[Boatanchors] 6146 question

[manualman at juno.com]

When I picked up a HW-101 at a flea market for $20 years ago, it didn't
have any final tubes. Brought it home and leaned it up, put in a pair of
6146B's (they were handy on the work bench) and the HW-101 worked fine
from the get go all the way to 10 meters. When I finally sold the rig, to
make it "original" I put in a pair of 6146A's. Saw no difference in
performance and the various transmitter knob settings for various bands
using the 6146B's had been recorded and the settings were almost
identical on every band using the 6146A's.

My Apache, which I built, was switched over to 6146B's in the 70's and
has worked fine all the way to 10 meters on AM and SSB(SB-10 was put in
operation a year or two after I built the Apache). The Apache had a very
rudimentary neutralization (a stiff piece of wire that struck through the
chassis and you moved it between the two final tubes). No oscillations,
no funny squeals. 6146B's are still in the rig and I still use it on a
regular basis.

My Valiant had three 6146B's in the final, and two 6146A's in the
modulator. Those were the tubes I had handy when I got the Valiant that
only had weak 6146's in it. I only paid $70 for the Valiant so I didn't
complain. No problem with the B's all the way to 10 meters. Sold the rig
several years ago but actually heard it on 40 meters AM several weeks
ago.

This issue of the 6146 family has come up numerous times over the years.
Several years back, I made a comparison chart of the inter electrode
capacitance of the various 6146 tubes. In some cases, the capacitance
values were identical between tubes or the variation was maybe a 1/2 pf.
I have no idea what I did with the chart and have no ambition to pull the
specs for various 6146's and regenerate it again.

This 6146 family P&M will probably go on as long as the tubes are still
available for sale used or otherwise. Personally, I really don't care,
since in 50 plus years , I've never found a valid reason or equipment not
to use 6146B's in place of 6146's or 6146A's.

Back over the years, some have had "bad" experiences and pointed to the
tubes. Maybe the tubes were the problem but maybe the real problem was a
circuit design fault. Life moves on. If it continues to bother you, annoy
you, makes your daily life miserable, or gives you digestive issues,
maybe you should get a solid-state rig.

Pete, wa2cwa


On Sun, 28 Jan 2024 22:14:47 -0500 "Paul Christensen" <w9ac at arrl.net>
writes:
> Back in 1973, I had horrid results when changing from 6146A to a 
> 6146B tubes in a Heath HW-101.   With the B tubes, I couldn't 
> neutralize the PA and get stable 15m and 10m performance.  On those 
> bands, the transmitter would "take off" as the mic gain/carrier 
> control was advanced while simultaneously producing a high pitch 
> screech from the PA.   I tried multiple sets of B tubes and had 
> identical results.  Switching to a new set of A tubes solved the 
> problem.  Back then, a pair of 6146 tubes from our local wholesaler 
> was about $10.  As I recall, Heath published a service bulletin with 
> a warning to only use 6146A tubes.
> 
> Given this experience, there's no way I'd consider all versions as 
> universally interchangeable.  Possibly better results would have 
> been attained with a slightly larger variable neutralizing cap value 
> but that's not something I would have considered at age 13.  That 
> said, I believe there's value in the work reported by K9STH and 
> K9AXN.  
> 
> Paul, W9AC