[R-390] TR: R-390 Woes

[Dan Martin]

My J4 has the Dallas Langford PD and AGC mods, as installed by Howard Mills, W3HM, who lives a short drive away. 

The Langford mod is similar to Orr’s and Paul Lee’s versions although with different component values here and there. The Langford version is featured in HSN, #28. I’ve been pleased with it.

Dan
WB4GRA

Sent from my iPhone

> On Oct 8, 2025, at 3:45 PM, Jacques Fortin <jacques.f at videotron.ca> wrote:
> 
> Hi Jim,
> Yes, this should have been the Bill Orr PD mod.
> As we are there, VE3TOU (Treetops Circuits) made a plug-in PD for it (well, kind of) see attached.
> About trying different tube types on a R-388 PD, I never do it, despite I have one Collins R-388 but it is still to be restored.
> 
> 73, Jacques, VE2JFE in Montreal
> 
> Jacques
> Good catch.
> I have a 51J-3 aka R-388 that also had the 6BE6 Product Detector mod installed.  It must have been inspired by the Bill Orr Ham Radio magazine article.  I agree that it doesn't work very well.  I removed the mod but haven't decided on what to do.   Either make it work better in SSB or return it to original condition.  I think that there are several pentagrid tubes that have the same pinout as the 6BE6 but are less noisy with higher gain.  Has anyone tried the 6BY6, 6CS6, 5915 or 7036 in place of the 6BE6?
> Jim
> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
> 
> <R-388_ProductDetector.pdf>
> <PD3Manual_Ver8.pdf>
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