check the reset circuit.
check power supply is stable and on voltage. +5V needs to be within TTL tolerance levels which is about 10% so even a crappy multi-meter should read close enough to be within 10%.
check that the write, read and chip select signals are reaching the RAM 6116.
check all of the data and address lines are at the RAM.
How did you assemble the 80C85 code? Other than me and one other person, no one on this yahoo group has ever created a working piece of 80C85 code.
sometimes chips fail, but rarely. let's keep assuming that it isn't the RAM itself, not just yet.
/Mike
From: "Gordonjcp gordon@... [korgpolyex]" <korgpolyex@yahoogroups.com>
To: "mmdatech@... [korgpolyex]" <korgpolyex@yahoogroups.com>
Sent: Monday, November 30, 2015 1:40 PM
Subject: Re: [korgpolyex] another dead 800
On Mon, Nov 30, 2015 at 10:35:28AM -0800, mmdatech@... [korgpolyex] wrote:
> I managed to write a small program to test 8085, 8155 and led drivers by lighting them all at once. It seems to work but the startup is flaky, it doesn't
> show up every time I switch the power on.
>
>
> any ideas on what I should test next ?
>
>
Doesn't start up every time? That sounds like evidence, to me...
--
Gordonjcp MM0YEQ