derkom's doings

[derkom]

have you tried without a long lead on the psu ? You would probably have to replace the 4700uf cap on the STE as the regulation will be pretty bad..

Yeah I remarked back here that I removed the PSU extension when I realized the voltage drop it was creating. Now I'm just using the standard PSU connection.

I've been wanting to replace that 4700 uF cap anyway. I've got one of your kits somewhere for that, which of course I've managed to lose in between ordering it and actually wanting to install it. Probably a little tidying up is in order.

[exxos]

You could try adding 100R in series with the 32mhz wire and see if that helps..

[derkom]

You could try adding 100R in series with the 32mhz wire and see if that helps..

I was wondering about that, but also wondering about what amplitude is necessary for this stuff to work at all. As it is, the 32 MHz clock is something like 1.7 V peak-to-peak, where the 8 MHz is around 7.5, and I don't know how much is required. The 68000 datasheet doesn't seem to say.

I will be poking at various things later today, and report back any progress.

[exxos]

The clock is tricky to measure.. Are you using X10 on your probe ?

[derkom]

The clock is tricky to measure.. Are you using X10 on your probe ?

Nope, X1.

CLK32-68R.png (9.22 KiB) Viewed 4329 times

[exxos]

Odd. I measured mine and I get like 2 volts over and under 5V.

[exxos]

Tell A lie, scope changed my settings argh, I get about 1V p-p direct on the F chip.

[derkom]

Tell A lie, scope changed my settings argh, I get about 1V p-p direct on the F chip.

So yours is perhaps even a bit weaker than mine. Probably means I'm safe to reduce the amplitude a little bit.

First I am going to poke around a bit and see if I can find the 4700 uF cap replacement kit I bought from you, because it seems like a good idea anyway, as my 32 MHz clock definitely has some kind of a secondary AC signal in it which certainly isn't helping things. Maybe I can give it a better sink.

[derkom]

Found the cap kit. It's amazing how much stuff can get lost in a small house.

[stephen_usher]

The clock is tricky to measure.. Are you using X10 on your probe ?

Nope, X1.


CLK32-68R.png

That looks massively sub-sampled. Is your 'scope able to resolve that frequency?