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I am trying to repair a half-nut 41CV for a friend. I found two cracked posts near the strip connection and fixed them using tips from this forum... this fixed the problem, Yes? No, it still will not turn on. Tried fresh batteries, still no luck. Can someone give me some more troubleshooting tips to keeping me progressing toward success?

Tracy

If you have a 6V supply (either a bench PSU, or even a 6V battery), connect it directly to the logic PCB with the machine apart.
The -ve side goes to the -ve terminal of the largest capacitor on the board, the +ve side to the commoned end of the 2 piggybacked diodes in the top left corner of the PCB (as you look at it).
If the machine will power up then, the fault must be in the flexible PCB in the I/O assembly, or cracked posts (etc) which are preventing it from making good contact with the logic PCB.
If the machine doesn't power up when the logic PCB is connected to the PSU, then there's a fault on that board. Could be just about anything -- 'on' switch contacts, CPU, diplsya hybrid, passive components.

The first thing to try is a "master reset". Short the leads together for a second or so of the 470uf (the largest) cap on the left side of the board and retry. Many times the processor will be in la-la land and will not respond otherwise.

If that doesn't do it, Tony's suggestion is spot on. The current consumption will help with a fault finding direction. If it powers up with a direct connection to the diode and capacitor, it is most likely a broken trace on the battery connector. This usually happens only with a battery leak.

Normal operation will be between 30 and 50 ua, standby will consume about 1 ua.

My money's on a master reset. Half-nuts are pretty darn hard to kill.

Edited: 12 Sept 2003, 7:49 p.m.

Thanks to Tony and Randy for the technical assistance!

Another 41CV is back into service! The calculator was revived by shorting across the capacitor as recommended by Randy. Good thing too, because I would have had to ask Tony for better directions, like a photo, on where to apply the 12V (I'm a CE, not a EE).

I feel great being able to return a working HP to my buddy at work, thanks guys.

Congrats on a job well done. Good thing you didn't apply 12 volts, you would have smoked it. 4 x 1.5 volt batteries = 6 volts. They'll actually work down to about 4 volts.

One other thing to mention is the classic green fuzz problem. Always look on the battery connector and springs in the battery holder for green stuff. If you see any, clean it up with cotton swabs and alcohol. The current levels at which a 41 operates does not tolerate cooties on the connections.

You can connect the test supply directly across the big capacitor. The low battery indicator will light up though.

Tracy, you have a Belgian name. Are you from Belgium ?

Randy,

I recognized my 12-volt error right after I sent the post, thankfully my electronic skills are somewhat better than my typing. Thanks again for you help you are a wonderful source of knowledge and I appreciate you sharing it.

My father immigrated to the US from Belgium after WWII- he was 13 yo at the time. I have never been there, but I hope to visit relatives over there some day.

I am curious, is Vermeyen a common name in Belgium? I know of one famous painter from the 15(?)th century with the same name, but very few others.

Take Care