JezC H5 C5B Build - one STep beyond...?

[exxos]

- 8/16 MHz clock select (both initially set to force 8MHz, H5CB also tested with GAL fitted & this set in both modes)
- force 720k/1.44M for drive 0 & 1 (H4 has these jumpers open, H5CB fails in the same way whether open or closed)

The 2 JP18,JP19 jumpers are closed for 720K mode, but its only to set the GAL registers.

JP22 (bottom right of GAL) top and middle pins linked set 8MHz to the 1772. GAL & JP18,JP19 jumpers become irrelevant then anyway.

I assume your floppy drive light isn't on all the time from power up ? As that normally means you have the floppy cable in upside down.

Probably be a good idea to post some images of your board overall and close up of all the jumpers etc

[JezC]

Thanks @exxos - will post some photos a bit later tonight if I can...

Floppy LED is off at boot until it pulses during the check for the TOS/RAM/FDD display (text on white screen) then off again until it tries to boot.

With no floppy present, it gets to the desktop OK (floppy still on).

With a floppy in it gives 2 bombs & needs a reset or power cycle to recover just after the TOS/RAM/FDD info is shown (i.e. before the desktop)

If I insert the floppy & open drive A after booting without a floppy, I get the same 2 bombs.

This is with JP 22 set to 2,3 & no GAL (JP18,19 open or closed - so makes sense if they are only used by the GAL ;))
Also with GAL present, JP 22 set to 1,2 & JP18 & 19 closed (or open).

So, as far as I can tell it is OK to detect that the FDD is connected & has power but not to actually read from...and other than the number of bombs being different (I think), this is the same behaviour that I have on the two H5C1 boards as well.

Using the FDD and cable and chips from the working H4 board in the H5CB doesn't change the floppy issues either, so it certainly seems to be related to the board itself rather than the chips or FDD (I've tried 2 different working ST drives plus a working HD drive and no discernible difference for any of them).

[JezC]

@exxos Pictures of the H5CB showing jumper positions as requested...

IMG_20250610_204957393_HDR.jpg

IMG_20250610_204950244_HDR.jpg

IMG_20250610_204934197_HDR.jpg

Would be great if I've just set a jumper (or three) set wrongly... :roll: :D

[exxos]

@JezC is that PSU recapped ? The surge from the floppy motor turning on can crash the system if the caps have gone bad. It gives the appearance you have DMA related issues when in fact you don't...


Your missing a solder jumper as well...

Capture.PNG

[JezC]

@exxos I'll try it with one of your PSUs to rule that out (but normal ST & STE's have been fine with that PSU - as has the H4)...AND blob over that link...

[exxos]

@exxos I'll try it with one of your PSUs to rule that out (but normal ST & STE's have been fine with that PSU - as has the H4)...AND blob over that link...

The H5 series likely pulls a bit more current than the H4.. Plus the H5 has a few 100uF caps which the H5 doesn't. Should always do debugging with a known good PSU ;)

[JezC]

I started with one of your PSUs but the short power lead to the motherboard meant I couldn't put it into the slots in the H5 board, so it was always in the way...

:sigh:

[JezC]

Ok, so blob connecting top 2 pads for default position & using the exxos blue PSU still has the 2 bombs when there's a floppy in the drive...

I have dug out my TRUDIE board, so next is to find a DIP connector for one of the 68k expansion ports...unless you have spotted any other issues?

[exxos]

I wouldn't use TRUDIE at this point, because I don't know the state of what it works with and what it doesn't. Its just going to complicate matters.

I can't spot anything else currently..

[JezC]

Ok, thanks for the pointers thus far @exxos

I still find it odd that I have the 3 H5C boards all showing a very similar problem...only the number of bombs shown when it crashes on a floppy access seems different across all 3 of them.
The idea was to get one working one & use that to help fault-find the others, not to get more with what appear to be very similar problems to each other.... :(