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OS9dude
December 10th, 2014, 07:48 AM
While seeking a B&W TV set to be able to use my ZX-81 computer I brought it in to my workplace's lab to test it with several of the LCD/TVs we have for day-to-day use. Most of them gave the overtly dark display one gets due to the back-porch issue the ZX-81 are known to have on their TV signal, two of the monitors worked perfectly though:

Sharp LCD Model LC-15S5U
Sharp LCD Model LC-13SH6U

Tried both with another ZX-81 and a TS1000 I own, no problems with those two machines whatsoever.

Passing it on so other enthusiasts of this computer may have an option. Granted, these TVs/Monitors are discontinued by Sharp but they do show up from time to time on flea markets and auction websites - have proven to be easier to find than a genuine BW TV set!

-- RP

SiriusHardware
December 10th, 2014, 10:43 AM
The early and middle versions of the ULA were the 2C158E and 2C184E respectively. These versions apparently do not generate the back porch signal correctly.

The late/final version ULA was the 2C210E, which does correctly generate a back porch signal.

...That's what the majority of people would say.

However, I was informed by one source (only) that all ZX81 ULAs originally generated a back porch signal, but failure of that particular aspect of the video output on the ULA (all versions) is very common.

Whichever is true, replacement of the ULA specifically with a never-used 2C210E version should make the machine generate a back porch on the video signal, at least for a while. Where there is room, fitting a full-length 40-pin IC heatsink may help to keep the ULA working correctly.

2C210E ULAs are still available, but they are not particularly cheap.

jltursan
December 10th, 2014, 11:07 PM
Cool info!.
A pity that the market is already flooded with Samsung & LG models, that AFAIK, they aren't very friendly with old machines :-P. I'll love to see some more actual Sharp hardware, I really like the brand!

As for the ZX81, I suposse that the best options are still the ULA replacement or the video mod (with extra circuitry).