exxos's Atari, Amiga & retro forum

Looks like there's no postal delivery again today, so no Z80 SIO/1 chips. There's still a slight chance that it will turn up today but as It's about 2pm it's a low probability.

P.S. Just as I posted this they arrived. *phew*

OK, it's not the SIO chip... Next one along, the serial clock chip, the WD8116. Oh dear. No oscillation on the 5MHz crystal. Tried bridging an 8MHz crystal and nothing, which suggests it may be this chip instead... and it's a rare one.

There's a Yamaha AY part which should be compatible and that's available.. so new order. Unfortunately this is another 2nd class post jobbie, so likely a another week until they arrive.

If it's the crystal then I'll have to get that from Mouser as none of the UK suppliers stock 5.0688MHz ones.

Anyway, I'll retrieve the Owon oscilloscope from work as that has a signal generator. I can't remember if it goes up to 5MHz or not. Anyway, I should get some life out of the chip if it's the crystal and I inject some frequency into the clock inputs.

stephen_usher wrote: 16 Feb 2024 22:57 If it's the crystal then I'll have to get that from Mouser as none of the UK suppliers stock 5.0688MHz ones.

Anyway, I'll retrieve the Owon oscilloscope from work as that has a signal generator. I can't remember if it goes up to 5MHz or not. Anyway, I should get some life out of the chip if it's the crystal and I inject some frequency into the clock inputs.

Damn clocks 🙁

Well, well, well...

Retrieved my Owon pocket oscilloscope from work and used the signal generator...

Firstly instead of the crystal, no go. The WD8116 chip is definitely dead.



Hooked it up instead of the 8116 output, going to the Z80 SIO port clock input... Nothing, not even bad characters.

Swapped out the SIO with one of the new ones... Strange characters... Tuned the clock rate and at 5KHz... BINGO!


So, BOTH the WD8116 AND the Z80 SIO were bad.

Actually, 4.8KHz is best, that's 300 Baud.

Nice bit of fault finding sir :)

Thanks!

I'm off to Leamington Spa in a bit to rescue a QL and a whole load of magazines and books.

stephen_usher wrote: 17 Feb 2024 13:30 Thanks!

I'm off to Leamington Spa in a bit to rescue a QL and a whole load of magazines and books.

You really do have all the luck when it comes to old computers

There's an Apricot XI available in Norfolk for free, but it's a bit too far.