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Hi Greg et al,
Following the procedure it is interesting that the power supply does not allow me to even get down to 4.8V. The closest I can get it 4.88V. So I set it to light at that point and reset the regulation of the supply back to 5.0V measured where the wire enters the main board. The zero reference I’m using the the fast-on tab ground point near the front panel connector.
Same thing… bunch of LEDs come on in the same pattern. No panel response or keyboard response. Signals on RAM and ROM address and data lines.
Sometimes the pattern of these signals looks too regular to be code executing… not sure about this. Looping?
With regards to the 6116s… I see so the -3 must mean 300… kinda makes sense. Anyway it appears I only have 6 ICs so that idea is moot.
I think something may be occupying the CPUs attention.
PREQ is patched to INT1 on the jumpers near the CPU - should that signal be always HI?
Lou
From: chromapolaris@yahoogroups.com [mailto:chromapolaris@yahoogroups.com]
Sent: June-02-18 11:23 AM
To: chromapolaris@yahoogroups.com
Subject: Re: [chromapolaris] Polaris broken.... help!
On load... you have to watch the led... once set, cycling the power should bring it back from this unresponsive condition.
Sent from my iPhone
On Jun 2, 2018, at 11:18 AM, 'Lou Champagne' lou@... [chromapolaris] <chromapolaris@yahoogroups.com> wrote:
Thanks for the suggestion Greg. OK I’m going to calibrate that again just to make sure.
Should I do this under load or with the PSU output disconnected from the main board?
Lou
From: chromapolaris@yahoogroups.com [mailto:chromapolaris@yahoogroups.com]
Sent: June-02-18 10:36 AM
To: chromapolaris@yahoogroups.com
Subject: Re: [chromapolaris] Polaris broken.... help!
Now, I didn't see any mention about adjusting your DC OK threshold as outlined in the service manual. This totally sounds like the problem!
Greg
Sent from my iPhone
On Jun 2, 2018, at 10:13 AM, Bob Grieb bobgrieb@... [chromapolaris] <chromapolaris@yahoogroups.com> wrote:
Sounds like the CPU is not executing the code properly, or is getting
stuck somewhere waiting for something to happen. I am not familiar with the
structure of the code, but sometimes panel scanning is initiated by an interrupt
to the CPU. Maybe check any external interrupt signals to see if they are pulsing?
Sometimes you can check address decodes and get a feel for whether the CPU
is stuck polling one particular device, waiting for something to happen.
Also, if you have some spare RAM chips, try temporarily replacing them to see
if that changes anything. A bad RAM will prevent proper CPU execution.
Since the Polaris can use two different sizes of RAM chips, you can infer
the minimum amount of RAM needed for it to operate, and only install that much,
then try different chips.
Of course Paul D is the expert on all things Polaris...
Bob