Garey;, Thanks for your input on the neutralization cap.. I agree that this TR-3 is one of the earlier models and appears to differ in several areas from another later model I have (SN:12478). I appreciate your willingness to check over your own inventory but I'm sure I can locate these items if they were used on the rest of the TR series. Lots of luck on getting organized after your move.. I'm still pulling stuff out of 30 year storage and trying to find places to put it. In fact, while trying to find that air cap replacement I ran across a bakelte Dejur in my shack.. now how old is that?
Doc >Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang >---------------------------------------------------------------------- >Doc - > >Wow, not pretty! :-) > >The original was a ceramic trimmer of 3 - 50 pF, with a single 27 pF 1 >kV cap in series with it. This is the neutralization cap and so has to >handle the full plate voltage (700 VDC no load) plus peak RF voltage. >This must be a very early TR-3 (s/n <4000) to have the ceramic trimmer >in that position. Later units used a small air variable here, a >Hammarlund MAPC, 2.7 - 8.4 pF, with a 12.5 pF @ 2KV disc ceramic in >parallel. I suspect they had problems with that ceramic trimmer >breaking down (as did Collins in early 75S-1s) and changed to the air >variable. The same air variable and parallel cap was used throughout >the rest of the TR-3/4 series, so you can get one from just about any >parts unit. > >If you can't find one, I may have one here somewhere. I'm not too well >organized after the move! Ya really shouldn't move after 25 years on >one house, especially if you're a pack rat......! :-) > >73, Garey - K4OAH >Glen Allen, VA >
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