[sdiy] BA718 and other obsolete parts..

[Seb Francis]

Hi Scott,

Scott Stites wrote:

>Hi Seb,
>
>I used MN5218's, but I can't recall the source for them offhand, and I've
>gotta leave here on a biz trip in a bit.
>
>  
>
I did find a source for the M5218L, but they're a bit pricey so I was 
going to try and get away with TL072s (having read here: 
http://home1.gte.net/res0658s/electronics/parts_subs.html that they are 
very similar).

>But, a dig through my notes brought up these past SDIY list posts from Mike
>Irwin:
>
>===
>"Regarding substitutions, most of the original Japanese parts are still
>available, including the different transistors, the MN3207 (and the
>companion MN3102 driver) are about as mainstream as it gets with BBD's,
>relatively easy to find compared with ther BBDs, the NE570/571 compander
>is also a mainstream part. Parts warehouses that cater to the consumer
>electronics repair industry usually have these (check Main Electronic
>Supply in  Vancouver or www.bdent.com). The single supply op amp used in
>the clock circuit (IIRC a BA718) may be hard to find, I tried several
>single-supply op amps with better specs (including TLC272) but achieved
>the best results with a lowly LM358."
>  
>
That's good to know .. I have a load of LM358s kicking around!

>And..
>
>"Not much difference at all between 570/571, NE/SE/SA for normal
>applications. The 571 is the economy version with less tight specs than
>the 570 (also has a lower max supply rating than the 570 so be careful)."
>===
>  
>
I was suprised how difficult it is to get the 570 in UK .. the only 
place I found is charging £10 each!!
I found the 571 for £2.48 .. worth losing a bit of spec for this difference.
I'm waiting until the Small Bear site is up again (after his holiday) to 
see if he has them for cheaper (since I'm also in the market for a 
SAD1024  from there - for my other BBD project ;)

>One final note.  The DC-2 schematic has a mistake that will make the thing
>shriek instead of produce chorus if you follow it:
>
>The unused section of the first NE570 has pins 9, 10 and 11 connected
>together.  Leave pins 10 and 11 connected together, but DO NOT connect pin 9
>to them - leave it unconnected.  This is another thing Mike Irwin figured
>out, too....
>
>Everything else on the schematic worked out fine, though.
>
>  
>
Thank you very much for this info :)  No doubt this error would have 
caused me a big headache!
 From the datasheet (and looking at the other 570) I think there should 
be a 100pF cap from pin 9 to ground.

>Good luck!
>  
>
Thanks :)

Seb