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 Post subject: micronta signal tracer
PostPosted: Feb Wed 17, 2010 6:28 pm 
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Joined: Aug Mon 24, 2009 8:12 pm
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Location: shreveport, la
picked up a used micronta transitorized signal tracer. Its well used take a 9 volt battery and has two leads. This is my first tracer and have a project that requires tracing.

Is there any percuations that should be taken with a transiortized vs a vt signal tracer.

Thanks in advance

Larry


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 Post subject:
PostPosted: Feb Wed 17, 2010 8:37 pm 
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Location: Northport wa. USA.
I have used mine with no problems. They seem to work OK. Small speaker, but it still works.


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 Post subject:
PostPosted: Feb Wed 17, 2010 9:31 pm 
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Location: NE Fla. 32043
Are you going to use it on any tube radios? Be forewarned that the ceramic cap on the input is not rated for a very high voltage!That should be changed if planning on using it on a tube radio.

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 Post subject:
PostPosted: Feb Wed 17, 2010 11:05 pm 
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Location: Long Island
There shouldn't be a problem as long as the DC blocking capacitor on the input (probe tip?) is up to the job. Whatever the unit came with, I'd replace with a brand-new 600-volt cap of the same capacity rating.

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 Post subject:
PostPosted: Feb Thu 18, 2010 6:13 pm 
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Mine came without test leads so I don't have the orginal tip. So the original tip came with a dc blocking capacitor ? Could a tip with a blocking cap be built? Any tips on how to build one?


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 Post subject:
PostPosted: Feb Thu 18, 2010 10:10 pm 
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Blocking cap is inside on the jack. Leads were just banana plugs and alligator clips, one red and one black.

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 Post subject:
PostPosted: Feb Fri 19, 2010 2:21 am 
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Location: shreveport, la
Mbird97x wrote:
Blocking cap is inside on the jack. Leads were just banana plugs and alligator clips, one red and one black.


Got it.

Thanks

Larry


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 Post subject:
PostPosted: Feb Sat 20, 2010 5:09 pm 
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Location: Long Island
For signal tracing in a chassis, a probe is a lot easier to use for the input (red) lead. The ground (black) lead should be a clip. In this case, an ordinary VOM test probe with a banana plug on the end would be fine.

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 Post subject:
PostPosted: Mar Tue 08, 2011 4:59 am 
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Location: Downers Grove Illinois
I'm a noob. :oops: I have one of these, too. It has two inputs, one for AF and one for RF. The RF input has a small cap, looks like it says 102M10,that goes to a diode and the first contact of the switch. The AF input has a .02 uf that also goes to the first contact. There is another cap that goes from the last contact to the first contact, it reads 501/MSK. Do all of these need to be changed with new ones for higher voltages? Could you recommend values? Thanks, John


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 Post subject:
PostPosted: Mar Tue 08, 2011 6:55 am 
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This was posted before but I am sure it will help you.

Image


Keith


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 Post subject:
PostPosted: Mar Wed 09, 2011 12:11 am 
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Thanks, Keith, that is a big help. So all I have to do is use caps of the same values, just higher WV?


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 Post subject:
PostPosted: Mar Wed 09, 2011 4:52 am 
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Just those input caps. Everything else should be fine.

Keith


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 Post subject:
PostPosted: Mar Wed 09, 2011 2:04 pm 
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Location: Sandwich, IL, USA
These simple schematics would make for a nice weekend project for a handy little tester like this. Over the winter I’ve been gathering up plans for signal injector/tracer units. I just finished putting together a Hendrick's Tracer/Injector kit but would like to play around with a few others.
The only problem with them for me is finding a readily available modern substitute for the active devices that wouldn’t run you broke. I’m at level one when it comes to SS design and it takes me a week to make it thru an AA5 repair.
Chance of finding a few original 2SD187 is next to impossible, NTE lists a NTE103 as a replacement but from what I’ve found at dealers like Mouser, those run about $7 or $8 each. Then there is a 2SB186B which converts to NTE102A at $6.30 so I’m up to $30 worth of transistors and I still haven’t found out for sure what the SDT20 is, I think it’s a thermistor but what it would convert to is way beyond me.
The idea of repairing one would be difficult for me and my thought of copying the design and building one as a DIY project an impossibility. It would sure be fun if one of our electronics engineers could sub some modern components into these old schematics and give them life once again.

Denny Graham
Sandwich, IL


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 Post subject:
PostPosted: Mar Wed 09, 2011 3:03 pm 
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The purpose of the thermistor is to prevent thermal runaway of the germanium output transistors. If silicon transistors were substituted for the output transistors, the thermistor could be replaced with a resistor.


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 Post subject:
PostPosted: Mar Fri 11, 2011 3:33 am 
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Joined: Dec Mon 20, 2010 7:23 am
Posts: 488
Location: Minneapolis, MN
If you're buiding one with silicon, a pair of forward biased diodes(1N914) to replace the thermistor and the 220 ohm resistor.

This circuit should be very tolerant to replace the transistors with silicon without changes. The voltage at the midpoint of the 5 ohm resistors should be pretty close to half the supply voltage. If not then an adjustment of one of the 22k input resistors will center output at 1/2 supply. If I were making this I would replace the bottom 22k resistor 18k and a 10k pot in series. That should be more than enough adjustment range.

You might have to salvage the input transformer from an old radio it should be an interstage transformer.


I'm not an engineer, however I do have a 2 yr associate electronic degree, and was fortunate enough to be one of the last classes that spent any considerable time with discrete circuits.


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