BillC

This was due to a bug in the 810 drive, DATA was read/written inverted. Atari stayed with this format on later drives for compatibility reasons.

Not all ICs fail under the same conditions, when I had an INGOT power supply go over-voltage it only damaged 41256 DRAM and all the other ICs were fine. It is possible that the 4116 on the good card were made by a different manufacturer and can tolerate slightly higher voltage. You don't have to open the 800 to check the +5V/+12V outputs, they are available on pins 10/12 of the SIO port, pin 4 being ground.

An LCD displays information that would be off the screen with a CRT, mytek developed a circuit called V-Gate that blanks the chroma/luma signals outside of the normal borders. https://ataribits.weebly.com/vgate.html

The power supply board has a 7805 and a 7812 voltage regulator, the -5V circuit is controlled by a zener diode. There is a 33 ohm resistor across the input and output of the 7805 regulator which requires a load to check the voltage, unless you disconnect it first. Since it appears to be only the RAM failing it is likely not the +5V at fault, since that would also tend to damage the logic chips. Schematics are available at http://www.jsobola.atari8.info/dereatari/schematy.htm, they do have some errors but are reasonably accurate.

Have you checked all the voltage outputs on the power supply board, 4116 chips need all 3 voltages to operate, any one of them being out of specification could damage chips. The +12V supply is only used for 4116 RAM, the color adjustment pot, and a power output on SIO, the -5V supply is only used for 4116 RAM and the power LEDs.

I mentioned COVOX in post#9, it's near the cartridge port and marked on the silkscreen. The module I don't know is in front of the stereo POKEY module, and to the right of the OS module.

The shipment was likely returned to Lotharek, which is why he sent the refund. I would have thought he would try to contact you first though.

1MB SIMM upgrade Stereo POKEY Lotharek2009COVOX module LotharekOS module There's another Lotharek module below the stereo POKEY that I don't know.

I've paid $5 or $6 for a DVI to HDMI adapter, which allows the use of any HDMI cable.

Just be aware that it still may not work properly, I don't think it will support the ESC/P commands that most Atari 8-bit printing software uses.

Available on eBay. https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=6532+dip+ic&_sacat=0&LH_TitleDesc=0&_sop=15&_osacat=0&_odkw=6532+ic

I'm not certain that I remember this correctly but I believe the PRC serial port may be capable of 19,200 BAUD, double that of the 850.

Atari Cassette Enhancer and Cassette Operating System are both available at atarionline under Utilities\5. Tape recorder: http://atarionline.pl/v01/index.php?ct=nowinki&ucat=1&subaction=showfull&id=1613724684

https://atariage.com/forums/topic/260646-new-hardware-atari-400800-super-color-cpu-card/?do=findComment&comment=3717999

You have a 256KB upgrade which replaces the original 64KB, so the increase is only 192KB or 3 banks of extended memory. The "missing" 64KB is doing what the original RAM did before the upgrade.