Sinclair ZX80 / ZX81 / Z88 Forums

Hello, after years of owning a TS1500 and not daring to open it because it's in perfect condition I was able to buy a broken TS1500 in near mint condition. This had to be opened in order to be repaired.
I was lucky, it was just a broken Z80 that was socketed and a brittle membrane.
I made a composite mod and want to change it from 60Hz to 50Hz.
Does anybody know which resistor number it is in a TS1500?
Kind regards Paul

Not certain it can be done that way, least i never was able on my ts1500, however you can use and external rom and hardcode it for 50hz

regards Andy

Hi Andy, I guess it would be possible internally as well?
Which bytes have to be changed?
Do you know how the channel 2/3 selection works? Maybe this could be (ab)used for ROM switching?
Kind regards Paul

Somewhere I’ve come across some comments from someone who wanted to do the same thing with his TS1500. If I remember correctly, although the ‘ULA’/gate array has a pin that is supposed to be the 50/60Hz input selection, changing the logic level made no difference.

I can’t for the life of me remember where I read about this.

Mark

Paul wrote: ↑Mon Apr 01, 2019 6:23 am Hi Andy, I guess it would be possible internally as well?
Which bytes have to be changed?
Do you know how the channel 2/3 selection works? Maybe this could be (ab)used for ROM switching?
Kind regards Paul

Nice idea, worth looking into for sure.

Inside the "Modulator" case there is a diode in the left front corner. The left pin of which is either 5V or 0V depending on channel selection.
I guess I don't need 60hz. Maybe I make an internal ROM with bigbang and sponzy. Black and white spectrum in a TS1500 case - crazy enough to get it done.

1024MAK wrote: ↑Mon Apr 01, 2019 12:03 pm Somewhere I’ve come across some comments from someone who wanted to do the same thing with his TS1500. If I remember correctly, although the ‘ULA’/gate array has a pin that is supposed to be the 50/60Hz input selection, changing the logic level made no difference.

I can’t for the life of me remember where I read about this.

Found it, read through this thread

Mark