810 Troubleshooting Suggestions Needed Please...

[Colleton]

I received a beater 810 I'd bought on eBay today.  It looked rough in the auction listing and I didn't expect it to work.  I was not disappointed. 

 

At power on you get both LEDs illuminated as expected and then the activity LED goes out leaving the power LED illuminated.  Okay.  Put a disk in and tried to boot it.  Nothing.  Very infrequent beeps as it tried to read the disk and then BOOT ERROR messages.  Took the top case off and found that someone in the remote past had used some type of thick brown grease on the head rails.  Unfortunately, the grease had hardened and had literally glued the head mechanism to the rails.  After a thorough cleaning with alcohol the head mechanism was unstuck and moved freely on the rails.  I also cleaned the R/W head with alcohol.

 

Tried to boot my DOS disk again.  The head moved at power on and moved again at boot, but I'm getting the same boot errors.

 

At this point I have no idea how to proceed.  It's a Tandon mechanism and I have two others, so I guess I could play swaptronics to try and find the bad part (drive mechanism, power board, analog board, side board(s)) but I'm hoping that someone here might have a better suggestion.  I've tried running the 810 Diagnostic cart but it fails during the initial read attempt and just sits there.  Maybe I'm using it incorrectly.

 

Any suggestions would be appreciated, thanks!

[+kheller2]

Is the RPM speed off?

[Colleton]

I have no idea at this point.  What software allows me to check that?  I know I just looked at it on another drive a few weeks ago.

[Colleton]

That was a most excellent suggestion, thanks!

 

Booted LJS DOS on a known good drive.  Checked the RPM on it and it was 287.  Set the suspect drive as D2 and checked the RPM - XXX, so 0.  Removed the disk and tried again while reaching in with my finger to feel the motor (?) and it wasn't moving.  Gave it a push with my finger and it came free and began spinning.  Reinserted a disk and tried again.  RPM is 288.

 

Set the drive to D1 and successfully booted LJS DOS with it.  It seems to be working like a champ now.  Awesome, thank you for pointing me in this direction.

 

Is there any lubrication I can do so that it doesn't become stuck again?

[+Nezgar]

Good to hear the drive is alive! I've had a few 1050's that the stepper motor was seized, requiring a manual 'crack' at moving it to set it free. This sounds similar, and is probably just a fact of having sat for decades with no motion. If it was the disk-turning motor, it could have also been the belt was stuck to either the main spindle or the DC motor itself.

 

If you open up the drive, I'd inspect the belt and ensure it's still mostly intact. If it was 'stuck' it may have torn a chunk off, and might cause variable RPM. Then you can clean the belt and the wheels it rides on too.

 

Also, that would be a good opportunity to verify the generation of 810 you have. There are basically three 'breeds' of stock drives you can expect to find:

1. Earlier MPI mech with combined power/analog board. No data separator daughterboard on the side board (inside the shield), and revision "B" ROM, possibly an earlier side board rev too.
2. Earlier MPI mech with separate power and analog boards, the analog board installed above the mech. Added data separator daughterboard, revision "C" ROM.
3. Later Tandon mech, with all of the upgrades of the prevous line.

#2 and #3's upgrades were called the "Grass Valley" upgrade board set. There may be cases of drives that have some but not all of the upgraded components.

 

#1 - The unstable power board and oxidization of socketed chips were a cause for unstable RPM's in the earliest drives. Lack of a data separator, relying on the one built into the WD1771 controller, resulted in unreliable read/writes. (Even the WD1771 specs recommended not using the internal data separator!)

 

Anyhow, it would be interesting to see what 'generation' drive you have there, this info should help you identify this quickly. Maybe post pics if you are so inclined! Sometimes there is a surprise mod, custom ROM, etc that has been installed by a previous owner that opening it might reveal.

 

Cheers.

[Colleton]

It's a Tandon drive mech, so I'm assuming that it has all of the upgrades.  Good point on inspecting/cleaning the belt.  I'll take a look at that in the near future, but don't want to damage it.  Would alcohol be a good choice for this?

 

It seems to be working okay, running an 810 diag cart burn-in right now with no issues.