On Mon, 27 Aug 2012 11:32:16 +0100 "Gareth Magennis"
wrote in Message id:
:



"JW" wrote in message
.. .
On Sat, 25 Aug 2012 19:30:12 +0100 "Gareth Magennis"
wrote in Message id:
:



"Gareth Magennis" wrote in message
. ..

"JW" wrote in message
...
On Wed, 22 Aug 2012 09:57:52 +0100 "Gareth Magennis"
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:

Hi,

can't seem to even find a printable datasheet for this well obsolete
device.

Its an 8080A controller/bus driver, just wondering if anyone knows
where
I
might find a replacement - perhaps someone knows of a common old piece
of
equipment that might have one I can salvage.


This is in an AMS DMX 1580, a digital delay from the last century.

Ebay?
http://www.ebay.com/sch/i.html?_from...&_nkw=uPB8228C

Datasheet:
http://www.datasheetarchive.com/UPB8228C-datasheet.html

Intel also made the 8228. Very likely that Intel designed it, and NEC
copied.


Oops, must have made a typo when I searched Ebay yesterday.
There's one on Ebay UK too which I've just bought.


Cheers,


Gareth.




Damn, replacement didn't work.

Reason for suspecting this device was that the systems _WR line was held
at
around 1 volt, other Address/Data lines look normal.
Isolating this device from that line produced a solid zero, so worth a
punt,
I thought.

Just a thought... If you can isolate it again, try putting a 2.2K resistor
pullup on the signal to see if the CPU can drive that lower than .8V

No I don't have a schematic, but it is a small PCB. The _WR line also goes
to 2 DRAM chips, but nowhere else as far as I can tell.

Normally I'd suspect the DRAM chips as well, but not so much if isolating
the _WR signal to the 8228 seemed to correct the voltage level.

Also, the 8080A had three power supplies (+12V, +5V and -5V), but you
probably already checked/knew that.

[snip]