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TeleVideo Trouble

maybe it's an AM not an HM. Hard to read. These are the drive select jumpers:

MX
DS3
DS2
AM? [JUMP'R] (or HM?)
DS1
DS0 [JUMP'R]
HS
 
FD-55BR = latch is on right side of drive.

HM, HS determine if the head is loaded (for those models with head-load solenoids) on receipt of the MOTOR ON or DRIVE SELECT signals respectively. Teac strongly advises against have both jumpered at the same time. For head-load solenoid-less drives, both jumpers should be open.

Manual here
 
jharre said:
Not being a real hardware technician by any stretch of the imagination, what things should I be looking for on the controller card?
Click to expand...

replace the 1793 chip on the drive controller (the small card directly attached to the mother board). That might be the entire problem.
 
billdeg said:
replace the 1793 chip on the drive controller (the small card directly attached to the mother board). That might be the entire problem.
Click to expand...

Seems like a reasonable thing to do. Got a couple of those on order from ACP for $7 each.

Don't remember what I was paying for WD FDC chips back in the early to mid-80's, but it was a heck of a lot more than that.
 
Chuck(G) said:
HM, HS determine if the head is loaded (for those models with head-load solenoids) on receipt of the MOTOR ON or DRIVE SELECT signals respectively. Teac strongly advises against have both jumpered at the same time. For head-load solenoid-less drives, both jumpers should be open.
Click to expand...

The 55BR strapping is highly abbreviated from the manual in the link - there isn't an HM jumper:
55BR_jumpers.JPG

I just have the DS0 and FG jumpers plugged. (Dunno what FG does, "Feels Good"?)
 
Look at PDF page 32 (Document page 229). You'll find your HM jumper there. Nobody said that Teac manuals are easy to read. Very often, several different models/PCBs are discussed in the same manual (you should see the wild assortment in the FD235 manual).

FG - frame ground. Jumpering it connects the power supply return to the metal frame of the drive. Sometimes used when the drive is installed in a non-conducting mounting. Otherwise, it probably doesn't matter.
 
Chuck(G) said:
Look at PDF page 32 (Document page 229). You'll find your HM jumper there. Nobody said that Teac manuals are easy to read. Very often, several different models/PCBs are discussed in the same manual (you should see the wild assortment in the FD235 manual).
Click to expand...

Yes, I saw that page - but the document is for a 55(L) and my 55B has a different arrangement as pictured in my attachment above. Teac probably had dozens of variations of their 48 tpi drives. It must have driven their tech document writers nuts.

Here's a photo of the board on my 55B with the jumpers:
FD55BR.jpg
 
Yup, I've got a pile of 5.25" Teac drives--55B, BR, F, FG and even a G; with HL solenoids and without. And I've got jumper docs FAXed by Teac tech support back in the day. Their jumper documentation usually didn't show the board layout--just the jumper names. So HM on any drive means the same thing. There was even a time that Teac would FAX you the drive schematic if you asked.

Teac changed their boards more often than some people change their underwear.
 
Update: The replacement FDCs didn't solve anything.

I bought a pile of parts from billdeg (thanks, Bill!) that should arrive in a few days. Hopefully they will go a long way towards bringing this old CP/M machine back to life.
 
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