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Texas Wanted: POLY-88 VTI S-100 video card

Covers: Texas
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voidstar78

Veteran Member
Joined
May 25, 2021
Messages
1,048
Location
Texas
Selling Price
1
Is the price negotiable?
Yes
Closest Major City
DFW
Delivery Options
International Shipping or Local Pickup
It looks to be mostly 74 series logic and other mostly standard components. Maybe you could make a scan of both sides of the board and use it to layout a new board using KiCad or another board layout software.

forum.kicad.info

Reproducing a PCB from scanned image (BMP, JPG, etc.)

Hi everyone. I am looking to reproduce an old PCB that is no longer produced. It’s fairly simple (to me). It has an edge connector to plug into a motherboard, 9x surface mount ICs, 9x decoupling capacitors and a few resistors. It’s only 2 layers, and a few vias. It’s a basically a proprietary...
forum.kicad.info forum.kicad.info

If your board is having strange issues, I'd probably look at the SRAMs first.
 
Yes, from what I've read, it's fairly close to what was used in a TVT.

I'll start inventoring the chips on what I have, since the old manual scans are tough to read.

But this one in particular I haven't been able to find yet:

1777464513032.png

And a video of what the display issues are on what I have:

 
voidstar78 said:
But this one in particular I haven't been able to find yet:
Click to expand...
A QUICK Google search for Signetics N8274 produces some references for a shift register in a DIP-16 package. I'd suggest looking for an old Signetics databook from the early 1970's. As that's from the early days of ICs, several years later Intel also used the 8274 number but for a VERY different chip, as have other manufacturers.
 
voidstar78 said:
Yes, from what I've read, it's fairly close to what was used in a TVT.

I'll start inventoring the chips on what I have, since the old manual scans are tough to read.

But this one in particular I haven't been able to find yet:
Click to expand...

I found this NoS Signetics N8274F, not sure if it's compatible with the "B" variant though:

Datasheet Archive: N8274F datasheet by Signetics

Preview and download the N8274F datasheet by Signetics on Datasheet Archive.
www.datasheetarchive.com www.datasheetarchive.com

This one has a date code of a decade newer than yours, so it's probably a much later version of a similar/same design. The little information I can find on it shows that it's a parallel 10 bit in to serial out shift register.

voidstar78 said:
And a video of what the display issues are on what I have:
Click to expand...

With the partial text corruption and random dots/lines, sort of looks like a bit of ROM corruption and bad SRAM.
 
GiGaBiTe said:
I found this NoS Signetics N8274F, not sure if it's compatible with the "B" variant though:
Click to expand...
Per the Signetics 1972 databook <here>, the N prefix is 0 deg C to +75 deg C and the B suffix is "16-PIN DUAL IN-LINE SILICON PACKAGE". The F suffix is "14, 16, 24-PIN CERDIP" so it should be compatible.
 
Thank you for the notes.

Testing the VTI that I have, I managed to get it working correctly again (meaning stable crisp font).

We thought it might be PSU related, so we tested that first. I know weird to have a tech ref here in sales/wanted, but in case anyone else ever needs to test/restore a POLY VTI S-100, here is the "works for me" VAC measurements I got across its 5-pin molex, and VDC values across the diodes:
1777694828110.png


The "fix" for my problematic characters was adjusting the left-side pot (the right side pot just shifted the whole video display left/right).

This might be a temporary fix, only because the card had been working fine, so still uncertain why it suddenly needed this adjustment. So this "fix" might not last forever.
 
Wanted to "archive" one more shot before I close things up. The big black wire in the foreground is the Composite video signal. Behind it is the main VDC diodes. And, that 5-pin Molex is "keyed"

I'd still be interested in a backup VTI S-100 card if anyone comes across a loose one that needs a home.


1777823350479.png
 
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