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Myarc cards for sale/repair tips

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On 8/6/2020 at 1:43 AM, dhe said:

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.

I took out all the chips and reseated them again (memory, Eprom MDOS 1.0, TMS9995 and the Yamaha 9938, but still

the same result. Went back to use the Composite output, which is stable no issues here (only difficult to read MDOS and

colours are a bit impacted).

 

I think I am back at troubleshooting the GBS8200 devices, I think these are the issues:

1. I need to remove the capacitor: https://github.com/ramapcsx2/gbs-control/wiki/GBS-8200-Variants

 

2. Add 100ohm resistor across sync and ground for RGBs input

   https://github.com/ramapcsx2/gbs-control/wiki/Hardware-Mod-Library

   Corrects sync level for 75 Ohm sources (such as game consoles)

 

3. Add a Sync Stripper circuit to RGBs input.   

Try this if sync is never quite stable

   Maybe need a SyncStripper ? 

    https://github.com/ramapcsx2/gbs-control/wiki/Inputs:-SCART-adapter,-optional-sync-stripper

 

4. Maybe I have this issue: Due to the high capacitance, the SOG extraction circuit in the 5725 sees too much of any eventual video content, instead of just the synchronization pulses. This leads to frequent short sync losses when the picture content changes rapidly, for example on a flashing screen.

https://github.com/ramapcsx2/gbs-control/wiki/Sync-on-Green-Capacitor-Replacements

 

5. https://github.com/ramapcsx2/gbs-control/wiki/RGB-Potentiometers

    This would correct the RGB termination resistance to the TV standard 75 Ohm.

 

 

or use a non-GB8200 type of device and find another RGB (RGBS) 15.7 kHZ converter to VGA

* any recommendations out of these 4 solutions:

 

1. https://www.ebay.com/itm/15Khz-CGA-RGB-RGsB-RGBS-VGA-XGA-Converter-Scaler-/323316354604?mkevt=1&siteid=1&mkcid=2&mkrid=711-153320-877651-5&source_name=google&mktype=pla&campaignid=10693959030&groupid=108029226440&targeted=pla-293946777986&MT_ID=&adpos=&device=c&googleloc=1012728&itemid=323316354604&merchantid=116792603&geo_id=199&gclid=Cj0KCQjwvb75BRD1ARIsAP6LcqtCxKQNS-sVTBXtc9GdFoO68GqCRcuB9gNN6DXz-dt0fkoCVwQhMaEaAiFnEALw_wcB

 

2. https://www.ebay.com/itm/MDA-CGA-EGA-to-VGA-Converter-on-Altera-FPGA-for-old-computers/143574569650?_trkparms=aid%3D1110011%26algo%3DHOMESPLICE.DISCLISTINGS%26ao%3D1%26asc%3D20191002092920%26meid%3D24dab42c13724f8babec9a2a80553149%26pid%3D100889%26rk%3D2%26rkt%3D12%26sd%3D164149429851%26itm%3D143574569650%26pmt%3D1%26noa%3D0%26pg%3D2332490%26algv%3Ddefault%26brand%3DUnbranded&_trksid=p2332490.c100889.m5204

 

3.  https://www.serdashop.com/MCE2VGA 

 

 

 

4. 

 

 

 

 

 

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Have you checked the composite/rgb selection jumper hidden between some capacitors behind the video port.

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36 minutes ago, Torrax said:

Have you checked the composite/rgb selection jumper hidden between some capacitors behind the video port.

Yes I did (to change between them). Composite works fine and is stable.

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On 8/5/2020 at 1:43 PM, dhe said:

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.

I doubt the problem is the crystal (or nothing would work).

 

But the clock crystal of 21.477 mHz is out there. It is 6 times the 3.57954 NTSC color burst frequency. (Your 9918 has 3 times NTSC.) So, odd at first, but understandable.

 

I tested these two with a 9958:

https://www.mouser.com/ProductDetail/520-HCU2147-SX

https://www.mouser.com/ProductDetail/695-HC49US-214-U

59 - 69 cents.

 

Not here, but I found Tayda had an oscillator for 4 times NTSC, 14.318180 MHz, for some other Yamaha chip. Also, I loaded up on 75 and 100 ohm resistors :)

 

Tayda has amazing customer service and fast shipping from US (they are focused on hobbyist electronics). They looked for the 21.477 for me.

https://www.taydaelectronics.com/crystals-resonators-oscilliators/crystals.html

 

 

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On 8/4/2020 at 9:48 AM, globeron said:

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)

If somebody has already solved GBS8200, great, I'm just jumping in here. I have been experimenting without one. I probably want to buy one.

 

I think you need a VSYNC. The 9938 doesn't output one, but CSYNC (VSYNC+HSYNC+Important Stuff) was accepted by some RGB monitors.  Try connecting CSYNC into VSYNC?

Then definitely do the essential GBS Control fixes (on the page you quoted) including the 75 ohm impedance match fix.  

 

I don't see how it could ever work at all without the VSYNC, unless it is very, very clever.

 

Shift838 built the SCART Genie which splits VSYNC off of CSYNC. On the gbs-control wiki it mentions Sync-Strike, which is the same idea: an LM1881 chip to get VSYNC out of CSYNC (or CVIDEO).

 

9938 does not output Sync-on-Green (just one of several RGB monitor standards) so never mind the SOG fix. (SOG puts CSYNC into the gaps in the Green signal. You have just 3 coax RGB then.)

 

The above is my amateur opinion - I have not gotten any of my experiments to sync with the  15kHz Acer 276g, either.

 

 

Edited by FarmerPotato
remove wrong HSYNC info
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It might be better to start a new topic for these devices or look in one of the existing GBS threads such as this one (where there is some info documented by @Shift838 )   since the problem does not appear to be a 'repair' issue. 

 

 

 

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38 minutes ago, InsaneMultitasker said:

It might be better to start a new topic for these devices or look in one of the existing GBS threads such as this one (where there is some info documented by @Shift838 )   since the problem does not appear to be a 'repair' issue. 

 

 

 

globeron, this is what you need. It does the things.

 

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3 minutes ago, FarmerPotato said:

globeron, this is what you need. It does the things.

 

 

@Shift838 Chris, helped me with this one, I do have it here. http://shift838.99er.net/support/GBSVGA-GenieV2.pdf

 

I just ordered all components to adjust the GBS8200 device

(I have now sent back 3x GBS8200 v4 (green board) devices, 1x similar but other type indicated) and I have now 2x GBS8200v5 devices (which work with Geneve9640 but loses the sync. once in a while, but with the Geniev2, the video output is not okay, I try with gbscontrol to configure, but cannot get a screen) and I have 1x GBS8200 (blueboard with HDMI output, no output.  (I am either unlucky that all GBS board, they come from China are all bad production or so?)

but let me try to change the boards to see if it improves.

 

 

But before moving the thread

assuming that all chips work okay, 

 

are there any components on the Geneve9640 related specifically for the RGBs output ?

that can impact the sometimes Sync issue?   (because Composite works okay)

 

Maybe I need to replace one of them on the GeneveBoard itself?

http://www.mainbyte.com/ti99/geneve/geneve.html

I believe one of the C68 components was re-soldered on the board by previous owner

http://www.mainbyte.com/ti99/geneve/g_schematic1.html

 

 

 

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When I repair and/or refresh the Geneve cards, I typically replace all of the electrolytic capacitors which include those connected to the RGB and sync lines. Depending on the age of the cap and how the card was handled, I have seen a few instances where the picture quality improved though I don't recall any sync-related improvements.

 

It's always a good idea to inspect the resistors and the related components for damage. 

image.png.4c7b2e06249e9a05d68f59c8c882162e.png

 

Here's a hand-written note from Lou to one of our MATIUG group members.  I no longer remember the purpose of this mod but it is CSYNC-specific.  Perhaps someone will be able to divine that from the schematic.

 

image.png.ad165b6442c7801b2eb0295c3636bcb5.png  image.png.9b2c545d6dec5ba0678fce4ab361cbd0.png

 

@Shift838 - see above schematic for possible enhancements to CSYNC

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10 minutes ago, InsaneMultitasker said:

When I repair and/or refresh the Geneve cards, I typically replace all of the electrolytic capacitors which include those connected to the RGB and sync lines. Depending on the age of the cap and how the card was handled, I have seen a few instances where the picture quality improved though I don't recall any sync-related improvements.

 

It's always a good idea to inspect the resistors and the related components for damage. 

image.png.4c7b2e06249e9a05d68f59c8c882162e.png

 

Here's a hand-written note from Lou to one of our MATIUG group members.  I no longer remember the purpose of this mod but it is CSYNC-specific.  Perhaps someone will be able to divine that from the schematic.

 

image.png.ad165b6442c7801b2eb0295c3636bcb5.png  image.png.9b2c545d6dec5ba0678fce4ab361cbd0.png

 

@Shift838 - see above schematic for possible enhancements to CSYNC

 

Thank you for this and guidance!

 

and if I look to the schematic, it looks that Composit/Sync is related to the C68 component, I will have a look into that one.

 

Edited by globeron

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1 hour ago, InsaneMultitasker said:

When I repair and/or refresh the Geneve cards, I typically replace all of the electrolytic capacitors which include those connected to the RGB and sync lines. Depending on the age of the cap and how the card was handled, I have seen a few instances where the picture quality improved though I don't recall any sync-related improvements.

 

It's always a good idea to inspect the resistors and the related components for damage. 

image.png.4c7b2e06249e9a05d68f59c8c882162e.png

 

Here's a hand-written note from Lou to one of our MATIUG group members.  I no longer remember the purpose of this mod but it is CSYNC-specific.  Perhaps someone will be able to divine that from the schematic.

 

image.png.ad165b6442c7801b2eb0295c3636bcb5.png  image.png.9b2c545d6dec5ba0678fce4ab361cbd0.png

 

@Shift838 - see above schematic for possible enhancements to CSYNC

 

The top circuit follows the V9938 data book example.

 

The bottom circuit changes the NPN transistor to PNP and adds an LS04 inverter. The effect is a double inverter. But the output is now at TTL levels. It's changed to a digital sync, not analog.

 

So this was probably for a specific RGB monitor that required digital sync. 

 

 

 

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This is the C68 component, seems to be resoldered on the board.(but I do not think they did the change to digital TTL).

20200811_104945.jpg

20200811_105015.jpg

20200811_104959.jpg

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Is there a list of all these components and what type it is? 

 

The guidance really helps i slowly start to understand and the components R47,R48,C68 are related to Composite Sync. Maybe that is the problem.

 

R47 also seems to be resoldered

 

20200811_110553.jpg

20200811_110542.jpg

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The schematics that I preserved long ago contain a parts list and placement sheet. (The ZIP should still be in the WHT FTP repository).   There are a handful of errors found over the years but none that I recall related to the video circuitry.  I would focus on the GBS device before going too far down the rabbit hole, though if you wish to replace the 330uF caps it won't hurt to do so.  The caps appear to be original though I'd need to look more closely at the pics on a larger screen to be certain.  Again, caps are unlikely to cause the problem you describe and of the 100s of cards I've worked on, I don't recall encountering sync-related issues with the caps or transistors or passive components. 

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An old school RGB monitor, would definitely act as a test and troubleshooting tool. If an old RGB monitor worked and the sync was rock stable, you'd know it's on to the GBS.

Or if you can find, Larry Hoffman created a device called the video turtle that would let old RGB equipment use a monitor with s-video as a display.

I saw one in action and it worked pretty well, doubt, if ebays full of them thought....

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One note, if your Geneve was originally purchased through Albert Visser of LCC, he made some mods to the boards to make them work better in Europe. . .and I don't remember what they were, offhand, but I think he posted the changes in either TIdjingen or TI Revue.

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15 hours ago, dhe said:

An old school RGB monitor, would definitely act as a test and troubleshooting tool. If an old RGB monitor worked and the sync was rock stable, you'd know it's on to the GBS.

Or if you can find, Larry Hoffman created a device called the video turtle that would let old RGB equipment use a monitor with s-video as a display.

I saw one in action and it worked pretty well, doubt, if ebays full of them thought....

That would be a good test, but they are very hard to find here (and shipment from US or Europe is quite expensive)

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23 hours ago, mizapf said:

Is it this?

 

page1.jpg

page2.jpg

 

Thank you for this info Michael!  Ksarul - I do not think this one is modified by Albert Visser.  As I got the card outside NL.

 

also was wondering what these items mean?  (my MDOS sticker mentions on the chip MDOS v1.00 (and non-Gen Mod in the bootprompt).

 

not sure what the mode change means?

image.png.1cf68719fa8399c4d744369a36101862.png

 

 

 

 

 

 

 

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4 hours ago, globeron said:

 

Thank you for this info Michael!  Ksarul - I do not think this one is modified by Albert Visser.  As I got the card outside NL.

 

also was wondering what these items mean?  (my MDOS sticker mentions on the chip MDOS v1.00 (and non-Gen Mod in the bootprompt).

 

not sure what the mode change means?

 

The Geneve v1.00 is just your boot EPROM.  there is the .0.98 version which shows the Swan at bootup and 1.0 allows you to be able to select a boot device by holding down the space bar.

 

 

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Finally!

 

I have a stable screen on the Geneve9640 via RGB.  The gbs8200 v5 is probably the problem, you need remove the C11 component and do not bridge the connection (otherwise the IC next to it becomes very hot a d GBS does not work): https://github.com/ramapcsx2/gbs-control/wiki/GBS-8200-Variants

 

@Shift838 now also the Genie works, but i did not cable as supposed to be as I could not got any screen it seems line sync or filters. 

 

 

 

But this works now and can control settings via gbscontrol over wifi

 

, pfff this was a long journey.

(I have some other boards one with HDMI and see if that one works).

 

20200815_121710.jpg

20200815_121706.jpg

20200815_121702.jpg

20200815_121657.jpg

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4 minutes ago, globeron said:

 

Finally!

 

I have a stable screen on the Geneve9640 via RGB.  The gbs8200 v5 is probably the problem, you need remove the C11 component and do not bridge the connection (otherwise the IC next to it becomes very hot a d GBS does not work): https://github.com/ramapcsx2/gbs-control/wiki/GBS-8200-Variants

 

@Shift838 now also the Genie works, but i did not cable as supposed to be as I could not got any screen it seems line sync or filters. 

 

 

 

But this works now and can control settings via gbscontrol over wifi

 

, pfff this was a long journey.

(I have some other boards one with HDMI and see if that one works).

 

 

Awesome!

 

Where did you get your GBS8200 v5 ?  I've been on the hunt for one and have yet to find one.

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4 minutes ago, Shift838 said:

Awesome!

 

Where did you get your GBS8200 v5 ?  I've been on the hunt for one and have yet to find one.

 

I ordered via lazada.co.th  and comes from China. But need to search with V5 and need to zoom into the picture. (most are v4)

 

There is a blue board with HDMI

 

And a red board (never got this one).

 

 

 

 

20200815_124025.jpg

Screenshot_20200815-125339_Lazada.jpg

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