Topics

HP 9821 - display and tape transport issues #VintageHPComputers

mariuszmleczko@...
 

Hi. I'm in position of vintage computer HP 9821A

Do you have any suspicion which exact part of display board might be broken that it cause such regular failure of every third digit in each of four LED sections  ?
I got also problem with a tape transport. Mechanically seems to be working OK, but during program search or load it stuck in a place trying rotate left and right.

Tape sound and photos here:
https://groups.io/g/VintHPcom/album?id=239610
https://groups.io/g/VintHPcom/files/HP%209821A/tape%20sound.mp3

Thank you in advance for help.

 

Hi Marius,

 

Congratulated, you’re one of the few people owning a HP 9821A.

The difference between a 9820 and 9821 is in essential the switch for mag card to cassette drive.

The drive is the same as used in the HP 9830A/B and 9865A tape drive.

 

First, the tape transport on the back side of the drive there are two wheels with a O-ring on it.

The motor drives the wheel by pressing the drive shaft to the O-ring if the O-rings are deteriorated the tape transport won’t work properly.

See the pictures: https://www.flickr.com/photos/hp-fix/5445928267/in/album-72157630819381098/

https://www.flickr.com/photos/hp-fix/6851031513/in/album-72157630819381098/

Replacing them is easy.

Another thing is the leader of the tape should be transparent and there must be a reflective coating (white, silver, etc..) on the inside of the left side of the tape housing.

So the small lamp can shine trough the tape leader and the light will be reflected on the LDR placed next to the lamp forming the EOT sensor.

https://www.flickr.com/photos/hp-fix/7676311616/in/album-72157630820029066/

https://www.flickr.com/photos/hp-fix/9426870925/in/album-72157634915270264/

 

The display, http://www.hpmuseum.net/images/09820-66541-Display-40.jpg

The display is multiplexed and uses column and row drivers, probably one of the row drivers is defective.

They are on the display board; you can use the schematics of the 9820A made by Tony Duell to locate the right IC.

http://www.hpmuseum.net/exhibit.php?hwdoc=52

Be careful when desoldering any components of the board because the vias on these boards will get bad contact problems when there is applied to much heat.

 

Hope this helps a little.

 

-Rik

 

Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens mariuszmleczko@...
Verzonden: maandag 27 januari 2020 11:32
Aan: VintHPcom@groups.io
Onderwerp: [VintHPcom] HP 9821 - display and tape transport issues #VintageHPComputers

 

Hi. I'm in position of vintage computer HP 9821A

Do you have any suspicion which exact part of display board might be broken that it cause such regular failure of every third digit in each of four LED sections  ?
I got also problem with a tape transport. Mechanically seems to be working OK, but during program search or load it stuck in a place trying rotate left and right.

Tape sound and photos here:
https://groups.io/g/VintHPcom/album?id=239610
https://groups.io/g/VintHPcom/files/HP%209821A/tape%20sound.mp3

Thank you in advance for help.

David Collins
 

From a quick look at the schematics, the display issue will most likely be caused by either;

 

  1. A bad transistor in U14 – check pin 12 with an oscilloscope if you have one – you will probably see no activity but it should instead be similar to pin 10.  Pin 13 on U14 drives the transistor and should show activity in the same way as pin 9.  If there’s activity at pin 13 but nothing on pin 14, then one of the driver transistors in U14 is probably bad – but you could connect in a common PNP transistor to fix it if you can’t find a replacement ; or

 

  1. If there’s no activity at pin 13 of U14, then u12 is probably bad.  U12 appears to be a 74145 IC which is still available on eBay.

 

The problem is I can’t find a board layout that shows which ICs are U12 and U14.  I suspect U14 is one of the 5 ICs on the right side of the displays.  U12 will be one of the 74175s below the displays.

 

I used the schematics here - http://www.hpmuseum.net/document.php?hwfile=6327

 

Hope that helps.

 

David Collins

 

 

From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of Rik Bos
Sent: Monday, 27 January 2020 10:55 PM
To: VintHPcom@groups.io
Subject: Re: [VintHPcom] HP 9821 - display and tape transport issues #VintageHPComputers

 

Hi Marius,

 

Congratulated, you’re one of the few people owning a HP 9821A.

The difference between a 9820 and 9821 is in essential the switch for mag card to cassette drive.

The drive is the same as used in the HP 9830A/B and 9865A tape drive.

 

First, the tape transport on the back side of the drive there are two wheels with a O-ring on it.

The motor drives the wheel by pressing the drive shaft to the O-ring if the O-rings are deteriorated the tape transport won’t work properly.

See the pictures: https://www.flickr.com/photos/hp-fix/5445928267/in/album-72157630819381098/

https://www.flickr.com/photos/hp-fix/6851031513/in/album-72157630819381098/

Replacing them is easy.

Another thing is the leader of the tape should be transparent and there must be a reflective coating (white, silver, etc..) on the inside of the left side of the tape housing.

So the small lamp can shine trough the tape leader and the light will be reflected on the LDR placed next to the lamp forming the EOT sensor.

https://www.flickr.com/photos/hp-fix/7676311616/in/album-72157630820029066/

https://www.flickr.com/photos/hp-fix/9426870925/in/album-72157634915270264/

 

The display, http://www.hpmuseum.net/images/09820-66541-Display-40.jpg

The display is multiplexed and uses column and row drivers, probably one of the row drivers is defective.

They are on the display board; you can use the schematics of the 9820A made by Tony Duell to locate the right IC.

http://www.hpmuseum.net/exhibit.php?hwdoc=52

Be careful when desoldering any components of the board because the vias on these boards will get bad contact problems when there is applied to much heat.

 

Hope this helps a little.

 

-Rik

 

Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens mariuszmleczko@...
Verzonden: maandag 27 januari 2020 11:32
Aan: VintHPcom@groups.io
Onderwerp: [VintHPcom] HP 9821 - display and tape transport issues #VintageHPComputers

 

Hi. I'm in position of vintage computer HP 9821A

Do you have any suspicion which exact part of display board might be broken that it cause such regular failure of every third digit in each of four LED sections  ?
I got also problem with a tape transport. Mechanically seems to be working OK, but during program search or load it stuck in a place trying rotate left and right.

Tape sound and photos here:
https://groups.io/g/VintHPcom/album?id=239610
https://groups.io/g/VintHPcom/files/HP%209821A/tape%20sound.mp3

Thank you in advance for help.

mariuszmleczko@...
 

Thank you a lot guys. I got it just a couple of days, haven't opened it yet.
Will do it as soon as I read service manual, maybe around the end of this week.
Last LCD board photo was taken from here (only for reference):
http://www.silicium.org/forum/viewtopic.php?t=43529

The history of model I got is also interesting.
It was used surely during soviet times in polish military factory PIT RADWAR
which is working on radiolocation systems, radio-electronic reconnaissance systems, anti-aircraft defense systems as well as command and fire control support systems
https://historiainformatyki.pl/historia/skan.php?doc_id=1221&type=pdf&for_download=1

Beside the computer and two standard ROM's (Mathematics, PC1), I got also "user definable functions I-III" ROM and three cables shown on the photos below.
https://groups.io/g/VintHPcom/album?id=239610

Do you have any Idea what kind of equipment could have been connected with those (seems reworked plugs) 11203A TTL I/O (female 50 pin d-sub) and 11203A BCD (male 50 pin d-sub) ?

mariuszmleczko@...
 

What is the diameter and size of O-ring used for 9865A tape transport ? Does anyone know ?

mariuszmleczko@...
 

Could you also suggest a way of cleaning the boards from a many year dust
Isopropanol + soft brush or which other cleaning fluid ?

mariuszmleczko@...
 

9821A finally opened

Here you can see photos of all the boards.
Some of them are not the best quality (sorry).
https://groups.io/g/VintHPcom/album?id=240360

So far I've repaired the lever for paper feed.

Next thing to do is a tape transport.
O-rings looks OK without any dents, cassette pulling strength and speed seems to be OK as well.

But it not behaves properly....

1) Rewinding.:
- when I execute "<>REW" command, it is rewindig but only for about one second and then stop immediately.
Here you can see video (few times executed <>REW command on execute keypress).
https://groups.io/g/VintHPcom/files/HP%209821A/rewinding.mp4

2) Program load "<> LDF 0".:
- after few tape turns when clear leader is finished it starts to behave strangely.
electromagnets on the both sides flip back and forward, then tape finally is rewinded back to begginnig.
This test was made on origin HP cassete which is OK in 99%.
https://groups.io/g/VintHPcom/files/HP%209821A/program%20load.mp4

3) Mark command:
- when I run "<>MARK 1, 5"; command it's running and running....don't stop.

Do you have any idea what shall I check first ?

 

A lot of transport problems are caused by a bad working EOT sensor, the LDR’s used in the system to detect the end of tape deteriorate and the resistance changes permanent to a low value.

The system then won’t detect the end of tape or thinks end of tape has arrived when it hasn’t, with all kind of nice tape behavior as result.

The LDR and Lamp are place left from the tape head and accessible when you remove the tape door, you can check the working of the LDR with a multimeter the resistance should vary between 100-1K and >1M roughly (light – no light condition).

Other problems with the tape boards are the 7403 (1820-0269) made by NI they die without notice 😉

They’re used in several boards but the most important is the control board.

Another problem early multi-layer boards suffer from via contact problems causing intermittent or permanent errors, boards I know off are mostly memory and memory control boards (M-register, T-register, display) dual-layer boards typically don’t suffer from this only multi-layer boards.

 

Hope it helps a little,

-Rik

 

Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens mariuszmleczko@...
Verzonden: maandag 3 februari 2020 1:30
Aan: VintHPcom@groups.io
Onderwerp: Re: [VintHPcom] HP 9821 - display and tape transport issues #VintageHPComputers

 

9821A finally opened

Here you can see photos of all the boards.
Some of them are not the best quality (sorry).
https://groups.io/g/VintHPcom/album?id=240360

So far I've repaired the lever for paper feed.

Next thing to do is a tape transport.
O-rings looks OK without any dents, cassette pulling strength and speed seems to be OK as well.

But it not behaves properly....

1) Rewinding.:
- when I execute "<>REW" command, it is rewindig but only for about one second and then stop immediately.
Here you can see video (few times executed <>REW command on execute keypress).
https://groups.io/g/VintHPcom/files/HP%209821A/rewinding.mp4

2) Program load "<> LDF 0".:
- after few tape turns when clear leader is finished it starts to behave strangely.
electromagnets on the both sides flip back and forward, then tape finally is rewinded back to begginnig.
This test was made on origin HP cassete which is OK in 99%.
https://groups.io/g/VintHPcom/files/HP%209821A/program%20load.mp4

3) Mark command:
- when I run "<>MARK 1, 5"; command it's running and running....don't stop.

Do you have any idea what shall I check first ?

Achim Buerger
 

The 'die without notice' applies to all TTL chips made by NI in the early 1970s. I had to replace dozens of ICs in my various 98xx calculators and peripherals and in 99% they where made by National Instruments. If I get a defective 98xx board I first check all NI chips by means of a logic comparator. NI seemed to have problems with long term stability of their TTL ICs in the 1970s. The dying already began in the 1990s and still continues. Some times I thought about exchanging all NI chips prophylactic, but that would cause a lot of work in my ~20 devices. Moreover, some chips are hard to find these days.

Dave McGuire
 

On 2/3/20 4:46 AM, Achim Buerger wrote:
The 'die without notice' applies to all TTL chips made by NI in the
early 1970s. I had to replace dozens of ICs in my various 98xx
calculators and peripherals and in 99% they where made by National
Instruments. If I get a defective 98xx board I first check all NI chips
by means of a logic comparator. NI seemed to have problems with long
term stability of their TTL ICs in the 1970s. The dying already began in
the 1990s and still continues. Some times I thought about exchanging all
NI chips prophylactic, but that would cause a lot of work in my ~20
devices. Moreover, some chips are hard to find these days.
Pretty sure you mean "Texas Instruments", not "National Instruments".

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

 

No, he and me are talking about NI not TI, TI 7400 logic has a longer lifespan as for the IC's used in the HP 98X0 series calculators.
Date stamp early '70th.

-Rik

-----Oorspronkelijk bericht-----
Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens Dave McGuire
Verzonden: maandag 3 februari 2020 15:47
Aan: VintHPcom@groups.io
Onderwerp: Re: [VintHPcom] HP 9821 - display and tape transport issues
#VintageHPComputers

On 2/3/20 4:46 AM, Achim Buerger wrote:
The 'die without notice' applies to all TTL chips made by NI in the
early 1970s. I had to replace dozens of ICs in my various 98xx
calculators and peripherals and in 99% they where made by National
Instruments. If I get a defective 98xx board I first check all NI
chips by means of a logic comparator. NI seemed to have problems with
long term stability of their TTL ICs in the 1970s. The dying already
began in the 1990s and still continues. Some times I thought about
exchanging all NI chips prophylactic, but that would cause a lot of
work in my ~20 devices. Moreover, some chips are hard to find these days.
Pretty sure you mean "Texas Instruments", not "National Instruments".

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

Achim Buerger
 

No, I really meant NI. I never had problems with TI chips. I have a box of TI spares from the beginning of 1970s, which still work without problem. Furthermore, all of my TI and other calculators with TI chips from beginning of 1970 had nearly no chip defects. Since nearly all defects occured just by aging and in power-off state, I have some assumptions of the defect cause:

1. Re-crystallization or diffusion within the die
2. Corrosion in the AL conductor tracks on the die
3. Detachment of the chip wiring

I observed that several of the defective chips exhibit one or more complete open contact pins. So the alternatives 2 and 3 seem likely. The corrosion could be caused by some acid, either from incompletely cleaned dies in the production process or acid in the plastic chip housing.

Dave McGuire
 

Ah ok, sorry. I'm a bit confused, I'm pretty sure National
Instruments was founded in 1976 or 1977, so NI chips from the "early
1970s" would have been a pretty good trick, but perhaps I'm wrong.

-Dave

On 2/3/20 10:01 AM, Rik Bos wrote:
No, he and me are talking about NI not TI, TI 7400 logic has a longer lifespan as for the IC's used in the HP 98X0 series calculators.
Date stamp early '70th.

-Rik

-----Oorspronkelijk bericht-----
Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens Dave McGuire
Verzonden: maandag 3 februari 2020 15:47
Aan: VintHPcom@groups.io
Onderwerp: Re: [VintHPcom] HP 9821 - display and tape transport issues
#VintageHPComputers

On 2/3/20 4:46 AM, Achim Buerger wrote:
The 'die without notice' applies to all TTL chips made by NI in the
early 1970s. I had to replace dozens of ICs in my various 98xx
calculators and peripherals and in 99% they where made by National
Instruments. If I get a defective 98xx board I first check all NI
chips by means of a logic comparator. NI seemed to have problems with
long term stability of their TTL ICs in the 1970s. The dying already
began in the 1990s and still continues. Some times I thought about
exchanging all NI chips prophylactic, but that would cause a lot of
work in my ~20 devices. Moreover, some chips are hard to find these days.
Pretty sure you mean "Texas Instruments", not "National Instruments".

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA



--
Dave McGuire, AK4HZ
New Kensington, PA

Achim Buerger
 

I HAVE TO APPOLOGISE: I wrote bullshit. I meant National Semiconductor (abbreviation NS), not National Instruments (which produce very reliable IEEE and other interface cards).

Dave McGuire
 

On 2/3/20 10:07 AM, Achim Buerger wrote:
I HAVE TO APPOLOGISE: I wrote bullshit. I meant National Semiconductor
(abbreviation NS), not National Instruments (which produce very reliable
IEEE and other interface cards).
Ahhhh ok, I'm far less confused now! This one threw me for a loop
since I'm only halfway through my first cup of coffee. =)

At LSSM we've had some trouble with Texas Instruments chips, but most
commonly in the form of corrosion on the exposed leads. Not
unreasonable (IMO) due to the age of the components, but we've seen it
more on TI than on other brands, so it must have something to do with
the alloy they used for their lead frames.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

Achim Buerger
 

That's interesting, since just a few days ago I pulled a TI RAM chip from 1977 out of a socket and two of the leads simply fell off. And all are very dark, nearly black. I thought they might be silver plated, but that doesn't explain the desintegration of the leads without excessive force.

Dave McGuire
 

On 2/3/20 10:17 AM, Achim Buerger wrote:
That's interesting, since just a few days ago I pulled a TI RAM chip
from 1977 out of a socket and two of the leads simply fell off. And all
are very dark, nearly black. I thought they might be silver plated, but
that doesn't explain the desintegration of the leads without excessive
force.
That's exactly what we've seen at LSSM. I do not know the chemistry
of that effect.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA

Steve Leibson
 

Well, someone finally got it right.

NI (National Instruments) generally makes IEEE-488, PXI, VXI, and PC-based test equipment and LabView system-development software (and they're very, very successful at it) although they did once sell their IEEE-488 chip (but didn't make it themselves). They're based in Austin, Texas. A very fine company.

Texas Instruments (TI) was the leading TTL chip vendor back when TTL chips were all important. Their 74xx/xxx series took the digital design world by storm starting in the late 1960s, effectively pushing Fairchild Semi off the map. No self-respecting digital design engineer would be caught dead without the burnt orange TI TTL databook series on their shelves. (I lost mine and had to buy another on eBay three years ago, or else I'd lose my self respect, and I don't even design stuff any more.) Generally very good chips but the 74LS240 octal transceiver family had problems. TI was originally in the oil well instrumentation business, but it bought an early Bell Labs license to make transistors (manufactured with alchemy, not science), and then dominated the TTL and DSP chip scenes for decades. TI owns half the patent for the IC.

National Semiconductor was an analog chip company that branched out into digital chips (and memory, and microprocessors, and PC x86 processors, and, and, and). They made a lot of different parts. Their quality was never the best (a colleague once commented on their original logo that contains an embedded, stylized "approximately equal" sign that's supposed to be an "S", as signifying that National Semi was "approximately equal" to a semiconductor company. They had some good parts, but in particular they had a guy named Bob Pease. He was one of two famous analog gurus. (Jim Williams was the other. Both are gone now.) National Semi is gone now too, having been swallowed whole and digested by TI. It is very strange these days to drive by National Semi's campus in Silicon Valley and see TI signs where National Semi signs had been for half a century.

--Steve



On 2/3/2020 7:07 AM, Achim Buerger wrote:
I HAVE TO APPOLOGISE: I wrote bullshit. I meant National Semiconductor (abbreviation NS), not National Instruments (which produce very reliable IEEE and other interface cards).
-- 
Steve Leibson

Phone (Cell): 408-910-5992
Phone (Home): 408-292-4930


Please feel free to link to me on LinkedIn


History site: www.hp9825.com

#Iwork4Intel

Steve Leibson
 

Plastic packaged chips are definitely not hermetic. Water vapor capillaries in between the metal/plastic interfaces, drags in impurities, oxidizes and erodes the metal, and the chip's lead frame falls apart or the silicon passivation layer fails. I had some chips plugged into black plastic foam for five decades or so. The foam deteriorated to powder, blackened leads, and the chips crumbled when touched.

--Steve



On 2/3/2020 7:19 AM, Dave McGuire wrote:
On 2/3/20 10:17 AM, Achim Buerger wrote:
That's interesting, since just a few days ago I pulled a TI RAM chip
from 1977 out of a socket and two of the leads simply fell off. And all
are very dark, nearly black. I thought they might be silver plated, but
that doesn't explain the desintegration of the leads without excessive
force.
  That's exactly what we've seen at LSSM.  I do not know the chemistry
of that effect.

          -Dave

-- 
Steve Leibson

Phone (Cell): 408-910-5992
Phone (Home): 408-292-4930


Please feel free to link to me on LinkedIn


History site: www.hp9825.com

#Iwork4Intel

Dave McGuire
 

On 2/3/20 10:35 AM, Steve Leibson wrote:
Plastic packaged chips are definitely not hermetic.
Right, they were never intended to be.

Water vapor
capillaries in between the metal/plastic interfaces, drags in
impurities, oxidizes and erodes the metal, and the chip's lead frame
falls apart or the silicon passivation layer fails.
Yes. What we're referring to here, though, is the specific type of
lead frame corrosion that seems to affect TI chips, and no others.

I had some chips
plugged into black plastic foam for five decades or so. The foam
deteriorated to powder, blackened leads, and the chips crumbled when
touched.
Yeah. Everyone stores their chips in that black foam, and we need to
stop doing that. I've eliminated most of it here, but I still have some
that I need to address.

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA