So if you look back in
post #71 you’ll read about problems with the power supply umbilicals that came with the console. The frame of my console is made up of three “buckets”, two 16-slot bucket and one 12-slot bucket, and there is one multi-rail power supply per bucket. To summarize, the guy I bought it from obtained the console from a university auction. The console had the power supplies but no umbilicals when he bought it…misplaced when the console was decommissioned at the university broadcast studios. So he made some up. He had a hard time finding the right components, mainly because I think he didn’t know where to look. So the cable was the wrong type (too heavy a gauge, too stiff, overall OD too big), and the result was the solder joints to the connectors had poor integrity (they were coming loose), and it wasn’t possible to fit the locking hoods for the Tuchel connectors at the console backplane…the seller said he couldn’t find the hoods anyway. So it was just two 30-pin Tuchel connector housings held in place by the friction of the pins and sockets, fighting the pressure of three large stiff cables. I was always either reaching back there and pushing them back in as they slowly tried to back out, or finding some crazy non-conductive way to wedge and hold them in place. And the circular connectors at the power supplies? He was never able to source the locking rings, and one of the three connectors was also missing the strain relief. So in all truth, the umbilicals were *super* sketchy, not really safe…not long after I got the console in January of 2019 I acquired all the parts and materials to make a proper set of umbilicals, but I hadn’t put the parts to use…until last year. But there was a related parallel project also summarized in post #71 regarding…power supplies.
There are basically two generations of Studer 928s…an early and a late. Production of the 928 started in the mid-1990s and the transition to the second generation happened sometime in the year 2000 I believe. There were no changes to control features or cosmetics, it was all PCB refinements, some changes to some components for better noise floor and isolation with the talkback system among other things…and changes to some of the ground scheme…all of those changes were detailed in TSBs for retrofitting to the 1st generation consoles. The other major thing that happened was a complete change in the power supplies. Studer designed and manufactured the power supply backplane PCB assembly on both versions of the power supply, which includes the low voltage logic power supply, but for both early and late generation versions the rest of the guts were farmed out. And so there are no technical documents included in the Studer documentation outside of the backplane PCB. I originally thought the complete tech docs for the later generation power supply were included with the Studer docs, but they are not. There’s a note that refers the reader to manufacturer of the guts for the tech docs. Well the guts of the early generation supply, as I noted in post #17, were made by a company called Delaire, Inc, which was acquired and dissolved by another company about 20 years ago…no tech docs to be had there anywhere. I tried. And I don’t like that because if repairs are needed in the future it’s more difficult without the docs. And both versions of the power supply are switching instead of linear type, which means they are more complex to troubleshoot and work on. At least for a guy like me. So at some point I learned the later generation supply, rather than a monolithic PCB housing the +/-15V and +48V power rails like the early generation Delaire supply, was made up of high quality TDK Lambda modular power supplies…high-performance, highly-regarded off-the-shelf power modules…so cool. You can still find modules NOS for cheap…I figured it would be easy to get ahold of schematics, layouts, parts lists, etc. for the Lambda modules, and I had an opportunity to buy a set of three later generation supplies…quieter cooling, nicer chassis, higher power, easier to service…more on-par with the console. So I bought them. I then discovered it wasn’t as easy as I thought to get the tech docs…but after some reasonable and congenial persistence with TDK, and signing a hold-harmless agreement with a number of conditions, they provided the docs. So I now have a full set of tech docs for the later generation supplies. I also found a pair of the 15V modules online NOS for $60 shipped for the pair. So I have backup. The later generation supplies have a slightly different pinout at the supply end, so it was a decision to make if I was going to build up the new umbilicals with the pinout for the supplies that came with my console, or use the set of later generation supplies and build the cables up for those supplies. I chose to do the latter. But before that I had a couple things to do first.
The set of later generation supplies I got originally powered a 928 operated by an Israeli broadcast company…television I think. What I know for sure is it was not in a clean environment. Here is what each of them looked like inside:
So I did my thing and cleaned them out, pulling the Lambda modules out, vacuum, brush, air duster, microfiber cloth and window cleaner where needed…got them all to look like this:
By comparison here’s the inside of one of the early generation Delaire power supplies…monolithic PCB…not so easy to remove, certainly not replace…if for some reason a Lambda module goes down, with a motorized screwdriver and one bit I could have the module swapped and back in service in less than 5 minutes easy…but here’s the inside of the Delaire supply:
It’s not a “bad” supply…powerful, clean, etc. It’s just nothing like the later generation.
Then the next thing I wanted to do was replace the fans. They were all working, but when executing a cold startup one of them would do a little whale song for a few seconds on, so that told me it was time to replace all of them. I purchased some fans that, on paper, where quieter than the original fans, with comparable airflow. I bought them, installed them, and it turned out they were louder…it all depends on the measurement parameters…the new fans may have produced less dB in sound pressure level, but the nature of the sound, including a resonance with the three fans together, made them more intrusive with mixing. So, back to the drawing board…I ended up getting some Noctua fans…they are much better than the factory fans, with even some improved air flow…a win-win.
I then noticed something odd with the output and redundant supply link connectors on the backplane of one of the supplies…two of the 10 sockets each on each connector are supposed to be linked via the PCB to which they are mounted…sockets for the +/-15V rails. So there are supposed to be two sockets for each rail. On one of the three power supplies there were no traces between the two pairs of sockets on each connector…everything else looked the same between all three of the PCB assemblies, it’s just on one of the power supplies there were two sockets not connected to anything; only one socket per 15V power rail. I didn’t like that. It’s easy to access the back of the sockets on the backside of the PCB, so to bond each pair of sockets I found some solid core copper wire that fit just perfect in the back of the sockets, and fashioned some pieces into short links:
There. That’s better:
So with the three power supplies tested, cleaned and polished up, with new fans installed, and the one backplane PCB revised to match the others, it was time to make the umbilical cables.
