sent me for the PFM512 modification. 

 

How did the DC-to-DC converters work out? My Geneve looks like it hates the heat from those 7805s.. and I'm not sure yet what is going on with some stacked ones that seem to come along with the genmod upgrade. 

 

I have to do some repairs on this old thing, the VDP RAM has gone bad. I've tried alternate VPDs. The screen will fill with snow, and I can see the computer still function, but it'll crash if the VDP data becomes important... And it is a heat thing... happens after less and less time using it each time I use it...  So, I suspect I need to replace the DRAM... not sure how to verify that without replacing the DRAM  LOL... 

 

[+InsaneMultitasker]

7 minutes ago, jedimatt42 said:

 

How did the DC-to-DC converters work out? My Geneve looks like it hates the heat from those 7805s.. and I'm not sure yet what is going on with some stacked ones that seem to come along with the genmod upgrade. 

 

The Heatwave Geneve has been running for a year or longer  (except for a quick maint now and then) with the Dc-to-DC converters in place.  12v input and the heat output was <100F when I last cracked open the case to take a look. 

 

[+dhe]

Hi,

 This thread hasn't seen much action lately.

 I was bumping it, to see if anyone else had installed the switching regulators on any of their cards and their experience with them?

 

[RickyDean]

5 hours ago, dhe said:

Hi,

 This thread hasn't seen much action lately.

 I was bumping it, to see if anyone else had installed the switching regulators on any of their cards and their experience with them?

 

I bought 5 of a version about two years ago, and tried them on a geneve, cf7+, and SAMS, but they didn't work. When I measured voltage in each case the regs only were putting out about 4.5 volts, instead of 5 and the cards didn't l like them. I was going to try again with a different brand, or slightly higher voltage at some point in time.

Edited July 31, 2020 by RickyDean
mispell and punctuation.

[+InsaneMultitasker]

There are quite a few different parts with varying output current and voltage. 

 

Here is the specific DC/DC converter part I used for my Geneve and Myarc FDC.  1.5A  5v  V7805-1500R , coupled with three ceramic capacitors.   Heatwave is still running strong 24x7 as documented elsewhere.

 

https://www.mouser.com/ProductDetail/CUI-Inc/V7805-1500R?qs=%2Fha2pyFadugUplnUVl6f%2B683G9lqv46MXRDC4otT2LPNj%2B6No%2F7IxQ%3D%3D

 

 

 

[RickyDean]

1 hour ago, InsaneMultitasker said:

There are quite a few different parts with varying output current and voltage. 

 

Here is the specific DC/DC converter part I used for my Geneve and Myarc FDC.  1.5A  5v  V7805-1500R , coupled with three ceramic capacitors.   Heatwave is still running strong 24x7 as documented elsewhere.

 

https://www.mouser.com/ProductDetail/CUI-Inc/V7805-1500R?qs=%2Fha2pyFadugUplnUVl6f%2B683G9lqv46MXRDC4otT2LPNj%2B6No%2F7IxQ%3D%3D

 

 

 

I will try that, the previous were supposed to be 5 volt, but I never got that from them.

[+InsaneMultitasker]

Here are the four related parts I ordered in April 2019 and the price at the time of purchase.  If I find the email with the direct parts links I'll share it here.

[globeron]

The only item that does not work on my Geneve 9640 is a stable RGB signal to the GBS8200 device (and I have tried many other devices unless they are all having the same error?).  I now have 2x GBS8200 version 5, which seems to be configurable to get a kind of stable screen and is workable, but once in a while I am loosing signal "no signal".

(In the mean time I also made a Composite cable and that result in a stable output, but I cannot read the MDOS characters as it seems to be overlapping).   The Geneve 9640 with GenMod v1 is working fine so far, everything works with Horizon, normal disks, RS232, etc.

 

Question:

1. Let's assume the GBS8200 device is okay (and accepts 15 KHz)

    (is there an alternative to the GBS8200. I do not have SCART TVs here, that's more in Europe)

    I tried v4, v5 and now have the GBS8200 blue version with HDMI also does not work (split in 4 screens)

    or I am unlucky with all the cards I got so far (about 5x I think, I all sent them back).

 

    What can be the issue on the Geneve 9640 card itself, is there a component that can cause the "no signal" ?

    (I wired R, G, B,  HSYNC, GND, used different cables, etc. all resulting in the same output)

 

    If there is a way to troubleshoot if there is a particular component giving this issue?

    (do I need to take out the chip GenMod and put it back, or the video processor ?)

 

     If the composite output is working fine, what other components are used for the RGB output to check on?

     (as the rest of the Geneve card works fine)

[+dhe]

Hi Globeron,

   Analog Electronics Mystifies me, but have you tried putting in a different 9938 chip?

[globeron]

Hi Globeron,
   Analog Electronics Mystifies me, but have you tried putting in a different 9938 chip?

No I did not try that. I am guessing here, but might the video chip make a difference between composite output (which is stable) and rgb output or should it be other electronic components?


Sent from my iPad using Tapatalk

[+dhe]

If the 9938 has issues, you can run in to all kinds of strange display issues. I think the 9938 on most geneve's is socketed, but it does have ALOT of pins - so it will be a pain to pull and a pain to reset, but that's what I would do next, up to you. Also, if I remember correctly the geneve uses a really odd clock crystal for the geneve, it's possible that's going bad, but I don't know if they are available anymore.