Thanks Walt
Been looking and looking for parts, but only have a
small portion of what I need so far, maybe I too should
look for a receiver that might have most all the parts.
Thought that last E-bay HBR13 was mine for the parts,
but had a hard time justifying the $250 : )
Not too sure of my skills and knowledge, so I think I
need to stick fairly close to the original schematic etc.
for the HBR 13C that has been my goal. Not gone to
many ham fests this last couple of years, maybe I need
to change that approach : )
Thanks for everyone's updates like Walt's here, lets a
guy know he's not alone and crazy : )
73 folks
Bill
On Nov 8, 2011, at 11:22 AM, Walt Hutchens wrote:
> In an effort to build up an HBR that:
>
> 1. Is based on an easily available set of basic parts, and,
>
> 2. Could be duplicated
>
> I bought a somewhat tired Heathkit HB-10. The first round of work
> was
>
>> ... to relocate the calibrate and antenna trimmer capacitors so
>> there'll be
>> room for the antenna and mixer coils. After that, it's into the
>> front end
>> with the wire cutters and nut driver ... "Strip to a bare chassis
>> and lay out
>> new holes as follows ..." However it shouldn't take more than a
>> couple of
>> days to get the major chassis work done.
>
> The front end has been rearranged, 80M coils wound, the new
> oscillator tube
> added, the mixer circuit/tube changed, and the necessary new panel
> made and
> installed: All of that went pretty well, though I may need to add
> one turn
> to the mixer coil to get perfect tracking. I did do these two coils
> without trimmers and that seems to work okay.
>
> I then started at the back end. Things were more complicated
> there: To even
> start the testing I had to replace the audio section because the
> 6EB8 audio
> tube (two sections -- triode-pentode) socket was so loose that you
> couldn't
> get all pins to make contact for more than a few minutes. Rather
> than
> clear out the whole area to allow building the new circuit I redid the
> original circuit using new parts and a new socket.
>
> Having shown that signals would go all the way through the set, I
> tackled
> the other changes in that area: moving the BFO and giving it a tube
> of its own, changing the detector circuit, and rewiring that part
> of the
> panel using the new toggle switches.
>
> Unfortunately I recycled the detector socket and got some of the same
> trouble as with the audio tube so I now have to rebuild my own work
> starting
> with a new socket. If a tube socket in one of these sets doesn't grip
> firmly it ought to be tossed right at the start.
>
> The BFO -- now a 6BH6 -- was relocated over by the detector. With
> the BFO
> tuning cap moved one hole to the left (on the panel) all the
> connections are
> shorter and the tangle (both electrical and mechanical) of IF and
> BFO has
> been eliminated. This has to be better than using the triode half
> of the
> 2nd IF stage as a BFO and I'm hoping it will get me most of the way
> to being
> able to use AGC and BFO at the same time.
>
> The original HR-10 design, however, has NO decoupling of various
> stages:
> Everything is on the same filament buss and most of the tube plate/
> screen
> voltages come straight off one B+ line just as in an All American
> Five BC
> design. So it's not as simple as just replacing stages: The
> interaction
> between stages has to be fixed at the same time.
>
> The one-step-at-a-time approach may make sense for developing this
> project
> but my guess is that if it gets to be possible to duplicate it,
> that should
> be done from a bare chassis. (Maybe just leave the power
> supply.) Between
> Heathkit compromises (like cheap sockets), worn out or failed
> parts, and
> original builder mistakes and workmanship issues, there's a lot of
> waste
> motion in a rolling rebuild.
>
> It will be important to get the foundation receiver working first
> since
> that's the easy way to smoke out parts and other problems. So far
> I've
> found one dead crystal, one rosin joint, one unsoldered joint, two bad
> sockets, and a worn-out volume control. Building these into a new
> set
> (even as part of one step at a time with testing) would not promote
> builder
> mental health.
>
> (The second set I had to buy to get a good pair of crystals came
> with a
> near-frozen bandswitch and I've seen others complain of the same.
> Since that
> part of the set is unneeded, that's not a problem.)
>
> The current status is that all stages sort of work, either in the
> original
> or as rebuilt but partly because I don't have enough AGC voltage
> and partly
> for other reasons, it sounds terrible. After I replace the
> detector socket
> I'll start at the audio section and work backward just as with any new
> receiver.
>
> Tube lineup:
>
> 6EH7 -- RF
> 6BH6 -- 100 kcs calibrator
> 6BH6 -- LO (ECO)
> 12AT7 -- Mixer
> 6LM8 -- 1st IF & AGC bias rectifier
> 6LM8 -- 2nd IF & AGC detector
> 6BH6 -- BFO (ECO)
> 12AX7 -- detector
> 6LF8 -- 1st & 2nd audio
> 6X4 -- B+ rectifier
>
> A gain of three tubes (to a total of ten) plus comprehensive
> changes to
> both tubes and circuits. The 6LM8's are one of just a couple of
> pentode-triodes with a semi-remote cutoff characteristic so I'm
> looking
> forward to seeing how they work out.
>
> I think I've made all the parts of this work before but of course a
> new
> chassis and 'details' mean that it'll take time to get them working
> here.
>
> Pictures shortly.
>
> Walt
> KJ4KV
>
>
>
>
>
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