9810 question and offer

[dramsey]

I just picked up a beautiful 9810 from TAS. Cosmetically, nearly perfect, with no dead segments in the display and a fully functional printer (which I assume means the rubber paper advance roller has been replaced sometime in the past). Haven't checked the card reader yet, but I've rebuilt these before so I'm not too concerned.

Here's my question: although the calculator does not have the "Printer Alpha" ROM, program listings include alpha key representations, something like this:

0030 -- |DIV| -- 053

..line number, key, and key code (the above line is made up and I'm pretty sure that's not the key code for the division key). Inserting the Printer Alpha ROM doesn't change a thing.

I thought the Printer Alpha ROM was required for listings like this. Am I wrong?

Now the fun part: the calc came with 25+ pounds of documentation, cards, and rolls of paper. It was apparently used by Chrysler's California emissions testing lab in the 70s and 80s. I have over a hundred 9810/20 mag cards, both long and short versions. If anybody needs a couple, let me know, and I'll send 'em out for cost of shipping.

Oh, yeah, one more question: many of these cards have their write protect tabs removed. Is there a simple way to write to these cards? (I suppose I could block the optical sensor on the card reader. If it's optical.)

[ArielPalazzesi]

Congratulations! Is a nice machine
And a lot of extra stuff !

[Geoff Quickfall]

Wonderful Dave!

Can't help on the specs though. Maybe an email to Tony Duell would be appropriate. He has been writing quite a few Data Files on rebuilding and trouble shooting these.

Cheers, Geoff

[Katie Wasserman]

(02-14-2014 07:27 PM)dramsey Wrote:  Here's my question: although the calculator does not have the "Printer Alpha" ROM, program listings include alpha key representations, something like this:

0030 -- |DIV| -- 053

I thought the Printer Alpha ROM was required for listings like this. Am I wrong?

You're correct. The Alpha ROM has to be in installed to see the programming mnemonics.

Quote:Oh, yeah, one more question: many of these cards have their write protect tabs removed. Is there a simple way to write to these cards? (I suppose I could block the optical sensor on the card reader. If it's optical.)

Yes, it's optical. You could probably just black electrical tape to cover up the cutout.

[dramsey]

Mystery solved! I just noticed that under the PLOTTER ROM label, in smaller type, is "Printer Alpha". So I do have the Printer Alpha ROM, and verified it by removing the cartridge and listing a program.

(Printer does have one pixel stuck on, dammit. But it doesn't obscure the listing.)

The printer roller and rubber drive belts are in great shape. I can only assume they've been replaced some time in the calc's life.

The card reader rollers, on the other hand, have disintegrated into that granular cork-like material I've seen before. Project for another day, but simple.

[Katie Wasserman]

(02-14-2014 09:16 PM)dramsey Wrote:  The card reader rollers, on the other hand, have disintegrated into that granular cork-like material I've seen before. Project for another day, but simple.

I had this problem too and wrote up what I did for the repair here.

The card reader is very forgiving as far as speed variation is concerned.

[dramsey]

Katie, I believe those were the same instructions I used to repair the card reader on my first 9810...

[dramsey]

Another question: As you can see, there are several printhead elements that fire all the time, leading to vertical lines in the output. I'm assuming this is an electronics issue rather than a physical printhead issue.

I have another 9810 I can use for board swaps. So: any hints on which boards I should swap?    

[Katie Wasserman]

(02-15-2014 04:49 PM)dramsey Wrote:  Another question: As you can see, there are several printhead elements that fire all the time, leading to vertical lines in the output. I'm assuming this is an electronics issue rather than a physical printhead issue.

I have another 9810 I can use for board swaps. So: any hints on which boards I should swap?

There's just one PCB for printer control/print head driver. It's the one attached to the printer. IIRC you need to remove the printer and it's PCB as one unit. You might was well swap that whole assembly to verify that the problem is with electronics on the printer PCB. The head driver uses a bunch of 5 bit shift registers feeding high voltage buffer/drivers. On the schematic in the HP DVD set it shows these buffer/drivers as IC packages, but on Tony's schematic he shows them as discrete transistors. Possibly they made these PCB's two different ways.

[dramsey]

Hm. I suppose I could swap it out with the printer in muy 9820. I believe they are identical.

[Tony Duell]

(02-14-2014 07:27 PM)dramsey Wrote:  Here's my question: although the calculator does not have the "Printer Alpha" ROM, program listings include alpha key representations, something like this:

0030 -- |DIV| -- 053

..line number, key, and key code (the above line is made up and I'm pretty sure that's not the key code for the division key). Inserting the Printer Alpha ROM doesn't change a thing.

I thought the Printer Alpha ROM was required for listings like this. Am I wrong?

You do need a Printer Alpha ROM to get the function names in listings, but it may not be a seperate module. Each plug-in module has space for 4 ROM chips, each chips is 512 bytes, they are arranged as 2 sets of 512*16 bits, with a separate chip select line on the connector for each set.

The Printer alpha module only contains 2 ROMs, it's only 512 words long. It can therefore be combined with another 'half size' (512 word) module, I think HP sold combinations of the Plotter+Printer Alpha and the tape cassette+Printer Alpha ROM.

On another point, the card sensors are optical, there are 4 sets of light bulbs and photodetectors arround the card path. It is not clear to me what blocking out one will do, it may well cause other problems in that the unit may be expecting a change of state at each sensor as the card goes through.

[Tony Duell]

(02-14-2014 07:50 PM)Geoff Quickfall Wrote:  Wonderful Dave!

Can't help on the specs though. Maybe an email to Tony Duell would be appropriate. He has been writing quite a few Data Files on rebuilding and trouble shooting these.

Cheers, Geoff

Ifr anyone wants my articles (in LaTeX, of course...) please ask me and I will e-mail the .tar.gz to you.

[Tony Duell]

(02-14-2014 09:16 PM)dramsey Wrote:  The card reader rollers, on the other hand, have disintegrated into that granular cork-like material I've seen before. Project for another day, but simple.

There are several ways to repair the card reader (and BTW I have never seen a good original roller after all these years!). The method I use is anything but simple, but it does work, and it is likely to stay working.

Basically, I strip the reader and remove the old roller hubs if I can. That needs a special puller tool that I made, any other method is likely to do damage. Sometimes the old roller will not shift without the spindle getting bent, even with a puller.

Anyway, I then turn a new hub, 7/8" in diameter with 2 grooves in it for O-rings (3/4" ID, 1" OD, 1/8" thick). Fit that onto the spindle with a grub screw to hold it -- I mill a flat on the spindle for the screw to go against. Then put it all back together.

Of course if the spindle was bent I have to make a new one of those too.

Doing this takes an afternoon or so, but it's going to stay working, and next time the reader fails it's just a matter of changing the O-rings.

Oh, I also suggest replacing the O-ring that's used as a drive belt on the reader. They do tend to slip after all these years.

[Tony Duell]

(02-15-2014 04:49 PM)dramsey Wrote:  Another question: As you can see, there are several printhead elements that fire all the time, leading to vertical lines in the output. I'm assuming this is an electronics issue rather than a physical printhead issue.

I have another 9810 I can use for board swaps. So: any hints on which boards I should swap?

Firstly, I am not going to help you to swap boards. I will help you to find the fault.

The printhead is 80 elements. Electrically they are wired as a 20*4 matrix with the diodes on the PCB on the bottom of the printer. The 4 power transistors on this board select one of the sets of 20 elements, each element in the set is then controlled by a transistor on the printer interface board on the side of the printer. In turn these transistors are controlled by a long shift register, in part it's the normal processor I/O register, the rest is on the printer PCB.

My guess is a failed transistor on the printer interface PCB. Take the printer out, take out the 3 screws on this PCB and ease it off the edge connector. Then you can check for shorted transistors there.

[Tony Duell]

(02-15-2014 07:32 PM)Katie Wasserman Wrote:  There's just one PCB for printer control/print head driver. It's the one attached to the printer. IIRC you need to remove the printer and it's PCB as one unit. You might was well swap that whole assembly to verify that the problem is with electronics on the printer PCB. The head driver uses a bunch of 5 bit shift registers feeding high voltage buffer/drivers. On the schematic in the HP DVD set it shows these buffer/drivers as IC packages, but on Tony's schematic he shows them as discrete transistors. Possibly they made these PCB's two different ways.

There are 2 PCBs on the printer. Most of the electronics is on the one on the side of the printer (I call it the Interface PCB), there's also one on the bottom containing the prinhead matrix diodes, the 'block' driver transistors and the motor controller. But I agree the most likely problem is on the interface PCB.

I have worked on half a dozen of these printers and all have used discrete transistors. It's possible HP used transistor arrays on some of them, if anyone comes across this version I would love to find out more.

[Katie Wasserman]

(02-16-2014 09:09 AM)Tony Duell Wrote:  [quote='Katie Wasserman' pid='5030' dateline='1392492753']



I have worked on half a dozen of these printers and all have used discrete transistors. It's possible HP used transistor arrays on some of them, if anyone comes across this version I would love to find out more.

Tony,

Yeah I forgot about the bottom board. On the schematic included in the DVD set they show these "high voltage buffer" IC's U1 and U2 with part number 1820-0668 (aka 7407 non-inverting hex buffer) and U3 and U4 as 1820-0471 (aka 7406 inverting hex buffer). The schematic is dated 1972, after the release of the 9810, so likely they changed the board design in later models.

[dramsey]

Tony, I have the PCB out. There is a 5x4 array of transistors (with two more below) that I assume are the ones you're talking about.

Googling "How to test a transistor" show that it's pretty easy, as long as you know the pins (E,B,C) and whether the transistors are NPN or PNP. Of course I don't know either of these things...

Also, as I know from the 9100 restoration project a couple of years back, it may not be possible to find replacement transistors with the same electrical characteristics as the transistors HP used in the early 70s.

These transistors are apparently Motorola units, part number 2N2907A 212.

[Steve Simpkin]

According to its data sheet, the 2N2907A is a PNP silicon transistor. It appears to still be available. Here is the ON Semiconductor (formerly Motorola Semiconductor) data sheet for the 2N2907A.
http://www.onsemi.com/pub_link/Collateral/2N2907A-D.PDF

Does this match the package of the 2N2907A you have on your boards?

[dramsey]

Cool. Yes, that's the transistor. I will start testing and see what I can come up with.

[Tony Duell]

(02-16-2014 02:58 PM)Katie Wasserman Wrote:  Tony,

Yeah I forgot about the bottom board. On the schematic included in the DVD set they show these "high voltage buffer" IC's U1 and U2 with part number 1820-0668 (aka 7407 non-inverting hex buffer) and U3 and U4 as 1820-0471 (aka 7406 inverting hex buffer). The schematic is dated 1972, after the release of the 9810, so likely they changed the board design in later models.

I don't have the DVD, or anything to read it, so I am not sure what that schematic shows. But my schematic (available on the Australian museum site) shows the TTL
outputs of the shift registers being buffered by '06 and '07 ICs, then feeding the 2N2907 transistors.

Since this side of the printhead element matrix needs to be pulled to +24V to turn the element on, I don't see how an open-collector TTL buffer could do it on its own.