As some of you may be aware I am trying to find a fault in a Rainbow H7842
PSU. I am using Tony Duell's schematic from here
I have been testing the Control Module by using a bench PSU to supply 15VDC
to the input of the 7812 regulator (p2, PSU Sheet 1).
My diagnosis shows that the control module is shutting down the PWM (p6,
Control Module Sheet 2) because it is detecting an overcurrent in the -12V
side (E3d on Control Module sheet 1, although I have determined that it is
This seems to be because I measure a steady 0.6V on pin 6 of the transformer
(p4, PSU Sheet 3). I just can't imagine where it might be coming from as the
chopper won't be running. I had previously removed the transformer and there
are no shorts between the pin 5-pin 6 winding and any of the other pins on
the transformer. I checked all the DC outputs of the PSU when powering the
7812 from the bench, both on a working PSU and the non-working one. They are
all at zero except the -12V output on the non-working PSU, which is +0.6V.
But the voltage can't come out of nowhere.
I am stumped and would appreciate any suggestions.
I have an HP 2875B paper tape drive that I want to interface to. It has
a 50 pin block connector (using well under 1/2 the pins). The connector
manufacturer was Continental.
I have already discovered, the hard way, that it is not a winchester
connector - the pins on the 50 pin Winchester connector I just obtained
via ePay that otherwise fits are too small in diameter and won't make
contact. I *could* increase their diameter using solder - but -- yuck.
The other connectors of this sort I am familiar with that have the same
general overall size and pinout were made by AMP. Does any one know if
the AMP connectors and the Continental connectors would be compatible?
a friend of mine is currently working on a FPGA implementation of the
CERES-3 workstation (cpu-ns32k.net/TRIPUTER.html#Ceres).
He currently lacks of information of the RTC chip M3001 which was
manufactored by Swiss company Microelectronic-Marin.
Does anyone have a pointer to the datasheet ?
I learned today about Dave’s Old Computer website http://dunfield.classiccmp.org/ which is listed as a subdomain under classiccmp.org. I wasn’t aware of subdomain sites. Can any one list any other ones or is a list of sites available ?
I’ve been picking my way through a PDP-8/L restoration lately. I’ve found that everything in the machine is covered with a uniform layer of dark “soot” (enough to blacken your hands while working with it) which I would like to clean up. Perhaps the “soot” is actually from a decomposed air filter, as I don’t imagine this machine was operated in a smoky environment, and there is no smoke odor.
I usually use 99 IPA and cleanroom wipes for spot cleaning these sorts of things, but in this case there is so much of it that I feel that would just push the soot around rather than clean it off. I think some sort of actual rinse would be needed here.
I’ve been eying the dishwasher, for the subset of flip chips that that are just DIP logic, carbon comp resistors, and ceramic bypass caps, anyway. But I haven’t been brave enough to try that yet... Most of the logic here has date codes to ’68 or ’69, so I’m inclined to treat it gently. Any suggestions for approaches to clean this up?
Follow-on question: the majority of the legs on these old DIPs are showing what I’d call “moderate” corrosion — nothing looks like it is in danger of being eaten all the way through, but the process is underway. I was wondering if something like a light shellac or other inhibitor could be brushed over these pins to at least slow their inevitable demise?
I did purchase and build out one of Vince’s flip chip tester kits, and have found it super useful for this project. Of the large percentage modules that have test vectors supplied, most have tested fine. Three M216 flip-flop modules and one M113 nand module were flagged for repairs this way.
Advice appreciated, as always!
I read today that “Maximum PC” is no longer in print just in digital. Past
issues are available in digitized format but it’s not the same as reading a
magazine while in bed! Our hobby is changing. Well, progress must not be
I've checked bitsavers.org (Al does a great job!), and a number of
forums, but no luck finding schematics for my ADM31 that I am trying to
resurrect. The power supply has issues and I need to identify a blown
out resistor - the switching supply is a Boschert model 1001 date code
7943 Revision J.
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7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
Call (604)872-5757 (Pinballs, Jukes, Video Games)
"Old pinballers never die, they just flip out"
I think I know the answer to this, but just in case:
Is there a way to image ESDI disks other than to hook them up to their
usual host controller and use the host? E.g. for MFM, I'd grab the MFM