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

[Rod Smallwood]

	Address			Contents

	000 000 000 000  		000 000 000 000
	000 000 000 001		000 000 000 000
      000 000 000 010		000 000 000 000
      000 000 000 010		000 000 000 000	             

-----Original Message-----
From: cctech-bounces at classiccmp.org
[mailto:cctech-bounces at classiccmp.org] On Behalf Of Mike Hatch
Sent: 14 May 2008 09:28
To: General Discussion: On-Topic Posts Only
Subject: Re: [personal] RE: PDP-8E diagnostic help needed

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/
>
>
>
>
>