[personal] RE: PDP-8E diagnostic help needed

Mike Hatch mike at brickfieldspark.org
Wed May 14 03:28:20 CDT 2008


0-24 thats 0-16 Dec.

Don't know the 8's but that would suggest to me that 4 bits (1 chips worth) 
are stuck somewhere leading to some address decoding ?. Does it repeat 
higher up the addresses ?.

Mike.

----- Original Message ----- 
From: "Rod Smallwood" <RodSmallwood at mail.ediconsulting.co.uk>
To: "General Discussion: On-Topic Posts Only" <cctech at classiccmp.org>
Sent: Tuesday, May 13, 2008 8:44 AM
Subject: [personal] RE: PDP-8E diagnostic help needed


> Now that's interesting..
>
> I have a PDP-8/e as well. I can't store in locations 000 000 000 000  to
> 000 000 011 000 (0 - 24 Dec)
> Above is OK
>
>
> If somebody has an answer to your problem. They might know something
> about mune.
>
> Rod Smallwood
>
>
>
>
> -----Original Message-----
> From: cctech-bounces at classiccmp.org
> [mailto:cctech-bounces at classiccmp.org] On Behalf Of Mark G. Thomas
> Sent: 09 May 2008 16:36
> To: cctech at classiccmp.org
> Subject: PDP-8E diagnostic help needed
>
> Hi,
>
> I've got a PDP-8E which I've almost got working.
>
> Can anyone here help me figure out this remaining problem?
>
> As I examine memory, the address lights count up to 01111, then go back
> to 00000, instead of 10000. I can manually enter an address higher than
> 1111, but the 10000 and 100000 bits don't stick -- they go low, as soon
> as I hit the examine switch to step to  the next memory location.
>
> I can manually load an address 1000000 or 10000000, and hit examine to
> see 1000001, 1000010, 1000011, etc..., but once I reach 1001111, it's
> back to 1000000.
>
> It was recommended to me that it might be the carry between E52 and E37,
> or the E38 input multiplexer for bit 7 (on M8300), so last night I
> socketed and replaced all three of those ICs, but I still see the same
> symptoms.
>
> I have extender boards, so can access M8300 during operation. I measured
> the carry line between E52 and E37 go low when I reach 1111, but the
> light for line 10000 doesn't light on the front panel on the next
> address, and I see the data from memory location 0000, 0001, etc.
> repeated, displayed as I continue to step through memory locations, as
> described above.
>
> Of course, if someone has a spare M8300 they would be willing to sell
> me, that's another option.
>
> Mark
>
>
> --
> Mark G. Thomas (Mark at Misty.com)
> voice: 215-591-3695
> http://mail-cleaner.com/
>
>
>
>
> 





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