Re: 11710B Down converter
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Futurlec has 2N2218 in stock.? The ubiquitous 2N2219 is the same part, just higher hfe.? HP knew about the 2N2219 so maybe they had trouble with instability.? You could probably select for low hfe.
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2N2222 is the same as 2N2219 except smaller package and consequent lower power dissipation.
The -A parts are the same except higher breakdown voltage.? Digikey and Mouser have 2N2218A and 2N2221A in stock right now, and of course everybody has 2N2222A or PN2222A.
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A quick skim of the A1 board schematic doesn¡¯t worry me about either breakdown voltage or power dissipation.
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Dave Wise
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From: [email protected] < [email protected]>
On Behalf Of Willie via groups.io
Sent: Friday, February 11, 2022 5:10 PM
To: [email protected]
Subject: [HP-Agilent-Keysight-equipment] 11710B Down converter
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My down converter is something i use a lot with my 8640B sig gen when I? need a signal below 450 KHZ.? Unfortunately a clumsy accident killed the output.? The failure was traced to Q1 and Q2 on the converter
amplifier assembly board.? Q2 is listed as a 2N2218A and Q1 is an in-house part number.? I used a 2n2222 for Q1 and that worked fine.? After repairs the difference between direct and down converted output was less? than 1 db.? This repair may seem mundane
but the reason I mention all this is that the 2N2218A is not listed in Mouser and although DigiKey shows stock it is listed as obsolete.? I bought a few for insurance against future mishaps.? If you have this down converter you might want to the same.
Bill, K3PGB
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