Restoring a PDP-11/40 and installing a RL-11

[PDP11GY]

I was getting involved by the computer museum in Munich to restore and repair
a PDP-11/40 with attached 2 x RK05 and a papertape reader/punch. It was getting
started to remove the much dust and all the dust-filters must be replaced with
standard parts From a local like DIY shop. That's very importend to prevent a
headcrash of the RK05 diskdrive. In the meantime I was able to power up the CPU
succesfully. My problem now is to install an additional RL-11 disk controller.
Enclosed, please finde the picture of the PDP-11/40 configuration. I have not
so much know-how with old PDP-11 unibus system but I can remember that there
was an issue concerning UNIBUS and modified UNIBUS. Have I to change some wire
on the UNIBUS backplane ? Concerning the attached picture, have you any
recommendation where I can install the RL-11, for example replacing one of
the M7800-YA 20mA serial line units by a Rl-11 disk controller.
Thanks and regards, Reinhard

 

[Lou - N2MIY]

Reinhard,

Although I too have no experience with an 11/40, I do have experience with my lowly 11/04. I have an RL11 in mine. You should be able to put the RL11 in any open hex-height SPC slot. However, since the RL11 is a DMA device, the NPR grant line on the backplane must not be chained on the SPC slot you are putting the card in. Check your desired slot and verify that CA1 is not bussed to CB1. If it is, then unwrap the jumper.

Lou

 

[PDP11GY]

Lou,

many thanks for this info , Reinhard

 

[billdeg]

I too have begun working on my pdp 11/40. In fact I plan to park it in my office at work so that I can play with it during the day when I need a break. Or will it be the other way round, do actual work when I need a break from the 11/40?

 

[RSX11M+]

...Think of it as a therapeutic activity either way Bill.

 

[marmotking]

11/40 Power Supply

11/40 Power Supply

I too have an 11/40 that I'd like to get restoring. Both of you have fired yours up. What precautions did you take first regarding the power supply? Did you replace or refurbish the capacitors, replace the supply with a modern one or just "let 'er rip" and see what happens? The power supply concern is what has been slowing me down in most of my restorations. Well, that and my day job. Perhaps trucking it to the office isn't such a bad idea!

 

[Lou - N2MIY]

If the 11/40 uses a number of smaller regulators, I suggest you get them all working one at a time, and put them under load and adjust the voltages. This is what I did when restoring the 11/04. I did not premptively change any capacitors. I only changed the parts I found broken. Only when all regulators were working properly did I then apply power to the backplane. Then I again checked all the voltages. Then I installed a minimal CPU configuration (enough to run proceessor maindecs) then checked the voltages again. Then I had confidence to plug in the rest of the options.

Lou

 

[billdeg]

If the 11/40 uses a number of smaller regulators, I suggest you get them all working one at a time, and put them under load and adjust the voltages. This is what I did when restoring the 11/04. I did not premptively change any capacitors. I only changed the parts I found broken. Only when all regulators were working properly did I then apply power to the backplane. Then I again checked all the voltages. Then I installed a minimal CPU configuration (enough to run proceessor maindecs) then checked the voltages again. Then I had confidence to plug in the rest of the options.

Lou

Pretty..much agree here. I am on the road for the next few days b ut when I return I will post the voltages I have for comparison purposes. I got some help last weekend to measure voltages...one person to probe one to watch the volt meter and write down results. Since then I have been away...