Dodd Battery Pre Amp Problem

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invicta51

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Dodd Battery Pre Amp Problem
« on: 8 Jul 2017, 04:52 am »
I don't mean to misdirect this to the GR AC thread, but I don't know where else to go. I am having a problem with my Dodd battery preamp. I bought new batteries but they don't charge up. The battery charge does not go into the green led to indicate charging and it stays re. I have googled on the charger model number and came up with nothing. What can I do?

S Clark

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Re: Dodd Battery Pre Amp Problem
« Reply #1 on: 8 Jul 2017, 05:57 am »
Hopefully Danny will chime in.  I understand that he has most of the Dodd schmatics.  Also Charlie Cocci in MA works on a lot of Dodd stuff. 

JakeJ

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Re: Dodd Battery Pre Amp Problem
« Reply #2 on: 8 Jul 2017, 06:15 am »
Do you have a multimeter?  If so, disconnect the battery(s) and check the voltage between the plus and minus.  I don't know what voltage the original batteries are but as an example let's say they are 12 volts.  If the voltage of the new batteries are low, say around 3-6 volts, the charging system may not "turn on" as they need to be a higher starting voltage.  Maybe 9-10 Volts.  If that is the case and you have a charger for your car battery (generally 12 Volt system) then you can charge to full voltage and start from there.

Just a thought.

TrungT

Re: Dodd Battery Pre Amp Problem
« Reply #3 on: 8 Jul 2017, 06:16 am »
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sfox7076

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Re: Dodd Battery Pre Amp Problem
« Reply #4 on: 8 Jul 2017, 02:02 pm »
Charlie fixes a lot of Dodd work, but I do not think he will do battery stuff.  He would redo it using rectified D.C.   

invicta51

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Re: Dodd Battery Pre Amp Problem
« Reply #5 on: 11 Jul 2017, 02:48 am »
I independently charged the batteries and the preamp seemed to play normally. I plugged the Dodd supplied battery charger and it did not go into green led charge mode.  I unplugged the battery charger from all power and disconnected from preamp to let it sit 5 minutes. Tried connect to the preamp again with the same result. I think I need a new battery charger.

JakeJ

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Re: Dodd Battery Pre Amp Problem
« Reply #6 on: 11 Jul 2017, 03:15 am »
Yup, sounds like a problem with the charger.  But now you can listen while you find a replacement!  :thumb:

mikeeastman

Re: Dodd Battery Pre Amp Problem
« Reply #7 on: 11 Jul 2017, 12:34 pm »
I found as have others found that the Ctek 7002 chargers work well on Dodd battery powered gear, you can leave it connected and charging when using the gear with out any lose in SQ. The charger also has a reconditioning feature to maintain the battery, which should be done every month or two to extend the life of the battery.

sfox7076

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Re: Dodd Battery Pre Amp Problem
« Reply #8 on: 11 Jul 2017, 01:24 pm »
Mike is correct.  I used that for my Dodd Amp, before it started to oscillate for no reason... 

invicta51

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Re: Dodd Battery Pre Amp Problem
« Reply #9 on: 12 Jul 2017, 04:48 pm »
Thanks for the info. I will have to replace the battery charger and I just don't know which one to buy. The Ctek 7002 is readily available. Would you have to cut off the connector that fits into the Dodd Pre rear panel and slice into the red and black output wires on the charger?  I have a 12V 1.25A Battery Tender, could I make that work??

S Clark

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Re: Dodd Battery Pre Amp Problem
« Reply #10 on: 12 Jul 2017, 05:39 pm »
Is this the original model with four 5ah batteries inside the preamp, or the later models with batteries that are external? The early models are 24V, aren't they??

TrungT

Re: Dodd Battery Pre Amp Problem
« Reply #11 on: 12 Jul 2017, 06:12 pm »
Can't use Ctek 12V charger, it is a older 24v system pre.
Ctek does make a 24v, but it's little pricey.

S Clark

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Re: Dodd Battery Pre Amp Problem
« Reply #12 on: 12 Jul 2017, 06:55 pm »
There are a ton of wheel chair 24V chargers from $10 up.  They won't be quiet, but charge overnight and disconnect when listening.  Slightly harder on the batteries, but it's cheap and it will work. 

invicta51

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Re: Dodd Battery Pre Amp Problem
« Reply #13 on: 12 Jul 2017, 09:16 pm »
Yes, this is the early batt pre with 4 UB1250 batteries inside. Originally it would switch between 2 batts depending on the position of the on switch. I had Gary Dodd convert it into charging and using all 4 batts at once. Yes the charger supplied from initial purchase was Zhonghui Electronics 24 V Model CH24-1.6D charger. Output was .1-1.6A.

invicta51

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Re: Dodd Battery Pre Amp Problem
« Reply #14 on: 12 Jul 2017, 10:14 pm »
Would this 24V 1.5A constant current charger work from Soneil - Canada?

https://www.batterystuff.com/battery-chargers/24-volt/gel-cell/Son2403SR.html#WayPointManuals


S Clark

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Re: Dodd Battery Pre Amp Problem
« Reply #15 on: 12 Jul 2017, 11:30 pm »
It should.  As a matter of fact, I think that's the unit Gary used on a battery powered DAC that he built for me years back.  If so, it's very quiet... quiet enough that I could never hear it. 

invicta51

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Re: Dodd Battery Pre Amp Problem
« Reply #16 on: 12 Jul 2017, 11:59 pm »
$64 plus $7.50 shipping seems reasonable. I just have to figure out how to attach the 2.5mm x 5.5mm connector from the original charger. Hopefully that is a 3 wire cable. Another thing that concerns me is the info the spec sheet says that it maintains battery voltage at 28.8 V. My concern is that it may overheat the batteries.

mikeeastman

Re: Dodd Battery Pre Amp Problem
« Reply #17 on: 13 Jul 2017, 01:49 am »
The 28.8 v should be the max voltage during charging, once it's fully charged it should drop down to the 26.4v range. If it really kept the voltage at 28.8 that would cook the battery.


gregfisk

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Re: Dodd Battery Pre Amp Problem
« Reply #18 on: 13 Jul 2017, 02:26 am »
$64 plus $7.50 shipping seems reasonable. I just have to figure out how to attach the 2.5mm x 5.5mm connector from the original charger. Hopefully that is a 3 wire cable. Another thing that concerns me is the info the spec sheet says that it maintains battery voltage at 28.8 V. My concern is that it may overheat the batteries.

From my experience "not in audio" 24v battery chargers charge at about 27.xx v which sealed lead acid batteries have no problem with. My guess is you will be fine and the batteries will only get warm to the touch but not hot. Then when there in no charging voltage they will drop down to about 25.xx or 26v and will work fine.

Greg

TrungT

Re: Dodd Battery Pre Amp Problem
« Reply #19 on: 13 Jul 2017, 11:41 pm »
Virtue Audio has 24v battery charger.
You need to  rewire the connection though.

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