2n30809 dual fet

[faggianfra]

Hi to everybody
this is my first thred, my problem is with my Leader scope, it has this 2n30809 dual fet dead and I can't find any datasheet or documentation about it.
anybody has any suggestion? how I can plot a curve and try to find a substitute for it.
thanks

 

[Hero999]

Maybe it's because you've got the part number wrong?

Could it be the 2N3809 which is a dual PNP BJT?

I couldn't find the datasheet but here's a list of similar transistors.
2N3808 pdf, 2N3808 description, 2N3808 datasheets, 2N3808 view ::: ALLDATASHEET :::

 

[faggianfra]

thanks to answer,
unfortunatly I'm sure about the part number , I have the schematic of the scope, tomorrow i'll attach the file, it will help for sure.

 

[faggianfra]

Here's the schematic, and a photo of the little beast

 

[Hero999]

How do you know it's bad, have you tested it?

Try the 2N3958 - it seems to be similar and is in the package, although you need to check the pinout.
https://www.electro-tech-online.com/custompdfs/2010/03/2n3958.pdf

 

[faggianfra]

this dual fet is from the channel 1 of my leader scope so I tried to sobstitute with that from ch2, now ch1 is dead and ch2 works!
So I'm sure it's fault. i tried to test and look like just half is burned.
Do you have any trick how I can get the charatteristic from a fet so I can get the correct one?
BTW, I ceck the price for the 2n3958... pay 20 Euro just to test...you know.

 

[Hero999]

How about matching some discrete FETs?

It won't be as good but dual matched FETs are expensive.

The following paper discusses this and suggests some alternatives to the 2N3958.
https://www.electro-tech-online.com/custompdfs/2010/03/col_01302004.pdf

 

[faggianfra]

hi hero 999
sorry to open a new thread, I didn't get your last message!that's extactly what is was looking for!
I send a new thread because I was totally demotivate, I'm spending hours in internet just to looking for some information about this dual fet and I can't find anything!
My electronic skill is not so high (how you already undensood) so I'm tring to hung to everibody can help me.
so, excuse me if the second thread was looking you as offend you ,it was just a desperate call for help.
thank you very much aniway.

 

[faggianfra]

Hi hero
Just to thank you for your help, I got a couple of 2n3958 for just 5 gbp (ok, I paid more for the delivery then the pieces!), anyway it was worth, I spend just some time to bias it like the old one , now look like my scope is working.
So thanks for your help it was very appreciate. (by the way I try to match two fets but It didn't work, ok I don't have so many tipeso I tried just with j112, j310, but I think they have charatteristic totally different then this one, and last my limits in elestronics are pretty evidents ;-)).

 

[Hero999]

Good, I'm glad it worked.

It's a shame, I've just found some 2N3958s in my junkbox which I would've let you have for not much more than the cost of delivery.

 

[faggianfra]

hi hero
it's me AGAIN! I have a second problem with my scope (you know when you pay 20$ for a scope ther's always a reason ;-)) so another obsolete part, now even worst because it's a couston IC.is the IC16 on the sch.
Now to find the part I think is almost impossible, I made some research but I don't found any Leader lab to ask for the speare.
Do you have any idea how I can retrace this coustum ic (its just some OP Amp with some SMD but to take out the resin is almost impossible to see which one is)

 

[Hero999]

These things are just designed to make life difficult for you.

Why do they bother providing a schematic?

I can't help you much here, I wouldn't know where to get hold of that IC.

You obviously need to remove the resin. There are some chemicals which can do it, but they're very nasty.

You could try designing your own IC purely by guessing what's inside it based on the surrounding circuitry, but that would be really hard to do and there's no guarantee it'll work.

I had difficulty reading that schematic so I flipped it.

 

[faggianfra]

I'm agreed with you about this jocking schematic.
Thanks anyway ,I will try to follow the "remove resin challange" first! If not I will try to redesign it, the problem is that is difficult to find schematic to copy the system.in any case I have 50% trigger working I will survive and for people like me that my time is for free I can do a lot of test before to give up!

 

[Hero999]

Good luck.

I'd like to see how you get on.