ditto what SparkEl said about input voltage...
Check out the National Semiconductor datasheet at
http://www.national.com/pf/LM/LM340.html... the V
IN shown on page 4 of the PDF file says that the
minimum input voltage required to maintain regulation is 7.5 Volts.
Also, here's what an old post (which now seems to be purged) said about the ratshack 7805 on the JB3 (but they probably change chip vendors all the time):
http://www.oade.com/cgi-bin/miva?Forum/technology/showmsg.mv+message=14780
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Re: Battery life of Jukebox 3 (anyone build a batt
Subject: Re: Battery life of Jukebox 3 (anyone build a batt Date: Mon, 28 Jul 20
03 12:50:03 - (EDT) From: datgeek
OK I have done LOTS of testing on external power sources for the JB3 1:) do NOT
run the INTERNAL batteries if youare using an external DC Source.. 2:) RE 5v Reg
ulator make sure it is a 1.5+A regulator, the 1amp ones I tried from Rat Shack w
ill NOT do. and get a BIG Heat sink.. 3:) WHat I use and works for me >> I got a
1.2amp 4.5v DC Adapter (I can't find the accuall Creative Labs DC Adapter in st
ock ANYWHERE) but I picked up a Rat SHack 1.2A multivoltage Car adapter, on the
4.5v setting it works GREAT (Remember take OUT the Internal battery first) I run
a 8AMP 12V SLA into my JB3 & My UA-5 I have gotten 10+ hours out of this with N
O problems theoretically the system draws about 600-800ma durring recording, the
Boot up process is where you suck the juice using the JB3, it might pull a full
1amp+ during startup... for regulay 4 hour shows a regular 4ah 12sla should do
just fine. hope this helps Dail Reed www.datgeek.net dail AT datgeek DOT net
Don't know if this will help, but here's some
very crude current measurements I took back in the day:
- Removed internal batteries from NJB3.
- Attached digital ammeter (accuracy +/- 20mA) to the NJB3 (microcode level 1.20.06) DC input, powered by a Jensen JCD22A Auto DC Adapter (1A max) at the 5V setting, hooked to a 12V 12Ah SLA battery.
- Performed a "Line-in Recording" WAV 44.1KHz with no microphone attached.
- When the hard drive was running, measured 870mA; during idle 330mA; but the measurements varied by 10's of milliamps.
- Total guess that the hard drive is drawing current very roughly 1/3 of the cycle (maybe less).
- If the guess is true, then rough average current draw while recording is (870 + 330 + 330) / 3 = 510mA
- Measuring current spikes is difficult with a digital ammeter, but saw short peaks in the upper 9XXmA range while recording.
- When not recording and sitting idle, the current draw was a steady 100mA. During same state with the backlight on, the draw was 140mA.
- Interestingly, the unit drew a steady 47mA with the JB3 powered off.
Here's wishing good luck on your project.