The Museum of HP Calculators

HP Forum Archive 20

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Would you take a chance on this auction?
Message #1 Posted by Michael de Estrada on 13 June 2011, 12:50 p.m.

Here's another auction for a Woodstock in questionable condition. I wouldn't like to bet that it's in good working condition and hasn't been fried. Would you?

HP-29C auction

      
Re: Would you take a chance on this auction?
Message #2 Posted by Etienne Victoria on 13 June 2011, 12:55 p.m.,
in response to message #1 by Michael de Estrada

I don't like the ominous Led glowing on picture 3.

And I don't like the direct connection between the charger and the calc contacts.

Rip, Amen.

Etienne

Edited: 13 June 2011, 12:56 p.m.

            
Re: Would you take a chance on this auction?
Message #3 Posted by Michael de Estrada on 13 June 2011, 1:17 p.m.,
in response to message #2 by Etienne Victoria

Quote:
I don't like the ominous Led glowing on picture 3.

Yes, but notice that it is not connected to the charger, and the batteries are dead, so it may just be a reflection from a camera flash. Still, I wouldn't want to trust that it is working properly. Note that the seller only states that it will "power up." Sounds like another infamous TAS seller we all know.

                  
Re: Would you take a chance on this auction?
Message #4 Posted by Juergen Keller on 13 June 2011, 4:36 p.m.,
in response to message #3 by Michael de Estrada

I think you are right, it is a reflection from the flash. Aside from the engraving (luckily on the backside) it looks quite nice. Regarding the working condition: ask the seller to clarify this point.

      
Re: Would you take a chance on this auction?
Message #5 Posted by Namir on 13 June 2011, 1:11 p.m.,
in response to message #1 by Michael de Estrada

I pass!

      
Re: Would you take a chance on this auction?
Message #6 Posted by bill platt on 13 June 2011, 1:43 p.m.,
in response to message #1 by Michael de Estrada

I refuse to buy a calculator off ebay if it has a reserve price. I did it once and I will forever regret it.

The reserve is ridiculous.

            
Re: Would you take a chance on this auction?
Message #7 Posted by Michael de Estrada on 13 June 2011, 2:32 p.m.,
in response to message #6 by bill platt

The reserve just adds insult to injury. I don't bid on reserve auctions either, but this one is just plain silly.

      
Re: Would you take a chance on this auction?
Message #8 Posted by Steve Simpkin on 13 June 2011, 3:25 p.m.,
in response to message #1 by Michael de Estrada

The statements "This is a working vintage HP 29C calculator." and "The calculator will power up by connecting the leads of the charger to the prongs on the calculator." do not add up. The Woodstock charger puts out 10+ Volts of AC power. The AC voltage is half-wave rectified to convert it to DC, passed through a current limiting resistor and placed across the battery pack which acts as a regulator keeping the voltage below 3 Volts DC. Removing the battery pack and connecting the charger would supply over 10 Volts of AC power to the internal calculator circuity. This would likely damage the calculator circuitry not only by over-voltage stresses but by reverse polarity stresses as well (at minimum to the continuous memory IC). My conclusion is that this seller is lying.

            
Re: Would you take a chance on this auction?
Message #9 Posted by Ren on 14 June 2011, 12:57 p.m.,
in response to message #8 by Steve Simpkin

Just playing Devil's advocate...

But the pictures don't show the charger connected WITHOUT the battery pack installed, so maybe it hasn't been fried (like I clumsily did once).

Ren

dona nobis pacem

                  
Re: Would you take a chance on this auction?
Message #10 Posted by Michael de Estrada on 14 June 2011, 1:06 p.m.,
in response to message #9 by Ren

You can damage the calculator by powering it up with the ac charger, even if there is a battery pack installed. If the battery pack is spent, as the seller readily admits, then its resistance can increase significantly to the point that it effectively acts like an open circuit. This is no different than powering the calc from the charger with the battery pack removed, which is the condition that results in damage to the calc electronics. Also, corrosion on the contacts can result in high resistance as well.

Edited: 14 June 2011, 1:07 p.m.

                        
Re: Would you take a chance on this auction?
Message #11 Posted by Michael de Estrada on 23 June 2011, 10:23 p.m.,
in response to message #10 by Michael de Estrada

Well, someone has met the reserve price and bought it. It will be interesting to see what if any feedback is given to the seller.

HP 29C

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