Sinclair ZX80 / ZX81 Forums

Looks great and thank for sharing.

Working from home these days and sorting out unfinished project in mean time. Sticker to my Jupiter ACE replica's keyboard finally done.

The hi-res schematic attached in the ZIP file.

Regarding Mark's query, any European TC2048 has got a UHF modulator which works on Channel 36. Timex used at least two makes of them, ASTEC UM1233 and Gintek UM-236E-1.

Hi,

Your TC2048 looks nice and I like the bright and good looking keyboard.

Anyway, there could be an issue with the RF modulator if the composite output works fine. The most accurate schematic diagram of rev.5 attached.

No, they are not. It was not an open project. Please see SMR where superfo sells them. If can't find any, send me a PM, because I've got one spare PCB if you are interested.

200Ohms speakers are not available, the closes what you can find are 150ohms units. Google for: AR027150MR-2-R, it might be a good replacement for the issue 2 speaker.

Looking at the issue 4a schematic, there are other parts worth checking like TR5 and both diodes D15 & D17.

BTW is any of memory chips getting hot?

I am worried at the electrical "hum" from the 4A, and the low 12V line (10.8V) - any suggestions appreciated I would not worry much about the hum, it seems that coil's windings became loose. I would worry about very low 12V line. As a first guess I would replace TR4 (ZTX650 type) with new one or ZT...

Long shoot but built and tested the clone and the cartridge: https://drive.google.com/open?id=1Gxqjv ... ytl58aGcAa

There is also renewed ZX1541 on the market which works with any SD2IEC well.