2600 repair suggestions needed

Joachim Verghese jocke at netcontrol.fi
Thu Jan 16 12:55:28 CET 1997

>Mouser has instrument grade OP-O7s for US$0.96 (I think) - I'd go for those,
>they've got better noise specs (I've got this thing about paying more than
>$1 for an opamp).

The OP-07 is very good in most respects, but its slew rate isn't any
better than that of the 741.

Also, in the case of Robot's broken S&H module, it would be preferrable
to use a JFET-input op-amp for the S&H's output stage, since the original
circuit uses a dual FET + LM301 combination. If and when the dual FET
(2N3958) breaks, you can just bypass it by shorting the G and S terminals,
provided that the LM301 has been replaced with a JFET op-amp such as the 
LF411. In addition, the LF411 has low offset and high slew rate.

> I wonder why the cost of 411/412's went up so much????

Can't think of any viable explanation - European distrubutors still
sell it for around $1.50, small quantity. The LF411A, on the other hand, 
which has even tighter offset specs, is priced at around $10.


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