The H7842 PSU in my Rainbow failed yesterday. At first the machine just
powered down and there was a slight burning smell, I wasn't next to the
machine when this happened, so I didn't see or hear anything to tell me
where the problem might be. Not being sure if there was a short in the
machine or a problem in the PSU, I disconnected the fans, FDD and HDD and,
probably foolishly, I applied power again to see if the machine would work.
At this point there was a bang and a flash in the PSU.
On opening up the H7842 power supply I found that one of the transistors had
completely disintegrated. It looks to be the main switching transistor, here
is a picture of it:
https://rjarratt.files.wordpress.com/2022/11/img_20221120_165850.jpg. I
have identified a source for this transistor, but if anyone can suggest a
modern replacement that would be useful too. However, that is not my main
problem.
Given that before the transistor blew up there had clearly been another
failure somewhere else, I tried to find the original failure. There were no
obviously damaged parts, so I just probed around near the transistor for any
parts that were open circuit or short circuit. I found a diode connected to
the base of the transistor that appeared to be short circuit. So, I decided
to lift one end to check it. As I de-soldered one of the leads, the diode
broke in two. So clearly the diode was either damaged by the failure of the
transistor, or it was the cause of the failure. This is the diode:
https://rjarratt.files.wordpress.com/2022/11/img_20221120_165913.jpg.
I can't quite make out the markings on the diode to know what to replace it
with. I think it says "D610". Would that be the right designation? If so,
can anyone suggest a suitable replacement please?
The diode seems to connect an inductor to the base of the switching
transistor and the collector of the transistor is connected to a
transformer. Should I be looking for other failed parts? Not sure if the
diode failed first and then caused the transistor to fail? Or if something
else has failed which caused these parts to fail?
I do know that there are no shorts in the Rainbow itself, because I have a
spare PSU that still works fine in the same machine.
I blogged this here (it repeats most of that I have said above):
https://robs-old-computers.com/2022/11/20/dec-rainbow-h7842-power-supply-fai
lure/
Thanks
Rob
Hi and thanks for reading...
I am on the way to getting a small Q-Bus PDP11 up and running (I used to work on and repair then in the 1980s) and have some boards and a chassis now, but I cannot find any documentation for a couple of less common boards I have got - any help would be greatly appreciated - but I have looked in the usual places...
The main issues are:
Mentec M70 CPU - There are jumpers for serial port config and speed.. I have got a glossy leaflet for it but no jumper info..
GRC MLV11 - two serial lines and 128KB memory, but configured with switches - lots of switches...
Also is anyone has any old Q-Bus parts in the UK (particularly any Baydel parts) that are looking for a good home, I would love to hear from you!
Thanks for reading - any help or info much appreciated!
Regards,
Robin Downs
Email: rdowns(a)radix.co.uk<mailto:rdowns@radix.co.uk>
I'm still looking for a copy of CP/M for the Holmes Engineering VID-80
board for the TRS-80 Model III. A manual would be helpful, as well.
Mike Loewen mloewen(a)cpumagic.scol.pa.us
Old Technology http://q7.neurotica.com/Oldtech/
Wild Hare Computer Systems is pleased to announce the public beta
release of its Data General Nova and Eclipse emulator.
This emulator allows the full range of DG 16-bit Nova and Eclipse
computer software to run on Microsoft Windows and Linux platforms, and
will become a major part of Wild Hare's increased efforts to preserve
Data General's significant contributions to computer history.
The emulator combines portions of Wild Hare's commercial products with
the SimH project structure to create a single emulator for the 16-bit
Nova and Eclipse computers. The program supports a wide range of
features, including:
Processors:
unmapped Nova, SuperNova, Nova 1200, Nova 800, Nova 2, Nova 3, Nova 4
mapped Nova 840
mapped Nova 3/D
mapped Nova 4/X
Eclipse S/130
Eclipse S/140
Eclipse S/150
Eclipse S/120
Eclipse Desktop Generation Model 20 and Model 30
Peripherals:
TTI/TTO primary console (TeleType) input/output
RTC real-time clock
TTI1/TTO1 secondary console (TeleType) input/output
PTR paper tape reader
PTP paper tape punch
PLT plotter
LPT line printer
MTA mag tape unit
DSK fixed-head disks
DKP moving head disks
DEP Desktop Generation disks
DZP popular "Zebra" moving head disks
QTY 4060 "Quad" asynchronous multiplexers
ALM 4255 Asynchronous Line Multiplexers
Software:
Operating Systems
DOS Novas (first DOS written for Nova)
URDOS RDOS for Novas and Eclipses (in unmapped mode)
MRDOS RDOS for Mapped Nova 840
NRDOS RDOS for Mapped Nova 3/D and Nova 4/X
ZRDOS RDOS for Mapped Eclipses
MP/OS Nova 4
DG/RDOS Eclipses
AOS Eclipses
MP/AOS Eclipses
Languages
ASM (Assembler)
MAC (Macro Assembler)
ALGOL
DG/L
FORTRAN 4
FORTRAN 5
FORTRAN 77
Extended BASIC
Business BASIC
MP Pascal
SP Pascal
COBOL
Interactive COBOL (ICOBOL)
PL/1
RPG II
IDEA
INFOS II
CEO
Prior Data General knowledge is beneficial to using the emulator and
corresponding DG software. For convenience, Wild Hare has created
container files of pre-configured operating system environments and
their corresponding languages to minimize the time needed to enjoy the
full DG "experience".
This "beta-level" software release is intended to gather user feedback
to help guide future product development. Bug reports, comments,
suggestions, ridicule and giggles can be sent to
beta(a)WildHareComputers.com.
Further information is contained in the emulator beta release web page:
www.NovasAreForever.org/dgbeta
Bruce Ray
Wild Hare Computer Systems, Inc.
Denver, Colorado USA
bkr(a)WildHareComputers.com
...preserving the Data General legacy: www.NovasAreForever.org
I'm working on cleaning up a bit of battery leakage in a MicroVAX 3100
Model 10 and while it's apart I decided to look inside the PSU (an
H7822-00).
It's nice and clean inside with no bulging caps. What it does have is an
X2 capacitor, as shown here: https://photos.app.goo.gl/dpdqJ3tuGfsRDR3Y6.
It doesn't appear to be damaged and I can't see the word "RIFA" on it
anywhere but I can't see two of the sides because of other components
that get in the way.
So does anyone know for sure whether it is a RIFA brand or not, or do I
have to desolder it to be sure?
Thanks
Antonio
--
Antonio Carlini
antonio(a)acarlini.com
I have a 5100 and 5106 both with a working tape unit.
But the tape unit in my 5110 is not working, and I believe it is the
read/write head. The REWIND command works, but the MARK command does not
(ERR 3).
I took the Tape Card from the 5110 and swapped it into the 5106, and the
5106 continued to work (and 5110 then had same result, ERR 3). This tells
me the issue isn't any electronics in the Tape Card electronics (such as
bad IC's).
Swapping the electronics card is easy. But I haven't yet tried taking the
read/write head from the 5106 and putting it into 5110's tape unit (they
both use all the same components) -- it's not that difficult, but I don't
really want to put a working 5106 at more risk of becoming non-working.
Hence, that's why I'm asking around first if anyone might happen to have
one of these NORTRONICS or a suitable substitute to try. For example, it
may be the same kind of read/write head used in some reel-to-reel systems
of that era (early/mid 1970s).
The various numbers on the read/write head are as follows:
NORTRONICS
PN 1608752
C584980
269
24256
I have measurements and photos of what I'm looking for at the bottom of
this link:
https://voidstar.blog/ibm-5100-internal-tape-and-5106/
The head is about a 15mm x 20mm, with a 26mm ground extension on one side
for mounting.
A few months ago I contacted Nortronics. They had some stock that was
close, but not this exact pin out (4-pins on one side, 6-pins on the other;
not sure which is read vs write). I think all the ones they had were
4-pin/4-pin.
I've also tried different brand tapes, DC6150 vs DC600A (which all of them
do work in the 5100, but not the 5110).
-Steve
Any Apple alumni (Al?) with documentation on AWACS registers? I'm trying to
figure out why the BeOS AWACS sound driver works on some Power Mac 6500s and
TAMs but not others (but works fine on 6400s and everything previously).
Yes, I'm aware that Be considered the 6500 "Unsupported but Compatible" and it
boots fine on my 6500/275 but is totally mute. An instrumented driver in debug
mode yielded little insight. The driver thinks it's initialized everything
correctly and reports no errors. I wonder if there's something about the SRS
sound enhancement that's different on later 6500s/TAMs.
--
------------------------------------ personal: http://www.cameronkaiser.com/ --
Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser(a)floodgap.com
-- God made the integers; all else is the work of Man. -- Kronecker -----------
Hello,
Does anyone have a REASONABLY priced source for 6" x 14" anti-static bags
with zip lock tops? I've looked on eBay and Amazon with no luck. I have also
looked online and have only found heat sealable bags. I am not sure if it is
the sizing which the issue or what as other size bags seems to be easy to
find. TIA!
-Ali
