Otrona Attache CRT brightness decay

[ThisPostContainsComputers]

Hello,

Since VCFMW is coming up in a few short weeks, I've been spending a decent amount of time getting my hardware in order. One such piece of hardware is my Otrona Attache CP/M luggable. For the most part, it works perfectly fine. Keyboard, PSU, CPU, floppy drives, etc... all seem to work. However, the longer that the machine is left on, the dimmer the internal CRT display gets. It takes about 15-20 minutes for the display to become illegible even on the highest brightness settings. I should note that it looks perfectly fine when the machine is first powered on.



If the machine is left off for a little bit and then turned back on, the brightness issue resets. This makes me fairly confident that it is a heat related issue. Additionally the external composite output of the computer does not decay, which makes me think that the issue is in the internal analog CRT circuitry.

My money is on a marginally functioning component that stops working when it heats up. Anyone got any ideas on how I can figure out exactly what is going on?

Thanks

 

[NeXT]

My DEC VR201 did the same. A full recap solved the issue and that I could tell it was not a thermal drift of a component as it warmed up.

 

[Altomare]

I'm in the process of repairing an Attache too, and I noticed some leakage under some caps. I assume yours have the same issue.

 

[ThisPostContainsComputers]

I didn't notice any capacitor leaking in the PSU or analog board, but that doesn't mean that the capacitors are OK either. The biggest point of concern I noticed is that the +15V rail that goes into the monitor is up around ~18-19 volts. It is pretty consistent at this voltage, and does not change as the monitor starts to dim. All of the other voltages in the system are right on point however.

I also noticed that sometimes sound simply does not work. I haven't found a rhyme or reason to this behavior, but I am betting it is also bad caps or a loose connection somewhere.

 

[CloudInMyHead]

Does anyone know if the Otrona with the 8086 use the same power supply as the CP/M only model? I have an 8086 Otrona that powers on and then shuts off within 5 seconds or less. I'm guessing I need to start with voltage checking the power supply. Not sure which of the manuals I should be looking at.

1. Attache_Technical_Notes_Sep82.pdf
2. Otrona_Attache_8_16_Service_Guide_Dec83.pdf
3. Otrona_Attache_Maintenance.pdf
4. Otrona_Attache_Service_Guide_Mar83.pdf
5. Otrona_Attache_Technical_Manual_Jul83.pdf

I'll be cracking it open some days this week. I'll be sure to snap some photos.

 

[Altomare]

Does anyone know if the Otrona with the 8086 use the same power supply as the CP/M only model? I have an 8086 Otrona that powers on and then shuts off within 5 seconds or less. I'm guessing I need to start with voltage checking the power supply. Not sure which of the manuals I should be looking at.

1. Attache_Technical_Notes_Sep82.pdf
2. Otrona_Attache_8_16_Service_Guide_Dec83.pdf
3. Otrona_Attache_Maintenance.pdf
4. Otrona_Attache_Service_Guide_Mar83.pdf
5. Otrona_Attache_Technical_Manual_Jul83.pdf

I'll be cracking it open some days this week. I'll be sure to snap some photos.

Hi, it's the same PSU between the two (Attaché & 8:16). You can fairly easily open the machine and remove only the PSU.

The interesting documents are:

• Service Guide: for disassembly
• Technical Manual: for schematics (section A-8) & theory of operation (section 1-8 & 2-57)

What's "Otrona_Attache_Maintenance.pdf"? I don't have it in my Otrona documents

 

[CloudInMyHead]

Ah. Upon opening "Otrona_Attache_Maintenance.pdf" it is just a subset of one of the other documents.
I attached it here. Not sure where I downloaded it from.