Archive for May, 2017:

2017-05-31 Is This a Thermal Fuse?

I have a bunch of these Ni-MH battery packs with 5 cells per pack for 6 volts. I want to use them to power 5 volt devices, so I remove one cell.  The metal straps are spot welded between cells, and the metal strip shown in the photo is between cells.  It has two strips

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2017-05-30 Tick Tock, A Bright Red Clock

I ordered these clock kits a few weeks ago and they finally arrived today.  I just couldn’t keep my hands off the soldering iron, so I started stuffing the board with components.  I was blindly winging it because the instructions that came with it were in Chinese.  I didn’t have any problems because all the

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2017-05-29 M-6013 Capacitor ESR Meter -Not

Several weeks ago I purchased a “M-6013 Capacitor Meter ESR Meter” from a Chinese seller on eBay.  It cost about $27, and I think shipping was 99 cents.  I received it two weeks ago and read all the instructions and tried all the buttons and functions, but I found nothing having the ESR test. I

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2017-05-27 Oscillator, AM BCB


I built this Oscillator to see how far a small loop of wire can radiate the RF.  I’m not using an antenna, just the radiation from the coil.  The coil is about 15 feet of solid insulated telephone wire jumble wound on a pill bottle with a diameter of 50mm or slightly less than 2

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2017-05-26 (Not A) Wien Bridge Oscillator 

Oops!  (posted to FB groups) ‚ÄčA Wien Bridge Oscillator that’s not a bridge.  It’s missing the negative feedback side of the bridge!  That must mean that the amplitude of the sine wave changes with changes  in the temperature, supply voltage, and other conditions.  Not a good design!

2017-05-25 I Buy Parts From…

From a comment in FB group I buy most stuff from Mouser because I found their prices are lower than Digikey.  I’ve had bad experiences with mouser, mostly shortages on quantity, but I had some disc caps thar were below tolerance.  Mouser has some cool ways to narrow down the selection to a manageable size.

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2017-05-24 DECWriter LA-36

From a comment I posted to FB Vintage Test Equipment group. I’m looking for some parts for a DEC DECWriter LA-36.  The model I have has the acoustic modem behind the paper feed.  I’m also interested in other parts.  If there are others who have this big, heavy printer, I also have some manuals for

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2017-05-21 22-120 Power Schematic Errors

Posted to FB group 2017 June 8, then a copy here. I found this Radio Shack power supply on  Looks like someone drew it up.  I found a few boo-boos, one being the LED having a 100k current limiting resistor.  It’s not going to be bright. I wonder if BK1 thermal breaker is capable

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2017-05-20 Telephone Line Kicker Meter

From a 2017-06-10 comment regarding a Weston capacitance meter on FB group vintage test equipment  Reminds me of the ” kicker” meters the phone techs used on the phone lines.  There was a polarity switch that reversed the pair, and the tech could tell about the line from the kick the meter needle gave when

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2017-05-17 Lamp In Audio Oscillator

This is from a FB comment by me. Speaking of audio signal generators, I made an audio signal generator, the classic Wien Bridge oscillator with the lamp, in my case it was a 28 volt low current lamp, I believe an 1869.  Well I got the lamps from Radio Shack, and the circuit had an

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