equivalent for 2n3904

[deji]

hi does anyone have an idea for an equivalent transistor for 2n3904 i am trying to build a touch activated alarm using a ne555 and a 2n3904 as the principal components but i cant get a 2n3906 any suggestions

 

[Netlist]

Possible replacement:
Pin assignment: pins up, front near you:
2N3904: CBE
BC546: EBC
Should be easy to get 🙂

 

[Jocko Homo]

Anything that is NPN will work..................you can always rearrange the pins.

Jocko

 

[markp]

If you can get NTE parts it is a '123AP'. Almost any NPN you find will work as it is the most common small signal transistor I can think of. Try an MPS05A too

 

[deji]

i guess i can use a bc109 too if almost any npn will work right

 

[Frank Berry]

2N2222 would also work.

 

[deji]

thanks i;ll see if i can get the 2n2222 and try it out but what about bc109

 

[pawleep]

nte123ap is rated 40v mps6531 is 60v, on a peavey 400 bass amp board are these substitutes ok?

 

[Enzo]

Wow, asleep for 12 years, and now gets a post.

Look at the specs again:
NTE123AP - Vceo 40v, Vcbo60v

MPS6531 - Vceo 40v, Vcbo 60v

I dislike using NTE for anything but emergencies, but in this case they have the same basic spec. Usually the real part is a lot less expensive than the NTE, and if I don't have the real part, chances are something else I have is just as good a substitute as the NTE.


In your specific application, are these the limiter transistors near the outputs? Those are not very critical, and are easy to sub.

You may find this company cross reference useful in the future:
http://bmamps.com/Schematics/Peavey/Peavey_Semi_Cross_Ref.pdf

 

[pawleep]

thanx enzo

will have to ck out the reference later...
is prolly a limiter... because there was a bad resistor and possibly bad big diode(s) & bad output xistor on the power transistor section board
😀
if I can see the numbers on some other boards I scavenged, I may be able to find a better quality than the NTE, go figure.. cheesy, Chinese garbage, I rekon?

I didn't know so this is good info u gave me...
ttys

 

[Enzo]

My objection to NTE is not that the individual parts are bad, but rather the parts cost 3-10 times more than the real parts, and they are only approximately similar to the original parts. Why spend $1.50 for a transistor that is close, when the real transistor is readily available for 60 cents and is exactly what the circuit wants. By themselves, transistors can vary, but especially in applications like output transistors, current sharing is important, and then we want all the parallel parts to be the same. One NTE in a row of Motorolas is asking for it to either hog current or sit there like a lump and do nothing.

 

[pawleep]

nice enzo

appreciate the suggestion.. am gonna look to see what is lurking on some scrap boards.. not an emergency (bak up amp)... is a peavey mark IV or something.. same main power section as an xr600 b

 

[pawleep]

where do i find a good quality MPS-6531 2N3642/MPS-6530 2N3642
for a peavey bass amp mark 4 or bass 400 type
heard the NTE123 is not the greatest

 

[Enzo]

Mouser has 1000 in stock:
MPS6531 Central Semiconductor | Mouser

And you can also order parts direct from Peavey, they may put a different substitute in its place, but it would be appropriate.

 

[Cjuried]

2N2222 will handle 3 times the current and is electrically equivalent.

 

[pawleep]

is the microtivity Pack of 4 2N2222 NPN Bipolar Amplifier/Switching Transistors
similar to the nte123? i hear they were not that good (the nte123's)
the mps6531's seem hard to find on amazon

 

[Enzo]

The MPS6531 on the Peavey 400BH board is just a limiter, it drags the base of the driver down if the output current goes too high. very common circuit. The 2N2222 is a heftier part, but there really is no current to speak of, so that becomes moot. Most any small NPN will work there.

I explained my objections to NTE in post #11.

 

[wg_ski]

Heftier parts like the 2222 will work. But there is something to be said for using low Cob parts in the current limit circuits. Smaller die = lower current and smaller capacitance. Part of the reason VI limiters are blamed for degrading the sound (compared to not having them) is their nonlinear parasitic capacitances. Always there, causing distortion, even when not in use. Really might not matter much in a Peavey product, but with higher end equipment you may need to watch things like this more closely.

 

[Enzo]

In pawleep's case, it is a 1980s era Peavey amp, which is totally insensitive to subtleties like that. Like a WW2 army jeep, it will pretty much run on anything. As you say, in the hifi world people might notice.