Sinclair ZX80 / ZX81 / Z88 Forums

Lardo Boffin wrote: ↑Tue Oct 06, 2020 2:49 pm

blittled wrote: ↑Tue Oct 06, 2020 4:04 am I do work by night as Z80 coder and have to deal with some pretty tricky stuff so at the end of the day, if a .Net programmer (C# and VB) project starts getting difficult I tend to lose interest.

That sounds familiar.

Corrected for you

There are a number of recommended modifications for issue 2 boards.

Improvements to the DC-DC converter circuitry is one, see this link.

For some of the other modifications, see also this web page.

It’s also well worth reading through the service manual.

Mark

Yes, it was Zsolt’s X2 BASIC ROM that I was thinking of

I was aware of it being faster, but I couldn’t remember if it improved other mathematical areas.

Mark

Quick question to Moggy, did one of the replacement BASIC ROMs for the Zeddy include more accurate/better mathematical routines?

Mark

It would also be a good idea to desolder the transistor from the circuit, then test using the resistance range between collector and emitter (positive lead to collector). Then test it on the diode test range (it should test as two diode junctions, with base being the ‘common anode’ and the collector...

So open circuit then. Therefore you need a new speaker.

Mark

What do you mean by nothing?
Do you mean zero ohms, or ‘O.L’ or another indication of over-range that indicates an open circuit?

The resistance of the speaker should be around 40Ω

Mark

Hello Jesper

Check/test diodes D9 and D13, and transistor TR7.

The diodes can be tested on the diode test range of a digital multimeter. The loud speaker can be tested using the 200Ω resistance range on a digital multimeter.

Mark

Me rushes off to see how many are remaining...!

Mark

...composite mod is something that I'd like to tackle... Hi Monty. The composite mod is a must I feel, as is the Zxpand+ which is more than just a storage/memory device. Hi Moggy, yes the composite mod is something that I'd like to tackle so that I'm not restricted to using my older TVs and RF. It'...