Archive for the ‘Transistors’ Category:

2020-06-01 Motorola HEP Catalog Transistors pp 10-12

These are scans of the specifications for most of the Motorola HEP line of replacement transistors. Germanium and Silicon. Pages 10, 11, 12.

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2019-01-15 Zenith Royal 200 Conversion to Silicon

I’m thinking of pulling up the end of the 100 ohm and looping the lead a few times through the ferrite bead. If that still doesn’t stop the ringing, I’m thinking about replacing the bead with an RF choke. Every time the ringing is reduced the reception gets better.  I checked to see if I

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2020-01-08 Sorting Transistors Compared to Picking Fruit

I started thinking about how the makers of transistors sort the different grades of transistors as they’re manufactured. I thought that a reasonable analogy would be similar to how a farmer might sort the fruit he harvests. Here’s what I came up with.The farmer starts with the fruit his workers have gathered.  The fruit is

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2018-08-24 2N3904 & 2N3906 for Output Transistors

From FB group Building Transistor Radios 2018-08-24 – The discussion was about the OTL complementary symmetry audio amplifier that Mr. Barnett has posted several times to the group, which uses a 2N3904 and 2N3906. Willie Barnett Let’s talk about current. Suppose your amp has a 9V supply. When the output transistor is turned fully on,

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2018-08-20 2N3904s From Mouser And Ebay

from FB group Building Transistor Radios 2018-08-22 Olek Kopyto I recently did some tests on 2N3904s I got from Mouser and from a Chinese eBay seller. The ones from Mouser had a current gain of right around 200, right in the middle of the 100 to 300 gain range according to the data sheet. The

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2018-08-29 High Temperature And Nylon Screws

From FB group Hobby Electronics, 2018-09-01 I faced this dilemma before. I’ve repaired power supplies where the transistor failed because it was not held tightly to the heat sink because of a nylon screw that got hot. I used a steel screw and a fiber washer, and heat shrink tubing over the threads to insulate.

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2018-07-26 Transistors, ECG, Motorola HEP Line, etc.

From FB group Building Transistor Radios Wayne Leake Yeah, the 2N3904 is E B C, THE ‘945 is E C B. Watch out the leads don’t touch and short. 😝 I have the Moto HEP catalogs, if you need to find out what it’s equivalent to. When National Semiconductor came out with their catalogs they

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2018-06-28 Bootstrapped For High Z Input

From FB group Building Transistor Radios For those who don’t want to or can’t use a JFET for high input impedance, you can use a regular transistor or two and bootstrapping to get a 10 Megohm high input impedance amplifier. This is from “Common Collector Amplifiers”, Electronics Now, Oct. 1993, found at For RFs,

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2018-06-20 2N176 PNP Ge Power Transistor Substitutes

From FB group Building Transistor Radios Nick Cook Have you found the reason for the failure of the 2N176? You could use the NTE equivalents NTE104 or NTE121. These may be expensive but they are the substitutes. But you have to make sure that the new one doesn’t burn out. You should be able to

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2018-06-19 2N3904 Transistors Betas

From a FB group Building Transistor Radios Markku Vuorensivu Tell me more! I’m all ears! I got a thousand 2N3904 BJTs from Mouser, and ten packs of 100 from eBay. I selected a dozen from each and measured their current gain using two methods: a cheap DMM, and a ‘transistor tester’ which has the ZIF

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