Any H3000 gurus here !
« on: May 26, 2013, 05:00:59 AM »
Hi Peeps
Decided to digout my non functioning H3000 which I obtained "not working"
A few years ago for a song,  from a friend who i did some work for and gave it to me
In part payment.
Had a quick look at it at the time and decided that this was going to be a challenge !,
Powers up ....with no display,(or occasionaly one line illuminated no charachters.....
None of the easy fixes apply here ie PSU connectors ,bit rot etc,etc ,.....eproms,processor,ram,
And some suspect TTL chips changed and socketed,no go,after many hours spent with scope and
Schematics alover the place...Put it to oneside "in the loft " and forgot about it
Being someone who will not give in and a tech for 30 yrs digital and analogue,
Decided to have a refresh on the situation and attempted another session of brainstorming.!
After many more hours of investigation the suspect seems to be the dreaded PALSL1-2 chip,
U56 which handles the address decode function,enableing Brain Page bus and several other
Enables etc,all Brain adress data is present ,but the output pins are not giving any thing out that
I would expect to see .
So the answer seems to be a substitute chip to confirm ....alas its a dreaded PAL,
Still available to buy but of course needs to be programmed, Unicorn comes to mind .
Anyone with a "dead beyond viable repair" H3000 board around,or sugestion for replacement !
I would hate to scrap this unit as I could now use it for a couple of projects ,
I  could put it on evilbay but if all else fails may just have to buy a working one and go from there !
OUCH ... :o
Regards and thanks

On the end of a Rural Twisted Pair.


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