Topic: m148 external power mod?

[Colin Liston]

Anyone know if you can mod an Oade m148 to accept external power?  I have no clue, anyone have any thoughts?

[dnsacks]

If memory serves me correctly, the m148 uses several sets of 3x6volt batteries wired in series (creating 18 volts), so you'd need to come up with a power source that would supply it with the correct voltage(s) -- the m148 charger (again if memory serves correctly) supplies 48v of power to the unit for charging.

I have a feeling that the hardest part of successfully converting a m148 to external power will be coming up with a reliable charging system for the external batteries. This has left me scratching my head and periodically replacing the m148's internals.  I can get full day runtimes with my mk4>kc5>pfa setup on fresh-ish m148 batteries.  If yours are no longer keeping a charge, battery replacement is a fairly straightforward process

[fsulloway]

I want to say tonedeaf did an external power mod but I could be wrong. It's just as easy to wire up 8 x 6 volt batteries and stuff them back in. If I can do it anybody can. Here's a pic Heath took a few years ago. Once I saw this I opened mine up and did it myself.



link to more pics.
http://taperssection.com/index.php?topic=29243.15

[dnsacks]

I BELIEVE Tonedeaf did the external power mod on an m118 -- thx for the foto, looks like the m148 requires 2x 18 volt power sources and 1x 12 volt power source to work.

I agree that simply replacing the internals is likely the path of least resistance here -- Doug Oade purposely designed the circuits this way to avoid the noise created by dc>dc conversion.

I've also had great luck making my m148 batteries last by following the following basic advice:

1) don't let the m148 fully drain the batteries (sla's HATE to be fully drained) -- be sure to turn off whenever not in use (I use a rubberband to help keep the on-off switch from being inadvertently turned on)

2) Keep the m148 fully charged whenever possible -- I charge for 18 hours after each use and "top up" overnight if I haven't used mine for a month -- I'll also throw it onto a charger for a few hours or so before taking it out and using it.

3) Don't Overcharge the m148 -- the charger is not a "smart" charger and will overcharge the batteries if left on for more than a day (or so)

Following these rules should allow your batteries to last for at least a couple of years

[fsulloway]

That's pretty much the procedure I use for charging/storing my 148. I've had it about 11 years now and have only changed the batteries once which was 4 years ago. I should probably throw the volt meter on there to see how it's doing.

[Colin Liston]

I've got to change out all 8, that's why I was asking.  You're right it does look fairly simple to change them out though.

[dnsacks]

FYI -- when I did this last, I used Amstron AP-605WL Batteries, which were direct replacements for the powersonic PS-605 used in the M148.  This was considerably cheaper for me at the time (I paid $11.99 each and powersonics were running $26 each).  Googling today, I can find the powersonics at an even cheaper price at http://www.mbsbattery.com -- you should be sure to check how long these have been sitting on a supplier's shelf before buying . . .

Replacement was easy, simply disassemble/replace one "set" at a time -- I simply crimped and taped the wires up and avoided soldiering altogether.