Need Help with my 82905 Printer - IL Version

[Michael Fehlhammer]

My recently purchased 82905 impact printer ( the rare HP-IL version ) obviously doesn't have a mechanical problem: the self test printout is fine.
But it ignores any print jobs from the calculators!
There is no error on the IL loop ( like timeout ); DEVID$ correctly shows "HP82905B". So I assume the IL interface is intact, but the connection to the print mechanism is broken !? Did anyone encouter a similar problem any time?
To me it seems this is a rare defect, but I don't understand much about electronics.
What could I do, is there a chance to fix that?
Or does anyone offer a repair service? It would be so sad if I had to trash it.

[Paul Berger (Canada)]

Well that printer is a epson MX-80 and I would expect that the HPIL interface is a separate card perhaps it is not fully seated. It seems to me that these printers are just a basic Epson MX-80 mechanism complete with the standard Centronics parallel connector (there may be a cover over it) and for the HPIB, HPIL, and serial versions they add an interface card that plugs in behind the Centronics connector. If you have a parallel printer cable you might want to give that a try but you would need to remove the HPIL card first. It been a long time but it seems to me that there are four screw that come up from the bottom that hold the top on, and once removed the top just lifts off but me careful of the operator panel cable.

Paul.

[TASP]

Don't mean to be a smart aleck, but if you're using the 82160 to run the printer, is the switch on the bottom set to enable ?

[Michael Fehlhammer]

Thank you Paul, I will check if the IL-card is fully seated.
And yes, my IL-modules always are switched to enable. Besides I also tested the printer using a HP 71b.

[Hans Brueggemann]

is that printer a recognized printer device, or do you have to print to it using MANIO (for the 41C) or PRINTER IS :LOOPDEV# (for HP-71B)?

[Michael Fehlhammer]

The printer is a recognized device, it's answer to DEVID$ is "HP82905B".
Meanwhile I swapped the IL PCB with the known-good one of my second printer ( which differs only in the input voltage, it's the US version). I also assured that the chips are firmly seated in their sockets. But: No reaction from the printer.
So I am sure that the printer mainboard is faulty. Hmm, I am afraid there isn't much that can be done?
I will try to get an Epson FX 80, maybe the main board is identical, but these printers are also rare meanwhile. Currently there is not a single FX-80 on Ebay.
Well, since I have got a working and a non-working 82905B:
How much effort would it be for an electronics expert to track down the faulty component, by comparing the two? And then - will there be a replacement part available? Is it more likely that common simple components like capacitors fail, or proprietary integrated circuits?
Or should I surrender? :-(

[Paul Berger (Canada)]

Looking at a schematic of MX-80 I would say it is fixable. The only components that are in any way proprietary are the main controller which may be a 8049, and there is a 8041 controlling a couple motors inside, however since you say that the self test works we can rule them out. There is one one unique voltage on the connector for the interface +12V, but it is probably not even used by the HPIL inteface. The schematic shows two switch blocks on the main board, one 8 position SW1 and a 4 position SW2. SW2-4 goes to the connector for the optional interface, the documentation I am looking at, which is for the original IBM PC Printer also a MX-80 in disguise, they say that switch is "coding table Select" and on the schematic, which appears to be a copy of the original Epson one, the line is labelled -PET/TRS so it may not even have any effect on the HPIL interface.

Paul.

[Michael Fehlhammer]

Thank you Paul; I'll take this information to my electronics expert nearby.
It will take some time, he is very busy at the moment.
But I will keep you updated about eventual proceedings.
Again thank you for your help!

[jebem]

(02-27-2016 02:01 PM)Michael Fehlhammer Wrote:  The printer is a recognized device, it's answer to DEVID$ is "HP82905B".
Meanwhile I swapped the IL PCB with the known-good one of my second printer ( which differs only in the input voltage, it's the US version). I also assured that the chips are firmly seated in their sockets. But: No reaction from the printer.
So I am sure that the printer mainboard is faulty. Hmm, I am afraid there isn't much that can be done?
I will try to get an Epson FX 80, maybe the main board is identical, but these printers are also rare meanwhile. Currently there is not a single FX-80 on Ebay.
Well, since I have got a working and a non-working 82905B:
How much effort would it be for an electronics expert to track down the faulty component, by comparing the two? And then - will there be a replacement part available? Is it more likely that common simple components like capacitors fail, or proprietary integrated circuits?
Or should I surrender? :-(

Paul mention that it is based on the once popular Epson MX-80 (also here).
I have done firmware modifications (EPROM based) on these machines in their time (specially character set localization) but I have not kept any documentation.

From your diagnosis results, we can assume that the printer main board is faulty at the parallel I/O interface.
This was a common failure if I remember it well.

I found this manual that may help as it contains the schematics.

I suppose the IC's supporting the parallel I/O are faluty and need need to be replaced, assuming the correct 5VDC power supply voltage are present at these IC's.

This parallel interface, also called Centronics in my time, uses 8 non balanced data lines (bit 0 to 7) operating at 5VDC TTL connected to the 8155 40-pin IC marked as 8B in the schematics.
The additional Centronics protocol is handled by discrete very common easy to find 14 or 16-pin TTL ICs marked as 2E (74LS00 2-in-nand-gate), 3C (74LS04 inverter) and 3E (HD14093 2-in-nand-schmit).

If you can use a multi-meter set to Volts and are willing to apply outlet energy to both printers (the working and non working ones) while the covers are opened (do this at your own risk):

- Check the +5VDC voltage between ground and the Integrated Circuits power supply pins.

- If the voltages are correct, then I would replace those parallel I/O IC's (one at a time).

- If not, check the power supply.
Sometimes these PCB's uses small fuses that do not look like fuses at all - They look like small radial capacitors but most probably they are marked in the PCB as fuses.
Check for burnt resistors as well - many times they are easy to spot by visual inspection, or else use a continuity (ohms) checker.

[Michael Fehlhammer]

Thank you Jose!
I won't try it by myself, but hand on your hints to a skilled person.
My 82905 is said to be an Epson FX-80 clone, but you discussed the schematics of the MX-80. Do you think they are enough similar, especially with respect to the parallel interface ICs ?

[jebem]

(02-27-2016 06:53 PM)Michael Fehlhammer Wrote:  Thank you Jose!
I won't try it by myself, but hand on your hints to a skilled person.
My 82905 is said to be an Epson FX-80 clone, but you discussed the schematics of the MX-80. Do you think they are enough similar, especially with respect to the parallel interface ICs ?

Yes, if my memory serves me after all these years, the FX-80 and MX-80 should use similar Parallel I/O circuitry.

Good luck with the repair.
As Paul has mentioned before, the repair should be easy to do as long as we can find the required kind of vintage spares.

I might have one of these Epson printers in the basement, from when I used it with some Sanyo CP/M Z80 based computers in the 80's. I have to check when I'm back home.
Problem would be the shipment costs for such a heavy beast like this (I'm based in Lisbon, Portugal).