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New member with early HP computers

SilverRay
 

Hello!

I'm newby in your group.
First of all excuse me for my English, I'm from Russia and have no practice. Therefore my posts may contain some mistakes so I'm sorry.

 I like vintage computers especially from HP. I have two early models -- HP 9825B and HP 85.
 Unfortunately my 9825 isn't work correctly -- I repaired the power supply module but the computer didn't resurrect :(
 
 I checked up all voltages and they are OK. If I disconnect KDP interface cable and make power on -- LEDs are light on and the beeper is sound on.
 I checked up the clock frequency -- all OK, approx. 6MHz.

 Could you help me with searching of solvetion?

Best Regards,
 Roman.

 

On Aug 25, 2019, at 10:50 AM, silverray.russia@... wrote:
Unfortunately my 9825 isn't work correctly -- I repaired the power supply module but the computer didn't resurrect :(

I checked up all voltages and they are OK. If I disconnect KDP interface cable and make power on -- LEDs are light on and the beeper is sound on.
I checked up the clock frequency -- all OK, approx. 6MHz.
If the memory board is not functional or is not responding to the CPU, it won't get very far during power up tests. Try reseating the connections between the board stack to see if that helps. If you have another memory board, you could swap it in place of the current one.

Paul Berger
 


On 2019-08-25 1:50 p.m., silverray.russia@... wrote:
Hello!

I'm newby in your group.
First of all excuse me for my English, I'm from Russia and have no practice. Therefore my posts may contain some mistakes so I'm sorry.

 I like vintage computers especially from HP. I have two early models -- HP 9825B and HP 85.
 Unfortunately my 9825 isn't work correctly -- I repaired the power supply module but the computer didn't resurrect :(
 
 I checked up all voltages and they are OK. If I disconnect KDP interface cable and make power on -- LEDs are light on and the beeper is sound on.
 I checked up the clock frequency -- all OK, approx. 6MHz.

 Could you help me with searching of solvetion?

Best Regards,
 Roman.
_._,_._,_

Does the PVAL signal from the power supply go high?  If it remains low the processor will be held reset.

What was the fault on the power supply?  Some failure modes can result in higher than normal voltages going to components in the system, for instance I had one that to +5V pass transistor failed short putting about +25V on the +5 line.

Do you have any instruments like an oscilloscope or a logic analyzer you can use to troubleshoot?  If all you have is a meter troubleshooting may be difficult.

I would second what Craig said, I would clean the edge connectors and reseat them a couple time to make sure they are ok.  I had one that would not start up until I cleaned the edge connector even though there was no visible contamination. 

Paul.

SilverRay
 

Thank You!
Unfortunately I have no any working parts for substitution.
Sure I reassembled the entire device and cleared slots by ethanol.
Is there a circuit  for memory module with signal check points?
I checked up the signals on internal slot (I think it's a part of 9825A model with system ROM module) and saw some signal activity on it.

 

Paul Berger
 


On 2019-08-25 3:09 p.m., silverray.russia@... wrote:

Thank You!
Unfortunately I have no any working parts for substitution.
Sure I reassembled the entire device and cleared slots by ethanol.
Is there a circuit  for memory module with signal check points?
I checked up the signals on internal slot (I think it's a part of 9825A model with system ROM module) and saw some signal activity on it.

 

_._,_._,_



I have spare parts but I am a long way away from you.

The B model has the OS ROMs along with most of the option ROMs and system RAM on one board (A24).  The T model has a second board (A25) with just RAM and a state machine that allows some of the RAM to overlay ROM.  This second board if present can be disconnected for trouble shooting.

The long ROM slot towards the right side of the machine is the slot for the 9825A OS ROM on the same circuit board along the front there are 4 slots for option ROMs.  Since most of the option ROMs are built into a B/T, only the Mass Storage, and Matrix ROMs will work all others will be ignored.

Paul.

The only schematics that I know of are Tony Duell's hand drawn schematics found at  http://www.hpmuseum.net/document.php?hwfile=1809 but they do not have labeled test points you need to figure that out for yourself from the logic.

SilverRay
 

Thank You very much!
I have TWO boards -- the first with ROM and RAM chips and the second with logic chips and set of RAM chips. Probably I have model T?
Please see the photos of boards by links.
http://ipic.su/img/img4/fs/img_20190825_125645.1566742349.jpg -- It's an A24 board?
http://ipic.su/img/img4/fs/img_20190825_130055.1566742351.jpg -- It's an A25 board?
Roman.

 

Yes, it appears you have a T model, you have them correctly identified.  Leave out the A25 board, see if you get any further.  It appears that the boards are physically in very good condition.

On Aug 25, 2019, at 12:39 PM, silverray.russia@... wrote:

Thank You very much!
I have TWO boards -- the first with ROM and RAM chips and the second with logic chips and set of RAM chips. Probably I have model T?
Please see the photos of boards by links.
http://ipic.su/img/img4/fs/img_20190825_125645.1566742349.jpg -- It's an A24 board?
http://ipic.su/img/img4/fs/img_20190825_130055.1566742351.jpg -- It's an A25 board?
Roman.

SilverRay
 

Yes, the entire device is in very good condition, only one key or it's spring is broken.

I tried to remove boards A24 and A25 separately but it had no effect. I tried to change positions of the onboard switches -- no difference.
Also I have the next question -- is the tape controller board nesseccary for startup this system or I can remove it for tests?

Roman.

Paul Berger
 


On 2019-08-25 4:05 p.m., silverray.russia@... wrote:
Yes, the entire device is in very good condition, only one key or it's spring is broken.

I tried to remove boards A24 and A25 separately but it had no effect. I tried to change positions of the onboard switches -- no difference.
Also I have the next question -- is the tape controller board nesseccary for startup this system or I can remove it for tests?

Roman.
_._,_._,_

The tape controller can be disconnected.

Paul.


SilverRay
 

> Does the PVAL signal from the power supply go high?  If it remains low the processor will be held reset.
Sorry I didn't see Your answer on time.

Of course I have all necessary equipment for research :)
I repaired the power supply module at my woking place, and controlled all voltages in order with information in Service Manual.
The PVAL is in high state, active. Line +5V is 5.07V when has no load and 4.96V when loaded.

Roman.

 

Hi Roman,

 

There is a small trick to determine if the main logic is working.

Switch the system on and type BEEP and then press the EXECUTE KEY if you hear a beep most of the main logic and memory are functioning and the problem is in the display/keyboard.

 

-Rik

 

Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens silverray.russia@...
Verzonden: zondag 25 augustus 2019 21:35
Aan: VintHPcom@groups.io
Onderwerp: Re: [VintHPcom] New member with early HP computers

 

> Does the PVAL signal from the power supply go high?  If it remains low the processor will be held reset.
Sorry I didn't see Your answer on time.

Of course I have all necessary equipment for research :)
I repaired the power supply module at my woking place, and controlled all voltages in order with information in Service Manual.
The PVAL is in high state, active. Line +5V is 5.07V when has no load and 4.96V when loaded.

Roman.

SilverRay
 

Thank You!
But I guess that this trick is insufficient indeed -- if the KDP doesn't work the typed command is impossible to send and execute. Or I am mistaken?

 

No, you’re right, did you look with a scope at the bus signals?

You should check if all bus signals are transferred to the keyboard and option rom boards.

On the rom connector board you’ll find a bus driver ic you should check if the bus signals are on both sides of the driver.

Another thing the 9825 can boot without the tape controller board, so to check if it doesn’t hang the system you can disconnect it and try to start the computer.

The tape controller board is the board above the processor with the cable to the tape drive.

 

-Rik

 

Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens silverray.russia@...
Verzonden: zondag 25 augustus 2019 21:48
Aan: VintHPcom@groups.io
Onderwerp: Re: [VintHPcom] New member with early HP computers

 

Thank You!
But I guess that this trick is insufficient indeed -- if the KDP doesn't work the typed command is impossible to send and execute. Or I am mistaken?

SilverRay
 

Thank All for assistance!
I guess that the proccess of resurrection will be very interesting but long...
The hand drawn scheematics from Tony Duell are very good source of information for research. First of all I wanna check the signals on KDP interface connector -- maybe the input signals from CPU board do not come in to KDP module.

Could you tell me what kind of ROM type was used on boards? It's an OTP ROM or reprogrammable? And is it possible to replace it to UVEEPROM?

Roman.

 

 

Roman,

The ROM chips are masked ROM and a HP  proprietary type.  On www.hp9825.com you can read about the history of the 9825 and its components.

-Rik

-Rik




On Mon, Aug 26, 2019 at 9:26 AM +0200, <silverray.russia@...> wrote:

Thank All for assistance!
I guess that the proccess of resurrection will be very interesting but long...
The hand drawn scheematics from Tony Duell are very good source of information for research. First of all I wanna check the signals on KDP interface connector -- maybe the input signals from CPU board do not come in to KDP module.

Could you tell me what kind of ROM type was used on boards? It's an OTP ROM or reprogrammable? And is it possible to replace it to UVEEPROM?

Roman.

 

SilverRay
 

Thank You, Rik!