HP9114B battery pack

At 12:05 AM 02/22/2000 +0000, you wrote: Good. The original packs carried the Panasonic LCR-226P, 6V, 2.4AH, which are not produced anymore. However, the LCR-062R4PU has the same form factor and capacity, and can still be obtained. I bought several at Digikey a couple of years ago. The only difference is in the location and orientation of the terminals, but bending them a little is enough for the battery to fit in the pack. By the way, I also used some of these to replace the larger 3.2AH cells in my HP3421's. Unfortunately, I could not find any modern battery with the same form factor of the original LCR-306P. The 1.5 V difference is big enough that the charger may actually damage them. Low duty lead-acid batteries are supposed to be charged using constant voltage (with initial current limiting, one amp for the ones in question). For standby use the charging voltage for these is 6.9V; for cycle use the charging voltage is 7.3V . Both are way too high for a 4.5V nominal pack. And I think that 4.5V is probably too low for the hp9114. I have two HP9114's, an "A" version and a "B" version. The charge circuits are different. The pack in the "A" version is nothing more than a series NPN/Zenner base voltage reference plus a fuse in series with the 9114A. The one in the 9114B does have the LM311, a 79L05, a 2N3906 and a 6102N/6240 marked "Q2", plus a couple zenners, an 1N4004 and other resistors/caps. Q2 could also be an SCR (not the first time one would have shown up in a charger).... in fact, I have just taken some readings and it definitely is not a bipolar transistor. It's looking more like an SCR. The gate would be the pin farthest from the board edge. And this charger is functional. Sorry, I don't know what a proper replacement would be, but I think that your Q2 might actually be good (it's hard to blow up an SCR with a source that has an internal impedance as high as that in a 82059 xformer).