8100A OP AMPS

[menotti1]

looking to update the TL072 op amps in the 8100.Looking at several,any of you 8100 experts care to comment?

The TLO72 is no sloppy performer. It's only shortcoming is that it will slew at different speeds negatively than positively .I feel there are several that will work better.thanks

 

[oldiesstation]

i read some place where you can use the 2134(same as 8400 uses,i believe), TLE2072 and AD712.You;ll have to shore up some mica and electrolytics,Heck send it to Bill Sacks and save that project time for something else IMHO

 

[cgould]

Dusting off the brain cells on this one....

I've used AD712's without issue.

You are kid of limited in the types you can put in as the 8100 doesn't have the bandwidth compensation circuitry to run very high slew rate Op-Amps. Also, the power supply bypassing scheme is "generalized" - i.e. the power supply pins of every op-amp socket do not have HF bypass capacitors. This can also be a problem when using Op-Amps with very high slew rates. If the power supply bypass caps that are in there check out in good shape, you could more than likely get away with running fancier Op-Amps.

I tended to shy away from shot-gunning the Op-Amps in the distortion canceling cards (8/9) as this can introduce some response variations / or phase shift differences that could compromise distortion canceling performance. I felt this way because if I could HEAR a difference from swapping out the '72's for AD712, my logic reasons that the compensation networks int he black boxes would have to be changed as well to make it work right...

YMMV

-Cornelius

 

[NE Miss Radio]

I don't have my books in front of me but Analog Devices (PMI if you're as old as me) has an OP-27, I think it is, that's a lower-power, improved, pin compatible op amp.

 

[rorban]

Cornelius is right about the need to be careful when replacing opamp types. At very least, you need to probe the output of every replaced opamp with a wide bandwidth, low-capacitance scope probe to detect possible RF oscillation. You need to do this with signal applied because some opamps will only add oscillation to certain parts of the waveform.

"Upgrading" opamps is definitely *not* a no-brainer.

Bob Orban

 

[TomT]

Answers a question that came up on a rebuilding project just today. 8100A with XT--"extensively modified!" Owner of the box wants it back to original--found a few modifications on the XT chassis, which I corrected, then I pulled the cards to re-cap the electrolytics.

TL0-72's replaced with the AD712 IC's on card 8. Card 9 missing several IC's entirely. Haven't studied the schematic to see if the card was raided, or these circuits are by-passed when the XT is in place. Looks like I buy a bunch of TLO72's. Diodes in safety clipper circuit lifted on both cards--hope Mouser has these. Fun.

 

[menotti1]

You may want to check the TLE2072.An improved version over the TL072.check the specs.

 

[LA_Guy]

looking to update the TL072 op amps in the 8100.Looking at several,any of you 8100 experts care to comment?

The TLO72 is no sloppy performer. It's only shortcoming is that it will slew at different speeds negatively than positively. I feel there are several that will work better.thanks

The TLO-72 is a VERY sloppy performer! It was fine when it came out in 1975-three years after I graduated high school-but it falls dramatically short sound wise today. Even TI has a replacement part that sounds MUCH better-the TLE-2072/2082.

The AD-712 also is a decent replacement, but it is also old by today's standards, and costs a lot more then the TLE...

I have never had any difficulty dropping TLE's in place of TLOs-even in places where 5532s wouldn't work.

By the way, don't forget to turn off the unused half of IC-310 on cards 3 and 4.