PDP11/24 New project

[Adriaan]

I started working on a PDP11/24, first thing to do is taking it apart, document all boards and take out the power supply.
Then I will open up the power supply, to check all the capacitors.

 

[fjalvingh]

Have a lot of fun! And I’m interested in the adventure

 

[Roland Huisman]

Cool! Another Dutch guy interested in dec pdp machines. Do you know anything about the history of this computer? And do you have more dec stuff?

Regards, Roland

 

[Adriaan]

@Roland Huisman This is not mine, I just work on equipement like this.
I'm a volonteer with the Studie Verzameling Universiteit Twente (Study Collection University of Twente, Netherlands) after working for 38 years as a technician in the field of biomedical engineering.
Was my day job more supporting students and phd's designing and building instrumentation using mostly micro electronics, for the Study Collection my field of expertise is old computers (check my content on this forum).

 

[Ed Groenenberg]

Which OS do you want to use / run on this machine?
I could lend you a RSX11M 4.8 distribution kit on 5 RL02's

 

[Adriaan]

Thank you for your kind offer, and maybe I'll get back to you on this matter later, but that might take some time since I only work at the shop 1 day each week..
The fact is, I have no idea nor knowledge about pdp11 software since I never worked on computers like this before, but I'm sure collegues at the study collection have and if I get the hardware going I'll ask them about this.
My field of expertise is hardware, not software but for a start I will try to use this:

PDP11GUI

Joomla! - dynamische Portal-Engine und Content-Management-System

www.retrocmp.com

 

[Jos Fries]

Nice to meet fellow countrymen on-line

I'm currently adding support for the PDP-11/24 to my PDP-11 simulator. (README and configuration files are in the pipeline). The simulator should be able to run the XXDP diagnostics. If you come to the point you can run XXDP diagnostics on your system it perhaps would be interesting to compare our results.

Success with your project!

 

[Roland Huisman]

@Roland Huisman This is not mine, I just work on equipement like this. I'm a volonteer with the Studie Verzameling Universiteit Twente (Study Collection University of Twente, Netherlands) after working for 38 years as a technician in the field of biomedical engineering. Was my day job more supporting students and phd's designing and building instrumentation using mostly micro electronics, for the Study Collection my field of expertise is old computers (check my content on this forum).

Interesting, I had the same kind of job at the University Groningen / UMCG for faculty pharmacy Now I'm working at Hogeschool Windesheim in Zwolle

I had some contact with Albert Schoute, you probably know him. I would love to visit the museum. Maybe some other dutch collectors want to visit it too

Regards, Roland

 

[Adriaan]

Hi Roland!
Sure you are most welcome!
Usually on wednesdays the collection is open for visitors, so just mail me and I make sure there are ppl to welcome you and show you around.
Here is our website:

Historic Study Collection EEMCS

Ps: I'm known as Ed Droog here

 

[Adriaan]

I’m using this Schematic and those Power supply connectors.



And I have no load connected to the power supply and I’m measuring strange voltages, is that because the lack of drawn current, or is the powersupply defect?

/PUZZLED/

 

[Roland Huisman]

Normally I test these things with a few car lamps on it. Not all old switching power supplies can work without any load on it. 24V bulbs are fine for every voltage, they are just a bit dim. The same is for a 12V bulb on the 5V.

Regards, Roland

 

[Adriaan]

I'm sure this is not a switching power supply.
And I even think that the connectors are not wired suggested by the picture

 

[m_thompson]

I'm sure this is not a switching power supply.
And I even think that the connectors are not wired suggested by the picture

The H777 +5V regulator looks like a crude switcher. The base of the pass transistors Q1 & Q2 is transformer coupled through T1. The current through T1 is controlled by Q6 which is controlled by the 555 timer E3. My guess is that the frequency of the 555 timer is controlled by the output of the op-amps E1 & E2.

The power supply in the PDP-11/05 has a similar design.

 

[Al Kossow]

I was just typing a reply. I agree with Mike

 

[daver2]

Yes, you need a bit of load on the voltage outputs.

As @Roland Huisman says, get yourself a few car lamps and have a disco!

Dave

 

[KM11]

FWIW, in my (rather limited) experience with a couple of these, an H777 works fine without a load and C5 (3900 uF @ 6 V) seems to be one of the more common failures.

 

[Roland Huisman]

Found my pictures from fixing my H777 in my 11/34. Caps caps caps...
And yes, it is a switcher, no doubt...

Post in thread 'DEC H780 Supply Caps'

Sep 27, 2024

I had the same with my low profile PDP11/34 and its H777 power supply. I never switch on these things before checking the mains circuit and power electronics. I ended up replacing all 14 electrolytic capacitors. But it was rewarding to have a working PDP11/34

• Roland Huisman

• 

Regards Roland

 

[Adriaan]

It runs!!


And now I have to figure out how to connect a terminal, using this:



And this:



Wish me luck

 

[Adriaan]

Connection established, checking RAM...