Re: [M100] adding 4xAA NiMH to M100

[Joshua O'Keefe]

On Nov 23, 2020, at 8:10 PM, Jim Anderson  wrote:
> Checking the T102 service manual, you're in luck - in the 102 it's still 
> called R108 and it's still a conventional through-hole resistor instead of a 
> surface-mount device like most of the rest of the resistors.  

Jim, your detailed information on applying the low battery circuit mod to a 102 
was excellent, thank you!  I’m happy to say that I had no real trouble 
performing the modification today — modulo my mediocre soldering skill — and 
the patient survived the procedure.  My current set of batteries ran flat about 
15 minutes after I reassembled the system but unfortunately I didn’t get a low 
battery warning.  Apparently either the Eneloop's voltage fall-off rate calls 
for a higher value of resistance here, or the fall-off is a bit of a cliff.

Re: [M100] adding 4xAA NiMH to M100

[Jim Anderson]

> -Original Message-
> It worked beautifully.  Later I installed a LM317 voltage regulator on a
> heatsink inside the uinti so I could power it with 12V, like the rest of
> my Amateur Radio gear.

Oh man... I wanted to do this, too, and I was going to make a rectangular 
opening in the top case above the barrel jack and mount an Anderson plug flush 
to the opening, in the empty space under the logo plate.  Again, never got 
around to it...

> Lesson learned:   Do not leave NiCads on charge for too long.

This is yet another reason why I'm afraid to charge the batteries inside the 
machine with just a resistor in series rather than a charge control circuit.  :)







jim

Re: [M100] adding 4xAA NiMH to M100

[Jim Anderson]

> -Original Message-
> Jim, this sounds like a fantastic solution to one of my problems.  I
> don't need in-circuit charging (I always have spare NiMH AAs, but I
> rarely travel with an AC adapter) but I would love for the low batt
> light to actually provide some function again.

Yeah, same for myself - although for different reasons.  I alternate between 
rechargeable and alkaline batteries, but I most frequently run the machine off 
a small USB phone charger battery (because it's perfectly happy taking 5V 
instead of 6V at the barrel jack - low battery indication doesn't start until 
4.2V and auto power-off is at about 3.7V IIRC so there's no issue running the 
machine on 5V all the time, it's just like being on half-exhausted batteries).  
I keep a set of AA batteries in the machine just to keep the memory alive when 
I disconnect my phone charger battery.

If I were going to use my machine on rechargeable AA batteries more frequently, 
I think I'd rather do what you do and have two or more sets to swap out in an 
external charger rather than have to plug my whole model T in for charging any 
time it's dead.  Arguably, my use case (usually using it with external power) 
might be the best for having it internally charge the AA batteries, but that's 
one thing 5V is not quite high enough for - I'd have to use a 10 ohm (or lower) 
resistor, no diode, and just make peace with the fact that the AAs would never 
really get fully charged... and then they'd get roasted if I used the machine 
on a 6V supply.  :(

If I were going to do this for my machine, I'd want to install a little dpdt 
switch that would mimic the jumpers in the T200 (which clearly were meant for a 
switch that they decided not to include - they're right next to the memory 
power switch and you can see a rectangular impression in the bottom case where 
the cutout would have been molded) - throwing the switch would connect the 
battery for charging and simultaneously bridge a 100k resistor onto R108.  But 
then, where to put the switch... so, I never got around to it.  :)

> Is the location for the mod also similar on the 102?  I may be a
> hardware novice but I'm pretty sure I could manage to piggyback a
> resistor if I knew where to put it.

Checking the T102 service manual, you're in luck - in the 102 it's still called 
R108 and it's still a conventional through-hole resistor instead of a 
surface-mount device like most of the rest of the resistors.  On page 7-4 
(which is page 73 of 111 in my PDF copy) you'll find the main PCB bottom view, 
and R108 is down at the bottom edge of the board as shown on that page, right 
next to the round power transformer OT2.  This would be the underside of the 
front right of the board as it's installed in the machine.  It shouldn't be too 
hard if you have moderate soldering skills to dead-bug piggyback a 100k 
resistor onto R108, or solder it to the pads on the top side, whichever you 
feel most comfortable with.  You'd probably want to extract the board from the 
bottom case to have a look and be certain you've got the right resistor even if 
you decide to solder your mod on the top side.  (In the M100 the resistor in 
question is in a clearly-marked neat row of resistors right on top in the power 
supply section, so you could do this without doing any more disassembly than 
splitting the case and folding it open...)







jim

Re: [M100] adding 4xAA NiMH to M100

[Joshua O'Keefe]

On Nov 23, 2020, at 1:47 PM, Jim Anderson  wrote:
> This could be done in exactly the same way by piggybacking a 94.4k 1/4W 
> resistor parallel onto R108 in the M100.

Jim, this sounds like a fantastic solution to one of my problems.  I don't need 
in-circuit charging (I always have spare NiMH AAs, but I rarely travel with an 
AC adapter) but I would love for the low batt light to actually provide some 
function again.

Is the location for the mod also similar on the 102?  I may be a hardware 
novice but I'm pretty sure I could manage to piggyback a resistor if I knew 
where to put it.

Re: [M100] adding 4xAA NiMH to M100

[Stephen Adolph]

thanks for that Jim.  I checked and I have the "silicon diode + resistor"
version of this mod on my M100 now.

In my M100 (powered off):
Wall wart voltage = 7.5V
Voltage @ 4xAA = 5.5V (while charging)
Voltage across resistor/diode = 2V
I'll monitor this as it charges up. Ideally I think one would want to see
the AA NiMH batts at 1.45V each, or 5.8V max during charging, and then
maybe 1.4V each for 5.6V when initially loaded.

Thinking in this case that the silicon diode is probably ok.



On Mon, Nov 23, 2020 at 4:47 PM Jim Anderson  wrote:

> > -Original Message-
> > Option 1: 47 ohm
> > - works, but does not prevent reverse conduction from batteries to an
> > unplugged wallwart
> >
> > option 2:  10 ohms + silicon diode:
> > - protects from reverse current, but drops the voltage for charging
> >
> > option 3:  10 ohms + schottky diode
> > - also protects , maybe a little  less voltage drop?
>
> I had a look at the T200 service manual to see what the official solution
> was for internal ni-cd charging, and essentially the jumper on J302 just
> places a 27 ohm 1/2 watt resistor between the barrel jack sleeve input and
> the AA-holder positive terminal.  So, same modification, but now we have
> three different resistance value suggestions.  :)
>
> I don't know enough about differences between charging ni-cd and ni-mh to
> comment on which resistor value would be most appropriate for each type.
>
> Also, your mention of a diode reminded me of the service bulletin 200:3
> which called for using a 1N914 diode in place of the jumper at J302 to
> prevent problems with lockup of the power-on circuit of the T200 in the
> event that the wall wart is unplugged and the power button is pressed while
> the barrel plug is still inserted... The service bulletin did not suggest
> changing the resistor value from 27 ohms to compensate for the voltage drop
> across the diode.
>
> The other half of the T200 mod is not essential, but nice - J301 which
> puts a 94.4k resistor (R93) in parallel with 22.6k resistor (R94) to shift
> down the trigger voltages for the low battery LED and auto power-off.  This
> could be done in exactly the same way by piggybacking a 94.4k 1/4W resistor
> parallel onto R108 in the M100.  Calculating it out, the resistance value
> would only be 1.1% higher by using a 100k resistor instead of 94.4k so that
> might make this part of the mod more appealing for those who have common
> resistors on hand.  :)  (The 94.4k resistor shifts the combined value of
> the two resistors 19.3% lower whereas a 100k resistor shifts the combined
> value 18.4% lower - not a huge deal imho.)
>
> All this just made me realize that this is why negative tip/positive
> barrel was so common on older gear like this - the insertion switch in the
> jack is connected to the barrel contact, so you have to use the barrel for
> whichever polarity you want to switch away from the batteries - to use tip
> positive/barrel negative you'd have to switch the negative side of the
> battery pack...
>
>
>
>
>
>
>
> jim
>
>

Re: [M100] adding 4xAA NiMH to M100

[Doug Jackson]

HI,

I did a similar modification to this when I was much younger.

It worked beautifully.  Later I installed a LM317 voltage regulator on a
heatsink inside the uinti so I could power it with 12V, like the rest of my
Amateur Radio gear.  The unit would stay plugged into permanent power for
days.  Then one day I realised that the Nicads had heated to the point
where the battery springs had melted into the plastic retainers.  It
took ages to repair the case melting issues around the battery compartment.

Lesson learned:   Do not leave NiCads on charge for too long.

I still use this machine for lots of interesting things, including talking
to a Nicolet Z80 pod when debugging other machines.

Kindest regards,

Doug Jackson

em: d...@doughq.com
ph: 0414 986878

Check out my awesome clocks at www.dougswordclocks.com
Follow my amateur radio adventures at vk1zdj.net

---

Just like an old fashioned letter, this email and any files transmitted
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your own use.

Please note that any interesting spelling is usually my own and may have
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Should any part of this message prove to be useful in the event of the
imminent Zombie Apocalypse then the sender bears no personal, legal, or
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Be nice to your parents.

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radio station, go fishing or sailing - just do something that makes you
happy.

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sing ^G ^G ^G ^G ^G ^G ^G ^G




On Tue, 24 Nov 2020 at 08:47, Jim Anderson  wrote:

> > -Original Message-
> > Option 1: 47 ohm
> > - works, but does not prevent reverse conduction from batteries to an
> > unplugged wallwart
> >
> > option 2:  10 ohms + silicon diode:
> > - protects from reverse current, but drops the voltage for charging
> >
> > option 3:  10 ohms + schottky diode
> > - also protects , maybe a little  less voltage drop?
>
> I had a look at the T200 service manual to see what the official solution
> was for internal ni-cd charging, and essentially the jumper on J302 just
> places a 27 ohm 1/2 watt resistor between the barrel jack sleeve input and
> the AA-holder positive terminal.  So, same modification, but now we have
> three different resistance value suggestions.  :)
>
> I don't know enough about differences between charging ni-cd and ni-mh to
> comment on which resistor value would be most appropriate for each type.
>
> Also, your mention of a diode reminded me of the service bulletin 200:3
> which called for using a 1N914 diode in place of the jumper at J302 to
> prevent problems with lockup of the power-on circuit of the T200 in the
> event that the wall wart is unplugged and the power button is pressed while
> the barrel plug is still inserted... The service bulletin did not suggest
> changing the resistor value from 27 ohms to compensate for the voltage drop
> across the diode.
>
> The other half of the T200 mod is not essential, but nice - J301 which
> puts a 94.4k resistor (R93) in parallel with 22.6k resistor (R94) to shift
> down the trigger voltages for the low battery LED and auto power-off.  This
> could be done in exactly the same way by piggybacking a 94.4k 1/4W resistor
> parallel onto R108 in the M100.  Calculating it out, the resistance value
> would only be 1.1% higher by using a 100k resistor instead of 94.4k so that
> might make this part of the mod more appealing for those who have common
> resistors on hand.  :)  (The 94.4k resistor shifts the combined value of
> the two resistors 19.3% lower whereas a 100k resistor shifts the combined
> value 18.4% lower - not a huge deal imho.)
>
> All this just made me realize that this is why negative tip/positive
> barrel was so common on older gear like this - the insertion switch in the
> jack is connected to the barrel contact, so you have to use the barrel for
> whichever polarity you want to switch away from the batteries - to use tip
> positive/barrel negative you'd have to switch the negative side of the
> battery pack...
>
>
>
>
>
>
>
> jim
>
>

Re: [M100] adding 4xAA NiMH to M100

[Jim Anderson]

> -Original Message-
> Option 1: 47 ohm
> - works, but does not prevent reverse conduction from batteries to an
> unplugged wallwart
> 
> option 2:  10 ohms + silicon diode:
> - protects from reverse current, but drops the voltage for charging
> 
> option 3:  10 ohms + schottky diode
> - also protects , maybe a little  less voltage drop?

I had a look at the T200 service manual to see what the official solution was 
for internal ni-cd charging, and essentially the jumper on J302 just places a 
27 ohm 1/2 watt resistor between the barrel jack sleeve input and the AA-holder 
positive terminal.  So, same modification, but now we have three different 
resistance value suggestions.  :)

I don't know enough about differences between charging ni-cd and ni-mh to 
comment on which resistor value would be most appropriate for each type.

Also, your mention of a diode reminded me of the service bulletin 200:3 which 
called for using a 1N914 diode in place of the jumper at J302 to prevent 
problems with lockup of the power-on circuit of the T200 in the event that the 
wall wart is unplugged and the power button is pressed while the barrel plug is 
still inserted... The service bulletin did not suggest changing the resistor 
value from 27 ohms to compensate for the voltage drop across the diode.

The other half of the T200 mod is not essential, but nice - J301 which puts a 
94.4k resistor (R93) in parallel with 22.6k resistor (R94) to shift down the 
trigger voltages for the low battery LED and auto power-off.  This could be 
done in exactly the same way by piggybacking a 94.4k 1/4W resistor parallel 
onto R108 in the M100.  Calculating it out, the resistance value would only be 
1.1% higher by using a 100k resistor instead of 94.4k so that might make this 
part of the mod more appealing for those who have common resistors on hand.  :) 
 (The 94.4k resistor shifts the combined value of the two resistors 19.3% lower 
whereas a 100k resistor shifts the combined value 18.4% lower - not a huge deal 
imho.)

All this just made me realize that this is why negative tip/positive barrel was 
so common on older gear like this - the insertion switch in the jack is 
connected to the barrel contact, so you have to use the barrel for whichever 
polarity you want to switch away from the batteries - to use tip 
positive/barrel negative you'd have to switch the negative side of the battery 
pack...







jim

Re: [M100] adding 4xAA NiMH to M100

[Kurt McCullum]

Steve,

It might be worth looking at the 8201 charging circuit since it's a similar 
platform. For the battery pack, all that is added is a resistor. I think it's 
something weird like 71.5k.

Kurt

On Mon, Nov 23, 2020, at 1:18 PM, Stephen Adolph wrote:
> thanks Bert,
> I found another document (M100SIG) that suggested the components to add were 
> a 10 ohm resistor and a silicon diode.
> Interesting.
> All hacks place a circuit between the orange and red leads.
> 
> Option 1: 47 ohm
> - works, but does not prevent reverse conduction from batteries to an 
> unplugged wallwart
> 
> option 2:  10 ohms + silicon diode:
> - protects from reverse current, but drops the voltage for charging
> 
> option 3:  10 ohms + schottky diode
> - also protects , maybe a little  less voltage drop?
> 
> 
> 
> On Mon, Nov 23, 2020 at 4:04 PM Bert Put  wrote:
>> Hi Steve,
>> 
>> Email from 2010... :-)
>> 
>> Hope this helps.
>> 
>> Cheers,Bert
>> 
>> 
>> 
>> From: Frederick Whitaker 
>> To: m...@list.30below.com
>> Date: Sun, 03 Jan 2010 08:15:53 -0500
>> Subject: Re: Recharging Circuit!
>> 
>> Thank you for finding that error, I didn't see it when I did the proof
>> reading. Anyone who wants to keep that information can make that change,
>> or they can use the change I am adding to this email.
>> 
>> Fred Whitaker
>> 
>> IZ2eib wrote:
>> > --- Dom 3/1/10, Frederick Whitaker  ha scritto:
>> >
>> >
>> >> Da: Frederick Whitaker 
>> >> Oggetto: Re: Recharging Circuit!
>> >> A: m...@list.30below.com
>> >> Data: Domenica 3 gennaio 2010, 02:56
>> >>
>> >
>> >
>> >> I have no idea why it calls for 4
>> >> watts.
>> >>
>> >> Fred Whitaker
>> >>
>> >
>> > Hi Fred and all member list.
>> > Resistor is 1/4W (0,25W), no 4W: 4W is a typo.
>> > Please look at http://www.club100.org/library/libp100.html,
>> > there are all Portable 100 Magazines, download Vol. 3 No. 7 Mar 1986
>> and read on page 44: you can read "The resistor you need for
>> self-charging is a 47 ohm, 1/4 watt resistor which you can find at any
>> electronics or TV repair store".
>> > I believe that the error is due to conversion of the original
>> document, nothing serious.
>> > Since 1983, and as usual, club100 is the bible of Tandy 100's family
>> laptops thanks to Rick Hanson!!!
>> >
>> > Regards,
>> >
>> > Fabio.
>> >
>> >
>> >
>> >
>> >
>> >
>> > A Simple Self-Charger for the 100
>> > BY JOHN L. MENKE AND SUSAN M. MENKE
>> >
>> > The Model 100 is easy to use, powerful and lightweight. It also eats
>> > batteries.
>> >
>> > If you're tired of hand-feeding it every few hours, you can modify its
>> > dietary habits to self-charge. All you need are a resistor, a power
>> > line adapter (current retail cost $5.95) and a quartet of rechargeable
>> > batteries.
>> >
>> > After you've owned your machine for 90 days, its warranty expires and
>> > this modification won't affect it. If your warranty is still in force,
>> > we point out that Radio Shack does not recommend what we're about to
>> > describe. However, we've had no problems with our two machines over
>> > several years of use.
>> >
>> > RECHARGEABLE BATTERIES Rechargeable nickel-cadmium (nicad) batteries
>> > have a nominal voltage of 1.2 volts (V). This remains virtually
>> > constant as the cell discharges, then drops quickly to near zero. Four
>> > such batteries give the Model 100 a combined voltage of 4.8 volts,
>> > which is lower than the recommended 6.0V. The 100 will shut itself off
>> > if voltage drops slightly below 4.8V. In spite of this relatively
>> > narrow voltage band, we have never experienced problems from low power
>> > shutdown.
>> >
>> > We have tried several brands of nicads. All give about 8-10 hours of
>> > use when fully Charged. Makers recommend occasionally letting the
>> > cells run all the way down before recharging. Our experience is that
>> > repeated partial discharge (or extensive use of trickle charging) will
>> > reduce charge life to 4-5 hours. One or two cycles of full
>> > discharge/recharge restores the 8-10 hour useful life.
>> >
>> > We have used the same nicads for hundreds of cycles over two years
>> > without evident degradation. Aside from the relatively limited life of
>> > each recharge, the only noticeable effect is a very short warning time
>> > after the lowbattery light comes on, before the 100 shuts itself off.
>> >
>> > Different brands of nicads have slightly different dimensions. The
>> > positive tips of Radio Shack nicads are somewhat shorter than those of
>> > other makers such as Lynacharge, so use of the Radio Shack cell can
>> > lead to poor positive contact and intermittent operation. If you
>> > experience this, the best solution is to switch to a different brand
>> > of nicad. However, it's possible to use needlenose pliers and
>> > partially uncoil the 100's positive spring terminals for better contact.
>> >
>> > HOW TO ADD THE SELF CHARGER RESISTOR
>> >
>> > You probably wonder, as we do, why all portable computers don't have
>> > built in 

Re: [M100] adding 4xAA NiMH to M100

[Bert Put]

No worries Steve,

I didn't dig too deep into my search results but this email references
an old issue of Portable-100... so it's certainly likely that there is
more recent information out there.  I'd say to use whatever solution
you're most comfortable with :-)

Cheers,Bert

On 11/23/20 3:18 PM, Stephen Adolph wrote:
> thanks Bert,
> I found another document (M100SIG) that suggested the components to add
> were a 10 ohm resistor and a silicon diode.
> Interesting.
> All hacks place a circuit between the orange and red leads.
> 
> Option 1: 47 ohm
> - works, but does not prevent reverse conduction from batteries to an
> unplugged wallwart
> 
> option 2:  10 ohms + silicon diode:
> - protects from reverse current, but drops the voltage for charging
> 
> option 3:  10 ohms + schottky diode
> - also protects , maybe a little  less voltage drop?
> 
> 
> 
> On Mon, Nov 23, 2020 at 4:04 PM Bert Put  > wrote:
> 
> Hi Steve,
> 
> Email from 2010... :-)
> 
> Hope this helps.
> 
> Cheers,    Bert
> 
> 
> 
> From: Frederick Whitaker  >
> To: m...@list.30below.com 
> Date: Sun, 03 Jan 2010 08:15:53 -0500
> Subject: Re: Recharging Circuit!
> 
> Thank you for finding that error, I didn't see it when I did the proof
> reading. Anyone who wants to keep that information can make that change,
> or they can use the change I am adding to this email.
> 
> Fred Whitaker
> 
> IZ2eib wrote:
> > --- Dom 3/1/10, Frederick Whitaker  > ha scritto:
> >
> >
> >> Da: Frederick Whitaker  >
> >> Oggetto: Re: Recharging Circuit!
> >> A: m...@list.30below.com 
> >> Data: Domenica 3 gennaio 2010, 02:56
> >>
> >
> >
> >> I have no idea why it calls for 4
> >> watts.
> >>
> >> Fred Whitaker
> >>
> >
> > Hi Fred and all member list.
> > Resistor is 1/4W (0,25W), no 4W: 4W is a typo.
> > Please look at http://www.club100.org/library/libp100.html,
> > there are all Portable 100 Magazines, download Vol. 3 No. 7 Mar 1986
> and read on page 44: you can read "The resistor you need for
> self-charging is a 47 ohm, 1/4 watt resistor which you can find at any
> electronics or TV repair store".
> > I believe that the error is due to conversion of the original
> document, nothing serious.
> > Since 1983, and as usual, club100 is the bible of Tandy 100's family
> laptops thanks to Rick Hanson!!!
> >
> > Regards,
> >
> > Fabio.
> >
> >
> >
> >
> >
> >
> > A Simple Self-Charger for the 100
> > BY JOHN L. MENKE AND SUSAN M. MENKE
> >
> > The Model 100 is easy to use, powerful and lightweight. It also eats
> > batteries.
> >
> > If you're tired of hand-feeding it every few hours, you can modify its
> > dietary habits to self-charge. All you need are a resistor, a power
> > line adapter (current retail cost $5.95) and a quartet of rechargeable
> > batteries.
> >
> > After you've owned your machine for 90 days, its warranty expires and
> > this modification won't affect it. If your warranty is still in force,
> > we point out that Radio Shack does not recommend what we're about to
> > describe. However, we've had no problems with our two machines over
> > several years of use.
> >
> > RECHARGEABLE BATTERIES Rechargeable nickel-cadmium (nicad) batteries
> > have a nominal voltage of 1.2 volts (V). This remains virtually
> > constant as the cell discharges, then drops quickly to near zero. Four
> > such batteries give the Model 100 a combined voltage of 4.8 volts,
> > which is lower than the recommended 6.0V. The 100 will shut itself off
> > if voltage drops slightly below 4.8V. In spite of this relatively
> > narrow voltage band, we have never experienced problems from low power
> > shutdown.
> >
> > We have tried several brands of nicads. All give about 8-10 hours of
> > use when fully Charged. Makers recommend occasionally letting the
> > cells run all the way down before recharging. Our experience is that
> > repeated partial discharge (or extensive use of trickle charging) will
> > reduce charge life to 4-5 hours. One or two cycles of full
> > discharge/recharge restores the 8-10 hour useful life.
> >
> > We have used the same nicads for hundreds of cycles over two years
> > without evident degradation. Aside from the relatively limited life of
> > each recharge, the only noticeable effect is a very short warning time
> > after the lowbattery light comes on, before the 100 shuts itself off.
> >
> > Different brands of nicads have slightly different dimensions. The
> > positive tips of Radio Shack nicads are somewhat 

Re: [M100] adding 4xAA NiMH to M100

[Stephen Adolph]

thanks Bert,
I found another document (M100SIG) that suggested the components to add
were a 10 ohm resistor and a silicon diode.
Interesting.
All hacks place a circuit between the orange and red leads.

Option 1: 47 ohm
- works, but does not prevent reverse conduction from batteries to an
unplugged wallwart

option 2:  10 ohms + silicon diode:
- protects from reverse current, but drops the voltage for charging

option 3:  10 ohms + schottky diode
- also protects , maybe a little  less voltage drop?



On Mon, Nov 23, 2020 at 4:04 PM Bert Put  wrote:

> Hi Steve,
>
> Email from 2010... :-)
>
> Hope this helps.
>
> Cheers,Bert
>
>
>
> From: Frederick Whitaker 
> To: m...@list.30below.com
> Date: Sun, 03 Jan 2010 08:15:53 -0500
> Subject: Re: Recharging Circuit!
>
> Thank you for finding that error, I didn't see it when I did the proof
> reading. Anyone who wants to keep that information can make that change,
> or they can use the change I am adding to this email.
>
> Fred Whitaker
>
> IZ2eib wrote:
> > --- Dom 3/1/10, Frederick Whitaker  ha scritto:
> >
> >
> >> Da: Frederick Whitaker 
> >> Oggetto: Re: Recharging Circuit!
> >> A: m...@list.30below.com
> >> Data: Domenica 3 gennaio 2010, 02:56
> >>
> >
> >
> >> I have no idea why it calls for 4
> >> watts.
> >>
> >> Fred Whitaker
> >>
> >
> > Hi Fred and all member list.
> > Resistor is 1/4W (0,25W), no 4W: 4W is a typo.
> > Please look at http://www.club100.org/library/libp100.html,
> > there are all Portable 100 Magazines, download Vol. 3 No. 7 Mar 1986
> and read on page 44: you can read "The resistor you need for
> self-charging is a 47 ohm, 1/4 watt resistor which you can find at any
> electronics or TV repair store".
> > I believe that the error is due to conversion of the original
> document, nothing serious.
> > Since 1983, and as usual, club100 is the bible of Tandy 100's family
> laptops thanks to Rick Hanson!!!
> >
> > Regards,
> >
> > Fabio.
> >
> >
> >
> >
> >
> >
> > A Simple Self-Charger for the 100
> > BY JOHN L. MENKE AND SUSAN M. MENKE
> >
> > The Model 100 is easy to use, powerful and lightweight. It also eats
> > batteries.
> >
> > If you're tired of hand-feeding it every few hours, you can modify its
> > dietary habits to self-charge. All you need are a resistor, a power
> > line adapter (current retail cost $5.95) and a quartet of rechargeable
> > batteries.
> >
> > After you've owned your machine for 90 days, its warranty expires and
> > this modification won't affect it. If your warranty is still in force,
> > we point out that Radio Shack does not recommend what we're about to
> > describe. However, we've had no problems with our two machines over
> > several years of use.
> >
> > RECHARGEABLE BATTERIES Rechargeable nickel-cadmium (nicad) batteries
> > have a nominal voltage of 1.2 volts (V). This remains virtually
> > constant as the cell discharges, then drops quickly to near zero. Four
> > such batteries give the Model 100 a combined voltage of 4.8 volts,
> > which is lower than the recommended 6.0V. The 100 will shut itself off
> > if voltage drops slightly below 4.8V. In spite of this relatively
> > narrow voltage band, we have never experienced problems from low power
> > shutdown.
> >
> > We have tried several brands of nicads. All give about 8-10 hours of
> > use when fully Charged. Makers recommend occasionally letting the
> > cells run all the way down before recharging. Our experience is that
> > repeated partial discharge (or extensive use of trickle charging) will
> > reduce charge life to 4-5 hours. One or two cycles of full
> > discharge/recharge restores the 8-10 hour useful life.
> >
> > We have used the same nicads for hundreds of cycles over two years
> > without evident degradation. Aside from the relatively limited life of
> > each recharge, the only noticeable effect is a very short warning time
> > after the lowbattery light comes on, before the 100 shuts itself off.
> >
> > Different brands of nicads have slightly different dimensions. The
> > positive tips of Radio Shack nicads are somewhat shorter than those of
> > other makers such as Lynacharge, so use of the Radio Shack cell can
> > lead to poor positive contact and intermittent operation. If you
> > experience this, the best solution is to switch to a different brand
> > of nicad. However, it's possible to use needlenose pliers and
> > partially uncoil the 100's positive spring terminals for better contact.
> >
> > HOW TO ADD THE SELF CHARGER RESISTOR
> >
> > You probably wonder, as we do, why all portable computers don't have
> > built in rechargeable power supplies. Radio Shack has been
> > consistently guilty of this fault, and even compounds it with new
> > battery-powered products that lack automatic shutoff.
> >
> > However, if you have ten minutes and twenty cents, you can wire in a
> > resistor (without soldering) that will recharge your IOU overnight
> > from a power line adapter.
> >
> > We repeat: This change may invalidate your 90-day 

Re: [M100] adding 4xAA NiMH to M100

[Bert Put]

Hi Steve,

Email from 2010... :-)

Hope this helps.

Cheers,Bert



From: Frederick Whitaker 
To: m...@list.30below.com
Date: Sun, 03 Jan 2010 08:15:53 -0500
Subject: Re: Recharging Circuit!

Thank you for finding that error, I didn't see it when I did the proof
reading. Anyone who wants to keep that information can make that change,
or they can use the change I am adding to this email.

Fred Whitaker

IZ2eib wrote:
> --- Dom 3/1/10, Frederick Whitaker  ha scritto:
>
>
>> Da: Frederick Whitaker 
>> Oggetto: Re: Recharging Circuit!
>> A: m...@list.30below.com
>> Data: Domenica 3 gennaio 2010, 02:56
>>
>
>
>> I have no idea why it calls for 4
>> watts.
>>
>> Fred Whitaker
>>
>
> Hi Fred and all member list.
> Resistor is 1/4W (0,25W), no 4W: 4W is a typo.
> Please look at http://www.club100.org/library/libp100.html,
> there are all Portable 100 Magazines, download Vol. 3 No. 7 Mar 1986
and read on page 44: you can read "The resistor you need for
self-charging is a 47 ohm, 1/4 watt resistor which you can find at any
electronics or TV repair store".
> I believe that the error is due to conversion of the original
document, nothing serious.
> Since 1983, and as usual, club100 is the bible of Tandy 100's family
laptops thanks to Rick Hanson!!!
>
> Regards,
>
> Fabio.
>
>
>
>
>
>
> A Simple Self-Charger for the 100
> BY JOHN L. MENKE AND SUSAN M. MENKE
>
> The Model 100 is easy to use, powerful and lightweight. It also eats
> batteries.
>
> If you're tired of hand-feeding it every few hours, you can modify its
> dietary habits to self-charge. All you need are a resistor, a power
> line adapter (current retail cost $5.95) and a quartet of rechargeable
> batteries.
>
> After you've owned your machine for 90 days, its warranty expires and
> this modification won't affect it. If your warranty is still in force,
> we point out that Radio Shack does not recommend what we're about to
> describe. However, we've had no problems with our two machines over
> several years of use.
>
> RECHARGEABLE BATTERIES Rechargeable nickel-cadmium (nicad) batteries
> have a nominal voltage of 1.2 volts (V). This remains virtually
> constant as the cell discharges, then drops quickly to near zero. Four
> such batteries give the Model 100 a combined voltage of 4.8 volts,
> which is lower than the recommended 6.0V. The 100 will shut itself off
> if voltage drops slightly below 4.8V. In spite of this relatively
> narrow voltage band, we have never experienced problems from low power
> shutdown.
>
> We have tried several brands of nicads. All give about 8-10 hours of
> use when fully Charged. Makers recommend occasionally letting the
> cells run all the way down before recharging. Our experience is that
> repeated partial discharge (or extensive use of trickle charging) will
> reduce charge life to 4-5 hours. One or two cycles of full
> discharge/recharge restores the 8-10 hour useful life.
>
> We have used the same nicads for hundreds of cycles over two years
> without evident degradation. Aside from the relatively limited life of
> each recharge, the only noticeable effect is a very short warning time
> after the lowbattery light comes on, before the 100 shuts itself off.
>
> Different brands of nicads have slightly different dimensions. The
> positive tips of Radio Shack nicads are somewhat shorter than those of
> other makers such as Lynacharge, so use of the Radio Shack cell can
> lead to poor positive contact and intermittent operation. If you
> experience this, the best solution is to switch to a different brand
> of nicad. However, it's possible to use needlenose pliers and
> partially uncoil the 100's positive spring terminals for better contact.
>
> HOW TO ADD THE SELF CHARGER RESISTOR
>
> You probably wonder, as we do, why all portable computers don't have
> built in rechargeable power supplies. Radio Shack has been
> consistently guilty of this fault, and even compounds it with new
> battery-powered products that lack automatic shutoff.
>
> However, if you have ten minutes and twenty cents, you can wire in a
> resistor (without soldering) that will recharge your IOU overnight
> from a power line adapter.
>
> We repeat: This change may invalidate your 90-day warranty if still in
> effect.but there is virtually no risk from adding a resistor, nor will
> it make troubleshooting difficult if your machine should ever need
> repair. Simply removing the resistor before sending the 100 for
> service will avoid any issue being raised. .
>
> The resistor you need for self-charging is a 47 ohm, 1/4 watt resistor
> which you can find at any electronics or TV repair store. A resistor
> twenty percent above or below those values will still work.



On 11/23/20 2:54 PM, Stephen Adolph wrote:
> Wondering if anyone recalls or can point to the small modification
> needed to be able to use NiMH or NiCd batts in the M100, and enable
> charging?
> Seems to me there was a nice little change you could make.
> thx
> Steve