10 May
2002
10 May
'02
1:44 p.m.
I just picked up one of these today but I didn't get the power cord. Does anyone of
the list have one and if so can you tell me the pin out of the power connector? It has
three pins and I beleive that the caclulator can ran off of AC or low voltage DC. Here is
a picture and article of the same model calculator
<http://www.vintagecalculators.com/html/sharp_el-8.html>.
Joe
10 May
10 May
5:43 p.m.
On Fri, 10 May 2002, Joe wrote:
I just picked up one of these today but I didn't
get the power cord.
Does anyone of the list have one and if so can you tell me the pin out
of the power connector? It has three pins and I beleive that the
caclulator can ran off of AC or low voltage DC. Here is a picture and
article of the same model calculator
<http://www.vintagecalculators.com/html/sharp_el-8.html>.
Joe, the 3-pin receptacle on the calculator accepts a cord from either
of two external power units. One being a unit that works off of 12vdc -
cigarette lighter - and the second works off of 110vac. The second unit
is capable of 8.7vdc @ 150ma as well as 9.6vdc @ 230ma. There are a
couple of charging modes as well as a charge while running on external
power and my suspicion is that this accounts for the 3 pins on the
connector. I will see if I can get something more definitive for you.
- don
11 May
11 May
8:42 a.m.
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3:49 p.m.
Tony,
That's a good guess but it doesn't have one. It does have a three position
manual switch on the side (DC-Off-AC). I pulled the thing apart today and it has some
very strange circuitry inside. I figured out enough of it to be able to connect power to
it and make it work but I don't understand all of the circuit.
In additon to the two power sources that Don memtioned you can also get an external
battery pack for it.
I think a lot of the power circuitry in controlled by the switch and the wiring in the
various power units. FWIW I talked to a guy today that has about six of the EL-8s (and six
AC power supplies) and none of his PSs work. It turns out that they have some kind of
hybrid circuit in them that seems to be very failure prone.
Joe
At 09:42 PM 5/11/02 +0100, Tony wrote:
Joe, the 3-pin
receptacle on the calculator accepts a cord from either
of two external power units. One being a unit that works off of 12vdc -
cigarette lighter - and the second works off of 110vac. The second unit
is capable of 8.7vdc @ 150ma as well as 9.6vdc @ 230ma. There are a
couple of charging modes as well as a charge while running on external
power and my suspicion is that this accounts for the 3 pins on the
connector. I will see if I can get something more definitive for you.
One totally wild guess (I've never seen an EL-8)....
It's possible that the 3 pin connector incorporates an internal switch
contact that shorts 2 of the pins together when the charger/PSU is not
connected. It could then be wired like this :
switch contact
-----------
V V
+------------o o--------------------- +ve to rest of machine
| o
------- |
----- |
------- |
----- |
------- |
----- |
| |
+-----------------+------------------------- 0V
When the charger is not connected, the battery pack is connected to the
machine and powers it. When the charger is connected, the battery pack is
disconnected. The charger is in 2 parts. A constant current supply
(conencted to the left hand pin in the diagram) to charge the battery and
a constant voltage supply (connected to the right hand pin) to run the
machine.
This is (of course) how the HP 'classic series' and the HP67 are wired.
But I've seen it used elsewhere too.
-tony
12 May
12 May
8:05 a.m.
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2:58 p.m.
At 09:05 PM 5/12/02 +0100, you wrote:
It is.
Tony,
That's a good guess but it doesn't have one. It does have a three
position manual switch on the side (DC-Off-AC). I pulled the thing
I still wonder about separate inputs for battery charging and logic
supply. That could be done with the 3 position switch you mentioned :
DC : Both inputs disconnected, battery supplies logic
Off : Charger input connected to battery, no connection to logic
AC : Charger input connected to battery, Supply input connected to logic.
Yes I traced it out between the jack, switch and battery connector. (Pretty bizzare
circuit IMO) I didn't want to tear any further into the calculator at this time. I
found out enough to allow me to power it up and test it. (Those Itrode (sp?) displays sure
look nice!) However I was wondering about the 2nd Dc voltage but I think Don Maslin's
message told me what I needed to know for that.
Joe
apart today and it has some very strange
circuitry inside. I figured out
Have you traced out the wiring to the swtich and the connector yet?
3:54 p.m.
On Sun, 12 May 2002, Tony Duell wrote:
Tony, I would question this as the manual states that in the OFF
charging mode the battery will come to full charge in 3 hours, while in
AC mode it requires about 14 hours. Obviously, in AC mode the battery
is being charged at a rather lower rate.
- don
Tony,
That's a good guess but it doesn't have one. It does have a three
position manual switch on the side (DC-Off-AC). I pulled the thing
I still wonder about separate inputs for battery charging and logic
supply. That could be done with the 3 position switch you mentioned :
DC : Both inputs disconnected, battery supplies logic
Off : Charger input connected to battery, no connection to logic
AC : Charger input connected to battery, Supply input connected to logic. apart today
and it has some very strange circuitry inside. I figured out
Have you traced out the wiring to the swtich and the connector yet?
-tony
8577
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8579
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