Hi David, Just did a spectrograph on the sound coming out of the terminal at the end of the video. Ive sent you an email with it. the horizontal frequency is way too low at 7688hz. it should be at about 15khz ish.. My hearing is poor due to too many live concerts so i use Spectroid app on my android phone to hear things i cant hear. I would check the horizontal ....
Used an ADM terminal in college to write 6800 assembly code and it eventually went to a teletype that could also produce punched tape. Then after college was able to use a TRS-80 Model-1 computer.
I just bought one of these and am waiting for it to arrive. My first thought would be remove the CRT and CRT power board from the equation. Can you pull a composite video signal from the logic board and send it to a known-good external video display? You might feel better spending time trying to fix an old analog CRT if you could see that the underlying brain of the terminal was already working, or if you should focus on that instead.
Interesting video. I also have an ADM 31 that was in need of repair but is working now. If you need anything let me know, perhaps comparing a working one with yours might lead to a solution. Best of luck to you. Those terminals, especially the ADM-31, are becoming more rare.
Hey Lorne, Thanks for the lovely comment! I'm sorry I missed this from a few days ago, I haven't been able to repair mine so knowing what a working one is like and comparing would be REALLY interesting. I have an email address listed in my profile, if you'd be kind enough to email me I'd like to discuss this more and perhaps make a part 2 video with our findings? Take care and thank you for your support!
@@lorneallaire4486 Thank you! I did read your email and was blown away by your offer of support, it's nice to know there are people out there so willing to help, it really means a lot actually. I've had a lot going on personally over the last 6 months so it was nice to read. I'll reply shortly, but yes! It would be great to compare notes. take care
Thanks for dropping a comment, such a shame I just haven't been able to fix it, don't quite have the right skills to get this one over the line at the moment.
@@TheRetroBristolian The terminal will wait for another day. Or perhaps another person with the right skills. What is important is that it is not bound for the landfill.
I just came across your video. I notice it was from a year ago but no updates since then. What happened with the restoration? Please try to jump pins 2 and 3 on the com port and type on the keyboard and see if any characters are displayed. Look to see if there are brightness or sub brightness adjustments on the video board and try to adjust thrm
So, The update was, I took it to work, managed to create a separate circuit to power the CRT stand alone and generate the signals needed to make it energise, managed to get a green dot on the screen. in terms of the terminal, there was a comment from a fellow TH-camr who kindly made some videos to show how a working terminal works - which is very useful and I will revisit this one day. At the moment personally I have a lot going on, my grans house has finally sold this week, she passed in 2022 so it's been a long and stressful road, I now have 5 days to clear the house and swap keys so that will be taking up my time. after that I'm trying to build a room for all my projects and work, but having issues with planning so it's delayed. Thanks for stopping by with a comment.
Have you made any progress on the terminal. I have one of these still in use on radio automation equipment. Make sure the contrast and brightness pots are ok and turned up. The solder connections on the pots can get lose. Also jump pins 2&3 on the serial connector this allows you to type and locally display. This will verify that the cursor is not hidden off the screen. As the pots were cleaned it’s possible the data is there just off screen due to size and position adjustments on monitor board. The high pitch whine noise is a good indicator that it’s possible out of adjustment with sizes causing yoke to deflect beam off screen. Some high pitch sounds are normal from those CRT’s. Mine has given issues with the bright and contrast pot on main board from getting dirty over years and causes blank screen issue. Try simple things first. Sounds as if the terminal is working. If you have a serial cable connect and set rates same and use a pc with terminal emulator and send and receive from keys this will check the communication. Might need null modem adapter or custom build cable
It's back in storage at the moment. your points are very interesting though for sure, when I get back to it it's all things to try. do you have an ADM-31? or a similar terminal? it would be helpful to see a video of one powering up, and being used - Thanks for stopping by and offering help/support.
Here is the second video I done on sync pulses measurements from the SMC CRT controller IC. th-cam.com/video/37neAAYg7xY/w-d-xo.htmlsi=WDL4_TMgUr2Xr9xs
@@rick601a I've watched both videos and have to say the information is fantastic! So much for me to unpick and test, very interesting how early your terminal is and how it has the different PSU and monitor. When I get more time I will do a follow up video next year and of course drop credit to you when fingers crossed I make some progress.
One day, sadly I haven't had time or gained any useful knowledge to move forward with this project. I have proven the CRT and driver board seem to be OK and it looks to be the terminal board not giving out the right sync pulse for some reason.
mine is even olderr than yours.whish we had a group that would attract more ADM-31 owners. I am in need of one of the roms. I can find YOUR roms but not for my older rev-1 board. what I need is rom labled 129867-3.
Thanks for the comment. It's a great shame, they seem to be forgotten to time don't they. can a full set of updated ROMs be put in the older rev-1 board?
Why won't it discharge it? there is a resistor between the probe and the ground point and it can be used to discharge as well as measure the high voltage.
@@TheRetroBristolian also if the crt has an anode capacitance of around 500pF and the high voltage is 25kV then it would take just over a second to discharge with a 1 gigaohm probe.
Hi David, Just did a spectrograph on the sound coming out of the terminal at the end of the video. Ive sent you an email with it. the horizontal frequency is way too low at 7688hz. it should be at about 15khz ish.. My hearing is poor due to too many live concerts so i use Spectroid app on my android phone to hear things i cant hear. I would check the horizontal ....
Used an ADM terminal in college to write 6800 assembly code and it eventually went to a teletype that could also produce punched tape. Then after college was able to use a TRS-80 Model-1 computer.
I just bought one of these and am waiting for it to arrive. My first thought would be remove the CRT and CRT power board from the equation. Can you pull a composite video signal from the logic board and send it to a known-good external video display? You might feel better spending time trying to fix an old analog CRT if you could see that the underlying brain of the terminal was already working, or if you should focus on that instead.
Interesting video. I also have an ADM 31 that was in need of repair but is working now. If you need anything let me know, perhaps comparing a working one with yours might lead to a solution. Best of luck to you. Those terminals, especially the ADM-31, are becoming more rare.
Hey Lorne, Thanks for the lovely comment! I'm sorry I missed this from a few days ago, I haven't been able to repair mine so knowing what a working one is like and comparing would be REALLY interesting. I have an email address listed in my profile, if you'd be kind enough to email me I'd like to discuss this more and perhaps make a part 2 video with our findings? Take care and thank you for your support!
@@TheRetroBristolian I emailed you but you never replied. Please reach out if you still need my help.
@@lorneallaire4486 Thank you! I did read your email and was blown away by your offer of support, it's nice to know there are people out there so willing to help, it really means a lot actually. I've had a lot going on personally over the last 6 months so it was nice to read. I'll reply shortly, but yes! It would be great to compare notes. take care
A beautiful machine.
Thanks for dropping a comment, such a shame I just haven't been able to fix it, don't quite have the right skills to get this one over the line at the moment.
@@TheRetroBristolian The terminal will wait for another day. Or perhaps another person with the right skills. What is important is that it is not bound for the landfill.
I just came across your video. I notice it was from a year ago but no updates since then. What happened with the restoration?
Please try to jump pins 2 and 3 on the com port and type on the keyboard and see if any characters are displayed.
Look to see if there are brightness or sub brightness adjustments on the video board and try to adjust thrm
So, The update was, I took it to work, managed to create a separate circuit to power the CRT stand alone and generate the signals needed to make it energise, managed to get a green dot on the screen. in terms of the terminal, there was a comment from a fellow TH-camr who kindly made some videos to show how a working terminal works - which is very useful and I will revisit this one day.
At the moment personally I have a lot going on, my grans house has finally sold this week, she passed in 2022 so it's been a long and stressful road, I now have 5 days to clear the house and swap keys so that will be taking up my time. after that I'm trying to build a room for all my projects and work, but having issues with planning so it's delayed. Thanks for stopping by with a comment.
The keyboard looks crunchy. What switches does it use?
Have you made any progress on the terminal. I have one of these still in use on radio automation equipment. Make sure the contrast and brightness pots are ok and turned up. The solder connections on the pots can get lose. Also jump pins 2&3 on the serial connector this allows you to type and locally display. This will verify that the cursor is not hidden off the screen. As the pots were cleaned it’s possible the data is there just off screen due to size and position adjustments on monitor board. The high pitch whine noise is a good indicator that it’s possible out of adjustment with sizes causing yoke to deflect beam off screen. Some high pitch sounds are normal from those CRT’s. Mine has given issues with the bright and contrast pot on main board from getting dirty over years and causes blank screen issue. Try simple things first. Sounds as if the terminal is working. If you have a serial cable connect and set rates same and use a pc with terminal emulator and send and receive from keys this will check the communication. Might need null modem adapter or custom build cable
It's back in storage at the moment. your points are very interesting though for sure, when I get back to it it's all things to try. do you have an ADM-31? or a similar terminal? it would be helpful to see a video of one powering up, and being used - Thanks for stopping by and offering help/support.
@@TheRetroBristolian I will do a video of my terminal and a few test results as well that you can try.
Here is a video of my ADM31 th-cam.com/video/i4m1EwCxV-Y/w-d-xo.htmlsi=OtRvgYO-hCx_kOEZ
Here is the second video I done on sync pulses measurements from the SMC CRT controller IC. th-cam.com/video/37neAAYg7xY/w-d-xo.htmlsi=WDL4_TMgUr2Xr9xs
@@rick601a I've watched both videos and have to say the information is fantastic! So much for me to unpick and test, very interesting how early your terminal is and how it has the different PSU and monitor. When I get more time I will do a follow up video next year and of course drop credit to you when fingers crossed I make some progress.
Part 2?
One day, sadly I haven't had time or gained any useful knowledge to move forward with this project. I have proven the CRT and driver board seem to be OK and it looks to be the terminal board not giving out the right sync pulse for some reason.
So 90% is power supply for h-sync and v-sync is down
mine is even olderr than yours.whish we had a group that would attract more ADM-31 owners. I am in need of one of the roms. I can find YOUR roms but not for my older rev-1 board. what I need is rom labled 129867-3.
Thanks for the comment. It's a great shame, they seem to be forgotten to time don't they. can a full set of updated ROMs be put in the older rev-1 board?
That probe is really not gonna discharge the crt if it had voltage. The probe really is just a voltage divider of REALLY high resistance
Why won't it discharge it? there is a resistor between the probe and the ground point and it can be used to discharge as well as measure the high voltage.
Well it will but you wont see or hear it discharge. But it might be actually better to discharge for a second or two because of dielectric absorption.
@@TheRetroBristolian also if the crt has an anode capacitance of around 500pF and the high voltage is 25kV then it would take just over a second to discharge with a 1 gigaohm probe.
Looks like your direction coils onna crt have no current
More things for me to look into when I get it back out of storage. Thanks for dropping by with a comment