The DEC H7441 regulator is a relatively complex circuit using 2 x 555
timers, 2 x LM301 op-amps, 2 x transformers and 2 inductors
I am struggling to understand how it is meant to work and was hoping to
find a maintenance manual for it.
Could anyone with such a manual please help?
Alternatively is there another explanation of the operation of this or
similar types of circuits?
The circuit implements a switch mode supply.
One of the two 555 timers operates as an oscillator, the second I think
operates as a monoflop with the pulse length controlled via one of the
LM301s.
Overall the circuit seems very complex and while I understand parts of it,
other parts are mysterious.
In particular the top left section around Q1/Q2/Q3 and T1/T2 and E3 is most
confusing.
I did not find anything remotely similar in "The Art of Electronics" from
Horowitz & Winfield.
The H7441 schematics are available from here:
https://deramp.com/downloads/mfe_archive/011-Digital%20Equipment%20Corporat…
Thanks for any help or suggested reading material.
Tom
I bought this giant GCR tape drive on eBay five years ago,
http://www.bitsavers.org/pdf/fujitsu/_brochures/M244X_Brochure_1984.pdf
hoping to be able to use it to extract analog signals from 6250 BPI
tapes to feed into my decoding program.
https://github.com/LenShustek/readtape
I failed to figure out how to get the right signals out, and
eventually abandoned the project. I now need the space it takes, so
I'm offering it for free before consigning it to the landfill. It's
big (20" x 24" x 30" on the wheeled stand I built) and heavy (160
lbs) so I won't ship it. Pickup only, on the San Francisco peninsula.
Hi,
who knows details about the DEC VT36 Color Graphics Display Control System (
https://classic.technology/vt36-color-graphics-display-control-system/)?
I'm looking for manuals for the VT36 as well as for the associated
VAX-11/PROVUE or RSX-11/PROVUE software.
Anyone with personal experience with the VT36 and/or PROVUE?
Ulli
Good afternoon to all,
I am starting the process of selling off some of my vintage computer systems, so as to not burden anyone I leave behind.
The systems I list here are available for viewing in Bedford, NH, just west of Manchester, NH. Anyone interested can send me an e-mail message and we can set up an appointment for you to visit. Cash and Carry, of course, and reasonable offers will be considered.
Altair 8800c — $2500
I constructed this system early in 2019. I built the front panel and front panel interface boards, and soldered up the backplane. The rest of the boards were purchased assembled and tested. You can see the Altair 8800c story here: https://deramp.com/altair.html The system is fully tested and working, currently using virtual Altair disk drives via the Deramp application. Plenty of documentation.
Single 8 inch disk drive in a dual drive cabinet — $500
This physical disk drive has been paired with the Altair 8800c in the past. Works fine. I included will be an 8 inch disk drive that used to be in this cabinet until the power supply failed. I believe this drive can be repaired. Included will be another 8 inch drive that is the wrong form factor to fit into the cabinet. Purchased on eBay, untested.
Altair 680 — $2000
I acquired this system on eBay back at the end of 2018. It was not working, but a bit of troubleshooting discovered bad ram which was replaced. The least significant LED of the address display does not light, but I’ve tested that the proper signals are there. I simply did not want to risk changing out the LED. This system comes with the 4-slot riser, but the connectors are not yet soldered in. No add-in boards. Plenty of documentation.
Complete SWTPC 6800 clone system from Corsham Technologies — $400
I acquired this system from Bob at Corsham in the middle of 2018. It is the complete setup, with the full 64K ram and the virtual disk drives. Documentation available at Corsham Technologies: http://www.corshamtech.com <http://www.corshamtech.com/>
Northstar Horizon — $800
I purchased this system on eBay as a running system. From time to time I had problems with the top 8K ram on the Horizon 64K ram board. The 64k ram board has been replaced with a Compupro Ram 17 (or clone), works great, no problems. I will include the glitchy Horizon 64K ram board. FYI, a Deramp Virtual Sector Generator works great with this system, eliminating the need for hard sector diskettes. https://deramp.com/vsg.html
Thanks for listening!
smp
- - -
Stephen Pereira
Bedford, NH 03110
KB1SXE
Good afternoon to all,
I am starting the process of selling off some of my vintage computer systems, so as to not burden anyone I leave behind.
The systems I list here are available for viewing in Bedford, NH, just west of Manchester, NH. Anyone interested can send me an e-mail message and we can set up an appointment for you to visit. Cash and Carry, of course, and reasonable offers will be considered.
Altair 8800c — $2500
I constructed this system early in 2019. I built the front panel and front panel interface boards, and soldered up the backplane. The rest of the boards were purchased assembled and tested. You can see the Altair 8800c story here: https://deramp.com/altair.html The system is fully tested and working, currently using virtual Altair disk drives via the Deramp application. Plenty of documentation.
Single 8 inch disk drive in a dual drive cabinet — $500
This physical disk drive has been paired with the Altair 8800c in the past. Works fine. I included will be an 8 inch disk drive that used to be in this cabinet until the power supply failed. I believe this drive can be repaired. Included will be another 8 inch drive that is the wrong form factor to fit into the cabinet. Purchased on eBay, untested.
Altair 680 — $2000
I acquired this system on eBay back at the end of 2018. It was not working, but a bit of troubleshooting discovered bad ram which was replaced. The least significant LED of the address display does not light, but I’ve tested that the proper signals are there. I simply did not want to risk changing out the LED. This system comes with the 4-slot riser, but the connectors are not yet soldered in. No add-in boards. Plenty of documentation.
Complete SWTPC 6800 clone system from Corsham Technologies — $400
I acquired this system from Bob at Corsham in the middle of 2018. It is the complete setup, with the full 64K ram and the virtual disk drives. Documentation available at Corsham Technologies: http://www.corshamtech.com <http://www.corshamtech.com/>
Northstar Horizon — $800
I purchased this system on eBay as a running system. From time to time I had problems with the top 8K ram on the Horizon 64K ram board. The 64k ram board has been replaced with a Compupro Ram 17 (or clone), works great, no problems. I will include the glitchy Horizon 64K ram board. FYI, a Deramp Virtual Sector Generator works great with this system, eliminating the need for hard sector diskettes. https://deramp.com/vsg.html
Thanks for listening!
smp
- - -
Stephen Pereira
Bedford, NH 03110
KB1SXE
Group,
Ive got a tape here from what I believe to be a VM system. The
structure is unknown to me, although I can possibly take a stab at it.
Lots of data between tapemarks that seems to consist of a number of
records that start out something like this (translated from EBCIDC):
> 00000000 02 43 4d 53 46 30 30 30 31 31 32 30 35 31 31 32 |.CMSF00011205112|
> 00000010 34 37 30 37 36 30 31 32 32 32 31 31 30 31 31 31 |4707601222110111|
Another example:
> 00000000 02 43 4d 53 46 44 41 54 41 20 5f 4e 55 4c 4c 5f |.CMSFDATA _NULL_|
> 00000010 3b 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |; |
> 00000020 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
The data itself appears to be a bunch of 80 character card images.
I found a mention on the old yahoo groups H390-VM discussions, but no
clarity was ever shed on the subject.
Does anyone know about this tape format?
--Chuck
Seems like rather than going through MUSIC/SP it'd be easier to just fire
up VM/CE 1.2 (which is VM/370 r6) and use CMS TAPE (which is present)
directly from the CMS UI. You can probably attach the file you've got as a
tape device; not entirely sure Hercules will like the format, but it
wouldn't hurt to try.
Adam
