[HBR] New HRR 16 Owner and intro

[John Landrigan]

Thanks for the suggestions, Walt.
I've been trying the same thing although not as systematically as you have laid out. I get frustrated too easily with the thing and call it quits until another time hoping the respite will allow me to look at things with a keener eye. I'll keep you posted.
John KA4RXP
----- Original Message -----
From: "Walt Hutchens" <waltah at earthlink.net>
To: "HBR Receiver List" <hbr at mailman.qth.net>
Sent: Wednesday, May 30, 2012 5:52:59 PM GMT -06:00 US/Canada Central
Subject: Re: [HBR] New HRR 16 Owner and intro

John Landrigan posted:

> Thanks for the layout photos and the coil diagram photo. This is a very nicely
> constructed version and continues my desire to get my version past the
> troubleshooting stage. The problem now is a non-oscillating HF oscillator. I
> still can't tell if it is a wiring issue or a coil winding issue. I thought I
> had the problem solved when I found a less than optimal soldering job on one
> of the coil pins but that wasn't the final answer.

1.  Examine the coil winding.   Assuming it is the usual tickler feedback
design (just a few were built with Hartley oscillator circuits) then the
windings should go in the same direction from one end to the other of the
coil:  If clockwise when seen from the bottom as you go from bottom to top
of the lower winding then the upper winding should also go clockwise as you
continue upward.

The coil ends that are closest together should be at RF ground.   One will
be the B+ lead (bypassed to ground for RF) and the other will be the grid
return -- directly to ground or through a bypassed grid resistor; I don't
have the circuit in front of me.

Getting either one coil or the connections to one of them backward is a very
easy mistake to make.

2. Is the tube known to be good?

3.  Check the coil with an ohmmeter at the socket pins.   Also check
connections to the APC cap.

4.  Check all connections to the coil and tube sockets.   A connection that
was okay 50 years ago might not be, now.   (I've found them NEVER soldered,
even in military gear and of course this is common in Heathkits and homebrew
sets.)   

5. Check the connections to the tuning cap, including contact springs for
the rotor.   Irregular or measurable resistance in any of these places must
be fixed. 

6. Do ohmmeter checks out through the circuit to B+, etc.

7. Check the supply voltages to the tube on each of the pins.   Grid voltage
can be checked with a DVM through a 10k or so resistor.   If grid voltage
checked this way is close to zero the tube isn't oscillating; if it is -1 to
-5 volts or so then it IS oscillating.   If the plate voltage is low and the
tube isn't oscillating then you're most likely looking for an RF problem
along the lines suggested above.   If plate voltage is high and tube isn't
oscillating suspect a bad tube or a mistake or omission in your ohmmeter
checks ... is the grid resistor actually grounded?   Could it be open?
Stuff like that.  

These problems are frustrating, but they can always be found.

Walt 
KJ4KV

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