22 Aug
2015
22 Aug
'15
2 p.m.
I have nothing to do with this...I just noticed it on alt.sys.pdp11 and
figured that I'd pass it along.
TTFN - Guy
Hi all,
I have a PDP-11/55 for sale (Ottawa, Ontario, Canada). Bids open
until 2015 09 15, buyer to arrange shipping, I will have it wrapped
and ready to go.
Please visit:
www.krten.com/~rk/museum/index.html
For pictures, detailed inventory and contact info. Sealed bids via
eamil please. Winner will be notified 2015 09 16, machine will be
ready to ship same day. Must be shipped / picked up no later than
2015 10 09.
Sold AS-IS / where is, untested, unpowered since received.
Comes with H960 rack and 2 side panels.
Cheers,
-RK
--
Robert Krten
Visit me at http://www.ironkrten.com
23 Aug
23 Aug
7:39 p.m.
New subject: SA-800/801 saga continues / schematic request
Anyone out there have:
1) The Schematic for the newer SA-800/SA-701 board part number 25229.1 ?
(It might also go by 25228 or 27121). The SA-800 maintenance manual on
bitsavers from Feb 78 describes the original discrete board (such as I
have on my Altos in the SA-800s) and an LSI-based board which is
apparently earlier than the one in my SA-801 drives - the parts layout
does not match the layout on these newer boards.
2) A source for Shugart ASICs, particularly 16270-1 ?
And the saga to date:
As you may recall, one SA-800 on my Altos was misbehaving. I decided to
swap in an SA-801 I had from a Data Systems DSD-440 (a two drive cabinet
with 2xSA-801, power supply, and controller intended to talk, I think to
a Q-Bus controller...). Anyway, that blew the fuse on my Altos on the
second track of a floppy test, but (IIRC), the Altos was not damaged.
Call this drive "X".
I then decided to swap in the second SA-801 from the DSD-440. That also
blew the fuse on the Altos, and this time the power supply was damaged.
Call this drive "Y" (The Altos power supply has since been repaired -
that saga was recorded earlier. ;) ).
Replacing the bearings on the problem SA-800 did not help appreciably
with its "wobble" problem. (The spindle shaft is still a possibility, I
suppose, along with a damaged clamping frame).
Today's news:
Having gotten my 20+ year-old home-built floppy supply all fixed up and
fused and load tested, I was still a little hesitant to apply it to
either of these drives X and Y. So, I disconnected X and Y, and checked
out the power supply on the Data Systems DSD-440 Except that the +5V is
low, at 4.5V, the supplies seemed OK, in particular, the +24V was fine.
So I tested the +24V under load, and it held 24V to 3A (and more, I am
sure).
When I connect up drive "X", the +24V series pass transistor gets very
warm and the +24V drops to around +8.5V (regardless of whether or not
the stepper motor leads are connected). On the circuit board, a
Shugart ASIC 16270-1 gets quite hot, and is clearly dead. This chip is
labeled WR/CHNL in an SA-850 schematic, and is listed in the Shugart
spares catalog as "IC, Write Channel". It is indeed fed from the +24V
line on pin 15, and connects to the erase and center tap terminals on
the head. [I have not measured the head to see if it was damaged - nope
not]. I expect that if I pull that chip, the board will not overload
the +24V supply.
When I connect up drive "Y", the +24V series pass transistor on the
power supply gets very hot, but nothing on the circuit board gets hot at
all, and the +24V drops to 0. The board measures as a dead short with
an ohmmeter (even "X" shows *some* resistance). The stepper driver IC,
a standard part UNL2074 (quad darlington power transistors in a 14-pin
DIP no less) has a suspicious bump on its head, so I will probably start
by pulling it and see what changes (I hope that is it), and if that is
the issue, I will also check the voltage clamping diodes in the output
circuit and the stepper windings and the 7404 that drives it to make
sure it wasn't collateral damage. I expect regardless of the cause, the
dead short will be not *too* difficult to find and correct.
So, now the saga of the Altos power supply is fully understood. It was
the second drive from the DSD-440 that actually killed it. Fortunately,
the DSD-440 power supply was apparently robust enough to put up with the
abuse.
With a little luck, I can make one whole SA-801 out of the pair
(focusing on "Y" since I have no source for that 16270 ASIC), and then
use the mechanism of "X" with the board from the Altos SA-800 to make a
working SA-800 for the Altos.
JRJ
24 Aug
24 Aug
6:21 p.m.
New subject: SA-800/801 saga continues / schematic request
On 8/23/2015 9:39 PM, Jay Jaeger wrote:
When I connect up drive "X", the +24V series pass transistor gets very
warm and the +24V drops to around +8.5V (regardless of whether or not
the stepper motor leads are connected). On the circuit board, a
Shugart ASIC 16270-1 gets quite hot, and is clearly dead. This chip is
labeled WR/CHNL in an SA-850 schematic, and is listed in the Shugart
spares catalog as "IC, Write Channel". It is indeed fed from the +24V
line on pin 15, and connects to the erase and center tap terminals on
the head. [I have not measured the head to see if it was damaged - nope
not]. I expect that if I pull that chip, the board will not overload
the +24V supply.
When I connect up drive "Y", the +24V series pass transistor on the
power supply gets very hot, but nothing on the circuit board gets hot at
all, and the +24V drops to 0. The board measures as a dead short with
an ohmmeter (even "X" shows *some* resistance). The stepper driver IC,
a standard part UNL2074 (quad darlington power transistors in a 14-pin
DIP no less) has a suspicious bump on its head, so I will probably start
by pulling it and see what changes (I hope that is it), and if that is
the issue, I will also check the voltage clamping diodes in the output
circuit and the stepper windings and the 7404 that drives it to make
sure it wasn't collateral damage. I expect regardless of the cause, the
dead short will be not *too* difficult to find and correct.
So, now the saga of the Altos power supply is fully understood. It was
the second drive from the DSD-440 that actually killed it. Fortunately,
the DSD-440 power supply was apparently robust enough to put up with the
abuse.
With a little luck, I can make one whole SA-801 out of the pair
(focusing on "Y" since I have no source for that 16270 ASIC), and then
use the mechanism of "X" with the board from the Altos SA-800 to make a
working SA-800 for the Altos.
JRJ
Some GOOD NEWS for a change. I pulled the UNL2074 from drive "Y", and
the short remained. The next most obvious component for a dead short was
actually a little 4.7uf filter capacitor - and indeed that was the
culprit. The board from drive "X" donated its corresponding capacitor,
as the odds of me fixing that board are not very good, owing to the
16270-1 Shugart ASIC. Returned the UNL2074 back into the board on "Y".
Erased (with a tape eraser for open reel tapes back in the 60's),
formatted a floppy and tested, including interchange with the original
second drive in the Altos, and all is well.
Tomorrow I get to test the 2nd 801 (drive "X") mechanism with the board
from drive "Y". I expect it will be fine as
well. Then I can swap out
the electronics from the original first Altos drive onto
drive "Y" (they
are plug compatible that way) to get another working drive.
BTW, the replacement FD-1791B-02 (I actually tested to) did help with
the hung floppy controller after errors syndrome - it happened
significantly less often that with a FD-1791B-01 .
JRJ
25 Aug
25 Aug
7:34 p.m.
New subject: SA-800/801 saga continues / schematic request
On 8/24/2015 8:21 PM, Jay Jaeger wrote:
On 8/23/2015 9:39 PM, Jay Jaeger wrote:
Both SA-801 mechanisms tested fine (with the board from "Y"). So now
the mechanism from "X" and the board from the original are in the Altos,
as the second drive, and doing fine. Drive "Y" was restored to its
original condition. The original SA-800 had its fancy new bearings
swapped back for the originals, and has the bad board from "X". - so
three drives to make two good ones. Drive "Y" and the bad drive will
take up residence in the Data Systems chassis for now.
All four of my good drives (the original Altos SA-800, the SA-801 drive
"Y" and the "hybrid fix" drive and my Siemens FD 100-8 (which says it
is
an FDD 120-8 on its serial number plate) also tested fine.
Whew.
JRJ
When I connect up drive "X", the +24V series pass transistor gets very
warm and the +24V drops to around +8.5V (regardless of whether or not
the stepper motor leads are connected). On the circuit board, a
Shugart ASIC 16270-1 gets quite hot, and is clearly dead. This chip is
labeled WR/CHNL in an SA-850 schematic, and is listed in the Shugart
spares catalog as "IC, Write Channel". It is indeed fed from the +24V
line on pin 15, and connects to the erase and center tap terminals on
the head. [I have not measured the head to see if it was damaged - nope
not]. I expect that if I pull that chip, the board will not overload
the +24V supply.
When I connect up drive "Y", the +24V series pass transistor on the
power supply gets very hot, but nothing on the circuit board gets hot at
all, and the +24V drops to 0. The board measures as a dead short with
an ohmmeter (even "X" shows *some* resistance). The stepper driver IC,
a standard part UNL2074 (quad darlington power transistors in a 14-pin
DIP no less) has a suspicious bump on its head, so I will probably start
by pulling it and see what changes (I hope that is it), and if that is
the issue, I will also check the voltage clamping diodes in the output
circuit and the stepper windings and the 7404 that drives it to make
sure it wasn't collateral damage. I expect regardless of the cause, the
dead short will be not *too* difficult to find and correct.
So, now the saga of the Altos power supply is fully understood. It was
the second drive from the DSD-440 that actually killed it. Fortunately,
the DSD-440 power supply was apparently robust enough to put up with the
abuse.
With a little luck, I can make one whole SA-801 out of the pair
(focusing on "Y" since I have no source for that 16270 ASIC), and then
use the mechanism of "X" with the board from the Altos SA-800 to make a
working SA-800 for the Altos.
JRJ
Some GOOD NEWS for a change. I pulled the UNL2074 from drive "Y", and
the short remained. The next most obvious component for a dead short was
actually a little 4.7uf filter capacitor - and indeed that was the
culprit. The board from drive "X" donated its corresponding capacitor,
as the odds of me fixing that board are not very good, owing to the
16270-1 Shugart ASIC. Returned the UNL2074 back into the board on "Y".
Erased (with a tape eraser for open reel tapes back in the 60's),
formatted a floppy and tested, including interchange with the original
second drive in the Altos, and all is well.
Tomorrow I get to test the 2nd 801 (drive "X") mechanism with the board
from drive "Y". I expect it will be fine as well. Then I can swap out
the electronics from the original first Altos drive onto drive "Y" (they
are plug compatible that way) to get another working drive.
BTW, the replacement FD-1791B-02 (I actually tested to) did help with
the hung floppy controller after errors syndrome - it happened
significantly less often that with a FD-1791B-01 .
JRJ
26 Aug
26 Aug
7:58 a.m.
New subject: SA-800/801 saga continues / schematic request
As long as you keep believing
in the power of loving, you will surely achieve
the victory that is yours alone.
- BubbleGum Crisis, lyrics from the song, ?Victory?, per
http://www.animelyrics.com/anime/bgc/bgcvtory.htm
(but if you go there, you see a whole lot of pop-up ads?.)
On Aug 25, 2015, at 9:34 PM, Jay Jaeger <cube1 at charter.net> wrote:
Both SA-801 mechanisms tested fine (with the board
from "Y"). So now
the mechanism from "X" and the board from the original are in the Altos,
as the second drive, and doing fine. Drive "Y" was restored to its
original condition. The original SA-800 had its fancy new bearings
swapped back for the originals, and has the bad board from "X". - so
three drives to make two good ones.
8:39 a.m.
New subject: SA-800/801 saga continues / schematic request
As long as you keep believing
in the power of loving, you will surely achieve
the victory that is yours alone.
- BubbleGum Crisis, lyrics from the song, ?Victory?, per
http://www.animelyrics.com/anime> /bgc/bgcvtory.htm
(but if you go there, you see a whole lot of
pop-up ads?.)
Completely off-topic, but this reminds me of something we sang at school almost
40 years ago. I have no idea what it came from, or who wrote it.
From memory, and thus with mistakes :
'Now
perhaps you'll see the moral of our tale
Never be scared to make a start for fear that you may fail
Life is full of puzzles, this we suggest to you
It's not so much how clever you are are as what you try to do'
And as sonebody who is not very clever I have lived by that ever since. My method of
computer
repair, etc, is not to be scared, just to have a go. It's worked so far.
-tony
3190
days inactive
3194
days old
5 comments
4 participants
participants (4)
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ard＠p850ug1.demon.co.uk -
cube1＠charter.net -
ggs＠shiresoft.com -
mtapley＠swri.edu