exxos's Atari, Amiga & retro forum

I think i've worked it out. There is a lot of 500khz noise getting though from somewhere. So just needs a tweak for a LPF adding..

viewtopic.php?p=87737#p87737 updated fix here. The 100K added which solved the audio fading out was supposed to be 1K. It was part of the YM circuit along with the 100nF which got missed somehow during the new amp design :roll:

Another pretty strange occurrence. Using the same floppy drive on one C1 board, certain floppies work fine ( albeit very old ones). And on the second C1 build, the same floppies do not read at all :shrug: I even swapped the DMA and 1772 between boards just to see if it made any odds and it didn't.

exxos wrote: 04 Jul 2022 20:55 Another pretty strange occurrence. Using the same floppy drive on one C1 board, certain floppies work fine ( albeit very old ones). And on the second C1 build, the same floppies do not read at all :shrug: I even swapped the DMA and 1772 between boards just to see if it made any odds and it didn't.

Reminds me that I still haven't worked out why my H5 C1 is bombing on floppy accesses...but probably not related ?!?

JezC wrote: 04 Jul 2022 21:58 Reminds me that I still haven't worked out why my H5 C1 is bombing on floppy accesses...but probably not related ?!?

Wouldn't think so no. It could be down to minor differences in clock speeds or something causing it :shrug: but a lot of these floppies are like 30 years old now. Some of them do actually work fine just not the odd couple. Just thought it was very odd.

If I ever get caught up with work I could probably take a look at your H5 ? if it is not being used because of faults then you could probably send it whenever, but really cannot say when I would have chance to look at it. But if it is "on the shelf" and I do end up with a couple hours one day free.. Otherwise it could be more towards the end of the year.

exxos wrote: 04 Jul 2022 22:07

JezC wrote: 04 Jul 2022 21:58 Reminds me that I still haven't worked out why my H5 C1 is bombing on floppy accesses...but probably not related ?!?

Wouldn't think so no. It could be down to minor differences in clock speeds or something causing it :shrug: but a lot of these floppies are like 30 years old now. Some of them do actually work fine just not the odd couple. Just thought it was very odd.

If I ever get caught up with work I could probably take a look at your H5 ? if it is not being used because of faults then you could probably send it whenever, but really cannot say when I would have chance to look at it. But if it is "on the shelf" and I do end up with a couple hours one day free.. Otherwise it could be more towards the end of the year.

Thanks for the offer - I'm mostly not using it ATM as the H4 is working well enough (and not had enough spare time to devote to my retro-hobbies for a while :( ) and that H4 now has the Trudie board working in there and sometimes the TF536 board as well :D .

I've borrowed a 4 channel Agilent 'scope from work to compare the working H4 with the H5 w.r.t. floppy accesses etc. for the faint hope that I do get the time sometime soon - but if work need it back then I'll probably post it down to you on the off chance!

It's not like I'm short of other retro projects if I do send it down (half a dozen ST's to fault find, numerous PSU's to recap, two Amiga 500s to fix not to mention building the v5 TF536 & a second v2 TF536 plus about 4 TOS switchers for Megas and STE's - and that 32MHz STE booster to test on the external blitter STE once I swap the 'S' chip to the 'F' chip...)

Life's too short!