12 May
2013
12 May
'13
5:41 p.m.
Hi guys,
A few of you might be aware of my UNIX PC emulator, FreeBee (also known
as 3b1emu) and the issues regarding it not being able to boot UNIX
properly... and my complaints about the quality of the PAL equations in
the technical reference.
Well, an anonymous donor very kindly freight-forwarded a UNIX PC to me.
Sadly the original sender didn't pack it very well... The machine was
sent unwrapped with only a few foam peanuts in the box. It arrived with
a "resealed by USPS" sticker, a "resealed by Parcelforce" sticker and
the keyboard hanging out of one edge of the box.
Here's what's missing or wrecked -- does anyone have any of the
following 3B1 or 7300 parts spare?
Keyboard -
* Top cover, several broken screw posts in the top cover. These look
difficult to re-glue...
* F8, HELP UP/DN, NEXT/3, ROLL DOWN/0 and RIGHT CURSOR/. keycaps.
Monitor -
* Monitor stand (tilt/swivel section) smashed to pieces. Probably need
a new lower monitor case from a scrap 3B1 to fix this :(
I'd also rather like to find out what sort of connector was used for the
power connector at the PSU side - the cable and connector are badly
burned (apparently a common problem).
On a lighter note, the machine is fairly well specified - with a P5.1
motherboard, two 67MB hard drives (both Miniscribe 3085 units) and some
unusual I/O cards. One is probably a modem (three RJ11 sockets), another
has a 37-way female D-sub and the third I can't remember off hand.
I still need to formulate a plan to power it up - I'd rather not use an
ATX PSU, and the original switcher is 115V only. The 20A current
requirement on 5V means none of my bench PSUs are suitable...
It also wants +12V (which I expected - the HDDs and line drivers need
that) and -12V (probably for RS232 and the modem)...
Much thinking needed, I dare say...
Thanks,
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
13 May
13 May
2:16 p.m.
Keyboard -
* Top cover, several broken screw posts in the top cover. These look
difficult to re-glue...
I have an HP keyboard where the origianl fixing posts were moslyu broekn
off (not from bad shipping, either). I eneded up puttign the casing in
the mill and milling off the remains of the old poosts, which were then
replaced by brass ones screwed in place. There are some extra screws o
nthe top face, but the the result is stronger than the original. and the
only parts to be modified wewre those where the posts had broekn off, so
if I ever get goo examples of the case parts I can make it 100% original.
I still need to formulate a plan to power it up -
I'd rather not use an
ATX PSU, and the original switcher is 115V only. The 20A current
So? Give it 115V. I would be very suprised if it cared abotu the
difference between 50Hz and 60Hz.
I find a 110V step-down transofrmer to be essential in the workshop.For
thigns that don't need one side of the mains to be close to ground
potential (which is 99.(% of stuff) I uses a power tool transofrmer
(55-0-55V with an adapter cable. That;s good to 3kVA. I have other
smaller transforms ( a few hundred VA) with totally floating outputs.
-tony
5:05 p.m.
On 13/05/13 22:16, Tony Duell wrote:
So? Give it 115V. I would be very suprised if it cared
abotu the
difference between 50Hz and 60Hz.
I find a 110V step-down transofrmer to be essential in the workshop.For
thigns that don't need one side of the mains to be close to ground
potential (which is 99.(% of stuff) I uses a power tool transofrmer
(55-0-55V with an adapter cable. That;s good to 3kVA. I have other
smaller transforms ( a few hundred VA) with totally floating outputs.
The problem is that it has a 400W power supply... the largest
autotransformer I can get locally is a rather nasty 300VA cheapie. :(
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
11 p.m.
Quoting Philip Pemberton <classiccmp at philpem.me.uk>:
The problem is that it has a 400W power supply... the
largest
autotransformer I can get locally is a rather nasty 300VA cheapie. :(
Did you try to post on comp.sys.3b1?
Probably somebody there would know how to convert the 110v to a 220v
power supply ...
14 May
14 May
1:11 a.m.
On 05/13/2013 11:00 PM, emu at e-bbes.com wrote:
Quoting Philip Pemberton <classiccmp at
philpem.me.uk>:
Why not just use one of those transformers made for portable power tools
that Tony keeps mentioning? Isn't it 110VAC out?--and probably much
more than 400VA if it's made for running a portable saw.
--Chuck
The problem is that it has a 400W power supply...
the largest
autotransformer I can get locally is a rather nasty 300VA cheapie. :(
Did you try to post on comp.sys.3b1?
Probably somebody there would know how to convert the 110v to a 220v
power supply ...
1:44 p.m.
Quoting Philip Pemberton <classiccmp at philpem.me.uk>:
How easy thst is depends on the design of the input stage of the PSU.
PSUs that are designed to run at either mains votlage with simple-ish
conversions run the chopper circuti from 350V or so. For 110V mains,
that's got by votlage-doubling the mains, for 230V mains by simply
full-wave (bridge) rectifying it. In amny cases, 4 diodes are fitted all
the time, it's just a matter of cuttign a link to convert from 115V input
to 230V input.
However, I have seen a few SMPSUs that were designed for 110V mains only.
They ran the chopper fof a 170V (or so) supply, obtained by full-wave
rectifying the 110V mains input. THere is no easy way to get that votlage
straight from 230V mains.
The qucij way to see if a conversion is going to be easy is to look at
the mains smoothing capacitors. If there ar 2, of equal value, with the
-ve side of one linked to the +ve side of the other, then it's very
likely to be a votlage doubler circuit and thus easy to convert.
Perhaps the OP can check this in his PSU.
-tony
The problem is that it has a 400W power supply...
the largest
autotransformer I can get locally is a rather nasty 300VA cheapie. :(
Did you try to post on comp.sys.3b1?
Probably somebody there would know how to convert the 110v to a 220v
power supply ...
16 May
16 May
8:04 a.m.
On 14/05/13 21:44, Tony Duell wrote:
How easy thst is depends on the design of the input
stage of the PSU.
PSUs that are designed to run at either mains votlage with simple-ish
conversions run the chopper circuti from 350V or so. For 110V mains,
that's got by votlage-doubling the mains, for 230V mains by simply
full-wave (bridge) rectifying it. In amny cases, 4 diodes are fitted all
the time, it's just a matter of cuttign a link to convert from 115V input
to 230V input.
This one seems to be a voltage doubler...
* AC enters via two wires soldered to the PCB
* AC enters a potted black Elmaco 511473-1K (AC line filter?). This has
L/N/E in and L/N out.
The rest of the circuit looks like this:
RT1
_____
L o---[_____]--*--|>|---------------*------------>
| | +
+--|<|-----+ --- C1
| ---
| | _____ R2
N o-----------------------|---------*------[_____]-----> To hybrid
| | +
| --- C2
| ---
| |
+---------*----------->
RT1 appears to be a MOV; there are also some resistors from C1+ to AC
neutral and the C1/C2 midpoint to some form of hybrid circuit.
Converting to a bridge rectifier would seem to involve the addition of
two diodes and the cutting of the link between AC neutral and the C1/C2
midpoint.
The question is, why does the hybrid have a midpoint reference via R2
(yel/vio/ora/gold -- 47K 5%, looks like about 0.5W to 1W rated)?
At this point, I think a power tool isolation transformer would be a
better option, but I have to replace the badly burned 18-pin 3.96mm
(0.156in) header on the power supply *and* the motherboard-side
connector first. It seems to be an ITW-Pancon Mascon connector:
http://www.iobium.com/wpc_idc_connectors.htm
http://itwpancon.com/Products/mascon_index.htm
I'm toying with replacing it with a Molex 0.156 KK, but I need to find
the crimp housings, crimps and headers. I may have to put an 8-way and a
10-way end-to-end...
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
12:15 p.m.
On 14/05/13 21:44, Tony Duell wrote:
Almost certainl a lien filter.
How easy thst is depends on the design of the
input stage of the PSU.
PSUs that are designed to run at either mains votlage with simple-ish
conversions run the chopper circuti from 350V or so. For 110V mains,
that's got by votlage-doubling the mains, for 230V mains by simply
full-wave (bridge) rectifying it. In amny cases, 4 diodes are fitted all
the time, it's just a matter of cuttign a link to convert from 115V input
to 230V input.
This one seems to be a voltage doubler...
* AC enters via two wires soldered to the PCB
* AC enters a potted black Elmaco 511473-1K (AC line filter?). This has
L/N/E in and L/N out.
The rest of the circuit looks like this:
RT1
_____
L o---[_____]--*--|>|---------------*------------>
| | +
+--|<|-----+ --- C1
| ---
| | _____ R2
N o-----------------------|---------*------[_____]-----> To hybrid
| | +
| --- C2
| ---
| |
+---------*----------->
RT1 appears to be a MOV; there are also some resistors from C1+ to AC
Much more likely to be a thermistor. It will limit the inrush current at
swithc-on until it has warmed up. Quiute common in SMPSUs.
neutral and the C1/C2 midpoint to some form of hybrid
circuit.
Converting to a bridge rectifier would seem to involve the addition of
two diodes and the cutting of the link between AC neutral and the C1/C2
midpoint.
And adding a couple of resisotrs across C1 and C2 to equalise the
votlages across them.
The question is, why does the hybrid have a midpoint reference via R2
(yel/vio/ora/gold -- 47K 5%, looks like about 0.5W to 1W rated)?
Mayeb prt of the starup circuit. Taking it from the 170V rather than 350V
rail means you don't need such a big dropping resistor ?
At this point, I think a power tool isolation transformer would be a
better option, but I have to replace the badly burned 18-pin 3.96mm
It's a useful thing to have anyway.
-tony
5:42 p.m.
New subject: Tony's typos - Re: AT&T 3B1 / 7300 UNIX PC parts needed
On 16/05/13 3:15 PM, Tony Duell wrote:
One of your better typos. A lot of people could use this device, I bet.
--Toby
On 14/05/13 21:44, Tony Duell wrote:
Almost certainl a lien filter.
How easy thst is depends on the design of the
input stage of the PSU.
PSUs that are designed to run at either mains votlage with simple-ish
conversions run the chopper circuti from 350V or so. For 110V mains,
that's got by votlage-doubling the mains, for 230V mains by simply
full-wave (bridge) rectifying it. In amny cases, 4 diodes are fitted all
the time, it's just a matter of cuttign a link to convert from 115V input
to 230V input.
This one seems to be a voltage doubler...
* AC enters via two wires soldered to the PCB
* AC enters a potted black Elmaco 511473-1K (AC line filter?). This has
L/N/E in and L/N out.
14 May
14 May
1:27 p.m.
On 13/05/13 22:16, Tony Duell wrote:
I thought you lived round the corner from the Farnell trade counter or
something...
Anyway, I didnt say 'autotransformer'. In fact I don't like runnign 110V
stuff from autotransformers. If the live and neutral gets swapped in the
230V circuit, the insulation of the 110V unit has to stand 230V. It
should manage that, but....
I would use a power tool transformer. That's an isolating transformer
with the secondary (55-0-55V centre-tapped to earth). Very common
(althugh not cheap), the common oen is rated at soemthign liek 2500VA
continuous, 3000VA for 30 minutes.
Just aobut any company that seels industrail portabel power tools will
sell them. Even places like Screwfix probably have them.
I have some 110V power tools (electric drill, etc) that I use if I am
working outside. It's not required that I do this, since I am a hobbyist,
but I prefer to be safe than sorry. Of coruse the transformer gets used
for running US stuff wehn it;'s not in user for power tools.
I am actually suprised you don't ahve such a transformer...
-tony
So? Give it 115V. I would be very suprised if it
cared abotu the
difference between 50Hz and 60Hz.
I find a 110V step-down transofrmer to be essential in the workshop.For
thigns that don't need one side of the mains to be close to ground
potential (which is 99.(% of stuff) I uses a power tool transofrmer
(55-0-55V with an adapter cable. That;s good to 3kVA. I have other
smaller transformser ( a few hundred VA) with totally floating outputs.
The problem is that it has a 400W power supply... the largest
autotransformer I can get locally is a rather nasty 300VA cheapie. :(
4237
days inactive
4241
days old
9 comments
5 participants
participants (5)
-
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
classiccmp＠philpem.me.uk -
emu＠e-bbes.com -
toby＠telegraphics.com.au