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 Post subject: Transistor types
PostPosted: Sep Sat 24, 2016 5:19 am 
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I'm restoring a 1967 transistor radio am only. What type of transistors are used in these? Or its modern day equivalent? Will TO-92 work in these? I'm getting no sound at all. Oscillator is not working either.
Thanks for the help!

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 6:42 am 
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A little more information is needed; at least the brand name and model number of the radio. Also, any designation on the Transistors themselves would help.

More than likely, either the earphone jack lugs aren't making contact, and/or the (usually) four Electrolytic caps are dried out and need to be replaced. These two remedies will fix >90% of Transistor sets.

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 12:13 pm 
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TO-92 is a package type. You need the actual transistor type number.

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 1:41 pm 
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Ok, was hoping you could use any npn or pnp as long as it was 1mhz freq. Plus amp and volt rated. Here is a photo fact sheet on it. I guess my question was would TO-92 work .or partially work lol.
Thanks!


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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 2:15 pm 
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Once again, TO-92 is not a transistor type......it is a package style.

A transistor needs to have several parameters specified:
PNP vs. NPN
Voltage, current, and power ratings
beta ( aka Hfe or current gain ) at a specified collector current
Frequency response...most often stated as f-sub-t, which is the the frequency at which the AC beta goes to 1.
There are a variety of cross-reference resources...eg do a Google for NTE

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 2:42 pm 
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Go to this page http://www.talonix.com/gehep.htm It tells you briefly what the GE-1 and GE-2 transistors are and the NTE equivalents.

Both are PNP Germanium (not Silicon) devices. The GE-1 is for all the RF/IF/Oscillator stuff and the GE-2 is for the audio stuff.

Curtis Eickerman

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 3:03 pm 
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Wouldn't it be great if the S/S world had stayed so simple?!! There is now a staggering number of transistor types, many of which are essentially redundant.

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 4:29 pm 
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Amen for simple. I'll check all that out. I have heard that the manufactures back in the day would add transistors that wasn't even needed and sometimes weren't even connected to anything so they could call it " 10 transistor"!!! 14 transistor,,etc. Oh 1 thing I have always wondered about was soldering transistors. Will heat from the iron burn Them up? I have a heat sink but it is impossible on these pocket transistor radios to use it. Any trick for this?
Thanks guys.

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 4:45 pm 
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devildog63 wrote:
Will heat from the iron burn Them up?
Not as long as you are using a soldering iron that is around 20-40 watt with a small tip and don't apply heat longer than necessary to get the solder to flow well. I would not worry about a heat sink.

If you were using a 275 watt soldering gun you would have to be very careful. With that kind of heat you can remove the track from the board. That's the kind of gun you would more likely use to solder things to a steel chassis or big piece of sheet metal where it takes a lot of heat.

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 5:43 pm 
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Quote:
Wouldn't it be great if the S/S world had stayed so simple?!! There is now a staggering number of transistor types, many of which are essentially redundant.


I started in the "S/S world" in 1967. Maybe I can explain some of the complication.

1. We would make a standard transistor, let's say a 2N3055. An audio amp manufacturer wanted only the high end of the gain (Hfe) range. Sometimes we would put a paint dot on a selected 2N3055. Sometimes the manufacturer would ask us to put his part number on it so it didn't get confused with standard 2N3055. Sometimes the manufacturer wanted his P/N on it so he could get the replacement/service parts business, or so a competitor would have a harder time reverse engineering.

2. When we made 2N3055s (60 V) we got a lot of 40 V parts. Don't want to toss them; maybe someone will buy them? RCA started calling these 40251. Sometimes you got a few 80 V parts, these became 2N6254.

3. Large OEMs often asked for parts that were "just like" a 2N3055, but with one or more parameters adjusted for their needs. If the volume was high enough, we would tweak the design and run special wafers. Unlike the tube business, there was no change in the physical/mechanical structure, so "specials" were easy to do and they proliferated.

It turned out that the "service parts" aspect was flawed. Unlike tubes, transistors didn't fail as often and even if they did replacing them was difficult. You couldn't go to Walgreens to test your transistor and buy one out of the cabinet below the tester.
By the 1980s, when I was with Siliconix, we made "application specific" FETs for almost all of our customers. Seagate would buy a million pieces a month and neither they nor we cared about repairability or service parts. It's in a hard drive. It has to work immediately and work for 5 years. Before it fails, the customer will have bought a better disk drive.

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 5:55 pm 
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soldering

clip-on heat sink, if possible (something that clips to the lead you are soldering

temperature-controlled iron** and small tips (I use the Weller WTCPT---the tip for S/S and PC work is 700F)

technique: on and off the joint FAST. You only need a small amount of solder, and there's no need to be on the joint more that a few seconds. get everything clean, small bit of solder on the iron. iron on the joint, then more solder, and then get off the instant it flows.


**IMHO, power is secondary----even a 20 watt iron will overheat things if you keep it on the joint long enough. What does the work is the temperature.

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 7:16 pm 
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pixellany wrote:
**IMHO, power is secondary----even a 20 watt iron will overheat things if you keep it on the joint long enough. What does the work is the temperature.
Agreed. It's just that a 20 watt iron gives you more leeway on time than a 275 watt flame thrower.

Curtis Eickerman

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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 8:22 pm 
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I happen to have a couple unused GE "Universal Replacement" transistors. One is the GE-1 that is shown in your list. It is a TO-5 case style, or "package" to use the term Pixellany chose. The other is a GE-51 in a TO-72 package. And no, that doesn't refer to the shrink-wrapped card on which they were sold. ;) The card includes the transistors specifications.

For comparison, a TO-92 transistor sits between them.

The GE line has been long discontinued so these "substitute" devices would need a substitute themselves! Unless you have one of the originals or can find them somewhere. You could also use the Delco or Sears numbers shown to try to locate a replacement that way. Meanwhile, the actual transistor soldered into your radio may have a different number yet.

Just as one example, a 2N396A made by RCA lists a GE-1 as a sub. The GE-2 meanwhile, would work to replace a 2N64.

Most all the major transistors makers from those years offered their own line of generic replacements. The goal was to replace as many different transistors as possible with the fewest number of generic types. As mentioned, there are many thousands of variations in both physical and electrical specs.

For transistor radios, it does indeed boil down to their use in the circuit. Your list shows the various stages in a particular radio such as converter, IF amp, audio amp and so on. But yet, just two different GE numbers will work for all. There would be many dozens of other transistor with similar characteristics that could be substituted as well.

Now you get into case or package styles. A you can see, the TO-5 case is much larger than either of the others, so in cramped quarters it may not physically fit, even though it might still function properly in the circuit.

So you need to match the size of what's in your radio as well as specs. In these small-signal types, size is not necessarily related to power handling or output. Nor is whether it's in a metal or plastic case. Older types tend to be metal.

Larger sizes or those with attached heatsinks are built for bigger and tougher jobs. Like a big, fat TO-3 types used in many stereo amplifiers for the final output to the speakers. But that much beef is not needed elsewhere, so again you'll find those smaller types.

If it's a TO-92 has relevance, since it will help find a similar type that will be likely to fit the space and suit the purpose in the circuit. Beyond that, you need to consider PNP or NPN, Germanium or Silicon and the electrical specs that define how it will behave in a given circuit.

Here's a pic of a few case styles, lacking their proper TO-nn designations unfortunately, along with a snippet of transistors from the 1963 Allied Electronics catalog. Note all the specs they list for each one. You can try your own subs by matching these specs or by just cross-referencing to modern types on the NTE website or other sources.

It's looks kinda daunting, but it does often boil down to just a few specs or things to consider in making your choices.

As mentioned by others, transistors don't fail nearly as often in a radio as do other parts, many of which die from simple old age. So it's best to apply some sort of testing procedure to first determine if it is indeed a faulty transistor before just pulling them to substitute.

A strand of fine, bare copper wire can be wrapped around the legs to provide some heatsinking. There are also some fine-tipped probes or tiny aluminum clamps to fit in the tight spots. Generally, you want to get in, remove the solder quickly as possible to free up a leg so it can be straightened and cleared for removal. The copper traces on the circuit board can be very delicate and don't cotton to much shoving around or lingering soldering iron.

There's several methods to assist with solder removal you can look into. I'm just trying to clarify what the basics of transistor identification are by showing a few common types. There's many books both in print and scanned that delve into the details in both simplified or technical terms. Happy Reading!! :)

(Boy, do I go on and on sometimes! Sorry for the Wall O' Text!)
-Ed


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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 10:15 pm 
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To ramble on a bit more :lol: here's the Allied list made easier to read.

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Let's take the first couple transistors as an example of what Rich was saying. Motorola's 2N627 and 2N629 share many of the same specs except for collector voltage. The 2N629 has twice the breakdown voltage and sells for twice the price. The manufacturer profited by selecting better devices for the upper tier and had an outlet for lesser examples. The consumer saved by choosing the lower cost version if it still fit his needs. They are both PNP, in a rugged metal T-03 case built for attaching to a large heatsink. I note my old GE cards use TO-3 instead of T-03. Same difference.

Next are two RCA NPN devices, the 2N647 and 649. The 2N647 is higher-rated, this time in several of the specs. The main difference here is in the collector current. Yet they both use the same "Design or Structure" (Allied's way of saying case style), guessing it's a T-004. Cost the same to make, but you pay a little more for that added performance.

In either example, the higher-powered device might sub for the lesser one. But more than likely not the other way. The lesser one would fail to work as well or fail outright and blow. When shopping, compare the specs to your original device and try to get a close (or better) set of specs and stay within budget.

There's lots of vintage transistor checkers to allow you to test and compare individual transistors, sometimes in-circuit, on other testers the transistors have to be removed to be accurately tested.

-Ed


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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 11:15 pm 
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"Package" is a commonly-used industry term for the mechanical outline. TO = Transistor Outline.

Quote:
The consumer saved by choosing the lower cost version if it still fit his needs.


In general, we did not try to accommodate the "consumer." GE, RCA, and Moto had "rack lines." That is individually packaged (carded) devices that hung from a rack at local distributors. Some of these were aimed at hams and hobbyists. The theory was that today's hobbyist might be next year's engineer. Better to get your brand introduced early. Those lines got dropped and folks like Sylvania ECG continued with a line of parts for service/repair work. Sylvania did not make these products. I used to sell 1000 PIV diodes to Sylvania. Then the re-branders got into the picture. They bought surplus and tested/re-marked it. Usually they bought stuff that we rejected at hi temp testing. As long as it worked at room temp, it was thought to be fine for hobby/service customers. NTE carries on that tradition now.

In this case "Design or Structure" refers to the physics of manufacturing the device.

AJ = Alloyed Junction

GJ = Grown Junction ( I think this was the first kind of epitaxial device)

SB = Surface Barrier (Philco and Sprague)

Hometaxial Mesa = RCA

Planar = Fairchild and National

Maybe more history that anyone wanted?

Rich


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 Post subject: Re: Transistor types
PostPosted: Sep Sat 24, 2016 11:18 pm 
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The above posts offer an excellent treatise on Transistors, but I doubt that even one Transistor will need replacing in the OP's radio. Recapping and checking the earphone jack contacts will most likely make it sing again.

pixellany wrote:
Wouldn't it be great if the S/S world had stayed so simple?!! There is now a staggering number of transistor types, many of which are essentially redundant.

Now? Eh eh, my ECG replacement guide from 1985 (31 years ago) is the size of a medium cities phone book... :wink:

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 Post subject: Re: Transistor types
PostPosted: Jan Sun 01, 2017 6:54 pm 
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I have one transistor in the output getting very warm, would it be safe to say that one is bad? Also shouldn't I be getting audio after the diode at test point 8? Here is the schematic.
Thanks


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 Post subject: Re: Transistor types
PostPosted: Jan Sun 01, 2017 6:56 pm 
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Maybe this is clearer .


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 Post subject: Re: Transistor types
PostPosted: Jan Sun 01, 2017 7:06 pm 
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devildog63 wrote:
I have one transistor in the output getting very warm, would it be safe to say that one is bad?

No---excess heat means too much current, which could be caused by many things. Diagnose transistors first with voltage measurements, and then--if necessary--remove and test.
Quote:
Also shouldn't I be getting audio after the diode at test point 8?

Since that is the feed to the volume control, answer is a big yes....

Can't really read that schematic--can you post a link?---if not, send me a copy and I can stick it up on my site.

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 Post subject: Re: Transistor types
PostPosted: Jan Sun 01, 2017 8:56 pm 
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Try this


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