Re: Some collecting questions Message #2 Posted by Thomas Okken on 30 June 2009, 10:46 p.m., in response to message #1 by Palmer O. Hanson, Jr.
I'm no expert but I'd expect that the market for slide rules has cooled down, not heated up. When the economy is bad and people are reluctant to spend money on non-essentials, it makes sense to hold on to your collectibles and wait for the market to recover, when you'll probably be able to get better prices as a seller.
Regarding swapping parts from an HP-27 to an HP-22: I think I read somewhere that the electronics in the HP-27 are not compatible with those in the other Woodstock models because they use NMOS technology, as opposed to PMOS in the earlier models and CMOS in the 25C and 29C. I googled a bit and found this link to an old HP Forum thread that may help shed some light on the issue.
Apart from the PMOS vs. NMOS question, I don't think you should gut a working HP-27 to repair an HP-22 or 25; the HP-27 is much rarer, you should treasure it, or sell it and get an HP-25 to gut, there are plenty of those -- although I personally have great nostalgia for the HP-25 and would not do this myself. :-)
- Thomas
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