Bias transistor revisited

[Mike Sweeney]

I read with interest this thread - http://audiokarma.org/forums/index....rly-serial-number.770102/page-2#post-10572328

And I liked it well enough to go back to my two boards and redo the two transistors I had just soldered in last night But I made a few changes. Here is the basic transistor with lead extensions and heat shrink in place


Here is the transistor attached to the board. All pretty standard stuff and follows whats been done before.

Now it is interesting. I saw in the thread where the circle in the OEM bracket was cut off. I didn't like that so I kept the circle and I'm using as a support for the leads. I did re-bend the bracket for the diode since I had to allow for the thickness of the transistor mounted to the heatsink. I also have to find some longer bolts ( 10mm should do it) to account for the same thickness. I'm using the original threaded hole

I'm also using 24 AWG wire to keep the leads from being too unwieldy in the tight quarters. I also put new heat shrink over the leg that holds down the diode.

 

[wlhd1610]

Nice work Mike!

Also for others doing this mod:
Don't forget the mica insulator when using MJE243G replacements or something similar.
Pay attention to the EBC layout of the old vs the ECB of the new.

Here's a couple I've done lately.

I snip the existing wires off flush with the old bias transistor soldering them onto the new transistor not disturbing the existing board connections.
They fit nice and tidy back in place like the originals did.

The last pic shows the EBC to ECB leg swap...

YMMV





Bob

 

[Mike Sweeney]

Thats funny Bob, I did almost the same drawing to make i had the legs right GMTA