NIM rack with no supply? solution...

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Richard Hull
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NIM rack with no supply? solution...

Post by Richard Hull »

I have at least 3 NIM bins with no supply. They are fully wired back planes and ready to work, but without any source of power. Someone removed the supplies. Anyway, I paid $75 for all three bins at an HEAS flea market probably 10 years ago. I also picked up two 4 slot factory empty Tennelec NIM modules ready for the end user to fill with whatever they thought was pretty. Yes, this only leaves 8 slots available, but this is not to be used as a full NIM system....Read on.....

As the AC 120 volt buss is wired to the plug plane, I though, why not build all the supplies in this plugin and feed the buss from there? So I began the process. I would never use this cage for more than testing newly acquired modules and manufacture of my own modules. I have a gang of factory powered NIM bins for serious work.

As this bin is never to be heavily populated I figure 1 amp for the four main voltages will be more than enough. So I can use nice classic linear regulators. I found an old 120 vac transformer with the following ratings. 28v-18v-CT-18v-28v, 10v, 5v. Using the center tap as ground and using two AC bridge diodes to the 2 18v and 2 28v terminals I get a plus/minus 28X1.4134 = 39.5 DC and a plus/minus 18 x 1.414 = 25.4 vdc filtered supplies.

As most regulators will not go past 32 volts DC input, the 39.5 to the positive and negative regulator is a bust. the 25.4 volts is ok but to 12 volts half the power would end up as heat in the 12v regulators. Having 25, 120volt 2 amp screw driver adjust, lockable, variacs on-hand helps here. I bought them here at the Richmond hamfest on a huge metal plate 20 years ago for about $40.

Why not use one of these small variacs to lower the transformer's primary voltage to say from the 39.5 vdc out of the filter bridge voltages to 28 volts dc and the 25.4 volts to 15 volts dc? In this manner plus and minus 12 and 24 volt regulators could be used and run cool.

In the images below All is now working at the transformer level and NIM plug populated to a terminal strip. It took about 2 days of metal work, cutting, boring, tapping and filing to get here. All that needs to be done is to feed the adjusted, variac'd voltages to the regulated filtered supplies.
I hope to add a Arduino which will have four line LCD to read out the buss voltages.

Again, zero cost. I'm using junk that has been in the lab for years. Lotsa' labor though...

I will update this post as I move forward.

Richard Hull
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A forlorn empty unpowered NIM bin.  Its only use is to store unused NIM modules.  What to do?...
A forlorn empty unpowered NIM bin. Its only use is to store unused NIM modules. What to do?...
Here is what you do!  Build a buss fed insert power module.
Here is what you do! Build a buss fed insert power module.
Close up of the variac adjustable transformer and wiring so far completed.  It works!
Close up of the variac adjustable transformer and wiring so far completed. It works!
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.
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Dennis P Brown
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Re: NIM rack with no supply? solution...

Post by Dennis P Brown »

Impressive, this should be a FAQ!
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Richard Hull
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Re: NIM rack with no supply? solution...

Post by Richard Hull »

I finished the above supply with all voltages supplied to the buss as needed. I did place + and - 5 volts on the 6 volt buss respectively as I can use the TTL voltage in custom designed modules in future. Works like a charm. I tested several modules and they worked fine. I also repaired a defective but much treasured, ancient, Ortec nixie tube NIM counter/timer module I had been putting off repairing for several years in the newly powered bin.

All power regulation is linear LM series save for the +/-5 volts as I found a 3 amp dual supply switcher in a box full of switcher supplies I had laying around.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.
User avatar
Dennis P Brown
Posts: 2656
Joined: Sun May 20, 2012 10:46 am
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: NIM rack with no supply? solution...

Post by Dennis P Brown »

Great idea; I bought two NIM boxes (since both were unknowns - figure one would likely work or parts from one would fix the other.) In any case, turns out that after some minor repairs one of the units works fine but the other needed a x-former. So I picked up a 24 volt AC x-former and will use your basic approch (and two of those interesting voltage regulators that you flagged in another thread) and get the other NIM box to work. I feel I do need backups for everything ... Lt. Murphy has not been kind to me of late.

Well my vacuum system is going good ...uh, maybe I'm tempting Karma by saying that ... .
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Richard Hull
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Re: NIM rack with no supply? solution...

Post by Richard Hull »

I note in your long preamp post thread you have a Berkley Nuclear Digital delay generator module. I have one a bit more ornate but nearly identical. I see yours also needs those +/- 6volt inputs. That and one of my LRS modules really gobble up the 6 volt buss currents!! (hundreds of ma!)

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.
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