CA3240, CA3140 Question

[Harry Dalek]

I was wondering about club circuit using this ic ,is there a replacement op amp comparator that would work apart from changing pin connections ?

I would be interested if any one thinks so .

[gary]

Harry, the CA3140,CA3240 are NOT comparators they are general purpose op amps and can be replaced with just about any other GP op amp including 741s. Another more modern op amp is the lm1458.

[Harry Dalek]

Harry, the CA3140,CA3240 are NOT comparators they are general purpose op amps and can be replaced with just about any other GP op amp including 741s. Another more modern op amp is the lm1458.

Thanks Gary !
i was wondering about these things could be replaced as i woudn't mind giving that a go.

[M3DVQ]

The benefit of the CA3140 over more abundant devices like the LM741 is that it can run off a single rail supply. Obviously if you have a split supply in your circuit anyway this isn't an issue!

[gary]

The benefit of the CA3140 over more abundant devices like the LM741 is that it can run off a single rail supply. Obviously if you have a split supply in your circuit anyway this isn't an issue!

A very good point, I overlooked that. If using a PC power supply that is not a problem but if you have built your own single ended supply then that is probably an issue.

But Harry, in any case why are you looking for a replacement? These are readily available from places like Jaycar, Futurlec, etc.

[Harry Dalek]

The benefit of the CA3140 over more abundant devices like the LM741 is that it can run off a single rail supply. Obviously if you have a split supply in your circuit anyway this isn't an issue!

A very good point, I overlooked that. If using a PC power supply that is not a problem but if you have built your own single ended supply then that is probably an issue.

But Harry, in any case why are you looking for a replacement? These are readily available from places like Jaycar, Futurlec, etc.

I was just wondering if it matters as the symbol of an opamp they are all the same gos in comes out the pointy end

I know the circuit would be different in all of the them but it would be nice to be more felxable with the club circuit knowing you can substitute with what you have handy.

I sort of did this in away useing the 8 pin version for all 3 ic's in the video driver circuit.

I didn't know BTW you could get these ic's at jaycar...that is handy to know /

[gary]

Well the short answer is yes any general purpose op-amp should do a reasonable job, with the caveat regarding the possible need for a split supply as well noted by M3DVQ.

BTW if you are prepared to wait Futurlec are a third of the price of Jaycar...

[Viewmaster]

I believe that a 741 is now available which will run off a single rail.

[Harry Dalek]

I believe that a 741 is now available which will run off a single rail.

That ic is an old friend its good they have improved it Albert .
I was looking in my ic spares i have a few MC1458p op amps...only need 2 of those theres 2 per 8 pin package.

Where by the way is the transistor addition to the club video circuit from i have not seen that circuit ad on before .

I have a Question about the circuit if you didn't want the sync detector part the first 2 opamps needed at all the input is the same.

[gary]

It would be a good idea to keep the dc restoration circuit in (IC1a) so you don't have level problems - although you could replace it with a simpler circuit I suppose.

But if you are going to do that why not use Klaas' one transistor circuit which, if you don't require the sync separator, includes every thing you need?

[Harry Dalek]

It would be a good idea to keep the dc restoration circuit in (IC1a) so you don't have level problems - although you could replace it with a simpler circuit I suppose.

But if you are going to do that why not use Klaas' one transistor circuit which, if you don't require the sync separator, includes every thing you need?

I suppose i have been happy with the club circuit,i have see the one transistor circuit , i tried the one he made before the 3 trany one and it was ok but not the same as the control i had over the video in the 3 ic one ,looks like the one transistor version as all the control .....have you had a go at that one ?

OH yes Gary i missed that in Ic 1 have to be a 2 op amp version then...

I noticed with the original 3 ic one and veiwing different video you really need to adjust the controls or at times you would loose all detail ,just a brightness control is not enough .

[gary]

I suppose i have been happy with the club circuit,

And that's a good enough reason I suppose, but I suppose what I was getting at is if you are going to modify it then you are really just ending up with the same thing...

I must say though I think the term "club circuit" is probably not really correct as I don't think the club "commissioned" a design, the one in the handbook is just an example of something that is known to work well.

looks like the one transistor version as all the control .....have you had a go at that one ?

No I haven't, I tend to design my own circuits, although in this case I admire the "minimalist approach" in it's design so I probably will somewhere down the track. I like Einstein's philosophy (paraphrased as) "things should be as simple as possible - but no simpler"

To be honest, I rarely do use any of the circuits published by the NBTVA, not because they are no good, or because I can do bette, but because it so often turns out that one part or another isn't available here and so on, then you have to start looking for alternatives and by the time you get it going you have redesigned the thing. In practice I use the designs as a "concept" - if it uses a technique I find interesting I will look at how I might implement that strategy with parts that are available to me.

One exception to this is the speed control circuit designed by Stan Kujawinski and Doug Pitt (Newsletter 14 V3) which I particularly like in that it is relatively easy to "tame" due to the fact that you can analyse the whole of the circuit.

OH yes Gary i missed that in Ic 1 have to be a 2 op amp version then...

Well, not necessarily, but that would probably be the easiest approach.

[Harry Dalek]

I suppose i have been happy with the club circuit,

And that's a good enough reason I suppose, but I suppose what I was getting at is if you are going to modify it then you are really just ending up with the same thing...

Hi Gary yes i was happy with that circuit idea ,just its nice to replace parts with what you have which is a good idea if you have the parts .
I have infact done this yesterday with your idea to replace that ic with the 1458 opamp...had a few of these so gave it a go and it works .
I used half the new circuit idea and half an older design i got from Albert + a little transistor BC548 i replaced the mosfet for now as i found this always works till i get a better replacement .

I must say though I think the term "club circuit" is probably not really correct as I don't think the club "commissioned" a design, the one in the handbook is just an example of something that is known to work well.
[/quote]


OH ok i didn't know that but does work well yes.



No I haven't, I tend to design my own circuits, although in this case I admire the "minimalist approach" in it's design so I probably will somewhere down the track. I like Einstein's philosophy (paraphrased as) "things should be as simple as possible - but no simpler"


[/quote]

Yes i can understand that i wish i was better at it but i gave up electronics for many years and the old saying if you don't use it you loose it happened to me and i found my eye sight was not the same looking at small part numbers ..dam this aging !

To be honest, I rarely do use any of the circuits published by the NBTVA, not because they are no good, or because I can do bette, but because it so often turns out that one part or another isn't available here and so on, then you have to start looking for alternatives and by the time you get it going you have redesigned the thing. In practice I use the designs as a "concept" - if it uses a technique I find interesting I will look at how I might implement that strategy with parts that are available to me.
[/quote]

I suppose i do that to a little depends how much i want to make something ,i do rather do it with knowing copying a circuit it should work and if i take the time it should work for me too..
I did what you are saying many years ago and i still have it noaa weather satellite detector that would switch on a relay that would turn on a cassette recorder and record each pass of the satellites all day night...and i have forgotten how i did it but you could feed the cassette taped weather satellite recording to the pc and it would be synced normally it was not possible to this just from a cassette tape due to the tape speed changing a bit on play back ...I should have a look and draw up a circuit copy .. i think the analog satellite will soon be gone mores the pity.



One exception to this is the speed control circuit designed by Stan Kujawinski and Doug Pitt (Newsletter 14 V3) which I particularly like in that it is relatively easy to "tame" due to the fact that you can analyse the whole of the circuit.
[/quote]

I will have a look at that you have a good memory for this stuff Gary !


Well, not necessarily, but that would probably be the easiest approach.[/quote]

Well as i said the 2 ic convert worked hes the circuit ...i think i will et more light from the luxeon if i by pass the 33k after the opamp to the trany as this has worked with all the other versions...the gray scale and adjustments all work fine ...light level is ok but could be brighter i will try the above ...also i found the 1meg on the top ic is a bit off for the sync so that should be replace with a pot .



Oh sorry again for a crappy screen shot once i get my camera settings right again which i couldn't do late last night doing a quick test..

The images were pretty good Gary just hard to do a photo when i inverted them and now i have control of the video settings again ....i will get to camera part again soon just got as you know side tracked on this side of it .

[gary]

Looking good Harry, and heh! no waviness