MPP-1150 Printer Interface: missing chip?

[Sleepy]

Hi,

 

I recently got a printer interface....

 

 

...which unfortunately does not run.

 

After opening it, an unpopulated IC socket presented itself:

 

 

Since the board seems to be designed for different assembly variants (probably CPU + program in external eprom(s) or CPU with internal ROM) and only what is necessary for the current variant is assembled, I assume that an IC is missing. A first search has unfortunately only the manual and a few offers on ebay brought to light.

 

It's not like I don't have enough different Centronics interfaces, but this one has a looped SIO port... All the other ones I have are pure end devices. So it would be worth trying to repair. 🙂

 

Does anyone know what goes in there or even have a schematic and/or component diagram? Or is it correct that the socket is free?

 

 

Thx

 

Sleeπ

 

 

 

Edited May 22, 2023 by Sleepy

[+Allan]

https://archive.org/details/mmp-1150-parallel-printer-interface-manual-early-version-mpp/page/n5/mode/2up

 

Maybe it's the Buffer mentioned on page 4?

 

 

[TGB1718]

Looks like the buffer would be fitted in those 2 empty chip spaces and this missing chip is part of that upgrade.

Have you tried the interface to see if it works as it is ?

[+DjayBee]

21 minutes ago, TGB1718 said:

Have you tried the interface to see if it works as it is ?

Quote: "...which unfortunately does not run."

[TGB1718]

8 minutes ago, DjayBee said:

Quote: "...which unfortunately does not run."

Ooops, missed that 🤣

[TZJB]

5 hours ago, Sleepy said:

Hi,

 

I recently got a printer interface....

 

...which unfortunately does not run.

 

After opening it, an unpopulated IC socket presented itself:

 

 

Since the board seems to be designed for different assembly variants (probably CPU + program in external eprom(s) or CPU with internal ROM) and only what is necessary for the current variant is assembled, I assume that an IC is missing. A first search has unfortunately only the manual and a few offers on ebay brought to light.

 

It's not like I don't have enough different Centronics interfaces, but this one has a looped SIO port... All the other ones I have are pure end devices. So it would be worth trying to repair. 🙂

 

Does anyone know what goes in there or even have a schematic and/or component diagram? Or is it correct that the socket is free?

 

 

Thx

 

Sleeπ

 

 

 

 

It needs to be a 14 pin chip so could be an LM3086 transistor array similar to the Atari 1050 drive SIO buffer. The actual spooler buffer would need the two extra large chips which were not populated at manufacture. The 40 pin chip is a PIA probably a 6520.

[cx2k]

8 hours ago, Sleepy said:

Hi,

 

I recently got a printer interface....

 

 

...which unfortunately does not run.

 

After opening it, an unpopulated IC socket presented itself:

 

 

Since the board seems to be designed for different assembly variants (probably CPU + program in external eprom(s) or CPU with internal ROM) and only what is necessary for the current variant is assembled, I assume that an IC is missing. A first search has unfortunately only the manual and a few offers on ebay brought to light.

 

It's not like I don't have enough different Centronics interfaces, but this one has a looped SIO port... All the other ones I have are pure end devices. So it would be worth trying to repair. 🙂

 

Does anyone know what goes in there or even have a schematic and/or component diagram? Or is it correct that the socket is free?

 

 

Thx

 

Sleeπ

 

 

 

 

@Sleepy Was hoping to be more help. Here's pics of my MPP-1150. Mine is branded by Supra Corp who I believe purchased the MPP company/products. Mine actually has 3 chips but the 14 pin socket you're seeing on yours is actually a ribbon cable header as shown on mine. My ribbon cable is 14 wires that terminate in a dip style connector and plug into that socket. Not sure why you have such a wider ribbon cable. I never really got into the Centronics/parallel stuff back in the day. 

 

 

[_The Doctor__]

PCB's are different

[cx2k]

40 minutes ago, _The Doctor__ said:

PCB's are different

Acknowledged. Just thought the 14 pin socket in his unit might not necessarily be for a chip but maybe an unused alternate ribbon cable.

 

[TGB1718]

7 hours ago, cx2k said:

Not sure why you have such a wider ribbon cable.

Centronics is 36 pins

 

[Sleepy]

Allan, TGB1718:
>Maybe it's the Buffer mentioned on page 4?
Yup, I found these instructions as well. The unpopulated xx-pin ICs could actually be space for optional memory chips or a printer buffer.

 

TZJB:
>It needs to be a 14 pin chip so could be an LM3086 transistor array similar to the Atari 1050 drive SIO buffer.

> The actual spooler buffer would need the two extra large chips which were not populated at manufacture.
A built-in buffer is a good idea. However, I already have an external 256 k buffer...
 

 

>The 40 pin chip is a PIA probably a 6520.
O.K., I think that the big bug is a bit more than a simple I/O device; it still has to fetch the data meant for the printer from the SIO bus, convert them from serial to parallel and prepare them for the printer. In the other interfaces I have, a CPU+EPROM+74??? is installed.

 

cx2k:
Thx for pics; it seems that there are different circuit designs in the same housing
The interfaces I know in Europe all have such a wide ribbon cable; it is as wide as the Centronics connector fits. Apparently there are variants of the MPP interface where only the necessary cables are wired.

 

Thanks @ all for the tips and hints. If the small IC is really not necessary, the programmed processor should be broken and the interface should be unrepairable - a suitable programmed chip probably can only be obtained from a working interface - it makes no sense to disassemble a working one for a spare part.

 

I have not found a circuit diagram yet.

 

BTW: I have already managed to kill the CPU in a printer interface twice in the long time I have had my little ATARI: Both times I had not switched off both devices (printer & Atari) before unplugging the interface... 😕 In both cases the CPU was damaged. But these were models with external EPROM - it was enough to plug in a new standard CPU.

Edited May 25, 2023 by Sleepy

[BillC]

45 minutes ago, Sleepy said:

Apparently there are variants of the MPP interface where only the necessary cables are wired.

Similar to the Atari 850, its printer port has only 15 pins(DA15).

[TGB1718]

4 hours ago, Sleepy said:

O.K., I think that the big bug is a bit more than a simple I/O device; it still has to fetch the data meant for the printer from the SIO bus

Not necessarily, I built a parallel/serial interface for my 130XE, lot's of 74 series chips, but main chip was a UART which handled

the serial to parallel conversion, although not an SIO device, it could have easily been converted. 

 

Although in this case, it's likely to be a CPU of some sort with a small internal RAM to store the current byte from

the SIO port, but a CPU would be needed to handle the buffer when fitted.

Edited May 25, 2023 by TGB1718