How to Find Substitutes for Discontinued Transistors 

Tony I've never seen anyone go to these lengths to explain how to find substitutions. This provides a strong message that repair techs for vintage gear that can do this kind of part substitution are worth every penny.

Help someone to find out the right device for some repair job and you help him once. Help him by showing him/ her to find the right device and you helped once for every time he/ she needs. Having learned exactly that stuff maybe 35 years ago I'm actually not in need to learn it again but I love and enjoyed every minute of that video when you showed how to actually find a proper solution! THANK YOU Tony, I really do love your videos!

I hope you'll never close your RU-vid channel because we learn a lot by viewing them, very useful.I like it when you explain the reasons for the choices we have to make. We must not just say that we must not do this, we must explain why.

Tony, thank you for all the time you spent putting this information together for the use of others. In light of your generosity with your time and your sincere attempt at teaching those with the desire to learn, I am truly sorry that some commenters here have the audacity to criticize and post negative comments. I guess this is just the time we live in. Please be aware that your efforts have helped a lot of people in this hobby.

A video with a wealth of information especially the navigation process of the Digi Key, Mouser type search engine. Back in the day, being a boomer and all, I would just open up my MCM Electronics catalog and place an order, they had everything. For all of you young folks, MCM was the Sears and Roebuck of electronics of the 80's. Love the videos, I always learn something watching.

I appreciate the deep dive. I can read a data sheet, but I can’t always ‘evaluate’ it correctly. As you point out, the application determines relevant criteria.

Very useful and a reality check of the care and understanding required, thank you.

Very long video --> as lon as important, usefull. And saved my life. Thank you for the job.

Very thorough and good explanation about transistors, Tony! Just to take a substitution table "for granted" will often show very different data when consulting the data sheets for both types. The "substitution" could be on a very specific parameter, not the one YOU are most interested in. Also, I saw the MJW1302/3281 transistors. I wonder, are these "On-Semiconductor's versions of Toshiba's 2SA1302 and 2SC3281? Seem equivalent! These _were_ fine transistors before the fake versions of them hit the market. I ordered some from a vendor, asked him "can you guarantee they are real"? A pause, then "No".. This was some 10 years ago. Too bad the market has turned into this

Very valuable tips Tony. I had figured a lot out but thank you for compiling it all into one nice review and tips video. I ALWAYS learn something from you. Much appreciated for your time and knowledge !!

Tony this is the best transistor substitution video I have ever seen. I love the one thing you covered is the frequency rating. I don’t see many cover this. I see too much focus too much on gain in the forums and other places. The older amps, I find, need the slower switch. When I go to Mouser the first thing I look for is the package and the other is the frequency, go from there. Hard part comes when no match in frequency is found. Also I look up the compliment, and that one will throw everything out of spec. Also you talk about the intended application by the manufacturer, fantastic note. Not all times I’m successful with a modern replacement. Oh and if mouser is out of stock, sometimes you can order directly from ON or ti. There is no quick answer and sometimes you just have to say enough. Thank you for this. Your content is a value.

Hi Tony, absolutely brilliantly explained, unfortunately these days it's not just about replacing transistors, but older components in general. It has happened to me several times that I received a reply from the manufacturer - "Production terminated without compensation". Here in the Czech Republic, it is even worse, on the one hand, stores are closing down and those that remain sell overpriced Chinese junk - an example I wrote in several comments - I am restoring an HP 3400 voltmeter and before I start ordering unavailable and expensive axial capacitors here, I wanted a gauge put into operation at least with new radial capacitors. After the purchase, I remeasured them and since I don't know how long they had been in storage, I reformed them to be sure, what I found out shocked me - some 40-year-old Sprague capacitors had better parameters than newly bought ones in a brick and mortar store. Shopping on the Internet is good - if you buy from reputable sellers, but the next link in the line is the shipping company - I've had them lose the shipment several times, in the last case it took more than a year before I managed to get my money back. Thanks for the video and have a nice day 🙂 Tom

I've done this before already, but I enjoyed the thoroughness of your search.

Great video, sir. 👍 Thanks for taking the time to explain a lot of the differences. I knew a lot of it, but still learned a few more things!

Another good video......thanks, Tony. I learned this through experience with the help of many AK'ers. What's getting frustrating (& expensive) is trying to find replacements for all the older power mosfets. I know there are some modern "equivalents", but even they're scarce.

Thanks Tony. I picked tsome great tips. You're spot on in everything you said. This is very time consuming but very doable.

Excellent as always Tony. Thank you for everything that you do.

Wow, that TO-3P trick was quite the revelation. How long have I spent staring at that odd design without realizing the back-compatability to TO-3?

I've had faked transistors before. I was fixing either a Sony or a Pioneer amplifier (can't remember which brand it was, was a few years ago), and it was a 5.1 channel. The centre channel was outputting DC, so I thought the output transistors were bad (turns out they, weren't, keep reading...). Removing the transistors made the amp come out of protect mode and allow the other channels to work. The centre channel transistors were Darlington transistors, SK branded. So, I went to evil Bay and ordered a pair of NPN and PNP transistors and waited for their arrival. Upon putting them in the amplifier and applying power, I heard a quick fizz noise and the amp stayed in protect mode again, as it did before. DC on the output. The transistors were ultimately fakes and could not handle the +/-50V DC required on them. To cut a long story short, the original transistors tested fine and were fine, the real problem was between the base of each transistor and the voltage amplifier stage was a small 2W 180 ohm resistor, or so. One was open circuit, which caused a similar fault of a shorted transistor... that transistor's DC rail on the output. I was really annoyed about those fake transistors, though, as I waited I think 2 weeks for their arrival. In that time, I could have found and fixed the real problem.

Definitely digging in to this today! I have a Citation 16 that needs a bunch of replacements on the amp boards that are unobtanium!

Very informative and has helped me a bit more on choosing a replacement..

Best video for me so far. You are a great teacher. Thank you.

Greetings, I hope you and your family are well, thanks for your video, very helpful as always.

As always thank you tony! another great contribution. I woul'd be greatefull if you could do a similar video on different type of fets.

this was just the video i needed. thanks.

Great Video Tony, thanks. There are reputable secondary suppliers like Quest Components and Talon Electronics that specialize in obsolete and hard to find components. They can often save your bacon when a given component is otherwise not available, and you don't want to gamble on eBay. I have used Quest Components for years and had zero issues. 👍

Excellent! Watched to the end and liked it. ))

Very valuable information here. Thankyou !

A very helpful video thanks

Common Sense, from experience! Very interesting concept. Thanks, enjoyed.

This was a big help to me!

Great video!!, I'm going to try this !, but I sure miss Radio Shack!!

A couple of notes on Mouser: 1) Depending how you search, your results can be very different. For instance, if you begin the search with "200W transistor" and filter down to in-stock BJTs, you end up with 9 results, not 2. Sometimes you'll get zero results with one search term, but going at it from another direction will find what you need. And 2), even if they claim a part is on order with a due date, that doesn't mean you'll ever get it. I've had one item on backorder since May, for December delivery. It's a common pot that our company has used for 40 years. Suddenly, instead of "16,000 due December 18", delivery is showing "Obsolete", with no replacement available. [sad trombone]

This is very useful for one me, thank you!

Some of the Pioneers like my SA8800 integrated amplifier have some pretty hard to replace transistors in them. The JFET constant current source in this generation of integrated amps and some of the X80 series have a few solutions that I've found depending on the voltage. The drivers have really high transition frequency for this particular amp and there are no TO220s that I've found in the ballpark of those, at least that are easily available! The outputs on these series are also challenging to find now that the MT - 200 Sankens that were good for these are now obsolete as of 2018ish if memory serves. I think there might be a way to finagle some of the TO 247s in there! (there are a few decent substitutes out there!) Thankfully mine seem to be all good, with the exception of the notorious 2SA979 dual device. My left channel gets that rice krispies sound after it warms up! I'll probably just thermally bond two well matched TO-92s for those! I also thought I found a suitable substitute for the STV stabistor diodes (sometime in 2016, I still haven't gotten around to fixing it!) in a surface mount package!!! Mine are still in good shape thankfully, so I shouldn't have to rig anything together for those!

good video . i wish the folks i do work for understand the time we put into crossing carts that have no cross . so many rca labled components have no cross . its to the point i keep 50 of each tip31c and tip32c for odd replacements

I think we need to work on a design of a time machine:) but for us it would have to be the size of a truck! Its been very interesting, we have groups in the UK who also like Tube equipment and then there is the voltage issues for the parts we need.Ray thank you for such a good video.

I really appreciate all that you do on this channel. I was wondering if at sometime in the future you would talk about replacing obsolete jfet transistors. You’ve done several great videos on selecting and matching bjt transistors. Jfets are somewhat of a mystery to me and anything you could do on the topic would be appreciated. Thanks Again

Note you can go over 15 to 20% or higher of transistor datasheet ratings transistors with higher gain can produce more output power. For example you can have a transistor that can only handle 40 volts but the gain is 400 to 800 it's going to be loud. Then you could have another transistor that can handle up to 300 volts but the gain is only 40 and the max would be 120. So to build a high-end quality amplifier I would go with the 40-volt transistor because of the gain almost all amplifiers use high-gain transistors a transistor that has a max gain of 30 would not be suitable for a amplifier application it would be more suitable for a switch mode power supply application or for use in place of a rectifier diode or for use such as pushing a motor. I'll give you another good example the A18 transistor TO-92 package it has a max gain of 1500 but it has low voltage capability such as 45 volts.This would be a hard one to replace when it comes to cross reference.

Hi, A blurb in three parts: 1. Thank you for an excellent class on how to substitute transistors. Your selfless sharing of information with the community is truly appreciated. 2. I do have a request. Often when you are addressing issues with a driver circuit, you state that a specific transistor is known to be problematic. If, over time, you could please make a list of these problematic transistors, I surely would appreciate it. I had 4 or so written down and then I lost the list. This is something only experience brings. I can’t look it up. Only the Tony knows. 3. What happened to xraytonya? Should I be concerned? And what if xraytonyc shows up, do we need to send a search party? These are questions that must be answered!

Seems to me that the component manufacturers, just want to eliminate our options on repairing vintage gear. This is definitely a Right To Repair equvalent problem. Thanks, Tony!

Usually those oddball obsolete parts you special order, require a minimum purchase. I have purchased 5000 capacitors before. At 2300 I could order the minimum number of catalog parts. At 5000 pieces I ordered similar parts to MY own custom specs.

Thanks Tony!

Also, another option is to strip components out of less-valuable/irreparable units. I am getting 7 pairs of Toshiba 2SC5242/2SA1962 out an Onkyo AVR that died because of a bad HDMI board.

Great video. I always learn from your discussions on transistors. Q: are there techniques for adapting surface mount transistors to a TO92 package…..like mini surface mount boards with leads? This would be very helpful for the small signal signal transistors. Just a thought. Thank You

Tony EXCELLENT VIDEO as usual, I have a question on the other STK modules, and that falls in line with the difference between STK-0100 in comparison to STK-0050? Are there big differences between these devices that fall in the STK-0XXXX series?

I have a question Tony. You rebuilt that Fisher with the STK outputs and the amp was rated for around 100w I believe and I want to say that model had +/- 57 to 59 volt rails. You replaced those modules with the board using the discrete components. Are you at all worried that you’re pushing the the NJW1302/NJW3281 to their limit with only one pair making that 100w? I’d think you were riding close to the SOA limits at that voltage. I have several hundreds of the NJW0302/NJW0281 so I use them for these boards when doing like the SX-780. Not sure I’d use them for a 100w unit with nearly 60v rails even though the only difference being that the 1302/3281 are 200w dissipation vs 0302/0281 are 150w dissipation. I do have several dozen of the 1302/3281 in both NJW and MJL packages, but if i can save them I will since parts are scarce. I’m wondering if while using that same board I can wire a second pair of outputs in parallel. I really hope that these through hole parts start becoming available again.

My goto cross ref manual used to be Towers International Transistors Selector (T.I.T.S) I wonder if they did that deliberately?

To the best of your knowledge will this technique work for RF applications? I am thinking that you would have to pay particular attention to the high frequency attributes but other than that... should it work? Thanks for the info!

It'd be nice to get a walkthrough of the Mouser Alternates Search Results table and what each column's value is/represents and how it relates to the audio equipment's (amps) functionality. Just a suggestion.

This would be a hard one to cross reference look at all the gain Type Designator: MPSA18 Material of Transistor: Si Polarity: NPN Maximum Collector Power Dissipation (Pc): 0.31 W Maximum Collector-Base Voltage |Vcb|: 45 V Maximum Collector-Emitter Voltage |Vce|: 45 V Maximum Collector Current |Ic max|: 0.1 A Max. Operating Junction Temperature (Tj): 150 °C Transition Frequency (ft): 100 MHz Forward Current Transfer Ratio (hFE), MIN: 800 max 1500 Noise Figure, dB: - Package: TO92 They are uses as a differential pair in one of my amplifiers

thank you X-Ray T

Some of those transistors packs don't use the 4 pins on the midle. So you can just replace them with two transistos.a toshiba TTA1943 B241, PNP on left side and a Toshiba TTC5200 B242, NPN to the right side.

Would adding an output inductor network work if only a high frequency transistor was available? Some of the newer power transistors advertise lower distortion so could replacing 60’s and 70’s outputs give a noticeable improvement? Thanks for all your videos.

Single output transistor to sziklai pair, with low power transistor? If we not found the same transistor, is that gonna make difference??

#1 if your not resourceful enough to find replacements for Obsolete components then this hobby/Career is not for you . Ive been doing this 35 years and i Can Assure you of this

Real world, real experience. Fail your way to success.

Thanks.

Interesting subject. One day we not be able to get any parts at all.

Been beating my head against the wall trying to find a T03 style resistors for a 1968 Scott stereo we've had since new. Part # bend qp-11 0689D. Can't find any cross reference to an updated T03 style. Any ideas?

Can we no implement a STK500 module using a stereo ADC and a DAC to drive and do all processing in C++

I'm looking to find a replacement for a cr160 transistor but I'm not a smart person don't no if you can help

5:15 comment couldn’t have came at a better time.

TIP35c/TIP36c are applicable in most situations, and will most often be superior to anything they replace, with TIP41c/TIP42c as drivers. BD139 can be safely replaced with MJE340 in the role of bias spreader, even with any TO-92 npn with at least 100mA, suitable C-E voltage rating and collector as the middle pin. Also if there is nothing else, for the power pair BD249c/BD250c, and BD243/BD244 as drivers.

Just an Idea what about copying the 5W Class A circuit on Google Images where you would use to identical Power Transistors you don't have to do it just an idea.

13:19 Seems like if I was an enterprising YOUNG MAN, I would take that STEM / Engineering Degree and take it to India and then build a se

all you need is a Perfboard And theoretically any power transistors would do be nice to use MOSFETs just design it in microcap it's free. as long as you know your lines in and out and voltages dead easy

There's some good information in the video but it's a little long winded. If we click on a "how to" video we probably don't need a 20 minute introduction telling us why we might need to do something... We already know we need to that's why we clicked on the video. Thanks for the info.

And, most of the Toshiba, Motorola and Hitachi power transistors are the most faked.

Not plastic don't melt

This substitution / obsolescence stuff is why I increasingly say no no no to vintage stereo repairs and yes yes yes to vintage tube guitar amp repairs. I don't even like PC boards.

Readily available from aliexpress

Just google equivalent it isn’t rocket science .