Commodore 3022 Printer

[ScottishColin]

OK.

PET turned on and cable connected but printer turned off - 1.76V
PET turned on and cable connected and printer turned on - 3.95V.

Colin.

Originally Posted by SiriusHardware

Can you (...always with power off on both units) connect the printer to one of the PETs, turn the PET and printer on and check the voltage on 4B (5) again?

Just heading off for lunch.

[SiriusHardware]

OK, power off both units, disconnect them from each other and working on the printer only again, what happens to the voltage on 4B (6) if you connect a lowish value resistor (~330R) between 4B (5) and GND, which you can find on 4B (7)?

[ScottishColin]

That was a quick lunch.

Stays low.

Colin.

Originally Posted by SiriusHardware

OK, power off both units, disconnect them from each other and working on the printer only again, what happens to the voltage on 4B (6) if you connect a lowish value resistor (~330R) between 4B (5) and GND, which you can find on 4B (7)?

[SiriusHardware]

Can you confirm the IC type of 4B? Looks like a 74LS0(blob) on the layout diagram and I can't find a pinout for that.

[ScottishColin]

HD74LS09P marked as 74LS09 on the motherboard - see attached photo.

Colin.

Originally Posted by SiriusHardware

Can you confirm the IC type of 4B? Looks like a 74LS0(blob) on the layout diagram and I can't find a pinout for that.

[SiriusHardware]

74LS09, OK, so that's another open-collector type, a quad 2-input AND gate confusingly drawn as an inverse-OR gate on the diagram. Commodore had an endearing(?) habit of sometimes drawing gates to show how they were being used rather than drawing the actual gate type.

In #53 I asked for the voltage / state on 7B (25). Although we got the state (low) in #54 we didn't get the exact voltage, could you look at that again and say exactly what the voltage on that pin is?

[SiriusHardware]

If I understand correctly that 7B is in a socket, after measuring the voltage on 7B (25), power down, remove 7B, power up, and measure the voltage on pin receptacle (25) of 7B's socket.

[ScottishColin]

re post 53 - it's 251mV. Apologies.

re post 67 - 7B out gives me 4.45V on 25 of the socket.

Colin.

[ScottishColin]

With 7B out I get the added bonus of magic smoke being released from the print head.....

Colin.

[SiriusHardware]

Oh, God, sorry about that. Mark did warn us. If you can see a way to disconnect the print head, do so.

[TonyDuell]

A few comments...

Yes, IFC (and most of the IEEE-488 lines) is biased to a TTL 'high' by the termination resistors. But remember that IEEE-488 lines are active _low_, so this means that IFC is inactive with nothing connected. The printer should do the 'sweep the head across and back' and respond to the paper feed button with no PET connected.

I don't find the convention of drawing an AND gate as an OR with all inputs and outputs inverted to be at all confusing, but perhaps that's just because it's second nature to me now after about 40-odd year. However here, look at IC 4B pins 4,5,6. It's an AND gate. Pin 4 is a logic 1 as it's wired to the +5V line. Pin 5 is logic 1 due to the IFC termination network. So the output is _floating_ -- open collector remember. Another device could be pulling it low.

I assume you've checked that C6 is not shorted....

Another word of warning. The Epson manual for the mechanism describes how to dismantle the printhead and replace the 'needles' (print pins) DO NOT dismantle the front section of the head unless you have a spare set of new needles. They come longer than necessary so you can feed them through the holes in the head, clip the retainer on, then cut/grind them to length. You will never get an old set to stay in place in the front end of the head against the tension of the return springs while you fit the retainer.

I am wondering why on earth removing 7B turns the printhead hard on. This implies the outputs from port B of 5B are on (or not initialised?) and that the monostable 2A is giving a 1. But isn't that being held reset?

[SiriusHardware]

I also can't see any direct connection between 7B and the print head driver which is why it seemed 'safe' to remove it but the object of removing 7B was to see if that would allow RESET to come up (which it appears that it did, because the voltage on 7B pin 25, previously only millivolts, came up to 4.45 and I suspect if there had been time to look we would have seen that the main RESET line was finally 'up'. 7B contains RAM and a timer as well as I/O and the absence of the RAM may have knocked the normal firmware control/ I/O setup process out of whack.

The print head is about the worst thing that could be damaged, so it depends really on just how bad the damage, if any, is.

We can keep on trying to troubleshoot the electronics (with the head and motor drive PCB disconnected) and hope the head is still serviceable. I'm going to keep a look out anyway, for anything which could serve as a parts donor or complete replacement.

[TonyDuell]

I am pretty sure you can remove the printhead (the flexible PCB tail unplugs at the end remote from the head, then a couple of screws hold it to the carriage) and the printer will work without it. By 'work', it obviously won't put dots on the paper. But it will go through the initialisation, the paper feed will work, and it will respond to commands from the PET, if connected.

Although I warned about removing the print pins, you can remove the entire front section of the printhead (2 screws), just don't remove the retainer clipped on the rear end (normally hidden inside the head). The solenoid section does come apart without too much difficulty, and in theory you could rewind the coils.

I don't think I have any spare heads for this series of printers, but I will check.

[SiriusHardware]

I assume you've checked that C6 is not shorted....

As best we can, two of the fixing screws for the PCB are seized and C6 is mounted close against the PCB so we have measured from the relevant lead of R5 down to ground.

Of all of the nodes in the reset circuit area the one with the lowest measured 'low' on it so far was the 7B (25) / 4B (6) / R14 node, with the voltage on the other side of R14 being somewhat higher. This made it look like the source of the pulldown was either the 7B (25) pin itself or the 4B (6) pin. 4B is not in a socket, 7B is, so that was the one to try disconnecting first, and the voltage did come up on that node.

Point taken about the action of 4B, so with a 'high' on its input, and assuming 4B 4/5/6 to be working, the output should be 'off', leaving something else connected to 4B (6) as the likely cause of the pulldown.

[Mark1960]

The document in post #1 describes a debug mode with the print head disconnected to check timing of needle drivers. May be a bit late now, but just because you saw some smoke doesn’t mean the head is definitely damaged, but you need to get the rest of the printer working first to find out.

[ScottishColin]

Thanks gents - I will disconnect the print head at the other end of the ribbon cable and see what's what. Hopefully we're still good and it was just getting a little cross.

I suspect there will be no activity tonight - try again tomorrow.

Colin.

[ortek_service]

Originally Posted by TonyDuell

It is a spool of ribbon, not a cartridge, so there's a good chance you'll be able to get something that will work. I _think_ the Epson TX80 used the same mechanism.

>>
>>

Incidentally I was given my 2023 because the bottom pin in the printhead was broken. I did get a replacement printhead in the end but before that I just soldered a jumper on the printhead connector to wire-OR the drivers for the bottom 2 pins. The output was a bit odd, but readable, and a lot better than no printer at all.

So I presume if it is on spools, then once it gets to the end, you have to manually swap it over for it to run the other way - Like typewriters?
(Rather than being a continuous loop of ribbon, loosely folded-up inside a plastic cartridge, that was the most-common system on later Epson's).

I did once enquire with Epson about getting a new head for my LX80, as they made a thing about how easy (2 screws either side and plugged-in) and 'low-cost?' it was to change, as the pins end guide was only plastic and seemed to have overheated as holes were no-longer straight. But IIRC, the price they quoted me for a new head was > £100, when I'd paid less than that for the printer.

I also recall buying an A3? dot-matrix Star? printer from Halcyon Electronics shop in S.London in 1991 for £10, which had a duff head. But I never managed to find one (pre-Internet days) got one, so I think I ended-up stripping it down. Cheap dot-matrix heads were hard to come by.

I think I do have a large box of assorted NOS dot-matrix printer ribbons - but now decades old so maybe all dried-up. And I never recall the TX80 model, so doubt I have any that fit that. But maybe typewriter ones can be made to fit.

[SiriusHardware]

So I presume if it is on spools, then once it gets to the end, you have to manually swap it over for it to run the other way - Like typewriters?

It may have a kind of auto-reverse mechanism which runs the ribbon back the other way once it gets to the end.

[ortek_service]

Yes, the '901472-03' out of the three 901472-0x files there, matches the number that is on the 2332 ROM fitted to yours, I'd found from the photo you'd earlier posted. So you should be able to read yours, as a 2532 EPROM, if your programmer supports those
- or as a 2732 with a pins 18 & 21 swap adaptor: https://wereallgeeks.wordpress.com/2...2_progadapter/

Even though Zimmers (incorrectly?) describe the 901472-03 as being CBM 2023 Firmware
- With 901472-06 described as being CBM 3022 firmware
And also 901472-04 described as being CBM 2022 AND 2023 firmware
(Well this 2022/203 Service Guide, does list the '6332' (But 2332 on both Commodore and Epson board schematics) ROM as being part no. 901472-04

And I did compare those 3 versions, and there are quite a few bytes different. Which would imply that the 3022 wasn't quite just a re-badged of the 2022, and there are ROM differences that may affect compatibility with some 2000-etc. series PET's. Although, luckily it seems your 3022 was untended to work with the 3016 PET.

But reading-out yours may be a useful quick-check, to ensure that reads-OK at least, once reset issue is sorted.

Hopefully the heads smoking a bit was only some dust etc. burning-off due to overheating as not designed to be permanently driven on . And none of the coils have burnt-out. But it should be possible to do a quick low-resistance range on DMM 'cold-resistance' check on all 7? head-coils, once the cable is disconnected, to ensure they all read about the same and none have gone o/c or maybe shorted turns.


I also spotted that the 6532 'RIOT' IC's are confusingly marked with a custom CO10750-12 part number and don't have the 6532 they are more-commonly known as (or 901458-01 Commodore parts-list number). I do recall that COnnnnn numbers were used by Atari, who also used 'RIOT' IC's, so maybe these were stock originally made for them.

Originally Posted by ScottishColin

I've not looked into these (apart from downloading them just in case) but these seem to be the ROMs:

https://zimmers.net/anonftp/pub/cbm/...022/index.html

Colin.

[ortek_service]

Originally Posted by SiriusHardware

It may have a kind of auto-reverse mechanism which runs the ribbon back the other way once it gets to the end.

Yes, I did wonder if there would be a way of doing this, but that seems it would be a bit complex to implement and not sure if typewriters did (It's probably been around 40yrs since I last used a purely (electro)mechanical one!)

If it is a TX-80 type, then a quick-Google finds they are still available from UK suppliers for < £10 (which the same one I found, also lists ones for the CBM 3022/3023 at the same price)
And this USA supplier has them in lots of (dual)colours, with picture: https://www.ribbonsunlimited.com/193...pson-tx-80.htm

There's also Epson TX5xx 'Typewriter' ones, if similar, from £4 on Amazon (MP?)

But although Amazon UK list a Red/Black (Flip over to change colour) type for the CBM 3022, it's currently unavailable.


EDIT: I've just found a copy of the original (80page!) 2022/2023 User Manual: http://www.zimmers.net/anonftp/pub/c...ter-Manual.pdf

And, as well as showing / explaining the different 2022 / 2023 models, and which is tractor feed, it also describes the ribbon
- Which has a tension sensing auto-reverse system, that typewriters did also use. So is rated to last 2 million characters (like endless loop cartridges were)