What prompted you to pull them in the first place? Just pull-and-replace "on general principles"?
Ok. I haven't had these go bad, and these days I back feed +5 and +12 from a current limited supply to see if anything is shorted/get the caps in line before powering everything up. Makes life a lot easier.
Just curious, how do you rack mount your BA11-M? I have one and haven’t figured out if it just is fastened through screws in the front or if it need some kind of support brackets in the rear of the box.
I've had to make several pairs of rear mounting brackets. I have an original set but it doesn't match the rack I have.I have one front-mounted above the PDP-11/10 at the moment (storage position) but it's not great. The drawings say there's supposed to be back-end support brackets. Neither my RKV11-D nor my regular QBus BA11-M have the support brackets. If someone has originals to measure/copy, I'd be interested in running some new ones; otherwise, I might see about drawing them up myself.
Make your own. I've seen what you can do.
Can you explain for me what “back feed” means?Ok. I haven't had these go bad, and these days I back feed +5 and +12 from a current limited supply to see if anything is shorted/get the caps in line before powering everything up. Makes life a lot easier.
If you decide to have them made I could use one pair. Only have one BA11-M box. But perhaps I can do one pair myself if it is just a 90 degree bend.Oh, sure, I could knock out one set on the sheet metal brake...but we also use a localish sheet metal shop that does good work at great prices and could make 25 pairs I just don't know if other people need it.
If you decide to have them made I could use one pair. Only have one BA11-M box. But perhaps I can do one pair myself if it is just a 90 degree bend.
It has to be quite long brackets since the BA11-M is so short. I was looking around for drawings for how it was supposed to be mounted in the cabinet but didn't find any. Could you share a link?
BTW. Do you have a picture of the small detail in the front that you screw the bezel into? Mine seem to be missing. Need to figure out how to manufacture those as well..
I usually backfeed switchers to test the crowbar and regulation circuitry. Current limited supply of course and without any input voltage on the PSU (except for the control circuitry). You have rectifiers directly of the transformer so not much current can flow in that direction anyhow. Usually just the filter and a crowbar there.
I especially like the "Typ both sides" comment in Note #1 (page 4 of 174) as well as a comment on Note #3. The SMPS side would probably be sufficient as a practical matter, however best to be safe :-}. Recessed flat-head machine bolts are critical as there's essentially zero clearance when extracting the backplane assembly or SMPS. I used flat aluminum sheet and bolted to the inner side-facing mounting points on the rear posts rather than extending all the way to the back and using a right-angle to reach the rear-facing mounting points.It's in the old PDP-11/03 printset:
The bracket is just noted as a customer-installed part and is not dimensioned, which is why I don't know exactly what size it's supposed to be
Diverging form the main topic, but ... I've heard of the use of blocking diodes to run SMPS in parallel but not seen much specific on this configuration. How do you keep the voltage-drop down across the blocking diodes? Does this configuration assume that there is remote voltage sensing on all linked SMPS so that they automatically compensate for the drop? Under normal conditions will the linked SMPS split the load more-or-less equally?Like everything, this may only work under certain circumstances. We use a lot of power supplies where they have output diodes (blocking diodes) so we can parallel them up (for redundancy purposes). In this case, this scenario would not work (the blocking diodes will be preventing the requisite current flow). However, if you already know this, you can put a red shorting link across the blocking diode and it will work. The wire colour is not important of course (!) it just stands out so you remember to remove it before using the power supply...
So there's some sort of side-band signalling between them then?Actually, we are just replacing our SMPS units with modern ones, and we have gone for a design where one runs with the full load and the other with no load. This just seems 'wrong' to me - but the SMPS units are designed for operation like this.
Which sort do you use to keep the drop down then?Most of the power supplies we use blocking diodes on are linear ...
Why "of course"?... are linear of course.