General Stuff(tm)

[stephen_usher]

Swapped the tape recorder from the Ferguson datacorder to an old Waltham cassette recorder, the same model I used with my ZX81 and Spectrum in the early 80s. The tape loads reliably every time now.

I also ordered a 6A, 5V PSU from Amazon as I'm getting a bit of a voltage drop on the 2A wall wart connection. By the time it gets to the PCB it's down to 4.73V, which goes down to 4.70V at the far side of the PCB. I know that to get a full 5V on the input I have to crank my bench power supplies up to 5.7V just to overcome the losses in the leads. Unfortunately the delivery window is late, as in (currently) 5:15pm - 8:15pm, and this is directly during the time I was going to pop over to the Model Railway Club to pick up the projector. *sigh* Usually Amazon deliveries for stuff I order the day before turn up at about 3pm.

I've deconstructed the TT stuff and put it into the box and done the same with the Enterprise stuff. The Lynx will need to wait for the new PSU to arrive so that I can test voltages before buttoning it up. It's current soak testing running Jet Set Willy.

[mrbombermillzy]

May be good enough to demonstrate on Saturday.

Hope its ok for Saturday Stephen.

(JSW was the first game I ever bought!)

[stephen_usher]

The new PSU has arrived and it's actually providing a steady 5V to the machine. No change in the machine's behaviour though.

[stephen_usher]

Actually, the behaviour has changed, it's got worse.

Jey Set Willy now loads to the hack menu, having passed all the CRC checks but crashes the machine when you try to start the game. Switching back to the old PSU and it works. The extra 0.3V has changed the timing, speeding up the chips, causing things to fail.

[exxos]

Sounds just like a Atari at this point !

[stephen_usher]

Sounds just like a Atari at this point !

Oh, this is *FAR* more finicky! It's all TTL logic with timings where you have to buy precisely the correct manufacturer's versions of chips. I'm probably hitting issues with the chips being later production runs and hence slightly faster than they original early 1980s chips.

[exxos]

Oh, this is *FAR* more finicky!

Not possible

It's all TTL logic with timings where you have to buy precisely the correct manufacturer's versions of chips. I'm probably hitting issues with the chips being later production runs and hence slightly faster than they original early 1980s chips.

Pool Table boards was the same back in the day. Small board, bunch of logic chips. Change every chip on the board and sit puzzling why it doesn't work all day.. then the boss then decides to tell you you need to use the same brand of logic chip else it doesn't work ! I mean all they did was trigger a few solenoids etc.. how can the manufacture screw the board up enough that a few ns faster TTL chip caused it not to work at all is beyond me..

[stephen_usher]

Yeah, not unusual in the early days of micros, as in mid-70s, for the manufacturer to not only specify the type of chip and manufacturer but also valid date codes and manufacturing plant codes as well!