A872e Replacement

[sketchyphish]

Hello i have to replace a transistor A872E i believe.

An externally hosted image should be here but it was not working when we last tested it.

Does anyone know where to get some or what to replace them with. It is originally from a C-Audio SR606.
Ive nearly got the amp fully working but need to replace a few parts to get it going again.

Thanks

 

[Ian Finch]

This is a Renesas 2SA872, from a complementary low noise pair with 2SC1775. You will only get near equivalence but to be helpful, we need to know the role and whether it is used with its complement, as possibly matched mirror input pairs in an amplifier, VAS in a discrete preamp, general purpose part or whatever.

Can you post the schematic? Otherwise, Google is your friend - type "buy 2SA872" into your browser and presto! - it seems futurlec.com is one seller at least.

 

[Ian Finch]

Also, take a look at the multiple cross references and equivalents listed on this page. For general purpose, low noise applications, Fairchild's KSA992/KSC1845 might be suitable up to 120V, as would Toshiba 2SA970/2SC2240 if complements are needed. 2SA872 datasheet and application note, data sheet, circuit, pdf, cross reference | Datasheet Archive
Note the E suffix means Hfe 400-800.

 

[wahab]

It has 90V Vce rating , the E being for a beta of 400 to 800.

It can be replaced by 2SA992/970 or , if the apparatus supply voltage is less
than 45V, by BC550C but there is no really accurate replacements as this decades
old transistor is among the best for audio and has some desirable caracteristics
that are hardly matched by seemingly equivalent devices.

As pointed by Ian , the choice of a replacement depend of its exact use
in a circuit.

 

[sketchyphish]

Right o first up the schematic

https://dl.dropbox.com/u/50713693/SR series.pdf

I believe that we are looking at TR17 here.

Im sure they are working in pairs so would be best to replace this whole section with a pair noted above.

It runs at about 86v rails so will be looking to install the Toshiba 2SA970/2SC2240 pair to replace.

I guess its best to replace both on each side so that the transistors are matched, and both channels operate the same.

If anyone has any ideas let me know otherwise i will go and order the bits.

Thanks

 

[wahab]

This amplifier has +-100V rails for the input stage ,so the 90V Vce 2SA872
was outspeced , the correct device would have been the 2SA872A wich
withstand 120V.

Both 2SA970 and 2SA992 are 120V Vce but the latter have 500mW TDP
while the former is only 300mW as was the original 2SA872.

The dissipation of the device is about 100mW in your schematic
so 300mW parts is somewhat short.

 

[Samuel Jayaraj]

KSA992E is easier to find and a good equivalent.