[Boatanchors] Acquired a 'dream rig' Collins 51j-4

[Richard Knoppow]

    Congratulations. As I posted before the Treetop Circuits 
product detector and slow AVC is excellent. Don't bother with the 
old Lankford mods, they are very poor especially the AVC.
     With the mod this is an outstanding SSB and CW receiver.
     The  51J was built with ceramic caps, no paper caps in it. 
The only cap that might require replacement is the power supply 
filter cap. It is a plug in can and a duplicate is available from 
Hayseed Hamfest at reasonable cost. Tom's caps are new, not old 
cans restuffed.
    The only other problem you might encounter is the VFO. For 
some reason the range of the VFO drifts. This is true of all the 
PTO oscillators in older Collins gear. The drift is enough to 
move the VFO out of the range of adjustment by the inductive 
trimmer. The usual solution is to remove a  half a turn from the 
trimming inductance. There are extensive intructions on how to do 
this on the web. Treetop suggested changing a capacitor but my 
analysis is that it won't work.
    Individual receivers may have other problems but, in general, 
the 51J series is very reliable.
    I have an R-388, the military version of the   51J-3, mostly 
the same as the 4 but without the mechanical filters. BTW, the 4 
still has the crystal filter, a good one, which gives you the 
advantage of a notch filter.
    Both Hammarlund and TMC made sideband adaptors that work at 
500Khz but the Treetop circuits one is built in and better.

On 6/3/2022 6:13 AM, Karel Jennings wrote:
> Well, Thanks to a very good friend in the USA, I just won a Collins 51J-4
> in the Schulman auction.
> 
> It's intended to be the companion receiver to the Central Electronics 100V
> that I'm in the midst of refurbishing.
> 
> So, I'll do the usual going over the radio etc etc.
> 
> Is there anything that is a known pain point with these rigs? Like caps
> that are known to go bad etc?
> 
> --Karel VE3KJX
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL