H5C1- firST STeps

[JezC]

Well, I just tried re-soldering some of the connections on the GLUE socket (4 or 5 looked a bit iffy)...but sadly that's not fixed it.

I'll re-test with the diag cart tomorrow & see if the errors reported are the same or not...if it's the same then I'd better dig out the schematics & see which connections might be faulty & causing the bus fault (especially with which address lines are required for the floppy accesses).

[JezC]

Yet more steps backwards on this...though the H5 is no better off, I've managed to damage the H4 somehow (possibly when testing the other keyboard, floppy drive/cable & PSU) so that won't power up now - no power LED on the keyboard, so I've probably managed to short something.

Even with all the other parts re-instated the H4 won't boot (but I've tried everything bar the floppy cable on the H5 & that is the same with all of them, so it appears to be the H4 board itself )...and with just the working PSU it still doesn't seem to boot.

I'll have to bell out the power & ground planes to see if I can locate the issue...ho hum.

Hope to get chance to look further into this over the Bank Holiday weekend...

[JezC]

Dug out my multi-meter & the H4 is showing ~0.7 ohms between GND & 5V (no keyboard, PSU or floppy connected, so just the H4 board and ICs fitted).

The H5 by comparison reads ~164 ohms, so that would explain the PSU not powering up into a near dead-short!

Since this H4 board was previously working, I'm hoping it's either something bridging across the supplies on the outer layers or a dead IC or similar.

Now all I need is the time to start investigating...

[exxos]

This is where a milliohm meter is useful.

https://www.exxosforum.co.uk/forum/viewt ... 305#p37305

https://www.exxosforum.co.uk/forum/viewt ... =60#p37822

[JezC]

This is where a milliohm meter is useful.

https://www.exxosforum.co.uk/forum/viewt ... 305#p37305

https://www.exxosforum.co.uk/forum/viewt ... =60#p37822

Yes, way beyond what my Fluke can do...I'll check if they have something similar at work (but I'm not sure if they do).

I've pulled all the socketed chips,SIMM module etc. & the short is still there

Probably time to start looking at the schematics to see where there might be a short.

EDIT: I'll start adding these H4 diagnostic steps to the old H4 build topic rather than confuse this H5 one...

[JezC]

Inspired in part by @exxos having some of the RasPi Pico-based hard drives in stock again, I'm going to try and connect up the logic analyser to the H5 & see if that shows something re the bombs on accessing the floppy...

Can any kind soul point me to the schematics for the H5C1 - I know I've seen them at some point in the past (or though I had)...but as usual when I actually want to use them they are hiding somewhere...

[exxos]

Don't think I have uploaded the C1 yet, but basically same as rev A anyway viewtopic.php?f=89&t=3457

EDIT:

viewtopic.php?f=89&t=6524

[JezC]

Don't think I have uploaded the C1 yet, but basically same as rev A anyway viewtopic.php?f=89&t=3457

EDIT:

viewtopic.php?f=89&t=6524

Thanks @exxos - now that is one less excuse I can use for not getting the H5C1 working....

[exxos]

Thanks @exxos - now that is one less excuse I can use for not getting the H5C1 working....

Yes we need to know what the problem is!

Looking back you seem to get bus errors from the diagnostic cartridge which is pretty bizarre as I will be more a CPU type fault.

Did you run RAM test from the cart and leave it running for a hour ?

Also if you can run floppy check on the diagnostic cartridge, have you looked to see the physical drive heads are moving and the disc is actually rotating etc ?

[exxos]

Looking back you posted this..

But SIDE 8 ?!

Floppy test failed, see below
Disk A: DS
Formatting Side 8 Track 00
EB Bus Error Access Address: 4E4E58 Program Counter: 3B001F
EA Address Error Access Address: 3B001F Program Counter: FA0E88
EA Address Error Access Address: FD3FFB Program Counter: FABE8A
EA Address Error Access Address: 00386D Program Counter: FAGESC