Tandy 1000 disk drives no longer spinning

[A-ko]

Hey all, I have a standard, original, vanilla Tandy 1000 that has always worked fine, but today I pulled it out and powered it on for the first time in a few months, and the drives aren't spinning up anymore. They are both configured correctly, and I lubed the rails and cleaned the heads before I noticed the motors just weren't spinning at all. Any idea a first place to look? The LEDs come on each drive when they go to seek, the cables are hooked up, and it's trying to access the drives, but they just aren't spinning. Is there a common fault on the disk controller part of the motherboard or anything, or am I just missing something really simple here?

Thanks!

 

[Eudimorphodon]

If you have a meter check the 12v line on the drive connectors. (Also, is the system fan spinning?) The drives and fan are the only things in a stock T1000 that use 12v so it’ll POST without it.

 

[A-ko]

If you have a meter check the 12v line on the drive connectors. (Also, is the system fan spinning?) The drives and fan are the only things in a stock T1000 that use 12v so it’ll POST without it.

the system fan is spinning, and the drive LEDs are lighting up, but i'll double check the 12V line on the connectors.

 

[Eudimorphodon]

Typically only the drive motor is driven by 12v, the LED lighting up wouldn’t necessarily be unusual.

 

[A-ko]

Typically only the drive motor is driven by 12v, the LED lighting up wouldn’t necessarily be unusual.

assuming purple is the 12V rail, i'm only getting about 3V. Power supply issue then, I'm guessing? Does it always send 12V even if it's not trying to access the drive?

 

[A-ko]

Typically only the drive motor is driven by 12v, the LED lighting up wouldn’t necessarily be unusual.

correction, I get 3V if one of the disk drives is plugged in. If I have the PS plugged into the motherboard but the other 3 connections loose, I get a consistent 12V (11.98V) at the drive plugs. I did a visual inspection of the power supply and everything LOOKS good, but that doesn't tell the whole story. As I'm fairly new to actually trying to FIX electronic stuff, what would be your next course of action?

 

[Eudimorphodon]

Unfortunately I'm not really the guy to ask about analog demons escaping, but I bet there are several other people here that can take over. Assuming you tested it properly against the ground wire it does look like we've likely found the problem, though. It should be a steady +12v whether the drives are running or not.

 

[A-ko]

well, for some reason the 12V rail has cured itself...temporarily, I'm sure...and everything is working correctly again.

 

[blackepyon]

If you get low voltage with the drives plugged in, but proper voltage without a load, it suggests a weak PSU. Assuming you want to keep the stock PSU instead of modifying a modern one as a replacement, the easiest thing to do is open it up and check the capacitors. If any look to be bulging, replace them.

 

[A-ko]

If you get low voltage with the drives plugged in, but proper voltage without a load, it suggests a weak PSU. Assuming you want to keep the stock PSU instead of modifying a modern one as a replacement, the easiest thing to do is open it up and check the capacitors. If any look to be bulging, replace them.

it's got an intermittent issue, people have told me the voltage regulators will act up when they're failing. All the caps look perfect still.

 

[blackepyon]

Possibly. The technical reference manual for the 1000 doesn't include the PSU schematics, so it might be hard for me to step you through troubleshooting, I'm afraid.