Commodore PET 4032 problem (4 beeps)

From: Dave Dunfield <>
Date: Wed Oct 6 11:52:28 2004

> I don't know much about PET's but I guess "working"
>means it beeps 4 times. That is working, isn't it?

I'm not the most knowlegable about PETs in this group,
but I have been working on a bunch of them lately - I've
recently debugged startup problems with a 4032 and several
8032s (essentually the same board), so I will try and
offer somewhat more helpful information .... :-)

The 4032 and 8032 normally give a "beep series", which
might be interpreted as "four beeps" - is it sort of one
long continuous beep that warbles four times, or is it
four distinct beeps?

If the former, then it's normal, if the latter, then I
don't recognize it. I dug through the starup code a fair
bit in debugging my SuperPet (8032 from 6502 point of
view) and I don't recall anything along the way before
video-init and startup message that would generate beeps
other than the "Warble".

First, make sure the monitor is working (There's a
brightness control on the back which may have been
turned down) - Check for power to the monitor, and
if you have a scope, look for drive signals.

If you think the monitor is working, then you can get into
the internal monitor by grounding the "diag" pin on the
User port - In my experience, this comes up a LOT easier
than BASIC, so it may come up even if Basic won't. Once
you get that far, then the rest should be easy.

In working on a 4032 and three 8032s recently, here's what
I found:

 - Bad 4116 DRAM's - I ended up replacing 5 DRAM's in total
   (IMHO This is a very likely reason for what you are
    observing - one of mine hung in the ram-size function
    due to a bad DRAM)
 - Bad 2114 Video SRAM's - I had to replace two of these
   (and a few more in Commodore disk drive units) - these
    will cause "bad video" but you should still get SOME
 - Bad power regulator the 12v regulator on one of my 8032s.

Didn't run across any this time, but I have seen bad ROMs
in PETs in the past.

dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools:
com Vintage computing equipment collector.
Received on Wed Oct 06 2004 - 11:52:28 BST

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