Beginner: OpAmp defective or not correctly wired

[ElectricDruid]

I dont recall having problems with +9v before with my 741 stash.

No, exactly. What _are_ Texas Instruments on about?!?

[Kipper4]

phase 90 uses them.

[thermionix]

phase 90 uses them.

And Dist+, DOD 250, etc.  It'll be fine, the TIs sound great.

[DrT]

I recently replace the U741 in a '79 Distortion+ with a TI, powered with a 9 volt (no DC in these) that has the voltage divider for +4.5v to the chip.  No issues.

[duck_arse]

there is a fuzz circuit about that runs +1V5 and -3V supplies.

[kipper - you need to differentiate your external/battery "+9V" from your post 100R "+9V". there may be a previous statement saying tie all points w/ same name together ....]

[PRR]

> What _are_ Texas Instruments on about?!?

When new, opamps were all +/-15V power.

And TI is a come-lately to the '741 market. (Seems to be Signetics with the ua741.)

The '301/'741 (and kin's) designers were clever enough to use a ~~7V reference {edit: this may be wrong} to set-up internal currents, so supply voltage "did not matter". Anything from 36V to 10V was all groovy.

Nobody has formally re-written the '741 data in decades. There are tons of newer designs aimed at low-voltage... why do you want to use THAT old thing? To repair your 1974 paper-pulper? Well if it worked in 1974 it probably will work with a 2016-batch '741 replacement.

Knowing the internal workings of a '741.... At some point below 10V total supply it starts to turn off. I would predict a semi-linear fall-off of performance from 9V down to 3V before it goes brain-dead. So if you feed 8V and get say 66% of rated slew and input current... do you even care? It is not rated to meet any of its datasheet specs at <10V, but is not likely to go cold-turkey at 9.99V, just work less-well. The whole point of opamp design is that the amp matters little, gain is set by stable passive parts around the opamp. It really can be working far below spec and still pass audio "clean", for many definitions of "clean".

[Rob Strand]

nowing the internal workings of a '741.... At some point below 10V total supply it starts to turn off. I would predict a semi-linear fall-off of performance from 9V down to 3V before it goes brain-dead.

I've got a Fairchild Rev5.0 2000 datasheet which shows variation of parameters with voltage (Figure 9).

The Fairchild datasheet only shows down to +/-5V as well.

I remember the common-mode range is quite limited, maybe 2V off each rail.   That's going constrain what you can do at low supply voltages for sure.

Edit:
http://pdf.datasheetcatalog.com/datasheet/fairchild/LM741.pdf

[ElectricDruid]

When I was a teenager, I remember selecting op-amps from the Maplin catalogue based on the two parameters that were important to me - supply voltage (wanted something that would work down to 6V or so on a dying battery) and low supply current (wanted something that wouldn't make the battery die later the same day). I was building fuzzes and distortions for friends at school. I don't remember it being hard to find things that fit the bill, so at some point, at least Maplin had some data about lower voltage operation of these things.

T.

[Tim Age]

What's the value for C4?

edit ohhhh nvm that's one of mine...

so I now got all the parts except for two caps...

[Kipper4]

Depends what's before it?
Start with 1uf or 100nf and work your way down.
Keep an ear out for the low end then the high end. Tune it to your rig.
Now your modding.

What caps have you spare.
Is it going on the breadboard?

I've got more questions than answers.......

[Tim Age]

Depends what's before it?
Start with 1uf or 100nf and work your way down.
Keep an ear out for the low end then the high end. Tune it to your rig.
Now your modding.

What caps have you spare.
Is it going on the breadboard?

I've got more questions than answers.......

I'm still missing the 47uF and one of the two 100nF caps and I only have one 1nF, 4 3.3nF and 5 47F caps to spare... guess I gotta go to the store tomorrow and get the missing ones.

Yep, I'll assemble it on a breadboard first and only solder it onto the perfboard when I'm sure it works as desired. I also got 072s to see if it made any difference in sound (and in case I accidentally fried the 741s when I wired them the wrong way).

The C4 I was confused about is the one labelled C1 in my schematic, it's the 3.3nF cap for the first filter.