Archive for the ‘Electronic Components’ Category:

2018-12-12 LM78xx Linear Regulator Disadvantages

from FB group Building Transistor Radios 2018-12-13 Joseph Rotello I agree with some of your claims. But I know far more about 3-terminal regulators than you think. First off, your claim that they are more efficient is unproveable. There are linear PSes that are more efficient. That was the reason LDO regulators were used. You

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2018 Dec 8 Sinclair Book 22 Tested Circuits Using Micro Alloy Transistors

from FB group Building Transistor Radios 2018 Dec 8 Nick Bastian posted the schematic of a Sinclair Micromatic radio. I found the book by Clive Sinclair about the circuits using micro alloy transistors. Germanium transistors and especially micro alloy transistors are no longer made so it’s better to use silicon BJTs instead. Here is the

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2018-12-04 FETs For Very Low Voltage Joule Thiefs

from FB group Building Transistor Radios 2018 Dec 4 Terry Harris I didn’t try to mimic the ALD, I used the FETs for a voltage booster. The typical 5mm LED needs somewhere around 60 mW for Max brightness. If I was powering it with 60 millivolts, it would require over an amp to get the

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2018-11-29 Fixing Badly Worn Volume Controls

from FB group Building Transistor Radios 2018-11-30 I’ve done some experimenting on volume controls that are badly worn and noisy. The idea is to substitute some resistance for the badly worn spot. The loud crackling will be reduced and the normal volume point will be moved to a higher point on the control. For a

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2018-11-26 Two 6 uH RF Chokes

from FB group Building Transistor Radios 2018-11-26 https://archive.org/stream/ETIA1983/ETI%25201983-03%2520March_djvu.txt Two 6 uH RF chokes The photo shows two different RF chokes, each about 6.4 microhenrys. The one on the left is a ferrite bead, made by Fair-Rite, Cat. # 2643000801. These were about 12 cents apiece from Mouser.com. Yes, the wire passes through the small hole

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2018-11-22 Homemade 9 pF Gimmick Capacitor

Also posted to FB group Building Transistor Radios Watson’s 9 picofarad homemade “gimmick” capacitor This homemade capacitor can be used for circuits were the capacitance is not critical, such as a wireless microphone for the FM broadcast band. The wire can be obtained from the cable used to connect telephone outlets. Solid (not stranded) plastic

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2018-11-16 Low ESR MLCCs

From FB group Building Transistor Radios 2018-11-19 Garry Heard I’ve found that a problem with using electrolytic capacitors to filter out the RF noise is their internal ESR, effective series resistance. They don’t filter out the RFI as good as they should. I found that MLCCs do a better job, if I used some multi

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2018-11-15 ESD and Weather

from FB group Building Transistor Radios 2018-11-19 Bob Johansen I worked at a company that had ESD mats on the workbenches, about 1980. We had wrist straps with a 1 Meg resistor in series with the cord to prevent shock hazard. I found that the leads of the resistors were broken but the heat shrink

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2018-11-13 PSI Pacific Semiconductors Inc.

from FB group Building Transistor Radios 2018-11-16 The guy I worked for got us some Pacific Semiconductor power transistors for use in aircraft radios. That was before they were bought out. The logo on them was the Greek letter Psi. I think I might still have one in my old parts drawers. PSI was one

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2018-11-10 LEDs Are Not Linear Resistances

from FB group Arduino Projects 2018-11-11 As it is, the 6 ohm resistor has 1 amp going through it. Your LED(s) is dissipating 6.55V times 1 amp or 6.55 watts. The LED is not a linear resistance, the voltage doesn’t go up directly as the current increases. The voltage across the LED will stay at

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