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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Wed 04, 2020 8:57 pm 
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Joined: May Sun 22, 2011 11:27 pm
Posts: 361
Location: Dallas,TX
Hi Jim,

Could you post a few pictures of the finished product? I'd like to see the top and bottom of the chassis.

Thnx, Mike

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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Wed 04, 2020 9:30 pm 
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Joined: Mar Wed 16, 2011 10:44 pm
Posts: 1652
Location: Peekskill, NY
Not finished, yet!

I will take a few snapshots but there has been hardly any attempts at cosmetic improvement. Most of the work
involving the mechanicals are pretty much invisible.

I have the bottom on right now, but it will come off when I get the new power resistors to install, and I'll take that
time to take a few snapshots.

Next big undertaking is stripping, de-rusting, and re-painting the top cover. Next stop is the auto parts store to get black wrinkle paint....


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Sun 08, 2020 6:16 pm 
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Joined: Mar Wed 16, 2011 10:44 pm
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Location: Peekskill, NY
Work on the cover:

Two photos of the original paint, which is in sort of rough shape. I decided to strip it, and repaint.
The citristrip stripper works, but the original paint is really really tough, needed multiple applications.

Interestingly the steel cover is plated, so bare steel does not really show through, even when the paint's gone.

Plan is to use black wrinkle paint to re-do it once the dirty work is done.


Attachments:
cover_1.JPG
cover_1.JPG [ 212.02 KiB | Viewed 547 times ]
cover_2.JPG
cover_2.JPG [ 289.38 KiB | Viewed 547 times ]
cover_strip.JPG
cover_strip.JPG [ 284.67 KiB | Viewed 547 times ]
wrinkle_paint.JPG
wrinkle_paint.JPG [ 271.69 KiB | Viewed 547 times ]
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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Sun 08, 2020 6:28 pm 
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Joined: Mar Wed 16, 2011 10:44 pm
Posts: 1652
Location: Peekskill, NY
And as promised, a few pictures of the set where it's mostly done.

As an aside, the BFO injection works much better with the actual coupling capacitor in place.

Front panel, chassis top, a view of the underside of the chassis, and three close-ups.

Front panel: the AVC toggle has been flipped to be correct. There are no dial pointers on the knobs yet.

Chassis top: the original eye tube that came with this set, with replacement wiring. Also the newly stuffed original
filter capacitor, and the replacement BFO adjust capacitor from the donor set.

Close-ups no. 1: there are the new power resistors installed, and top band coils. The top band is still dead, so it's scope time.

Close up no 2: there's a pair of candohm resistors, which are the cathode bias resistors for the 6L6 pair. The wiring here again
does not agree with the diagram, this may be a previous retrofit that was done wrong - each 6L6 cathode goes to ground via
a separate resistor. All the information I see says the cathodes should be tied together, and from there just one resistor to ground.

Close up 3: visible are the new fuse, the re-done phone jack wiring, and the new wiring for the eye tube - not period but it works.


Attachments:
front.JPG
front.JPG [ 185.82 KiB | Viewed 546 times ]
chassis_top.JPG
chassis_top.JPG [ 285.66 KiB | Viewed 546 times ]
chassis_underside.JPG
chassis_underside.JPG [ 254.45 KiB | Viewed 546 times ]
under_1.JPG
under_1.JPG [ 311.09 KiB | Viewed 546 times ]
under_2.JPG
under_2.JPG [ 339.52 KiB | Viewed 546 times ]
under_3.JPG
under_3.JPG [ 321.83 KiB | Viewed 546 times ]
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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Sun 08, 2020 8:47 pm 
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Location: Dallas,TX
Thanks for the progress pictures. It's coming along! What are your plans for cleaning the chassis?

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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Mon 09, 2020 1:47 am 
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Location: Peekskill, NY
Plans for the chassis incudes removing about 50 percent of the rust with a wire brush, and removing 90 percent of the dust and grime with brushes and compressed air.

I would consider stripping the machine and glass beading the steel chassis - but there are still issues with the wiring that need to be dealt with. Glass beading would leave the steel very clean which would really require re-plating or painting of some sort.

So that cosmetic issue is down the road a bit.


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Mon 09, 2020 7:20 am 
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Jim, I have bead blasted rusty chassis and had them plated with bright zinc and it worked very well. I also restore coin-op antiques. The bead blast cabinet is an indispensable piece of equipment.

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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Mon 09, 2020 4:43 pm 
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Location: Peekskill, NY
Bead blast cabinets, are great and inexpensive - the real problem is a source of abundant, dry compressed air. That's the thing that keeps me from doing this.

Also, finding a good plater these days, not so easy.


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Thu 12, 2020 9:40 pm 
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Location: Lafayette, CO
This has come a long way. It needed a LOT of help. Craig


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Fri 13, 2020 4:47 pm 
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Location: Peekskill, NY
I now have the Rider manual printed out, actually much better than the original - it has the component values penciled in, and it has the various mods called out.

I have the top cover stripped to bare metal, that was *tough* paint. Photos soon, paint likewise, when the humidity level drops a bit.


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Sat 14, 2020 6:59 pm 
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Location: Peekskill, NY
Cover ready for paint, as mentioned - stripped down to plated steel, there's only one badly rusted spot and it's on the underside of the top.
Phosphoric Acid treatment didn't do much good on it. Will wire brush it hard before paint.


Attachments:
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cover_clean_4.JPG
cover_clean_4.JPG [ 236.45 KiB | Viewed 442 times ]
cover_clean_2.JPG
cover_clean_2.JPG [ 231.12 KiB | Viewed 442 times ]
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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Sat 14, 2020 7:35 pm 
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Location: Dallas,TX
Jim, could you tell me where I could find the Rider manual information? That would be a big help when I start on mine.
Thanks, Mike

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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Sat 14, 2020 9:13 pm 
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Joined: Mar Wed 16, 2011 10:44 pm
Posts: 1652
Location: Peekskill, NY
Nostalgia air:

http://www.nostalgiaair.org/Resources/887/M0008887.htm

Actually I'm going to sneaker-net that schematic file to staples and see if they can print it out 11X17 for me.


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Sat 14, 2020 9:57 pm 
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Location: Dallas,TX
Thanks Jim!

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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Mon 16, 2020 9:41 pm 
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Location: Peekskill, NY
The top band (5) is still dead. I can see the oscillator above around 20 MHz which is where my alignment generator quits. So the theory
is, maybe some wiring error in the oscillator stage coil for that band. I doped out all the wiring and it seems correct, and the various components
all measure correctly now. Have not tried testing the 6C5 oscillator tube but had swapped out another one, which was also untested.

But I decided to try some kind if independent test, so with the set off, I tacked a 100K resistor into the plate circuit, and excited that with my
signal generator, and checked at the grid of the tube with a scope.

The signal levels I see are about right, although they are noticeably smaller on band 5 than on the other bands. The measured values are on the
table on the right below - and the signal driving the measurement is 8 volts P/P into the 100K. I can't drive above 20 MHz until I borrow a better
signal generator from work.

There's no smoking gun here - the other question is how do I tell if the 6C5 is up to the task, is is running across the entire band 5?


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osc_test.jpg
osc_test.jpg [ 137.51 KiB | Viewed 399 times ]
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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Mon 16, 2020 9:54 pm 
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Posts: 1965
Pin 5 of the 6C5 is the grid. If you have a high impedance VTVM, measure the grid voltage. If it's negative, the oscillator is running. If it's zero, it's not. It should be over a volt I think. For a reality check, see what it reads on the other bands.


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Tue 17, 2020 2:05 am 
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Joined: Mar Wed 16, 2011 10:44 pm
Posts: 1652
Location: Peekskill, NY
Hmm, the scope probe is already on that point, and it's 10 megohm impedance, might try that.


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Tue 17, 2020 2:59 am 
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Joined: Mar Wed 16, 2011 10:44 pm
Posts: 1652
Location: Peekskill, NY
Good diagnostic.

Band five has zero volts at the grid of the 6C5. All the other bands are overall negative and the scope sees the
oscillator signal clearly.

Band 1:

0.6 MHz - 130 volts P/P
0.85 --- 183
1.2 ----- 129

Band 2:

1.3 MHz - 128 volts P/P
2.0 ---- 115
2.8 ---- 77

Band 3:

2.8 MHz - 58 volts p/p
4.0 ---- 47
6,0 ---- 35

Band 4:

7.0 MHz - 30 volts p/p
11 ---- 17
16 ---- 9.6

Band 5:

16 MHz zero
30 ---- zero

This does fall off as you go up, this could mean a weak 6C5, I don't see any wiring errors here.

All the coils seem to be in more or less the same condition, physically - no obvious contamination or damage.


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Tue 17, 2020 4:06 am 
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Joined: Jan Tue 10, 2012 8:39 am
Posts: 1965
In order to sustain oscillation, gain must override loss. The gain comes from the tube. The loss is everywhere but mostly in the inductance. If the Q is too low or if the load is too heavy, it won't oscillate.

The gradual progession of weaker oscillation vs higher frequency implies a lossy coil or poor switch contact or the tube has been pushed to a lower gain point by resistor aging or capacitor leakage. Something as strange as the switch structure providing a parasitic current path is a possibility, maybe contamination.

There are so many possibilities that your patience will be tried as you look at the circuit. The chances are that it once worked and probably hasn't been modified so there is that.


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 Post subject: Re: Hallicrafters S-11 project
PostPosted: Nov Tue 17, 2020 5:12 pm 
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Joined: Mar Wed 16, 2011 10:44 pm
Posts: 1652
Location: Peekskill, NY
Thanks - I've gone over all the components on that stage and they were either all in spec, or have been replaced with correct values.

The switch contacts are not heavily oxidized and have been given a gentle application of conductive cleaner.

The highest band coils is made of the same material as all the others, and is not obviously contaminated. It would be easy to remove it
and re-wind it on a higher quality form (teflon would be my first choice). The wiring is also just thin bare wire, and could be replaced with
copper strip or braid. The wiring in this area does appear to be factory original, with no apparent mods from a prior owner. I'm a bit
hampered by not having a spec for the B+ values for this radio, apparently hallicrafters never wrote that down anywhere.

I'm hesitant to start tearing it apart before verifying the tube is not the issue. I will probably just attempt to source a known good 6C5
and sub that in there.

Thanks for your comments.


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