VT240 Post error - HELP PLEASE! - Two right hand keyboard LEDs ON - Has anyone seen this??

[Radix]

Hi All

Looking for any more insight than the pocket service guide gives with :



I have the highlighted code - I think the T11 cpu is failing an early test - it can send data to the keyboard LEDs and then stops, but no obvious documentation as to what each LED code means...

Already checked and swapped all the ROMs, tried a different T11 and (cringe) piggy-backed ram chips on both sets of DRAM

It was in use when it failed - no smoke (!) - picture still on screen, just totally unresponsive, not receiving data, keyboard not responding, after power off/on just the keyboard LED error, no beep or text display

Just hoping someone might have seen this in the past - I'm rather desperate to get the VT240 back up and running ASAP...

Thanks,

Robin

 

[Radix]

Well - finally fixed it... so in case anyone else gets one like this, in my case it was one of the two 74S189 4x4 RAM chips at E133 / E134 causing the problem - of course, there are many other possibilities

Also - FYI, I replaced the 8 x 4164-12 DRAM with -20 200nS parts I had on-hand and they seem OK after short testing

Robin

 

[dtih]

I'll keep you in mind, I have a couple of VT240's, but haven't used them in a while.

 

[Radix]

Hi there DTIH, Thank you - anything to help is always appreciated! - This is the sort of thing I'm doing for the museum (TNMoC - The National Museum of Computing www.tnmoc.org)

Amongst other things, we have a VT240 on in the DEC gallery showing various graphics, next to a Gigi - but we have only the one VT240, no spares, which is a worry, if it fails like mine did!

So below, I have created a regis graphic from a photo of the gallery (traced as an svg, converted to regis and annotated on a PDP-11) - this will be added to the graphics on rotation in the gallery display..

We are working on more demos that visitors can use and interact with as well to keep it fresh and interesting

Robin

 

[reinhardtjh]

That's a nice DEC display.