Raccoon1400
Super Member
A lot of people ask how to find a replacement for a transistor, so I thought I'd write this guide.
In most cases when replacing transistors, it is not advantageous to track down the original part number. Most of these parts are no longer made, and many available on ebay, especially from china are counterfeit. Pulls from working units sold on ebay may be acceptable, although in most cases they will be more expensive and not necessary. Sources such as Digi-key, Mouser and Newark have a wide selection of transistors that are as good or better than the originals. They are guaranteed to be genuine parts, and they ship very fast.
The first step in replacing a transistor is to find the specs of the original transistors. Datasheets can be found online easily most of the time by searching the transistor number. Datasheets contain as much information as one could possibly want to know about the part.
The most important specs when choosing a transistor are maximum voltage, maximum collector current, type (NPN, PNP) and maximum power. Frequency is often important, for example when selecting driver transistors. (Drivers are the transistors in a power amp that come before the outputs.) It is not important when selecting power supply transistors, or relay drivers. An amp will not perform to its potential if the frequency the parts can handle is less than the circuit design required, though nothing will be damaged. (Can someone elaborate on frequency, where it matters, why, and how high a frequency is beneficial)
Pinout should be noted. It is not normally necessary to select a part with the same pinout, but you want to make sure the new part is installed correctly. If the transistor is installed with its legs in a row, it will be hard to install a collector centered part in place of a base centered part. If the legs are arranged in a triangle, it is easy. Most TO-92 parts used in vintage gear, especially Japanese parts are collector centered. But don’t assume, or you may release magic smoke. TO-220, TO-3, and TO-3P transistors always have the same pinout. Common TO-92 pinouts include ecb, bce, ebc.
There are two types of transistors, NPN and PNP. Mixing up the two will result in magic smoke being released, or at least the circuit will not work. Echowars' thread "Bipolar Junction Transistor Testing Basics" gives more detail on what this means. The thread is linked at the end of the post.
Transistors are normally replaced with the same case style, though in some cases a bigger case may be selected. (For example, Pioneer SX-3800, SX-3900 power supplies benefit from beefier transistors in places, originals were underrated and held up poorly over time) Relay driver transistors can also be beefed up to TO-126 replacements. For common case styles, see the Echowars thread linked at the end of the post.
The next step is to select an appropriate transistor with equal or greater ratings, of the same type. The main parts suppliers are very well setup to sort and filter parts by any spec we could want them to, so we can go to one of those sources and narrow down their massive stock of transistors to find ones that match the criteria we need. Much of the time though a replacement can be selected from the list of commonly used parts in this post.
Some people like to use a cross reference sheet, this can be useful but it is not my preferred way of selecting a replacement. There are probably dozens of transistors that I would replace with the same part. In some cases, I may replace the same part with a different replacement depending on what it was doing in the circuit. And no matter how compete a cross reference sheet is, it will be very hard to include every part that is used in gear we work on. In those cases, it is important to know how to work with datasheets.
Gain (or Beta, B) is sometimes worth noting. A high B transistors is advantageous in differential pairs in the input of the power amp section for example. A properly matched high gain pair will keep distortion and DC offset to a minimum. Many of the replacement transistors available now aren't as high gain as the originals, because the industry is moving toward surface mount components as opposed to through hole. One of the letters in the suffix of the transistor may refer to gain. Many parts are sorted into several different gain groups. However for most of the KSC/KSA parts only the lower gain groups are still available. Most of the time though the available KSC1845/KSA992 transistors will be fine. If higher gain is desired, the zentex transistors are a good option.
Occasionally you may run into a darlington pair transistor. This is two transistors in one package connected together for higher gain. They need to be replaced with darlington transistors, none of the transistors mentioned in this thread are darlington. Sometimes the designers used separate transistors are used to create a darlington pair. They did this in the relay driver circuit in many Marantz receivers.
There is a style of output transistors known as batwings. They have a tab on each side, instead of on the top. There are no new subs for these. For the smaller ones, TO-220 transistors can be made to fit by drilling a new hole in the heatsink. For bigger types, a hold down bar can be made, as discussed in this Echowars thread:
http://www.audiokarma.org/forums/index.php?threads/pioneer-sx-1980-transistor-modification.60536/
There are also no new subs for TO-66 output transistors (These look like small TO-3). TO-220 can be made to fit here.
Can someone describe what special considerations may need to be taken into account to find a good bias transistor?
Here is a list of parts that are commonly recommend on this forum. I keep a stock of most of them.
TO-3 Output transistors. The following transistors are very heavy duty and can be used to replace just about any TO-3 transistor. Note some amps like the Kenwood 600 need the original outputs to sound correct. I’m not sure of the difference between these parts, but the MJ21196/MJ21195 are a bit cheaper.
MJ21193/MJ21194 16A 250W 250V
MJ21195/MJ21196 16A 250W 250V
TO-3P transistor replacements
NJW21193/NJW21194 16A 250W 200V
MJW21195/MJW21196 16A 250W 200V
2SC3856/2SA1492 15A 130W 180V Sanken (digikey)
TO-247-3 replacements
MJW21193/MJW21194 16A 250W 200V
MJW21195/MJW21196 16A 250W 200V
TO-264 replacements
MJW1302/MJW3281 15A 200W 230V
MJL4281A/MJL4302A 15A 230W 350V
MT-200 output transistors:
Sanken parts available from digikey. Specific recommendations to come.
TO-220 replacements: These parts are great as output transistors, power supply regulator transistors, or driver transistors.
MJE15032/MJE15033 8A 50W 250V 30MHz
TO-92 (these are the normal style of small transistors)
These parts are great replacements that can be used as signal transistors in preamp sections, phono sections, and differential pairs in power amp input stages.
KSC1845/KSA992 50mA 500mW 120V
KSC945C/KSA733C 150mA 250mW 50V (Suffix C for collector centered, base centered versions are also available.)
TO-92 heavier duty
Collector centered and base centered versions are available for these, suffix C for collector centered.
KSC1008C/KSA708C 0.7A 0.8W 60V
TO-92L transistors
KSC2383/KSA1013 TO-92L 1A 0.9W 160V
TO-126 replacements. KSC2690A makes a good relay driver replacement.
KSC2690A/KSA1220A 1.2A 1.2W 160V(A version is higher voltage than Y version)
MJE253/MJE243 4A 15W 100V
KSC3503/KSA1381 100mA 1.2W 300V (A good replacement for 2SC1451, used in pioneer, etc)
TO-220 driver transistor replacements. Note these have an insulated tab, so there are not suitable for places where the collector lead is cut off and the tab is used as the contact instead. I think a couple of these are NLA now but I’ve included them for some reason anyway, I still have a couple sets in stock.
2SC5171/2SA1930 2A 20W 180V 200MHz (NLA?)
2SC4793/2SA1837 1A 2W 230V 100MHz (NLA?)
2SC4381/2SA1667 2A 25W 150V 20MHz (digikey)
Other resources:
Bipolar Junction Transistor Testing Basics, by Echowars
http://www.audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/
Common Transistor Case Styles, by Echowars
http://www.audiokarma.org/forums/index.php?threads/common-transistor-case-styles.116021/
Counterfeit transistors (There was another Echowars thread about this, can anyone find it?)
This post, by dlucy:
http://www.audiokarma.org/forums/in...r-substitution-question.754182/#post-10253865
Transistor cross references:
http://www.audiokarma.org/forums/index.php?threads/transistor-substitutions.688515/
http://www.audiokarma.org/forums/in...ilure-prone-whatever-and-replacements.731653/
http://www.audiokarma.org/forums/index.php?threads/once-more-sansui-transistor-substitutions.583009/
This is what has come to my mind as important. Contributions, elaborations, corrections are welcome.
I will add some pictures of datasheets with important information highlighted.
In most cases when replacing transistors, it is not advantageous to track down the original part number. Most of these parts are no longer made, and many available on ebay, especially from china are counterfeit. Pulls from working units sold on ebay may be acceptable, although in most cases they will be more expensive and not necessary. Sources such as Digi-key, Mouser and Newark have a wide selection of transistors that are as good or better than the originals. They are guaranteed to be genuine parts, and they ship very fast.
The first step in replacing a transistor is to find the specs of the original transistors. Datasheets can be found online easily most of the time by searching the transistor number. Datasheets contain as much information as one could possibly want to know about the part.
The most important specs when choosing a transistor are maximum voltage, maximum collector current, type (NPN, PNP) and maximum power. Frequency is often important, for example when selecting driver transistors. (Drivers are the transistors in a power amp that come before the outputs.) It is not important when selecting power supply transistors, or relay drivers. An amp will not perform to its potential if the frequency the parts can handle is less than the circuit design required, though nothing will be damaged. (Can someone elaborate on frequency, where it matters, why, and how high a frequency is beneficial)
Pinout should be noted. It is not normally necessary to select a part with the same pinout, but you want to make sure the new part is installed correctly. If the transistor is installed with its legs in a row, it will be hard to install a collector centered part in place of a base centered part. If the legs are arranged in a triangle, it is easy. Most TO-92 parts used in vintage gear, especially Japanese parts are collector centered. But don’t assume, or you may release magic smoke. TO-220, TO-3, and TO-3P transistors always have the same pinout. Common TO-92 pinouts include ecb, bce, ebc.
There are two types of transistors, NPN and PNP. Mixing up the two will result in magic smoke being released, or at least the circuit will not work. Echowars' thread "Bipolar Junction Transistor Testing Basics" gives more detail on what this means. The thread is linked at the end of the post.
Transistors are normally replaced with the same case style, though in some cases a bigger case may be selected. (For example, Pioneer SX-3800, SX-3900 power supplies benefit from beefier transistors in places, originals were underrated and held up poorly over time) Relay driver transistors can also be beefed up to TO-126 replacements. For common case styles, see the Echowars thread linked at the end of the post.
The next step is to select an appropriate transistor with equal or greater ratings, of the same type. The main parts suppliers are very well setup to sort and filter parts by any spec we could want them to, so we can go to one of those sources and narrow down their massive stock of transistors to find ones that match the criteria we need. Much of the time though a replacement can be selected from the list of commonly used parts in this post.
Some people like to use a cross reference sheet, this can be useful but it is not my preferred way of selecting a replacement. There are probably dozens of transistors that I would replace with the same part. In some cases, I may replace the same part with a different replacement depending on what it was doing in the circuit. And no matter how compete a cross reference sheet is, it will be very hard to include every part that is used in gear we work on. In those cases, it is important to know how to work with datasheets.
Gain (or Beta, B) is sometimes worth noting. A high B transistors is advantageous in differential pairs in the input of the power amp section for example. A properly matched high gain pair will keep distortion and DC offset to a minimum. Many of the replacement transistors available now aren't as high gain as the originals, because the industry is moving toward surface mount components as opposed to through hole. One of the letters in the suffix of the transistor may refer to gain. Many parts are sorted into several different gain groups. However for most of the KSC/KSA parts only the lower gain groups are still available. Most of the time though the available KSC1845/KSA992 transistors will be fine. If higher gain is desired, the zentex transistors are a good option.
Occasionally you may run into a darlington pair transistor. This is two transistors in one package connected together for higher gain. They need to be replaced with darlington transistors, none of the transistors mentioned in this thread are darlington. Sometimes the designers used separate transistors are used to create a darlington pair. They did this in the relay driver circuit in many Marantz receivers.
There is a style of output transistors known as batwings. They have a tab on each side, instead of on the top. There are no new subs for these. For the smaller ones, TO-220 transistors can be made to fit by drilling a new hole in the heatsink. For bigger types, a hold down bar can be made, as discussed in this Echowars thread:
http://www.audiokarma.org/forums/index.php?threads/pioneer-sx-1980-transistor-modification.60536/
There are also no new subs for TO-66 output transistors (These look like small TO-3). TO-220 can be made to fit here.
Can someone describe what special considerations may need to be taken into account to find a good bias transistor?
Here is a list of parts that are commonly recommend on this forum. I keep a stock of most of them.
TO-3 Output transistors. The following transistors are very heavy duty and can be used to replace just about any TO-3 transistor. Note some amps like the Kenwood 600 need the original outputs to sound correct. I’m not sure of the difference between these parts, but the MJ21196/MJ21195 are a bit cheaper.
MJ21193/MJ21194 16A 250W 250V
MJ21195/MJ21196 16A 250W 250V
TO-3P transistor replacements
NJW21193/NJW21194 16A 250W 200V
MJW21195/MJW21196 16A 250W 200V
2SC3856/2SA1492 15A 130W 180V Sanken (digikey)
TO-247-3 replacements
MJW21193/MJW21194 16A 250W 200V
MJW21195/MJW21196 16A 250W 200V
TO-264 replacements
MJW1302/MJW3281 15A 200W 230V
MJL4281A/MJL4302A 15A 230W 350V
MT-200 output transistors:
Sanken parts available from digikey. Specific recommendations to come.
TO-220 replacements: These parts are great as output transistors, power supply regulator transistors, or driver transistors.
MJE15032/MJE15033 8A 50W 250V 30MHz
TO-92 (these are the normal style of small transistors)
These parts are great replacements that can be used as signal transistors in preamp sections, phono sections, and differential pairs in power amp input stages.
KSC1845/KSA992 50mA 500mW 120V
KSC945C/KSA733C 150mA 250mW 50V (Suffix C for collector centered, base centered versions are also available.)
TO-92 heavier duty
Collector centered and base centered versions are available for these, suffix C for collector centered.
KSC1008C/KSA708C 0.7A 0.8W 60V
TO-92L transistors
KSC2383/KSA1013 TO-92L 1A 0.9W 160V
TO-126 replacements. KSC2690A makes a good relay driver replacement.
KSC2690A/KSA1220A 1.2A 1.2W 160V(A version is higher voltage than Y version)
MJE253/MJE243 4A 15W 100V
KSC3503/KSA1381 100mA 1.2W 300V (A good replacement for 2SC1451, used in pioneer, etc)
TO-220 driver transistor replacements. Note these have an insulated tab, so there are not suitable for places where the collector lead is cut off and the tab is used as the contact instead. I think a couple of these are NLA now but I’ve included them for some reason anyway, I still have a couple sets in stock.
2SC5171/2SA1930 2A 20W 180V 200MHz (NLA?)
2SC4793/2SA1837 1A 2W 230V 100MHz (NLA?)
2SC4381/2SA1667 2A 25W 150V 20MHz (digikey)
Other resources:
Bipolar Junction Transistor Testing Basics, by Echowars
http://www.audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/
Common Transistor Case Styles, by Echowars
http://www.audiokarma.org/forums/index.php?threads/common-transistor-case-styles.116021/
Counterfeit transistors (There was another Echowars thread about this, can anyone find it?)
This post, by dlucy:
http://www.audiokarma.org/forums/in...r-substitution-question.754182/#post-10253865
Transistor cross references:
http://www.audiokarma.org/forums/index.php?threads/transistor-substitutions.688515/
http://www.audiokarma.org/forums/in...ilure-prone-whatever-and-replacements.731653/
http://www.audiokarma.org/forums/index.php?threads/once-more-sansui-transistor-substitutions.583009/
This is what has come to my mind as important. Contributions, elaborations, corrections are welcome.
I will add some pictures of datasheets with important information highlighted.
Last edited:
