Update and Pictures: It's been a hell of a day! HP 9845/2x i8008/Sage II/2x Grid/TI Silent 700/Alpha Micro
16 May
2005
16 May
'05
7:33 p.m.
I finally had a chance to look at some of the stuff today. I was wrong
about the i8008 comnputers. They each have SIXTEEN 1101 RAMs on them and
eight 1702 EPROMs. One of the machines has some non-Intel brand 1101
memories that are dated 7114!!!! (See the yellow arrow at
<http://www.classiccmp.org/hp/i8008-1/board.jpg> ). I haven't had a chance
to look them up yet but those two white ceramic parts are marked uA3656 or
something like that. Anyway the red arrow is pointing to the i8008 CPU. The
yellow arrow is pointing to the column with the 1101 RAMs and the blue
arrow is pointing to the column of 1702 EPROMs. More pictures of this
machine at <http://www.classiccmp.org/hp/i8008-1> and pitures of the second
machine at <http://www.classiccmp.org/hp/i8008-2>. The circuit board
appears to be the same in both machines despite the very different cases.
I didn't get a chance to get pictures of the TI Silent 700 yet but I did
open it up and check it out. It's a model 733KSR and IT'S SWEET! It's
mounted in the transit case with spring loaded clips and it's in excellant
condition and still has the interface cable attached. It also works
perfectly :-) According to the labels on the case, it is a part of the same
system(s) as the i8008 computers.
The Visual terminal also works perfectly :-)
I checked the HP 9845B and it's absolutely dead. The fan doesn't even
run. However the fault should be easy enough to locate. It's odd though,
their is no sticker listing the options and it has a hand written serial
number on the SN label.
I didn't get to the Sage or the other stuff yet. I HOPE to do that
tomorrow.
Joe
17 May
17 May
4:08 p.m.
New subject: Update and Pictures: It's been a hell of a day! HP 9845/2x
I checked the HP 9845B and it's absolutely
dead. The fan doesn't even
run. However the fault should be easy enough to locate. It's odd though,
Be warned that thr 9845 PSU is _very_ complicated, even worse than the
PDP11/44 PSU (!).
Anyway, the input circuit isn't too bad. There's a mains-frequency
transformer (the laminated-core one on the metal bracket) that has 2
primary windings. They're in series for 230V, in paralell for 115V. The
output of this transformer provides the startup supply. There's also the
conventional bridge/doubler circuit with the 2 massive capacitors in the
middle of the PSU mainboard to supply 350V DC to the choppers
Anyway, the fans are connected in parallel with the startup transformer
primaries. So on 115V they're essentially connected across the mains.
There is a fuse at the back (10A IIRC for 115V) that I'd check first,
otherwise look at the wiring on the back panel, the barrier strip on the
side of the PSU casing (be warned that the screws that hold the cover
over that go into loose nuts inside the PSU casing, so pull the PSU
module first), etc. This is one of the not-too-complicated parts of the
machine.
-tony
18 May
18 May
6:37 a.m.
New subject: Update and Pictures: It's been a hell of a day! HP 9845/2x
Hello,
the PSU's of the 9845 are always a pain.
Esp. for the 9845s produced in Germany once, at first all capacitors
have to been checked before applying power. Several of them are of an
epoxy based package and like to produce a failure of the PSU (I killed
two PSUs up to now and I'm not daring to power on the third).
As you seem to know the PSU quite well, do you have schematics?
Andreas
I checked
the HP 9845B and it's absolutely dead. The fan doesn't even
run. However the fault should be easy enough to locate. It's odd though,
Be warned that thr 9845 PSU is _very_ complicated, even worse than the
PDP11/44 PSU (!).
Anyway, the input circuit isn't too bad. There's a mains-frequency
transformer (the laminated-core one on the metal bracket) that has 2
primary windings. They're in series for 230V, in paralell for 115V. The
output of this transformer provides the startup supply. There's also the
conventional bridge/doubler circuit with the 2 massive capacitors in the
middle of the PSU mainboard to supply 350V DC to the choppers
Anyway, the fans are connected in parallel with the startup transformer
primaries. So on 115V they're essentially connected across the mains.
There is a fuse at the back (10A IIRC for 115V) that I'd check first,
otherwise look at the wiring on the back panel, the barrier strip on the
side of the PSU casing (be warned that the screws that hold the cover
over that go into loose nuts inside the PSU casing, so pull the PSU
module first), etc. This is one of the not-too-complicated parts of the
machine.
4:52 p.m.
New subject: Update and Pictures: It's been a hell of a day! HP 9845/2x
Hello,
the PSU's of the 9845 are always a pain.
Esp. for the 9845s produced in Germany once, at first all capacitors
Argh! I think my 9845 is a German one....
have to been checked before applying power. Several of
them are of an
epoxy based package and like to produce a failure of the PSU (I killed
Which capacitors are these? Are you thinking of the snubber networks on
the main chopper transformers -- the 2 large non-electrolytic caps on the
mainboard?
two PSUs up to now and I'm not daring to power on
the third).
>> I checked the HP 9845B and it's absolutely dead. The fan doesn't even
>>run. However the fault should be easy enough to locate. It's odd though,
>>
>>
>
>Be warned that thr 9845 PSU is _very_ complicated, even worse than the
>PDP11/44 PSU (!).
Perhaps I should clarify that although it's complicated, it's not too
unfriendly to work on.
The little PCB at the front contains the 4 chopper transistors (2
push-pull chopper circuits). These, of course, are on the mains side of
the PSU, but the little pot-core transformers on this board isolate the
base drive signals. Therefore the 4 chopper drive transistors (on one of
the output PCBs) and the entire control circuit (on the complicated PCB
at the back) are isolated from the mains.
Moreover, there's a nice, simple, linear startup supply for the control
circuit.
So checking waveforms and debugging the most complicated part of the
supply shouldn't be too unpleasant.
7159
days inactive
7160
days old
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