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I need to replace a transistor in my guitar amplifier. The model number listed on the original schematic is 2N2148. It is in a TO3 package and the rest of the specs are listed here.

I am having trouble trying to find a suitable modern replacement and I am unsure whether I should buy a NOS given that it is a germanium component. I found a few on Ebay here and here but I could really use some advice as to what to do in this situation.

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I hope people should explain why they are down-voting questions. –  shimofuri Dec 19 '12 at 18:11
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The intention of the OP is about repairing a circuit. Research effort is shown and the question is both practical and answerable. It is my opinion that this question is beyond a simple "buying or shopping recommendation" one. We have the "repair" tag available to support the question and a precedent here: electronics.stackexchange.com/questions/30459/… Perhaps the moderators would like to deliberate on this in meta? –  shimofuri Dec 19 '12 at 18:39
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@Chetan: I have read the FAQ and still don't see a reason for the downvote. –  Olin Lathrop Dec 19 '12 at 20:23
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The text of the question is okay quality. But the title is low quality and leaves an impression if helplessness. " How to find a replacement for an antiquated transistor 2N2148? " might be a better title, IMO. –  Nick Alexeev Dec 19 '12 at 20:31
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I don't see this as "not a real question" on the repair front because the question is reasonably scoped and answerable. I don't think it is off-topic as shopping advice because it is closer to "how do I choose" vs. "pick something for me". –  W5VO Dec 19 '12 at 20:39
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2 Answers

up vote 5 down vote accepted

The process of looking for a similar part is called "cross referencing." That is usually done to look for replacements or to approximate the specifications of the original part.

One of the established electronic cross reference database is the former ECG line of Philips. That business was bought out by NTE Electronics and you can access their service here.

Searching for 2N2148 in NTE, the suggested replacement is NTE121. Use the "Check Stock" button to search for where you can buy the replacement.

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Hello and thank you for your help! Do you think that I should buy a new product rather than a NOS then? –  Mike Stumpf Dec 19 '12 at 18:24
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This is more of an opinion (and "buying recommendations" are technically off-topic in this site): I would rather buy from an established business that had specialized in parts replacement than from Ebay. For one, NTE parts carries a warranty both in their suitability as replacement and quality. The ECG line, if I recall correctly, has been there since the 70s. –  shimofuri Dec 19 '12 at 18:28
    
Sorry again. I am asking for the purpose of the electrical circuit, not for the best price, etc. I know that germanium transistors are more prone to fail as time goes on compared to silicon. I just was not sure if a NOS part made in the 70's would be a safe bet or if a newer part was necessary/recommended. Thank you for your advice and I understand that I am skirting the edge of acceptability in terms of "buying recommendations" but I am still new to electrical circuits and just trying to make the best decision. Thank you for all your help –  Mike Stumpf Dec 19 '12 at 18:32
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Given your concerns, buy more than one... –  Chris Stratton Dec 19 '12 at 19:04
    
Thanks for the advice! :) –  Mike Stumpf Dec 25 '12 at 0:39
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There are many replacements for the 2N2148 germaniun PNP transistor:

You can use any of the following transistors listed in www.icreplacements.com for the original part to replace it: 2N3617 2N3618 AL102 AL103 AUY22

Complete information source: http://www.icreplacements.com/2/2N2148-replacement-compatible-Germanium_PNP_transistor-substitute-equivalent-part-cross-reference.htm

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Thank you very much! –  Mike Stumpf Mar 24 at 18:38
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