One trick I found with the -5V if it is driven by a charge pump: check
the voltage. If it is being pulled down since the charge pump cannot
supply the current, just disconnect the charge pump and put a lab supply
in its place. The increased current will clean out whatever is shorting
it to ground without harming any good chips. If you are lucky a puff of
smoke will identify the chip. Otherwise there may be enough memory
running to give you a diagnostic message to say which bit.
I did it once on an $1800 board, all chips soldered in, results in minutes!
cheers,
Nigel
On 11/06/2020 16:33, Ethan Dicks via cctalk wrote:
On Thu, Jun 11, 2020 at 2:37 PM Adrian Graham via cctalk
<cctalk@classiccmp.org> wrote:
The 4116's are soldered to the board, too....
You’ve just mentioned the magic 4116 word, I’d bet some of your dollars that
it’s either one of those that’s gone south or the -5V required to run them
Definitely check the -5V for the 4116s.
-ethan
--
Nigel Johnson
MSc., MIEEE, MCSE
VE3ID/G4AJQ/VA3MCU
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