I am trying to resolve a problem with a H7842 PSU from a DEC Rainbow. The AC OK output is not being asserted. I am looking at Tony Duell's schematic https://bitsavers.org/pdf/dec/rainbow/duell_schematics/psu.pdf and specifically at the Power OK circuit.
I am using a test load of 1R on the 5V output and 6R on the 12V output, which is within the spec of the PSU. I see that under load the 5V output is only 4.4V, so I suppose it is to be expected that AC OK is not asserted. If I (briefly!) remove the load from just the 5V output, the 5V output is 5.27V, but the AC OK output is still not asserted.
Using Tony's schematic, I looked at the input to the inductor on the secondary side (sheet marked "H7842 PSU Sheet 3") and it looks like this: https://rjarratt.wordpress.com/wp-content/uploads/2025/10/h7842-5v-secondar… I can't tell if that is correct or not. If I remove the 5V load the peaks narrow but are slightly higher.
However, the puzzling thing is the 5V Pulse signal, it doesn't pulse, it is a steady 32V. I see that the 12V Pulse signal *does* pulse. The name would suggest it is supposed to pulse and its inputs do pulse as shown in the trace pictured above. I don't see how it is possible for 5V Pulse to be at a steady 32V, even if the diode or resistor that create the 5V Pulse signal was somehow bad. I guess this non-pulsing might be the problem, but I don't really know what to check here, I have lifted the diode and tested it, it seems fine.
Does anyone have any suggestions please?
Incidentally, for those who helped me with my Olivetti M24, I had already reassembled it and got this PSU out to look at next before receiving further suggestions on the M24. Once I have the H7842 sorted out I will go back to the M24 again.
Thanks
Rob
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Jeff Brace
VCF Fundraising Manager
Going through my endless piles of *stuff* I have come across some
manuals that might already be scanned, might not. So anyone know if
these are archived somewhere?
* TSX Plus: 4 RX02 floppies. Version 6.40, 6.5
o Along with release notes for 6.40 dated Jan 16, 1989
* SDC-RXV31 floppy controller manual: Sigma information systems, 1984
* DHV11 Technnical manual
* DLV11 users guide ek-dlv11J-ug-001
* RA80 disk drive service manual (booklet, tough to scan)
* RLV12 disk controller user's guide
* MSC4806 Expansion memory board User's manual (10-29-1982)
o MSC is Monilithis Systems Corporation
o I think I have some of these boards
* Computer Products: Instruction manual, Model 307 Clock Calendar
* GTSC: Instruction manual, Model 304 Serial IO board
* Fortran 11 reference manual (unsure of title)
Thanks!
Chris
I was poking around eBay and up came a listing for a DEC "mini exchange", DFMSA. What is that? The name doesn't sound familiar. It looks like a box with a bunch of DB25 connectors on the back, but that doesn't help much.
paul
A little while ago I was contacted by a person working for a big swedish
company that asked if I was interested in saving a HP 2116B from being
scrapped. On Monday I was able to pick up not just the HP 2116 but also
some other HP21xx series machines that all were destined to be scrapped
next week.
When looking deeper into the HP 2116 I discovered that it was missing two
non-optional boards. Without these boards the machine will not even power
up. The boards missing are the power failure board ( 02116-6175 or
12588-6001) and the memory module decoder board ( 02116-6300 or 02116-6274
).
It is probably possible to create some kind of replacement boards but it
would be really nice to have the original boards in such a nice machine.
Is there anyone that has these boards that want to sell or trade them for
something?
/Mattis
Anyone in the 603 area code interested in this (below)? I received an
inquiry through kennettclassic.com but we don't need it. If interested
contact me through kennettclassic.com/conatct.cfm or by private email. I
don't know the person, but it looks like they want to sell, not donate.
Bill
"... *Hello, I have an old HP 1611A logic state analyzer from the 80's that
was previously owned by Parker Brothers, no doubt used to test out chips
for their electronic games and toys. I was wondering if you might know
where I might be able to sell it or if you have any interest in it
yourselves. It has all the documentation, including a leather bag intended
to hold all the manuals. It powers on and still works. While I don't have
any chips to test it with, I have seen it function and work with chips when
I purchased it. *..."
Hi all!
I noticed that while the Emulex SC03-B1 manual is on Bitsavers, the
instructions for how to patch and use this board on a 22 bit Q Bus
system are not. In the manual it says to "Write emulex".
Fortunately I did 40 years ago and I have the "Emulex Disk Capacity
Patches to DEC PDP-11 Operating Systems" manual which is now scanned and
online at https://www.crystel.com/dec/sc03
Emulex document ID is PD9951002 Rev A, March 1983. Covers Rsx11M 3.2,
4.0, RSTS/E, and M+ versions at that time.
Every page is scanned as a 300 DPI TIFF image, and there is a PDF
version of the whole manual as well.
Apparently they use the RH70 Unibus driver (which supports 22 bit
without the unibus map) and then change a few bits to make it work on Q
Bus.
Enjoy and bitsavers owner please stick this in your archives as well.
Chris
