Best I can tell the diodes are Passivated Silicon, Bead diodes, of which there are three flavors.
On EEVBlog it was suggested that these were Sintered Glass Bead diodes.
I do believe they are still in okay working condition. My thought process is that they are probably quite noisy. Installing a modern type of diode would also I believe dramatically reduce generation of heat.
It is nice that a Power Supply board is laid out in a way that you can access all of the components. Nothing like some of the small 5v switching supplies in which most of the components are shoved close together.
I downloaded the 1977 GE Semiconductor manual, but it’s not easy to find it without a part number.
Back when I was in my early 20’s a neighbor whom was an Engineer at Xerox in the power supply division at 701 South Aviation Blvd. El Segundo, gave me a bundle of those soft bound Motorola reference manuals, some RCA TTL manuals, Zener Diode reference etc. The books sat on my shelf for many years until I ran out of room. I moved them to my shed which at the time was safe from the weather. After years of storage many of them were damaged from dampness etc.
In the last 10 years I realized I should have taken better care of them. I realize they are almost worth their weight in gold.
I was able to find a few of those books used and purchased them at (luckily) reasonable prices.
I regret that and a home brew vacuum tube combo preamplifier/amplifier stereo unit. I was forced to part with. My father referred to it as “junk taking up space”.
It contained 4 6V6GTs, 2 12AU7As, and a 5U4 Rectifier. The front end was early GE (germanium I suppose) transistors. They were of the metal oval shaped black painted metal can type with the pinched evacuation nipples.
From: Joshua Rice <Rice43(a)btinternet.com>
Sent: Thursday, October 13, 2022 9:44 AM
To: D. Resor <organlists1(a)sonic.net>
Subject: Re: [cctalk] Re: Xerox 820II U07 Power Supply magic smoke....
On Oct 13, 2022, at 2:32 PM, D. Resor <organlists1(a)sonic.net <mailto:email@example.com> > wrote:
A couple reasons I'd like to have a circuit diagram is to know what the RIFA capacitors purpose are. The other is, a couple of the electrolytic capacitor are double covered with what appears to be rubbery heat shrink tubing, therefore I cannot read what their value are.
Generally, though not always, these are simply “coupling” capacitors, that are used to limit RF interference from appearing on the mains supply. Most, though not all, PSUs will work fine without them. Some others won’t function right as they’re used for generating clock signals from the mains supply. I believe that some PDP-11 supplies use them for this purpose.
One of these two electrolytic capacitor appears to have a dried substance around the top. The over-pressure venting cuts in the top of these two capacitors are not split. At this point I cannot tell if it is dried electrolyte, cement to hold the sleeve on, or possibly paper.
Sometimes it’s just glue , but better safe than sorry, Cut off the sleeving (it’s used for electrically isolating the cap from other components), get the rating off of it, and replace with like. Probably worth heatshrinking them again as well.
Seems someone was in hurry on the day this PS was tested. I cannot make out date, is it 1983?
Looks like ‘85
What type are the diodes, their rating etc.? I seem to remember this type with a black band were rated at 3 amps, but that's all I remember.
The TO-3 transistor/regulator has no P/N silkscreened on it.
Having a circuit diagram helps to cover many bases. Apparently it's an Astec AA12070.
It’s unlikely that these would have failed. If they have, i would (as another person suggested,) just replace the unit with a modern Meanwell supply. At that point, it’s probably not worth the time and effort to replace all the parts.
Placed the PS board back in the garage to continue airing out! 😉
Don’t fear the RIFA, but keep the windows open, just in case.
Where might I find a schematic diagram for the Xerox U07 8" FDD,HDD
expansion cabinet for the 820II, and/or the 105P80450 power supply?
The Xerox Professional Computer Technical Reference Manual I downloaded from
bitsavers.org doesn't seem to have those particular schematic diagrams.
For your enjoyment the part which smoked.
I certainly am glad I have the lid off while testing. Unfortunately these
capacitors which appear to be film type were hidden from view.
The fuse didn't blow, but that .22uf 250v capacitor certainly stunk up the
house. It smelled like burnt popcorn, plastic and the bottom of a coffee
pot which has boiled dry, yech!
I know that if I had pulled the power supply board first I might have seen
the physical cracks in these boxed capacitors.
Wasn't it Marc V. that said in one of his videos, you don't need to shotgun
them all! Oi, lol
It's when things like this happen that I most always worry about not going
over vintage equipment fine tooth comb.
anybody has some GCC or any other tool chain for the above?
Or some pointers, which was the last version of the GCC tool chain which
supported the i860, and would be still compile-able on this days tools/OS's?
Thanks in advance!
> Date: Wed, 12 Oct 2022 15:54:33 -0500
> From: Steve Lewis <lewissa78(a)gmail.com>
> Subject: [cctalk] datapoint 2200 programming
> Does anyone know how the 1970/1971 original Datapoint 2200 was programmed?
> It had tapes containing terminal programs to access different types of
> systems. And the instruction set was said to be similar what became the
> 8008. But how were these terminal programs created and how were the tapes
> written? Were they under emulators on larger systems, like a PDP-10?
> Were there any tapes that had something like a machine code editor and
> tape-write routines? I assume no kind of ROM was built into the system
> (unless it had a built in machine code editor, and routines to write that
> content to a tape?) Was a version of BASIC ever built for the 8008 that
> ran on a Datapoint 2200 or similar system?
While in college, 1973 to 77, I had a part-time job where one of the things we did was use a Datapoint 1100 dual cassette model to act as a data entry terminal for a database system running on a Cascade 80 minicomputer.
I did the Datapoint programming, which was to query the db over an async line for a form template, allow the operator to fill in the form, then upon entry, send the data back. The db would provide the next form to display. A rudimentary state machine at several levels.
The Datapoint came with a Cassette Tape operating system, called CTOS I believe. You booted it up, and the second drive was your working drive. The Programmer’s manual referenced shows you the commands. There was an simple tape file system, Editor, Assembler, Debugger, and a library of subroutines for common access to the system’s I/O.
I remember very little about the details of working on it, but I had no problems getting the data entry system working. You just sat down and started programming it. The instruction set was the model for the 8008, but it preceded the popularity and availability of that chip.
My boss did some real inspired work on the Cascade Data side. He managed to insert the database access code into high memory of the system, and hook into the native OS. So we could use the system normally, but the database serviced the terminal in the background. I did other Cascade programming in assembly, I wrote my own instruction card for the system.
In my senior year, the facility switched over to using IBM System 3 equipment, and I got to work with RPG, 8-inch diskettes, and 96-column cards.
Sent from Mail for Windows
Been working on my 386i's, all the power supplies are smoked, so I
bought a totally burned out one, gutted it, and connected a PC/AT power
supply up to the card edge. Sure enough it works, and I now know that it
needs +5, +12, -5, -12 (for the ISA bus) and a 5 volt "supply ready"
signal as well.
Also found the serial console interface works, and realized I should
update the 386i FAQ with this information. So what would be the best way
to do that in this day and age?
Trying to tar a directory and transfer it to my AT&T 7300 (SVR2 unix).
Tar -tf works fine on the Mac OSX, but when I copy it over the Unix (not
gnu) tar gives me a:
Tar: blocksize = 20
directory checksum error
When I try to tar -tf the file. Which usually means the block size is off.
Any way I can check to see what the block size is on a modern system
(like a Mac)? tar -tvf doesn't seem to tell me.
> Yes. I have a description of my recreation of the Gazelle on my web site, as well as notes on restoring the one for
Very interesting! Reading through it all now. I notice you use Tarbell
disk controller... difficult to use the SCP DiskMaster? I don't find many
references to systems running it. It supports SD/DD 5.25/8... I had
planned to go 5.25"
At 09:16 AM 10/11/2022, Sellam Abraham via cctalk wrote:
>Yes, eBay charges the seller the same commission on shipping as it does for
>the item price, and the taxes charged to the buyer as well.
A year or so ago, I tried to figure out how to even see a detailed
breakdown of eBay's costs and commissions on several servers I'd sold
for a client. I gave up. I'm convinced it is purposefully opaque.
You get what you get.
Is there a 3D print gcode for the hardware that connects a PDP8a front
panel to the chassis?
Is there anyone who has a spare clips/clamps hardware to attach a PDP 8a
console to the chassis?
I picked up the donated PDP 8a mentioned earlier on this list, I got it up
and running. I need to track down the hardware to attach the front panel
to the chassis. I do have spares of the hardware that attaches the ON/OFF
panel to the chassis.
AS with all "free" donations it's the final mile that costs the big $$
At this point I have achieved the SCP CPU card, a CPU support card and a
Disk Master card. So hopefully all I need is some kind of 16 bit RAM board
and a 4 slot S100 backplane and I can boot 86-DOS.
I have started to read through the documentation on the hardware.
Has anyone else been down this road and built a system to run this?
: Ethan O'Toole