HP Forum Archive 13

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Does anybody have information on a 30 series power supply? Message #1 Posted by Harry on 6 July 2003, 8:02 a.m. I recently bought a HP 37E. It has lots of corrusion from a leaky battery inside. I cleaned it all up, but it still does nothing. The "power supply" (don't know what you would call it, the part inside the calculator) does not seam to work at all. Now I am am wondering how to fix it. Does anybody have a shematic of it or at least specifications, like what output voltage at wich pin? I would also need information on the LED display. Do they have common Anode? And wich pin is connected to wich part of the display. Thanks a lot, Harry from Germany, sorry for my bad english, i need some more practice :)

Re: Does anybody have information on a 30 series power supply? Message #2 Posted by Emmanuel, France on 6 July 2003, 8:09 a.m., in response to message #1 by Harry Instead of the HP battery pack, you can use two 1.5V Alkaline batteries. It works. Yours.

Thanks, but that was not my question... Message #3 Posted by Harry on 6 July 2003, 8:39 a.m., in response to message #2 by Emmanuel, France i was talking about that electronic cirucuit inside the calculator. It generates diffrent voltages out of the 3V battery voltage. Haryy, Germany

Re: Thanks, but that was not my question... Message #4 Posted by Emmanuel, France on 6 July 2003, 9:27 a.m., in response to message #3 by Harry Please accept my apologies. Read your message too quickly. However it's an extra solution. I also sometimes use two 1.28V rechargeable batteries that an external standard recharge. Good luck !

Re: Does anybody have information on a 30 series power supply? Message #5 Posted by Jon on 6 July 2003, 11:33 a.m., in response to message #1 by Harry Hi Harry That calculator doesn´t work without batteries. If you plug the charger be sure you have rechargeable batteries inside or you could damage it. These calculators always fail because of broken flex connector. I have found just once one spice non working after repairing this connector. I replaced all the capacitors in the AC/DC circuit and it worked. First of all try to replace the flex connector for wires. And test it with alcaline cells. Take care with the poarity. The contact closest to the top of the calculator is "minus". You have to apply 2.4-3V in the contacts (two alcaline AA batteries work fine as Emmanuel said) Good luck Jon

Re: Does anybody have information on a 30 series power supply? Message #6 Posted by Harry on 6 July 2003, 1:19 p.m., in response to message #5 by Jon I already did replace that connector with wires. All capacitors seam to be fine. I might have had the batteries in the wrong way round though (this is my first spice), what kind of damage would that do? I can see one bridge that has been cut on the circuit board, i am not sure if it came from HP like that or if somebody else did that. To me it looks like it bridges the "On/Off" switch to test the circuit at the factory. I am quite sure the problem the calculator has is that little power-suply-circuit. I think i will test the transistors next. But i can't read anything on them, so i would not know what to replace them with. Thanks, Harry

Re: Does anybody have information on a 30 series power supply? Message #7 Posted by Vieira, Luiz C. (Brazil) on 6 July 2003, 2:33 p.m., in response to message #6 by Harry Hi, harry; for as long as I remember, this is the only jumper available in the power board. Compare it to the image below: Believe me: this jumper allows you to select if you want comma or dot as radix mark. The relation is: Jumper closed - dot for radix mark Jumper opened - comma for radix mark In your case, you'll have to use a small wire and connect both terminals if you want to keep north-american number representation. If you check for the serial number, your calculator will have a country ID letter in its fifth position, and the origin COUNTRY is usualy written right below it. Let us know when you have success repairing your unit. Luiz (Brazil) Edited: 6 July 2003, 2:40 p.m.

Thats the jumper i was talking about! Message #8 Posted by Harry on 6 July 2003, 3:34 p.m., in response to message #7 by Vieira, Luiz C. (Brazil) Thanks for that interesting information. And for the very good pictures. With the help of the link to the older post I found out that my power-supply is definatly not working as it should. So i will try and find out whats wrong with it. Regards, Harry

I second Jon's advice Message #9 Posted by Vieira, Luiz C. (Brazil) on 6 July 2003, 1:08 p.m., in response to message #1 by Harry Hi, Harry; I'm adding an image with a partial view of an HP31 with wires replacing the flex circuit. You can see the points I used to solder the three wires that go to the battery/AC connections assy. I did not take any measures in this board, but Ellis Easley made a complete description of what he found in this post, along with some other interesting reports. And be aware of the fact that continuous memory Spices (HP33C, 34C and 38C) have a power board that's different of the ones found in regular units (HP31E, 32E, 33E, 37E and 38E; there is no HP34E). If you need further advice, let us know. Luiz (Brazil) Edited: 6 July 2003, 1:10 p.m.

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