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Sharkonwheels
February 17th, 2008, 06:54 PM
I know others have had issues...Terry...Curtis...

What's the deal with CRT failures on the Execs? I have 2 machines, and the external video works, but not the CRT.

I look at my commodore 1084 monitor, lights turned off, and the yoke is lit up.
On the Exec tubes, neither has any glow.

Are the CRT's the part going bad, or the video boards?


By the way, in that stash I acquired last year, there was a lon EPROM in a box. It was V1.21 ROM for the Exec.
Both mine had V1.2, so if anyone needs a copy of it, lemme know.


T

Druid6900
February 17th, 2008, 06:56 PM
Well, if the filament isn't glowing, it's either broken or it's not getting heater voltage.

Sharkonwheels
February 17th, 2008, 07:10 PM
How can I check that? Think it's something fixable?
Shame - I have 2 working units, nice cosmetically, but both CRT's are out.


T

Druid6900
February 17th, 2008, 07:13 PM
How can I check that? Think it's something fixable?
Shame - I have 2 working units, nice cosmetically, but both CRT's are out.


T

Well, it's just a DC voltage (probably 12V) that (usually) comes off the video controller card and, not having a schematic for the unit, I can't tell you where to check.

Some video boards have a fuse on them, so, that might be it, if there is one and, pretty much anything is fixable, it just depends on if it's worth the time and money.

chuckcmagee
February 17th, 2008, 07:56 PM
It is strange. Video is out on mine too. In my case, it's just a loose connection on the horiz amp transistor. I had it working for a few seconds but I need to take it apart again and redo the soldering.

Sharkonwheels
February 17th, 2008, 08:08 PM
I just checked the 12V coming from the mainboard, to the video board, and it is 12.53V.

I can scan in the schematics on Wed at work. I have the full tech ref manual set for the Executive, which includes full schematics.

I don't know if it is already available elsewhere....Chuck?

Oh, chuck, did yours have same symptom? I mean, mine doesn't even glow at all on the rear of the CRT tube - neither of them! Checked voltages at the power supply connector feeding the mainboard, and according to the tech ref, all seems OK. What is the +/- figure on the voltages that is acceptable?


T

Sharkonwheels
February 17th, 2008, 08:10 PM
OK - scratch that - VERY DIM glow on the back of one of them. I mean REALLY dim, and it's near to the end of the neck.

T

Sharkonwheels
February 17th, 2008, 09:02 PM
Druid, found the link:

http://bitsavers.vt100.net/pdf/osborne/2F00040-00_Service2ndEdition_1983.pdf

monitor coverage starts on (acrobat page number) page 236


T

EDIT: Scratch that - that's for the 5" O1 monitor...

chuckcmagee
February 17th, 2008, 11:03 PM
No, not the same. I do get something on the screen, a nice THIN bright green vertical line -- sometimes. Sometimes it would get nothing. I had to do the now infamous "universal fix" which, of course, it tapping it heavily on the top. Occasionally, I would get a full readable screen that would then collapse to the vertical line.

I had it fixed but not well enough. I have to get up the motivation to get back in there. Lot of work with hard to get to screws.

mloewen
February 19th, 2008, 03:53 AM
No, not the same. I do get something on the screen, a nice THIN bright green vertical line -- sometimes. Sometimes it would get nothing. I had to do the now infamous "universal fix" which, of course, it tapping it heavily on the top.

Your Exec has a green monitor? Weird.

My Exec has just had a similar monitor failure, with a very faint vertical line. The internal monitor is a Zenith DT4. Someone on CCtalk posted a link to a schematic:

http://oldcomputers.dyndns.org/public/pub/rechner/osborne/executiv/manual/sheets/osbe_video.png

It's not exactly the same monitor, but I'll have to get into the guts to see how close it is.

Sharkonwheels
February 19th, 2008, 04:31 AM
That SHOULD be the monitor...
That's the schematic out of the back of Volume C of the Exec Tech Ref library, and matches (what I've checked) my monitor.

T

Druid6900
February 19th, 2008, 05:49 AM
OK, give me some time to print and look at the schematic, but, from what I remember, you might have an inter-element short in the tube.

Although this may sound like sacrilege, try smacking the case around and see if you get any reaction.

The vertical line is a sign of a problem in the horizontal deflection circuitry and with Chuck's, the fact that it pops back could indicate a poor solder joint (possibly on either the H Osc. or H Output)

chuckcmagee
February 19th, 2008, 10:28 AM
Hmm, ok, now that I think about it, it is NOT a green monitor. Been awhile since I have smacked it around :rolleyes:

And, yes, I know, mine is a loose connection on the horiz amp transistor. I had it fixed briefly. Of course it worked fine until I got it all back together.

Sharkonwheels
February 19th, 2008, 11:44 AM
We wouldn't have it any other way...

I had one of the Execs completely closed up....powered it up...didn't go....
complete disassemble AGAIN to realize I had left one of the power cables unplugged!


<sigh>

Remind me again why do we go through this?


T

curtis
February 19th, 2008, 04:27 PM
<sigh>

Remind me again why do we go through this?


T

Because we were all dropped on our heads as infants?

http://img145.echo.cx/img145/1536/sc0734ig.gif

Druid6900
February 19th, 2008, 07:25 PM
We wouldn't have it any other way...

I had one of the Execs completely closed up....powered it up...didn't go....
complete disassemble AGAIN to realize I had left one of the power cables unplugged!


<sigh>

Remind me again why do we go through this?


T

Does that mean you don't need me to print and study the schematic or are we talking another unit?

Sharkonwheels
February 19th, 2008, 10:05 PM
Oh HECK no - that was just a stupidity i did.
Both CRT's are still non-functional - I was referring to closing it up, and forgetting to plug something in, and having to do the massive disassembly yet A G A I N !


Thanks for the help!


T

MikeS
February 20th, 2008, 12:49 AM
Oh HECK no - that was just a stupidity i did.
Both CRT's are still non-functional - I was referring to closing it up, and forgetting to plug something in, and having to do the massive disassembly yet A G A I N !

Thanks for the help!

T

Probably not the CRTs anyway, and most unlikely that they'd be the same, but I *am* about to throw out some 5" and 9" CRTs, JIC.

m

Sharkonwheels
February 20th, 2008, 10:36 AM
Much appreciated, but these are the 7" displays in the Exec

T

MikeS
February 20th, 2008, 12:54 PM
Much appreciated, but these are the 7" displays in the Exec

T

Just split the diff...
m

Sharkonwheels
February 20th, 2008, 01:02 PM
I think it's more the mounting, and maybe compatibility of the electronics.

I dunno - don't know enough about it.


T

MikeS
February 20th, 2008, 06:11 PM
I think it's more the mounting, and maybe compatibility of the electronics.

I dunno - don't know enough about it.


T

That was s'posed to be a ;-)
(9+5)/2=7

m

Druid6900
February 27th, 2008, 07:40 PM
Tony,

Finally got a chance to study the schematic for the video card and there are about a dozen things that could cause "no video" in the system.

It's rather difficult to diagnose a problem over the 'net when you can't take a few readings and you sure as hell don't want to ship that sucker half way across North America so I can fix it. You could probably buy another one for less than what that would cost.

I just thought that, perhaps, I could pick out something glaringly obvious.

Sharkonwheels
February 28th, 2008, 02:58 PM
I can take any readings ya need.
Have an O-Scope as well, not that I know how to use it.

Tek 2235 I think? Got the manual even ;)


T