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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Tue 09, 2016 2:00 pm 
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Location: Wilton,IA
The Don Bosco which I have runs on
1 AAA battery.
Good unit for diagnosing.
Jim


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Wed 10, 2016 3:09 am 
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Location: Yukon, OK USA
I have made a second circuit and plan to put it into an aluminum tube from a broken R5 vertical antenna. Good quality aluminum and just the right size for the square 4 cell AAA battery pack. I have some 1.25" delrin rod on the way to make the end caps. Just need to pick up another blank PC board with holes. I think I have a good switch....... somewhere.

Question; on the Micronta circuit; what the purpose of the diode? In doing some experiments with different values of components I found that the amplitude and shape of the waveform was better with a small capacitor in place of the diode.

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Wed 10, 2016 3:21 am 
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Location: Portland, TN, USA
Has anyone ever worked on a Don Bosco?

I have one I foolishly bought on the bay
that does not work and I can't seem to get at the circuit board.

As the nose piece is likely brittle, I have been loathe to put too
much force into getting it out of the barrel.

Any ideas or experience out there?

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Want Hallicrafters S-76 with good cosmetics; Can fix electronics issues.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Thu 11, 2016 9:11 am 
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Chuck, it appears that the Don Bosco Mosquito and Stethotracer probes were not intended to be serviceable, and were sealed. Disassembly may require some destruction. It is rare for one of these signal injectors to fail, but a leaking battery could do it. I presume that you have tried cleaning the contacts. Also note that the Stethotracer, a signal tracer rather than an injector, looks almost identical to the Mosquito; the former has a tiny two-hole jack on the side, for an ear phone.

Black85Vette wrote: Question; on the Micronta circuit; what the purpose of the diode?

That is a very interesting question, and the answer has never been clear to me. Certainly the germanium diode is acting as a “detector” of what is in a sense a modulated radio frequency signal produced by the circuit. Thus, a test just now, with the oscilloscope probe connected before the diode, disclosed a lovely long ringing, such as you showed on the first page of this discussion. After the diode, the ringing part of the waveform is very brief and much more highly damped, and it has a D.C. offset.

It would appear that the intention was to increase harmonic generation, but I tried the injector with receivers at widely varying frequencies, and had similar results with and without the diode. The signal was generally stronger without it. The ideal way to make the comparison would be by means of a spectrum analyser.

When I have experimented with this circuit in the past, I used a coupling condenser rather than a diode, and had equivalent results—in the particular applications I tried.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Thu 11, 2016 12:36 pm 
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Philip; Looks like we had about the same thoughts on this. I think I will just go with the capacitor since everything test I did with an AM radio was fine. It can always be swapped at a later date.

Thanks

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 3:13 am 
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Have to make a change in my plans. I built the circuit and did a quick test by putting it inside the aluminum tube. Signal on the scope just went flat. It appears this type of inductor does not like being surrounded by metal. Think I will go with PVC.

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 4:26 am 
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Location: Minneapolis, MN USA
PVC not a bad idea.
Safer for the operator to be holding a non conductive object when probing the underside of a live chassis.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 11:53 am 
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Black85Vette, I was afraid that might happen. It means that I may not be able to use the splendid anodised aluminium housing as planned, though I’ll probably experiment a bit.

As discussed in the other signal injector thread, it is surprisingly difficult to find suitable attractive and well-proportioned housings for signal injector probes.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 2:44 pm 
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Hi
Has anyone tried aluminum cigar tubes?
I'm not sure what size you guys need but I searched "the bay"
and found a lot of different sizes.
I also searched plastic storage tubes and found more possibilities.
Good luck
Bill

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 3:38 pm 
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I have some plastic cigar tubes with screw on plastic caps which would be perfect.
Rick


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 4:10 pm 
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gridleakrick wrote:
I have some plastic cigar tubes with screw on plastic caps which would be perfect.
Rick



What is the inside diameter and over all length? Never thought of using them.

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 4:38 pm 
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Hi
Cigars are measured by a gauge size. 50-60 gauge are some of the largest
sizes. I don't think the gauge size is a standard. Try Google and search cigar
gauge sizes to give a general size chart.
Then look for tube sizes that will fit the size you need.
I hope this helps.
I don't want to send you guys on a WGC (wild goose chase)!
You might have to go to a cigar store to get a idea of diameter
and length.
Bill

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 6:03 pm 
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Location: Minneapolis, MN USA
Perhaps the toughest part about putting these in a cylinder shaped container is the power switch.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 7:48 pm 
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Maybe a U-shaped slot could be cut at the cap end and a slider switch
be slid in.
Battery placement would also be a challenge. BTW what would be the minimum
voltage for operation?
If you guys are wondering why I am not making one of these myself is because
my bench is in boxes after moving so I have to watch you guys have all the fun.
Bill

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 9:26 pm 
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Here is how the PVC version turned out. Got some of the thin wall stuff that is about 1.35" O.D. Would have preferred the aluminium at just under 1.25" but close enough. Had to arrange components to fit a tighter space and lay flat. The limiting factor is the battery pack for the Micronta circuit using 6 volts. A holder for 4 AAA batteries needs about 1.125" to fit in the handle. I made ends out of round delrin rod, put a rotary switch in one end. The other cap got a piece of brass rod threaded 6/32 on one end. Used two nuts and a solder lug to mount it in the end cap. Then instead of a lamp I used an LED and put it in the end with the probe. Dual purpose; indicator light and it shines a light on place you want the probe to go. Not as snappy or cool as the pen light sized but good enough for me.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 10:05 pm 
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Great workmanship. Looks that factory made. I used PVC drain pipe for( see earlier posting) for mine. Just a bit lager in diameter, but fits my hand well.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sat 13, 2016 10:25 pm 
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Very nice Rick!
I really like the rotary switch and light.
Good design!
Bill

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sun 14, 2016 5:12 am 
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Following FauxTech’s excellent suggestion, I had a look on eBay and found an enormous variety of cigar tubes, many of which would make superb probe bodies. I have never smoked, so knew nothing of these products.

The “Micronta circuit” is, as far as I know, unique amongst signal injector probes, because of the ringing tank circuit tuned approximately to the modern medium wave broadcast band intermediate frequency. But otherwise, it is a blocking oscillator like most other injectors. A blocking oscillator does not require a high-Q coil, and will work in a metal housing. It seems that the metal housing will kill the Q of the coil in the Micronta circuit, preventing ringing. What I am getting at is that an ordinary injector circuit, such as shown on the other thread—

http://www.antiqueradios.com/forums/vie ... p?t=109446

—should work properly in a metal housing. Those who wish to construct a Micronta style injector should consider a non-metallic housing.

I agree that Black85Vette has done an excellent job in fabricating his injector. However, many of those who would like to construct a signal injector may not have a lathe available. I found that Hammond manufacture some small project cases, which are available in translucent blue. I ordered a 1591XXATBU case, which has dimensions of 3.9 X 2.0 X 0.8 inches, and should make for a reasonably attractive example probe, if lacking the cachet of a tubular housing.

http://www.hammondmfg.com/dwg2XXTBU.htm

Note that the size I selected is small for 4 AA cells; I will use a 9-volt transistor radio battery.

These housings have stand-offs for mounting the perforated circuit board, and are translucent to blue or white LEDs, so the indicator can be mounted directly on the board.

Although small coils and transformers that would be suitable for blocking oscillator circuits are widely available, I have not found an ideal, currently manufactured coil for the Micronta circuit. The best option may be to wind a single-layer coil on a small ferrite rod, as Black85Vette has done.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sun 14, 2016 5:59 am 
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black85vette wrote:
gridleakrick wrote:
I have some plastic cigar tubes with screw on plastic caps which would be perfect.
Rick



What is the inside diameter and over all length? Never thought of using them.


They are the same size as the aluminum ones I have. They are not readily available right now so I cannot measure them.
Rick


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sun 14, 2016 5:11 pm 
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Location: Tarpon Springs, Florida
Thanks Philip
I'm glad you liked my suggestion.
I was thinking about smaller batteries.
Would coin batteries (stacked) @ 3 volts per battery be a solution to get
the size down for a smaller diameter?
I guess the question would be how long they would last.
I have seen them dirt cheap on "the bay".
Bill

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