Last updated: 18 April 2004
Sent: Saturday, April 17, 2004 15:39:13 From: "Jacky Poupot" (email@example.com) On your site I searched an article that could help to build an external power supply like the #541 from Meade. I read that this little box gave a maximum current of 1.4 A !! Amazing... But some friends gave there informations about the current on a ETX-90.So.... I decided to build a cable with a 2.5mm power connector and plugged in my ETX-125. On the other side I used my 12 V Radio-Ham Power Supply with 30 A max output. With an Amp. meter I checked the current used by the ETX-125 and the results are : 1) when the scope is waiting without "working" : 130 mA 2) when the scope runs with all the motors : 580 to 600 mA max 3) when the scope is tracking : 200 mA So, we can say that 1.4 A is not really necessary. With all this informations I have built an asymetric power supply that give 12V at 750 mA.This is very simple to build and very cheap. (sorry the input voltage is 220 / 60 Hz it's used here) Here is the scheme : First, It should be possible to join these electronic part to make a good symetric power supply. For now, It should be OK. (tested on my scope one). The parts to be used : F : fuse : 100 mA TR1 : 12V sec. / 9VA / 750 or 850 mA C1 = C2 : 0.1F/Plastic C4 : 47F/25V C3 : 4700F/25V IC1 : LM7812 on a disipator But, this sheme can be used to make some power supply from 5V (1A)to 24V(400mA) by changing the TR1, IC1 an C3. I can give the informations for the parts and the drawing to build the plate. Hope you will enjoy this on the BEST EXT Site of the World ! Thanks Mike !! Best Regards from France Jacky - F6JFD
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