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Author Topic: Another Oade M148 Charger Question  (Read 6456 times)

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Offline mec111272

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Another Oade M148 Charger Question
« on: September 13, 2015, 09:32:09 PM »
I acquired an M148 w/o a walwart.  I then contacted Doug who told me;

"Mike, it's 300ma 36 volt transformer fused at the primary. It's
converted to DC inside the M148"

I then went out and replaced the SLA's and built myself a charger.  Since then I have been having issues getting and keeping a charge.  Most of them revolve around stupidity for sure.  First left it on for a month and totally depleted the batteries.  This killed the 12v pack.  So I replaced them. Next I charged it with the power on.  Not sure what that does to things, but it didn't help. 

I have readal l of the threads and feel like there are some inconsistencies, maybe someone could chime in and set me straight.

1.  Is the walwart really 36 volt AC and not 16 volt AC as has been reported in other places?
2. When fully charged what is the phantom power voltage in the XLR connection? Most I have ever gotten is 53 volts.
3. Assuming normal conditions and a full charge, how long should I expect the unit to run?
4. People have said about 2 or 3 hours of charging for each hour of use.  This seem right?
5. If you put the charger on with the unit "ON" how long before you really botch something?
6.  It has been noted that the charging system will "turn off" and that leaving the unit on the charger for extended periods wont be an issue.  Anyone able to confirm this? Other places say it isn't a smart charger and you can't just leave it on.

The occasions that I have managed to run this have made some of the sweetest sounding recordings I have made,  I love the sound I am getting out of it, but the power issue is a problem.

Thanks in advance
Neumann KM-140,Church Audio Ca-14, Card Omni, CAD e70

Edirol UA-5 (T+ mod), Church Audio CA-9200, M148

Tascam DR2D, Marantz PMD 660 (Oade Songcatcher)

stevetoney

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Re: Another Oade M148 Charger Question
« Reply #1 on: September 13, 2015, 10:10:33 PM »
I'll defer to others for the answers to questions 1 and 2, though I know I've tested the voltage on my m118 and I also get a higher phantom voltage reading than nominal, so the 53V you're reading seems logical to me.

3) It's been years since I had an M148, but I seem to remember people saying they got around 8 hours of run time from a full charge.  Someone will surely correct me if my memory is wrong on this.

4) Again going from memory, 16 - 24 hours to charge the unit seems about right, assuming the wall wart you got is 300ma.  If it's bigger you can expect shorter charge times...if it's smaller, charge times will be longer.

5) The switch inside my M118, which is the sister of the m148, has a three position slider switch.  When in the on position, I'm pretty sure that the charge circuit is disengaged and cannot be completed.  So I'm pretty sure that with the switch in the on position, the batteries are connected to the M148 circuit and not the charge circuit.  In other words, with the switch in the on position, you can't recharge the batteries even if the charger is plugged in.  Someone please correct me if this isn't right.

6) For long time periods, you'd want to keep the unit connected at trickle voltage, which is a lower voltage than the charge voltage.  So, unless your charger changes to trickle voltage once the batteries are fully charged, you should unplug it once the batteries are charged.
« Last Edit: September 14, 2015, 12:55:46 PM by tonedeaf »

stevetoney

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Re: Another Oade M148 Charger Question
« Reply #2 on: September 14, 2015, 07:55:04 AM »
This article should help you with some details to supplement the responses I provided last night...

http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

Offline mec111272

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Re: Another Oade M148 Charger Question
« Reply #3 on: September 15, 2015, 05:26:09 PM »
Thanks for helping out.  Does anyone out there have a charger they can slap a multi-meter on for me!  After having opened it up again I am just not seeing where this thing is is converting AC to DC from the charger. 

My thought is that to charge this thing you need DC at or above 48 volts, no?

Neumann KM-140,Church Audio Ca-14, Card Omni, CAD e70

Edirol UA-5 (T+ mod), Church Audio CA-9200, M148

Tascam DR2D, Marantz PMD 660 (Oade Songcatcher)

Offline Colin Liston

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Re: Another Oade M148 Charger Question
« Reply #4 on: September 15, 2015, 07:09:43 PM »
I  can when I get home.  If I recall I thought it was 65 volts.  But maybe I am thinking 36v.  I know its something weird.

I  have to replace my batteries for the second time.  I have accidentally switched mine on twice mine killing the batteries.  I really would like to make an external box that housed the batteries with a disconnect,  so I  don't accidentally switch it on
Occasionally....music mics record

stevetoney

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Re: Another Oade M148 Charger Question
« Reply #5 on: September 15, 2015, 07:56:25 PM »
I  can when I get home.  If I recall I thought it was 65 volts.  But maybe I am thinking 36v.  I know its something weird.

I  have to replace my batteries for the second time.  I have accidentally switched mine on twice mine killing the batteries.  I really would like to make an external box that housed the batteries with a disconnect,  so I  don't accidentally switch it on

I got tired of replacing batteries as well.  I have an m118 though and the wiring scheme inside a 118 is alot more straightforward than the 148.  So I modded my 118 to remove the internal SLAs and added a pair of jacks on the casing that are connected to where the battery poles used to be connected.  It's strange, but in the 118 design each channel had it's own 18V battery (two banks of 3 six volt SLAs wired in series).  So, now I power my 118 from a pair of external batteries.  I use two Naztech PB15000 batteries at the 18V setting.  It's a bit of a PITA to power a single preamp with two batteries, but it beats the hell out of spending $120 replacing six batteries every time I accidentally leave it on.
« Last Edit: September 15, 2015, 08:08:35 PM by tonedeaf »

Offline mec111272

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Re: Another Oade M148 Charger Question
« Reply #6 on: September 15, 2015, 11:21:13 PM »
Agreed.  It seems like you get one shot at killing them entirely and they are done.

From what I can see there are 5 in series plus three in series but it looks like they have a weird grounding condition.  Heard back from Doug and he insists that it is 36 volt AC 300 ma.  This makes no sense as I thought you would need to hit 7.2 volts for each battery in the series so like 58 volts. 

I am going to replace the other 5 and leave it on the charger for 24 hours then leave it running my mikes and see where I am.

PITA for sure.

Neumann KM-140,Church Audio Ca-14, Card Omni, CAD e70

Edirol UA-5 (T+ mod), Church Audio CA-9200, M148

Tascam DR2D, Marantz PMD 660 (Oade Songcatcher)

stevetoney

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Re: Another Oade M148 Charger Question
« Reply #7 on: September 16, 2015, 06:54:45 AM »
Agreed.  It seems like you get one shot at killing them entirely and they are done.

From what I can see there are 5 in series plus three in series but it looks like they have a weird grounding condition.  Heard back from Doug and he insists that it is 36 volt AC 300 ma.  This makes no sense as I thought you would need to hit 7.2 volts for each battery in the series so like 58 volts. 

I am going to replace the other 5 and leave it on the charger for 24 hours then leave it running my mikes and see where I am.

PITA for sure.

I'm pretty it's two banks of three cells wired in series and one bank of two...basically two 18v batteries and one 12v.  It's how those three integrated batteries are connected into the M148 that confused the daylights outta me. 

When I figured out how to power my m118 externally, I thought I might try to design a similar fix for the m148, so I borrowed one from another member and reverse engineered the wiring scheme.  I'm sure I could have figured it out, but I ended up giving up the idea because the wiring scheme just confused me and I didn't think there would be many people that would want me cutting wires in their m148 anyway.  If I owned one, I'd try it but I'm not going to pay for one just to experiment.


Offline Colin Liston

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Re: Another Oade M148 Charger Question
« Reply #8 on: September 16, 2015, 08:14:21 AM »
Agreed.  It seems like you get one shot at killing them entirely and they are done.

From what I can see there are 5 in series plus three in series but it looks like they have a weird grounding condition.  Heard back from Doug and he insists that it is 36 volt AC 300 ma.  This makes no sense as I thought you would need to hit 7.2 volts for each battery in the series so like 58 volts. 

I am going to replace the other 5 and leave it on the charger for 24 hours then leave it running my mikes and see where I am.

PITA for sure.

I'm pretty it's two banks of three cells wired in series and one bank of two...basically two 18v batteries and one 12v.  It's how those three integrated batteries are connected into the M148 that confused the daylights outta me. 


This is correct.  I don't get it either.  It would make sense if they were all together giving 48 v, but the two 18's and the one 12 is what I don't understand.

Tone can you send me a picture of your battery set up?
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Offline Colin Liston

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Re: Another Oade M148 Charger Question
« Reply #9 on: September 16, 2015, 08:43:26 AM »
 I just put the meter on my charger and I don't get anything.  Nada.  Looks like I need to take apart the charger. [Edit]  The cable coming out of the charger is cut almost detached.

Here are a couple of photos of the inside though.
« Last Edit: September 16, 2015, 08:45:15 AM by Colin Liston »
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Offline Colin Liston

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Re: Another Oade M148 Charger Question
« Reply #10 on: September 16, 2015, 08:53:50 AM »
My charger outputs 44 volts. 

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stevetoney

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Re: Another Oade M148 Charger Question
« Reply #11 on: September 16, 2015, 09:45:57 AM »
Tone can you send me a picture of your battery set up?

Rather than sending a picture which would probably just confuse you, I'll describe it.  After reading this, if you still need pictures, let me know.  I'm glad to take them, but figure the description would help you out more.

OK, so remember my box is an m118.  The functional difference between an m118 is that my box provides nominal 18V phantom power, whereas yours provides 48V.  Since all of the Schoeps mics I own operate off of 12V phantom OR 48V, the m118 is a nice solution for me because it will run much longer than the M148.  Other than that, it's my understanding that all of the sound characteristics of the two preamps are identical.  For example, mine has the same two Jenson input transformers as those shown in your pictures.

I'm not completely sure of all the technical differences between my box and yours (since Oade covers the board with gunk), but the most fundamental technical difference is that it only needed six batteries instead of eight.  They're the same batteries as you have...those 6V powersonics that have I think 0.5 watt-hour of capacity.  However, when I reverse engineered the wiring scheme for my preamp, the wiring is alot more straightforward and logical that it is on your preamp.   

So my batteries were arranged in two banks of three cells each.  So that's two 18V batteries.  Obviously each of these two batteries has a positive pole and a negative pole...four total poles...two blue wires and two red wires.  The wires from those four poles are routed to distinct points in the circuit. 

So when I removed the batteries from the box, all I did was to first snip the wires from the four battery poles (paying attention to which wires attached to which battery poles).  Then I installed two sockets onto the external casing of the preamp box.  I soldered the four wires to the two terminals on each of the sockets.  One red wire and one blue wire to one of the sockets (corresponding to how the wires had been connected to the battery terminals) and the other red and blue wires to the other socket. 

Then I built two cables to connect my external Naztech batteries to the two sockets that I installed on the case.  Obviously, when I soldered the cable jacks, I paid attention to the polarity of the cable to the red and blue wires on the preamp socket to maintain a consistent polarity between the two external batteries and how the preamp was wired up when the two 18V internals were wired...making sure that the positive terminal on the externals supplied one of the positive/red wires soldered to the jack.

Now it doesn't matter anymore if the preamp switch is on or off because I simply unplug my batteries when the show is over anyway. 

By the way, I used two standard size socket/jack sets from Ratshack.  I can't remember whether I used 'n' or 'm', but whatever I used it's the same jack size as I already have on my Naztech batteries.  The only reason I did this is so that the two cables I made are reversible. 


Offline mec111272

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Re: Another Oade M148 Charger Question
« Reply #12 on: September 16, 2015, 12:34:32 PM »
Thanks for the input guys. I replaced the other 5 batteries and have it on the charger.  Time will tell. 

Mike
Neumann KM-140,Church Audio Ca-14, Card Omni, CAD e70

Edirol UA-5 (T+ mod), Church Audio CA-9200, M148

Tascam DR2D, Marantz PMD 660 (Oade Songcatcher)

Offline mec111272

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Re: Another Oade M148 Charger Question
« Reply #13 on: September 29, 2015, 07:37:38 PM »
After a fresh set I charged for 24 hours.  Voltage peaked at about 54.  Been a week and it has steadied out at 52.3 when I check it just about every few days.

Lesson learned here.............batteries on this are kind of a pain in the ass.
Neumann KM-140,Church Audio Ca-14, Card Omni, CAD e70

Edirol UA-5 (T+ mod), Church Audio CA-9200, M148

Tascam DR2D, Marantz PMD 660 (Oade Songcatcher)

Offline fsulloway

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Re: Another Oade M148 Charger Question
« Reply #14 on: September 30, 2015, 11:07:18 AM »
Looks like you've got it sorted out now. Is it possible the first batch of batteries were bad to begin with? I think you'll find over time that this pre is as simple as it gets and the batts really shouldn't be an issue.
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