19 Jan
2015
19 Jan
'15
7:18 a.m.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Diane Bruce
Sent: 19 January 2015 14:17
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: VT101 8085 CPU Fault
On Mon, Jan 19, 2015 at 02:07:08PM +0100, Johnny Billquist wrote:
Sorry, I know, but the terminal controller board appears to be significantly different to
the VT100, the VT100 does not use the 8085. I will have a read of the sections you
indicate though.
On 2015-01-19 09:04, tony duell wrote:
>>
>> I just found something interesting, the pin activity on the address
>> lines, RD, WR, ALE etc appears normal for a bit, and only after a few
seconds does it all become inactive.
http://tkc8800.com/images/vt100/VT100_Technical_Manual.pdf
Look in section 4.2.8
The POWER-Up adn Self-Test section.
I linked this pdf before ;)
"Assuming there are no hard logic failures present on the board, "
And yes the 8085 has a HLT instruction.
Are the keyboard lights lighting up at all?
Some do, but not all, and I don't hear the beep from the keyboard. HLT is looking
likely.
If it *is* the ROM which is unlikely if it is a masked ROM, it might simply be
lose in the socket you mentioned. It may be sufficient to wiggle the ROM
slightly to break any oxide on the pins. Some sockets are notorious for allowing
the chip to wiggle up due to heat and cooling down.
Your ROM may simply be lose.
I will reseat the only socketed chip on the board to make sure. Thanks for the
suggestion.
Regards
Rob