HP Forum Archive 20

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Repairing a 82022B charger (with P.S. to Geoff Quickfall) Message #1 Posted by Karl-Ludwig Butte on 20 Feb 2011, 3:45 p.m. Dear all, one of my 82022B chargers broke some days ago. A first investigation showed that the fuse was melted. But after replacing it, the same thing happened again immedeately. A further search for the root cause showed that transistor Q3 shortcircuited. It's a NPN power type with a "M726" printed on it. Alas I couldn't find any datasheet at the Internet. Does anyone know with which transistor available today I can replace it ? Any hint will be very much appreciated - thank you very much in advance. Kind regards Karl P.S.: By the way, Geoff, if you're reading this, may I ask how about your book ? Will it be ready for ordering soon ?

Re: Repairing a 82022B charger (with P.S. to Geoff Quickfall) Message #2 Posted by Ignazio Cara (Italy) on 21 Feb 2011, 2:43 a.m., in response to message #1 by Karl-Ludwig Butte Hello Karl, take a look at this fantastic job of Jacques Laporte about the HP-35 and more old HP calculators: http://www.jacques-laporte.org/HP35%20power%20unit.htm Take care and regards. Ignazio

Re: Repairing a 82022B charger (with P.S. to Geoff Quickfall) Message #3 Posted by Karl-Ludwig Butte on 22 Feb 2011, 3:22 p.m., in response to message #2 by Ignazio Cara (Italy) Hello Ignazio, thanks a lot for your answer - I'll try my luck. Best wishes and kind regards Karl

Re: Repairing a 82022B charger (with P.S. to Geoff Quickfall) Message #4 Posted by Karl-Ludwig Butte on 23 Feb 2011, 11:44 a.m., in response to message #1 by Karl-Ludwig Butte Dear All, thanks again for the link Ignazio and thanks Jacques for the excellent technical content. I succeded to repair the charger by replacing the defective Q3 with a BD128 which should be available at any electronic shop. A bit more difficult was to find a supplier for the fuse, a so called pico-fuse, which also was defect. For people living in Germany I found it at Reichelt Elektronik. Best wishes and kind regards Karl

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