Okimate 20 Printer Issue

[robert_sissco]

I recently got an Okimate20 printer as part of a lot of Commodore stull I bought from someone on Craigslist, and the printer is the only thing that noes not work. When I turn the system on, the carriage assembly moves the print head about a third of the way across the bar, clicks as it disengages and then returns to the left position, and the ready light blinks steadily indicating an error. Checking the Sam's manual I found online (https://tinyurl.com/huawujwf) it says to check the Home Sensor Connector, but the pin 8 is always putting out the 4.5 V, which says should be OL when it is not in the home position, does any one have any idea on what this may be? I am not finding much about this printer online but would hate to toss it.

 

[powerlot]

Have you followed the procedure in the manual about the sensor and its resistors and does everything check out?

I came across a printer where deoxiting connectors, dip switches and IC sockets (including removing and reinserting the ICs) resolved erratic behaviour.

I would also check the voltages and the CPU operation as described in the Sam's, just to eliminate general issues.

 

[robert_sissco]

I did follow the SAM'S guide on the voltages, that is how I count pin 8 was always kicking the voltages out (assuming pin1 is where the red stripe on the connecting cable connects to), but I can give the IC's a shot, I just need to figure out how to get to the main board then, but I will let you know how that goes.

 

[RussBlakeman]

IIRC it has a carriage rod? If so have you rubbed a light sewing machine (or 3-in-1) oil on it then moved it manually with the power off? if it's dry or has some contamination on it the carriage would be slowed or even stick without going to the home sensor fully. Just a thought.

 

[robert_sissco]

IIRC it has a carriage rod? If so have you rubbed a light sewing machine (or 3-in-1) oil on it then moved it manually with the power off? if it's dry or has some contamination on it the carriage would be slowed or even stick without going to the home sensor fully. Just a thought.

That was the first thing I tried actually since it was stiff to begin with

 

[robert_sissco]

Checked the circuit boards on the printer itself, no ICs or sockets I could see, only IC's on the connector card for commodore. When I remove the connector card, the head does not move (did not know that), and the voltages test proper there on CN5. Reseated the ROM as it was the only socketed chip, reinserted the card, powered it on, same off behavior.

Any advice on the next steps, I think the issue is on the card giving it bad commands.

 

[powerlot]

You can try to compare the contents of the eprom to check for corrupted data if you manage to find an dump of it. If not it would probably be good to have a backup anyway.

Else you need to track down where the faulty components and / or connections are by testing them...Does the CPU behave as described, is there continuity where there should be etc.

 

[robert_sissco]

Yea, I am thinking that it is an issue with the EPROM, when I move the left paper guild and this the home position, the system always pulls the print head as far left as it can go, I think something on the connector board is reporting back false position that is causing it since the voltages and everything and good with the board removed (and this the brains from what I have found online. I will also need to find a way to get the printer out so I can get full access to the circuits under it without interference in the way.