HP 41C Video interface test. Howto?

HP 41C Video interface test. Howto? - Printable Version

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HP 41C Video interface test. Howto? - tribidouille - 07-06-2020 11:13 AM

Hello hpmuseum forum members,

I have a HP 41C and a 82163B video interface.
I used to program a lot on the 41 some 20 years ago but don't remember much about how it works.

I cannot make the Video interface work.
After having been searching the forum and found these threads:
https://www.hpmuseum.org/forum/thread-2401.html?highlight=82163
and
https://www.hpmuseum.org/forum/thread-12579.html?highlight=82163
But still, I don't find any simple action that I understand to print something on the screen.

Here is the situation:
HP-IL works as the cassette drive used with the HP-IL works
Print output of the 41 works as the printer works.
TV output is ok: when I plug the power and the tv cable, set the right frequency, a display appears, full of small triangles. (picture)

[Image: E2Qm7pf.jpg]

When I switch all off, plug the 41, switch the 82163B video interface on and the 41 on, I get the triangles but nothing else happens when I make calculations or try, for instance PRA.
HP-IL switch is set to "enable".

Any Idea?
Thank you

RE: HP 41C Video interface test. Howto? - Sylvain Cote - 07-06-2020 04:09 PM

Let's clear out the hardware requirements first, there were two versions of the original video interface:

HP 82163A for North America (60Hz, 525 lines, 75 ohms) [NTSC]
HP 82163B for Europe (50Hz, 625 lines, 75 ohms) [PAL]

The interface has two outputs:

Monitor => for monitor who has composite input
TV => to be used with the TV antenna adapter

To connect the interface to your composite monitor, you must:

have a video interface and a composite monitor with the same specs
connect the cable between the video interface monitor output and the composite monitor input
activate the desired input on your composite monitor, if needed

To connect the interface to your TV, you must:

have a video interface and a TV set with the same specs
connect the cable between the video interface TV output and the TV antenna adapter
then connect the TV antenna adapter to the antenna input of the TV [NA: VHF antenna / Europe: I do not know]
select TV option on TV antenna adapter
activate antenna input on your TV
select appropriate channel on your TV [NA: channel 3 / Europe: I do not know]

Sylvain
Edit: typos and clarifications

RE: HP 41C Video interface test. Howto? - tribidouille - 07-06-2020 09:54 PM

Hi Sylvain,
Thank you.
Yes, I get to this point. My description was not clear enough.
Actually, it is exactly at this point (after having set the frequency of the TV to 62MHz to get an image from the video converter) where I get stuck. The Video Converter version B (europe) is sending a picture with characters.
But what do I have to do on the 41 to modify what is displayed, to print something else than these triangles (pic on post 1)? This is what I have to find.

I searched the Video Converter manual and also the HP-IL manual but didn't have success.
xeq ALPHA PRA ALPHA or xeq ALPHA PRX ALPHA...such tries didn't give any success.

I also tried to read the flag 55 with Video Converter on, plugged through HP-IL and 41 switched on (after VC has started), HP-IL switch to "enable": the 41 answers there is no printer.

Is there something to setup in the 41 like an address for printer or something of this type?

Thanks

RE: HP 41C Video interface test. Howto? - tribidouille - 07-06-2020 10:05 PM

Sylvain,
(I just posted a reply that I cannot edit yet as it has to be read by the moderator)
I misunderstood "TV adapter". I don't use any.
I thought it was referring to a cable to adapt different kind of plugs but I now see you talk about ad proper device.
The strange thing is that without this adapter, I get a clear image fron the HP Video Converter when I reach the right frequency. As you see on the picture, it really looks like clean and defined.

I have no idea of this kind of devices. I have to search further into documentation.

RE: HP 41C Video interface test. Howto? - tribidouille - 07-06-2020 10:19 PM

I went back to the documentation.
For the recall and for other users: the frequency to set the TV to is 61.25Mhz for the 82163A (usa) and 62.25Mhz for the 82163B (eu)
The adapter referred in the manual is to be allow to switch between the antenna and the cable input if I understand correctly.

But anyway... I print nothing else than these triangles and the 41C's flag 55 says "no printer"...

RE: HP 41C Video interface test. Howto? - Ken S - 07-07-2020 06:06 AM

Probably a long shot but have you tried manually setting flag 21(printer enable flag)? It is automatically set when Flag 55 (printer existence flag) is set but can be set independently.

RE: HP 41C Video interface test. Howto? - vassilisprevelakis - 07-08-2020 10:32 PM

(07-06-2020 11:13 AM)tribidouille Wrote: When I switch all off, plug the 41, switch the 82163B video interface on and the 41 on, I get the triangles but nothing else happens when I make calculations or try, for instance PRA.
HP-IL switch is set to "enable".

Hi,

If you connect just the 82163B video interface to the HP-41C HP-IL interface (with the switch on the HP-IL interface set to ENABLE), then, after powering up the TV and the 82163B video interface, you should get a blank screen (i.e. no triangles or any other character).

If you then print anything (e.g. PRx, PRA, or PRP "") you should see characters on the screen.

There is no complicated setup, you just plug everything in and you are good to go.

The appearance of the triangles shows that the 82163B video interface can display stuff on the TV, but, unfortunately its the wrong stuff. I suspect that the video RAM in the 82163B video interface has a problem (maybe a stuck bit) or something.

If the HP-41C has no problems sending data to the 82163B video interface (ie. its does not complain or report bus timeouts), then the HP-IL part of the connection is OK, and the problem is in the display part of the 82163B video interface.

If you get bus timeouts, check the cabling.

Best Regards

Vassilis

http://www.series80.org

RE: HP 41C Video interface test. Howto? - tribidouille - 07-09-2020 06:23 AM

Hi,

@Ken S, the 41 still can't see any printer.
@vassilisprevelakis, yes, the HP-IL is ok because it works with the paper printer.
The most interresting point, in this case, is how the 82163B should display when we switch it on. Thanks for that. Only triangles, triangles, triangles...

The circuits at this time were big and human-repairable. Would it be possible to replace the ram or any other part, you think?

Cheers

RE: HP 41C Video interface test. Howto? - Garth Wilson - 07-09-2020 08:13 AM

What happens if you select the HP-IL device number and output something to it, for example if it's the second device, do 2 SELECT OUTA (with something in ALPHA to show)? That's the simplest way I can think of that should display something. Make sure the devices on the interface loop are connected and turned on when you turn the 41 on so it finds a completed loop and initializes it.

(07-09-2020 06:23 AM)tribidouille Wrote: The circuits at this time were big and human-repairable. Would it be possible to replace the ram or any other part, you think?

The first thing I might suspect is if there's an EPROM whose data has faded and it needs to be re-programmed. If someone else has the same model and an EPROM programmer, perhaps they could read theirs out and either send you the file or offer to refresh yours or program a new one. I have the HP92198 80-column video interface and I've refreshed the EPROMs a couple of times over the decades to make sure they don't lose the data. I kept copies of the files so I don't need to read valid EPROMs to be able to program them again. I believe one has the program material and one has the data for generating the characters, which interestingly gives the option of programming in different ones, like if you wanted them to match what the common Epson dot-matrix impact printers that were ubiquitous used, which is the DOS/ANSI character set.

RE: HP 41C Video interface test. Howto? - tribidouille - 07-09-2020 07:28 PM

Hi,

I tried that with no other modules into the slots and HP-IL plugged into slot 2. Doing every time switch off all and starting the 41 at last.
2 [xeq] [ALPHA] SELECT [ALPHA] [xeq] OUTA [ALPHA]
After that, the 41 says "TRANSMIT ERR"
The same with other ports.
The HP-IL is working as I said, as it was used for the cassette drive (not the printer, which has its own plug)
So you might be right, something is lost into the 82163B, components or program.
I'll try to give a check inside...but I have no eeprom programmer

RE: HP 41C Video interface test. Howto? - Dave Frederickson - 07-10-2020 03:32 PM

(07-09-2020 06:23 AM)tribidouille Wrote: The circuits at this time were big and human-repairable. Would it be possible to replace the ram or any other part, you think?

Yes, I have done this. Here's a peek inside.

[Image: 82163-60001-50.jpg]

Some parts can be found at Sphere. https://www.sphere.bc.ca/test/hpparts.html

The 2114N SRAM chips, center left in the pic, are readily available.

Dave

RE: HP 41C Video interface test. Howto? - tribidouille - 07-11-2020 06:54 AM

So, here is how it looks like inside.
Frankly, I really don't know what I could make with this!
I think I will sell it as is, for part or something.
Regards,
[Image: Zs73LqE.jpg]

RE: HP 41C Video interface test. Howto? - vassilisprevelakis - 07-11-2020 01:08 PM

Hi,

The Intel 8048 has an internal ROM, so if this is losing bits, then you need a new CPU.
The RAM is the Intel P2114 part which is a 1024x4 static RAM (4 kilobits).

But let's start from the basics. First check that the power supply is giving correct voltages. E.g. the RAM chips have GND on pin 9 (bottom left) and +5V on pin 18 top right. If you have an oscilloscope you may also want to measure the ripple in case the electrolytic capacitors are feeling their age.

I am not sure what's the other big IC. Its an HP part (on my unit it has ILF4 01 and 82241 written on top), but I guess its the video chip, and since you are getting a picture, its probably OK.

So since you can't do anything about either of the big ICs, assuming the voltages are OK, I'd replace the RAM chips and hope for the best.

Vassilis
http://www.series80.org

RE: HP 41C Video interface test. Howto? - Sylvain Cote - 07-11-2020 01:35 PM

I finally have some free time to write this small test plan.

Test #1: closed empty loop

Code:

Setup: HP-41C, HP-IL module printer activated, loopback mode

Loop : 41C <IL-cables> 41C

ON

FS? 55   // LCD: NO

FS? 21   // LCD: NO

PWRUP    // LCD: nothing expected, will show "TRANSMIT ERR" if loop is broken

OFF

Test #2: loop with video interface without power

Code:

Setup: HP-41C, HP-IL module printer activated, 82163 off , no monitor attached

Loop : 41C <IL-cables> 82163 <IL-cables> 41C

ON

FS? 55   // LCD: NO

FS? 21   // LCD: NO

PWRUP    // LCD: "TRANSMIT ERR" loop is broken, expected, video interface is not powered

OFF

Test #3: loop with video interface with power

Code:

Setup: HP-41C, HP-IL module printer activated, 82163 on , no monitor attached

Loop : 41C <IL-cables> 82163 <IL-cables> 41C

ON

FS? 55   // LCD: YES

FS? 21   // LCD: YES

PWRUP    // LCD: nothing expected, will show "TRANSMIT ERR" if loop is broken

OFF

Test #4: send text to interface

Code:

Setup: HP-41C, HP-IL module printer activated, 82163 on , no monitor attached

Loop : 41C <IL-cables> 82163 <IL-cables> 41C

ON

FS? 55   // LCD: YES

FS? 21   // LCD: YES

PWRUP    // LCD: nothing expected, will show "TRANSMIT ERR" if loop is broken

"TEST"   // test string

PRA      // LCD: nothing expected, send ALPHA to printer/video

OFF

At this point, if no error has shown up, the HP-IL side is working.

Part #2, later today, I have a HPCC meeting in 30 minutes.

Sylvain

RE: HP 41C Video interface test. Howto? - Sylvain Cote - 07-11-2020 11:12 PM

Part 2, 82163B interface video output ...

As specified previously, the interface has two outputs:
Monitor => for monitor who has composite input (50Hz, 625 lines, 75 ohms)
TV => to be used with the TV antenna adapter

Connecting the 82163 Monitor output to a TV cable input with RCA plug (if such a thing is possible in France) should not work.
Connecting the 82163 Monitor output to a compatible composite monitor input will work.

Antenna adapter example
[Image: 5ayppnx932j01.jpg]

Connecting the 82163 TV output to a composite monitor input will not work.
Connecting the 82163 TV output to an antenna adapter game/computer input, the antenna adapter to the TV antenna and set TV to channel 3 (or 4) will work.

Test #5: send text to interface and monitor/TV

Code:

Setup: HP-41C, HP-IL module printer activated, 82163 on , monitor or TV attached and properly set

Loop : 41C <IL-cables> 82163 <IL-cables> 41C

ON

FS? 55   // LCD: YES

FS? 21   // LCD: YES

PWRUP    // LCD: nothing expected, will show "TRANSMIT ERR" if loop is broken

"TEST"   // test string

PRA      // LCD: nothing expected, send ALPHA to printer/video, TV/monitor should display TEST on the screen

OFF

If you have done one of the "will work" part and still have the triangles on the screen, then you probably have a hardware problem.

Sylvain

RE: HP 41C Video interface test. Howto? - tribidouille - 07-12-2020 10:55 AM

@vassilisprevelakis. Thanks a lot, very interesting. I'll search in this way when done with Sylvain Cote's tests.
@Sylvain Cote, Thanks also much.
These step tests are teachfull. #1 ok, #2 ok, loop works.
Effectively, the test #3 fails: Even with 82163 plugged and powered (before the 41), flags 21 and 55 show NO and I get a "Transmitt ERR".
I can deduce the failure is in the loop part of the 82163. One of its components for communication may fail.

RE: HP 41C Video interface test. Howto? - tribidouille - 07-12-2020 10:56 AM

Side question: The antenna adapter is useless until you don't want to plug/unplug cables all the time isn't it?

RE: HP 41C Video interface test. Howto? - tribidouille - 07-12-2020 11:21 AM

(07-11-2020 01:08 PM)vassilisprevelakis Wrote: ...
But let's start from the basics. First check that the power supply is giving correct voltages. E.g. the RAM chips have GND on pin 9 (bottom left) and +5V on pin 18 top right. If you have an oscilloscope you may also want to measure the ripple in case the electrolytic capacitors are feeling their age.
...

I measured the DC voltage on the RAM chips: 4.75V.
I could try a tast with the oscillator but I don't know where to plug (pin 9 and 18?) it and what I should see (a flat line for DC?)

RE: HP 41C Video interface test. Howto? - tribidouille - 07-12-2020 11:58 AM

I was thinking the problem revealed by Sylvain's test #3 could be caused by a bad contact between HP-IL and the 82163.
I tested circuit continuity until where I could (not far). Until there (contacts under the red circles), no bad contacts.
Further, I don't know what and how to test.
[Image: VyCyxSF.jpg]

RE: HP 41C Video interface test. Howto? - Sylvain Cote - 07-12-2020 01:33 PM

(07-12-2020 10:56 AM)tribidouille Wrote: Side question: The antenna adapter is useless until you don't want to plug/unplug cables all the time isn't it?

It is necessary if you want to plug the 82163 TV output to your TV.
To my limited knowledge, the 82163A TV output has the big part of the RF modulator in it but it need the VHF adapter to finish the job.
I would assume that some old TV did had a VHF adapter in it with a RCA plug but I do not remember having seen that.
I have never opened an VHF adapter, but since it is passive, I would assume that it only contains basic components in it. (resistors, caps and coils)