JezC H4 Build - in slow time

[JezC]

@JezC if you're struggling, I'm happy to take a look at some point?

@PhilC Appreciate the kind offer... I'll have a bit of a probe around to see if I can spot anything obvious (and try to hone my diagnostic skills in the process!).

If I don't make any progress then I will send it your way!



I think the most likely cause is that the keyboard slipped & pulled the connector off the pins on the mobo...so I had to straighten the pins.

[JezC]

And we have progress!

Over 2 months since I broke it...I finally managed to finish the fault-finding & get it back to some level of a working state!

Turns out that one of the large SMT capacitors had failed short circuit (which has happened to @exxos on one of his boards IIRC), so I've finally managed to remove that & the machine now boots once more.

Sadly, when removing a couple of the ICs (one 6850 & the 2149F) the sockets have failed so they need replacing before I do much more...but we have a resurrected H4!

Next step will be to fit the floppy drive/Gotek and then try to see what is different between my H5 and this (currently working) H4...

I now need to be careful not to make a habit of this or @PhilC will be out for revenge!

[JezC]

One other "minor" irritation during the above is that the old LCD TV that I've been using for my H4/H5 investigations has decided to stop powering up...

It now sits there with the power LED coming on briefly & then flicking off again, so I suspect a cap has succumbed to age.

Rather than get diverted by this new catastrophe, I just moved over to the Benq monitor I usually use with the original machines & fortunately that works enough to prove the H4 is alive.

I'd vaguely remembered some comments about the UBE video adaptor not working on the H4/H5 (no 12v on the monitor socket on the H4/H5???) so I snaffled the Exxos one out of one of my Megas & that worked well enough for this first test.

[exxos]

I'd vaguely remembered some comments about the UBE video adaptor not working on the H4/H5 (no 12v on the monitor socket on the H4/H5???) so I snaffled the Exxos one out of one of my Megas & that worked well enough for this first test.

They have 12V on the socket. Mine still need power to the chip on the ST2VGA board. I don't remember any comments about the UBE not working unless anyone else does ?

[JezC]

I'd vaguely remembered some comments about the UBE video adaptor not working on the H4/H5 (no 12v on the monitor socket on the H4/H5???) so I snaffled the Exxos one out of one of my Megas & that worked well enough for this first test.

They have 12V on the socket. Mine still need power to the chip on the ST2VGA board. I don't remember any comments about the UBE not working unless anyone else does ?

Thought @terriblefire had a problem in his build thread? I'll check & add a link if I can find it...

EDIT: Link to TF build below with comment about UbeSwitch...
https://www.exxosforum.co.uk/forum/viewt ... =70#p39419

[JezC]

Ok, so I've tried both the Exxos 'value' VGA adaptor & the Ubeswitch version on my H4 & both seem to work just fine!

So, next planned job is to fit my Trudie board & get that working...then I'm hoping to solder in the cartridge port & try out a couple of MIDI programs, then maybe even re-fit my TF536 to see what will work on the 030 with all that RAM....

Now where did I put that CF card...

[exxos]

Ok, so I've tried both the Exxos 'value' VGA adaptor & the Ubeswitch version on my H4 & both seem to work just fine!

H4 seems so long ago now

[rubber_jonnie]

Wow, the first post in this thread was Feb 2020, it has really been a build in slow time!!

I have a couple of H4s to build, I'd better get on it so my finished one has company

[JezC]

H4 seems so long ago now

Yes, though I do like the greater ease of working on the through hole parts compared to surface mount stuff (that's not a dig at the H5, more the fine pitch TQFP & BGA packages we use at work).

Just glad to be back to having it working again...and this time I'll try not to do a @PhilC and break it again...or at least not until I've got that H5 floppy issue sorted!

[JezC]

Wow, the first post in this thread was Feb 2020, it has really been a build in slow time!!

I have a couple of H4s to build, I'd better get on it so my finished one has company

I did get it first working back in June 2020, so not quite that long really...it's just that I broke it earlier this year when trying to sort out some issues with the first H5 build (getting there, though the floppy issue is still not resolved yet).

I still have one H4 and an H5B1 to build at some point (plus the second TF536...waiting on PLD & DRAM courtesy of the global shortages).
Maybe it should be a friendly competition to see who builds up their next system first? Spoiler alert - it's almost certain to be you!