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Olivetti M24 - No POST

Well once I have more of the collection running I'm hoping to start taking some of the machines to UK shows.

In the mean time Im expecting my mum to spend some time in front of it tinkering with the thesis she wrote on an M24 many years ago :)

Once I've reinstalled the floppy and the HDD I'm looking forward to seeing what is actually on it!

Then as you know probably too well I have a Kaypro that needs my attention - and about 100 more machines :p
 
Seems I'm not entirely out of the woods yet. Decided to leave it on a while to make sure its ok, and I'm seeing some flickering on and off of the screen, and flickering brightness.

The display itself doesnt seem to jump or deform at all.

It's just variation in brightness.

I'll try to check the stability of the 15v monitor supply whilst it's under load tomorrow.
 
I am so fustrated with this computer it is unbelievable. Just when I thought I was past the hardest bit!!!!!

As it stands the display "brightness" on the monitor is altering randomly in a flickering way over time, and it has taken to displaying what looks lie a 40 collumn post screen rather than 80, where part of it is off the screen!

Because of the way it is done it is hard to see how I can take readings of the 15v supply to the monitor whilst the powersupply is still connected to the monitor - there seems to be nowhere I can find that I can actually get a probe to take a reading.
 
Pop the top cover off the M24--you'll see that the +15 feeds to the video controller via a pair of wires (one orange, one black, IIRC). You can take your reading where the thing plugs into the video controller.
 
If the 15v rail is losing voltage am I right in thinking that would in this case cause variation in brightness?

Is it possible that if the voltage being supplied is lower than 15v that the guns in the tube would effectively project over a larger area making it look like a 40 collumn image partially off the screen?
 
Well, yes, although if the voltage was fluctuating, you'd also get "bloom" (focus and size variation). Doesn't sound as if that's the case. I'd tackle the obvious--get some contact cleaner (I like DeOxIt, but pick your poison) and squirt some into both the contrast and brightness control pots, agitate, repeat and see if that doesn't make a difference.
 
Had the monitor apart and used some contact cleaner on the contrast and brightness control pots. Haven't tried it yet though.

Next to the flyback transformer there is a radial electrolitic capacitor (25v iirc, size not visible at the moment) that is bulged and burst.

I'll remove the board tomorrow and desolder the offending capacitor and get replacements in for Tuesday. At the moment Im guessing its a 220uF because all the other identical size and make caps on the board are 220uF 25v.
 
It was a 220uF 25v capacitor.

Having replaced it the screen display is now the right size again although the first character on each line of text is squashed and the brightness of that character is somewhat higher. If I remember rightly this symptom can be altered using one of the various trim pots on the monitor board.. perhaps horizontal position?

Would you expect changing a capacitor to require these pots to be altered a bit?

Do you think I should replace the other capacitors in the monitor too?
 
Yes, you can use a pot to change the thing. It might be labeled "Horiz Pos." or "Horiz Phase" or sometimes just "Phase".

If the capacitor affected the voltage situation in the horizontal section, yes, absolutely.

Are any other capacitors bulging or leaking? If not, I say if it isn't broken, don't fix it.
 
Ok all the other caps look good. Cannot recreate the screen symptom now - it is displaying fine. There clearly is a bad connection somewhere because if you tap the monitor housing sometimes the screen flickers off. I'll try to find out what is causing this.

The HDD controller fitted to the machine is an LCS-6210C Rev C and the HDD is a Shinwa Digital D220. I'm unfamiliar with both these items and can find very little information especially about the HDD at the moment.

The HDD spins up, and other than being quite loud, there is click when the machine is turned on, and that is a small locking mechanism retreating from a gear wheel on the front right hand side of the drive. This gear wheel doesnt seem to move at all, and I hear nothing that suggests the drive attempted to seek.

The machine reports a drive error.

There is one bank of jumpers on the controller card, none of which have any jumpers on them at all.

If the jumpers are the same as a revision G version of the card this is for 306 cylinders and 4 heads as drive 0 and drive 1 disabled.

Any ideas please?
 
I found a document that says a Shinwa Digital D220 is a 20Mb 614cyl 4head Spt 17 drive.

Assuming the revision C and G jumpers for the controller card are the same I tried both settings for a 614cyl 4head drive and still get no seek sound at all.
 
All it says is "Primary boot strap: DISK READ ERROR.".
Still no indication of any seek activity.
I see the error message of "Primary Boot-Strap DISK READ ERROR" in the M24 BIOS, not in the LCS-6210C's BIOS.

It's like the M24 is not 'seeing' the LCS-6210C. If the M24 was seeing the LCS-6210C, it would hand control to it at POST time, and if then, the LCS-6210C detected a problem, the LCS-6210C would issue errors like "POWER ON TEST ERROR - BAD CONTROLLER" and "1701" (both of which appear in the LCS-6210C BIOS).
 
I doubt it. Controller cards rarely just go bad.

Let's make sure. DIPSW-1 should read (postions 12345678 ): 10010001 (1=on, 0=off). That means that if you take the HDC out, the BIOS shouldn't be looking for one.
 
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