• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Transistor Substitutions

Dutch9600 said:
Looking for a good sub for 2sd1944(j,k). Thank you for any and all help.
Click to expand...
IThe 2SD1944 has a relatively high transition frequency (ft=50MHz) and quite a high current gain part, does that matter where that part is being used in the circuit? Do you need an exposed collector tab?. If so, your best bet would be an MJE15028, they have an hfe in the 200-300 range. Ic=8A, 120V, 30MHz.

If you can use an isolated TO-220 transistor, you may consider the KSD1408Y Veo=80V, Ic=4A, ft=8MHz available at digikey. Depending on where is your location, there may be other alternatives that you may find like the UTC 2SD313 (exposed collector tab) , or the KEC KTD2058 (isolated) , both with similar specifications, (60V, 3A, 3MHz).
 
Last edited:
Cheers rottalpha i'm new to electronics at 61 never messed with this stuff in my life but hey it's good to keep the brain active. I've had the issue of trying to find substitues only to see they are discontinued. This will be a great referance point if it's being updated regularly.
 
billathome65 said:
Cheers rottalpha i'm new to electronics at 61 never messed with this stuff in my life but hey it's good to keep the brain active. I've had the issue of trying to find substitues only to see they are discontinued. This will be a great referance point if it's being updated regularly.
Click to expand...
Thanks, and thanks to all contributors.
This is a community effort so the updates happen as time permits. The thread started years ago and production of TH parts is in constant changing, but generally speaking, the information is up to date.
 
Dutch9600 said:
Memory is fading and I can't remember what it was in
Click to expand...
You will get more help if you open a thread dedicated to the unit you are trying to repair, so you can post a picture of the part of the schematic where the transistor to be replaced goes.
Often times the original parts used have less hfe than the typical or maximum that the datasheet specifies even when they were new. You will see this if you manage to get NOS parts of the type you are trying to find. It will most likely be near the bottom of the range of hfe values specified by its datasheet.
It is also rare for a circuit to depend on exact values of hfe because that parameter changes as the transistor ages, it is temperature dependent and it was not well defined in early parts like the one you are trying to replace. With regards of the suggestions not being "close enough", with the information you provide, i would say they are rather good choices. You could try to fing NOS parts -and may be Ceitron has it- but if you can not find you must make an educated decision on the part to replace the faulty transistor. I hope that the help provided you was useful to fix your amp.
Good luck with your repair!
 
Last edited:
JoseHH said:
You will get more help if you open a thread dedicated to the unit you are trying to repair, so you can post a picture od the part of the schematic where the transistor to be replaced goes.
Often times the original parts used have less hfe than the typical or maximum that the datasheet specifies even when they were new. You will see this if you manage to get NOS parts of the type you are trying to find. It will most likely be near the bottom of the range of hfe values specified by its datasheet.
It is also rare for a circuit to depend on exact values of hfe because that parameter changes as the transistor ages, it is temperature dependent and it was not well defined in early parts like the one you are trying to replace. With regards of the suggestions not being "close enough", with the information you provide, i would say they are rather good choices. You could try to fing NOS parts -and may be Ceitron has it- but if you can not find you must make an educated decision on the part to replace the faulty transistor. I hope that the help provided you was useful to fix your amp.
Good luck with your repair!
Click to expand...
I was replying to rottalpha's question, what's not close enough and what was the transistor used for, as I said he answered the questions back in post #604. That amp was completed back in Nov., but thanks for your reply.

​

 
You must log in or register to reply here.
Back
Top Bottom