Quote:
Originally Posted by Dave S
I have heard that a 3RP1 can be subbed for a 3KP4, with some extra expenditure of effort, but haven't monkeyed around with that yet myself. There are also at least two different versions of the 3RP1. The standard one, and a shorter one also identified as DG-32 or CV2431 that was used in the Marantz 10B tuner. A standard 3RP1 will not work in the tuner. I assume that they are electrically identical, but don't know that for sure.
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I think the tube for the 10B tuner is a DG7-32, which is shorter than a 3RP1. Although the pinouts appear to be the same, the specs for the two tubes are different, most notably, the heater current of the DG7-32 is only 300 mA, and would likely blow out quickly if used in the Pilot circuit unless the heater is shunted. The DG7-32 also has a conductive coating on the crt face which apparently allows the tube to be used at lower voltage.
DG7-32 datasheet:
https://frank.pocnet.net/sheets/152/d/DG7-32.pdf
3RP1 datasheet:
https://frank.pocnet.net/sheets/049/3/3RP1.pdf
Save your DG7-32s for Marantz 10B tuners!
jr