which transistor for 2*5*2*0 BC 550/560

[JRE Productions]

I am trying to figure out which transistor to order. I think I am going to use the BC550 and BC560. But there are quite a few variations.

Here is the mouser page for the 560. But what is the difference between 560/bt/c ect.. http://www.mouser.com/index.cfm?&handler=data.listcategory&D=*bc*%2b*560*&terms=bc+560&Ntt=*bc*%2b*560*&Dk=1&Ns=SField&N=500&crc=false

Which is what I would use for the opamp?

Joe

 

[AnalogPackrat]

Get the TO-92 package (thru hole style) in the "c" grade (suffix)--BC5x0CTA. The devices are binned into three Hfe ranges with "a" being the lowest and "c" the highest. Get the ones on cut tape from Mouser and they're cheap. Buy 100 or more. You'll use them eventually and matching will be easier. Do you know how to match Vbe?

A P

 

[JRE Productions]

Nope, don't even know what that means! But I am willing to learn. I think one of my DMM has a place to test Transistors.....

Joe

 

[JRE Productions]

Wow only .04 cents each for 100. Will I use these for other projects? I'll buy 100 of each if they will get used.

Joe

 

[AnalogPackrat]

Well, I don't know what other projects you plan to build, but it's always nice to have a stash of decent high Hfe parts around. I bought from Mouser and have been sorting by Vbe for the diff pairs in 1731 and 2520s with good luck--most of mine fall into a 3mV range. I use the outliers for the Q5 and Q6 positions (on the 1731). On a 2520 you can use the unmatched ones for Q5, Q6, and Q9.

There's a couple of simple BJT matching test jig circuits floating around. Here's a nice little RAP write up.

A P

 

[JRE Productions]

For the caps do I want Axial or Radial and what voltage should I look for?

Thanks. Do you have the schematics for the 1731? I have two boards.

Joe

 

[AnalogPackrat]

Axial or radial? Whatever fits! You can mount small axial caps vertically like the resistors and diodes, but the radial ones need really tight lead spacing. Of course you can contort the leads to make them fit, too. 50V is fine. Some could be less, but most caps you'd use here won't come in a lower voltage than that anyway. PM me with an email addy and I'll shoot you what I have for 1731 schemos. Fabio has them on his page, but it's down at the moment.

A P

 

[JRE Productions]

I just started working up the parts order from mouser. THe parts for about 6 opamps will cost around $30. I guess that still cheaper than buying them!

They only have 1/4 and 1/2 watt resistors. Are the 1/8 watt resistors any cheaper? Will I have problems stuffing the 1/4 watt resistors in that small space?

Thanks, and I sent you a PM.

Joe

 

[AnalogPackrat]

I'm using 1/4W and they fit fine. In fact, I got some 1W for the low ohm output stage Rs and they fit, too (but they are much smaller than your usual 1W--got them from Mouser, but don't recall the brand). No matter what you do it's pretty cramped. I first got my transistors matched up and then started stuffing. Start near the center of the board and work your way out. Stuff a few components, solder, snip leads, repeat. Don't forget those jumpers!

A P

 

[JRE Productions]

Thanks for all the help! Sorry, but I did not get a lot of info on this project, so I am trying to piece it all together from different posts.

Jumpers? I did not see anything on the schematic. I did see something somewhere saying a resister was not used. Can you point me to the spot of the jumper?

 

[Guest]

I may be wrong - but I think the jumpers are the pins that connect it to the motherboard

 

[AnalogPackrat]

I was referring to the on-DOA pcb jumpers on Fabio's (and maybe others?) board. I know there's one from a hole beside the V- pin to another hole near the center of the board which is also labelled V-. I believe there's a second one, but I could be wrong. I don't have one to look at right now...

A P