Atari SMM804 printer question?

[+DarkLord]

So I picked up a SMM804 ST printer of Ebay the other day. It was sold "as is" and no warranty so

I was under no illusions when I purchased it.

 

I got it in and picked up a top cover, printer paper wire guide, 2 ribbons and a printer cable from

Best Electronics for it.

 

The printer does turn on, power LED lights up. It reports no paper, etc. Putting paper in and that

warning light goes off.

 

I can run the self-test and it does indeed print out.

 

However, I can't print anything out from my Mega ST4. The On line/Off line light is flashing all the

time. I did try using the button to turn it off and on. However, it never goes to a solid color - it's

always flashing, which according to the manual that came with it means it's receiving and printing
data from the ST.

 

But it's not... Using any text editor on the ST side always reports that the printer is not responding.

 

I also tried turning the printer on first, then the ST, as well as the ST on first, then the printer. That

didn't make any difference either.

 

It's been so long since I used a printer on an ST that I can't remember - will a standard printer cable

work or is it something specific/special?

 

Open to any suggestions at this point. 

 

PS BTW, I only paid $10.00 for the printer. 

 

[TGB1718]

According to the manual, it uses a standard Centronics interface, handshaking it says on ACK OR BUSY, with

STROBE from the ST.

 

If you have a scope those are the only signals that need to be checked.

 

You get STROBE (low) from ST, the printer will send ACK (low) although this is generally not needed for the printer

to work unless the driver on the ST is looking for it.

 

EDIT: just had a look at the ST circuit diagram and it does only use STROBE and BUSY for handshaking, other than DATA, no other signals are connected.

 

BUSY goes high when the printer is in one of the following states and means the printer can't accept data. (handshaking can be done on this and STROBE alone)

1. Printer is busy (printing)

2. Printer is processing data input

3. Printer is offline

4. Printer error

 

STROBE is Pin 1

ACK is pin 10 (not used in ST)

BUSY is pin 11

DATA pins are 2 thro 9

 

 

[TZJB]

14 hours ago, DarkLord said:

So I picked up a SMM804 ST printer of Ebay the other day. It was sold "as is" and no warranty so

I was under no illusions when I purchased it.

 

I got it in and picked up a top cover, printer paper wire guide, 2 ribbons and a printer cable from

Best Electronics for it.

 

The printer does turn on, power LED lights up. It reports no paper, etc. Putting paper in and that

warning light goes off.

 

I can run the self-test and it does indeed print out.

 

However, I can't print anything out from my Mega ST4. The On line/Off line light is flashing all the

time. I did try using the button to turn it off and on. However, it never goes to a solid color - it's

always flashing, which according to the manual that came with it means it's receiving and printing
data from the ST.

 

But it's not... Using any text editor on the ST side always reports that the printer is not responding.

 

I also tried turning the printer on first, then the ST, as well as the ST on first, then the printer. That

didn't make any difference either.

 

It's been so long since I used a printer on an ST that I can't remember - will a standard printer cable

work or is it something specific/special?

 

Open to any suggestions at this point. 

 

PS BTW, I only paid $10.00 for the printer. 

 

 

If you have not yet seen it, there may be a solution here regarding the interface board and a 74LS38:-

 

https://www.atari-forum.com/viewtopic.php?t=25233

 

 

 

Edited September 1 by TZJB
Typo

[+DarkLord]

4 hours ago, TGB1718 said:

According to the manual, it uses a standard Centronics interface, handshaking it says on ACK OR BUSY, with

STROBE from the ST.

 

If you have a scope those are the only signals that need to be checked.

 

You get STROBE (low) from ST, the printer will send ACK (low) although this is generally not needed for the printer

to work unless the driver on the ST is looking for it.

 

EDIT: just had a look at the ST circuit diagram and it does only use STROBE and BUSY for handshaking, other than DATA, no other signals are connected.

 

BUSY goes high when the printer is in one of the following states and means the printer can't accept data. (handshaking can be done on this and STROBE alone)

1. Printer is busy (printing)

2. Printer is processing data input

3. Printer is offline

4. Printer error

 

STROBE is Pin 1

ACK is pin 10 (not used in ST)

BUSY is pin 11

DATA pins are 2 thro 9

 

 

Thanks for all that information, appreciated.

 

Unfortunately, I don't have a scope.  

 

[+DarkLord]

1 hour ago, TZJB said:

 

If you have not yet seen it, there may be a solution here regarding the interface board and a 74LS38:-

 

https://www.atari-forum.com/viewtopic.php?t=25233

 

 

 

 

 

Just read that:

 

"I fixed it... There is a 74LS38 TTL chip on the interface daughter board of the electronics. This one controls the BUSY signal (and other things) on the Centronics interface. After swapping it to a new one it prints with my STacy."

 

This is something I should be able to take a look at. Thanks! 

 

[mickster]

On 9/1/2024 at 8:21 AM, DarkLord said:

 

 

 

 

 

 

On 9/1/2024 at 8:21 AM, DarkLord said:

Just read that:

 

"I fixed it... There is a 74LS38 TTL chip on the interface daughter board of the electronics. This one controls the BUSY signal (and other things) on the Centronics interface. After swapping it to a new one it prints with my STacy."

 

This is something I should be able to take a look at. Thanks! 

 

 

 

If you can't figure it out and have room to bring it to vcfmw.  I will buy it (and the parts off of you) and some money for your time and effort.  I should be able to go a little deeper with diagnostics and repair it if you are stuck.

 

No big deal either way, just thought I would throw out an offer.

 

[+DarkLord]

Well, I've not given up on it just yet.

 

I appreciate the offer and will keep you in mind if/when I "thrown in the towel".  

 

 

 

[Zogging Hell]

Probably a bit of a long shot but it couldn't just be some gunk shorting out the online/offline button could it? Might be worth giving that membrane or whatever it is underneath the button a clean and checking for shorts there perhaps?

[+DarkLord]

I actually took it apart a couple of days ago, just to check things out.

 

It's relatively clean inside and things look good on the surface.

 

But...(there's always a but with me, right?) 

 

I was looking for the "74xxx" series chip and I did find it. It's not socketed

though so I'd have to completely remove the main PCB to be able to get

enough access to it to de-solder and replace it.

 

There is a daughter-board that sits on top of the main PCB. There's a green

wire that runs to it that's pretty short. In fact, once you pull that board loose

from the main board, there's not enough room to even turn the daughter-board

over and look at it. One harness releases easily but this green wire was a new

one for me in Atari hardware. It's not a clip or plastic end that plugs into the

board but rather a sliding black piece that lets the wire pull completely out,

leaving it bare. Anyone seen that kind of connection before on Atari stuff?

 

I'll try to post some pictures later.

 

Anyway, you pull the daughter-straight up to remove it. After I got it to the

point where I could flip it over and examine it, I noticed right off that one

pin was bent out, almost 90 degrees. Now, I'm clumsy and I make a lot

of mistakes but I don't know how I could have done that just pulling the

daughter-board off - especially since this bent out pin was in the middle of

the row, not on the ends.

 

There was one socketed chip on the main board so I pulled it, cleaned it

and reinserted it.

 

I reassembled everything but now it's behaving differently than before. Now,

the On/Off line button does not blink continuously, but turns completely off

or on, no blinking. I thought, "ah-ha!" and proceeded to hook it back up to

the Mega ST but now the printer won't even turn on if the printer cable is

connected to the Mega ST. Weird, huh?

 

So I ordered a brand new printer cable from Amazon that's supposed to be

here today. I'll try that and see what happens. If it still doesn't work, I'll

go back to the plan of removing that "74xxx" series chip and replacing it.

 

Just another day at the ranch here...  

 

[+DarkLord]

Okay, I got the brand new, never been used printer cable from Amazon in.

 

No go. It displays the same behavior as the cable from Best Electronics.

 

When it's connected to the Mega ST4, the printer will not turn on.

 

With it unconnected, it won't even do the self-test anymore - it just prints

out any paper that's in it then stops.

 

Back to square 1, I guess...

 

[Zogging Hell]

That would seem to suggest something you did in your dismantling has provoked the issue further, rather than it being a chip failure... to me anyway. Perhaps the socketed chips pins on the socket itself are not making good contact. Either that or that connector you were puzzling over. Does the daughterboard have anything to do with the buttons for controlling the printer?

I do have one of these in storage, but sadly don't have access to it at the moment, otherwise I'd get it out to check what mine does

[+DarkLord]

I'm going to take it apart again (and this time I'll take pictures),

and try to go over everything again.

 

We've got the midwest VCF (Vintage Computer Fair) this weekend

so I'll have to wait until I get back from that to investigate further.

 

Onward and forward, I reckon...