Can a CA3140E replace a failed CA1458? - UK Vintage Radio Repair and Restoration Discussion Forum

'LIVEWIRE?' · 15th Sep 2016, 8:39 am

Having traced a fault in my TES(Italian) AM/FM Signal Generator to a duff CA1458 8pin DIL dual Opamp. I rummaged around in my spares boxes and found a brand new CA3140E, which is also an 8pin DIL dual Opamp, and wondered if this could be substituted, hence my question. I gather that the 3140 is a MOS device, whereas the 1458(and equivalents such as the 4558) are bipolar, but would any circuit changes be required. Not having a scanner which will work with W10 I cannot post diagrams, but the circuit around the 1458 is conventional.

Restoration73 · 15th Sep 2016, 8:45 am

741, 3130, 3140, TL071 etc are all single op amps. Another dual op amp is LM358, TL082.

Radio Wrangler · 15th Sep 2016, 8:50 am

Opamps are used in feedback circuits and those feedback loops have to be designed carefully to be stable. Without seeing the circuit and doing a few simple calculations I can't be sure substituting one dual opamp for another would work. The 1458 (originally Motorola MC1458) is a bread-and-butter dual bipolar. Nothing very special about it, while the CA3140 is a much more unusual part and a bit faster, though the 3140 was touted as capable of replacing 741s in almost all applications.

If the pinouts match, give it a go.

David

mhennessy · 15th Sep 2016, 8:53 am

No.

The 1458 is dual; the 3140 is single.

And the front end of the 3140 is rather fragile - I'd never fit a 3140 as a substitute - only when the original design calls for something particular about it.

The 1458 is a dual 741 - about as "jellybean" as it gets. There are many dual 741-equivalents about.

I use the 1458 in a simple project at work, but the National Semiconductor version. No particular reason - they're all the same - but I mention it because including LM1458 in your searching will bring more results. They're 63 pence plus the VAT from Farnell, for example:

http://uk.farnell.com/texas-instrume...rfnonsku=false

'LIVEWIRE?' · 15th Sep 2016, 9:08 am

David and Mark. Thanks for your replies. I should have checked before posting, as, since typing my query I've discovered that the 3140 is a single opamp. I've also checked CPC's website and have ordered 10 1458s for a few pence over £2.00 inc. Vat. from them
Incidentally the fault in my Sig gen. was that, when switched to Stereo mode, the meter needle would swing fully to the right against the stop, with about 200mV being present at the meter's +ve terminal. By swapping 1458s (easy in this instrument as they are all inserted in sockets) a zero reading was obtained on the meter. The other functions (AM mod %, FM Deviation, RF o/p level) all function as designed, as this IC is only in use in the Stereo FM mode. Incidentally, in that mode the meter goes to FSD even with the internal modulation switched off!

15th Sep 2016, 8:39 am	#1
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Can a CA3140E replace a failed CA1458? Having traced a fault in my TES(Italian) AM/FM Signal Generator to a duff CA1458 8pin DIL dual Opamp. I rummaged around in my spares boxes and found a brand new CA3140E, which is also an 8pin DIL dual Opamp, and wondered if this could be substituted, hence my question. I gather that the 3140 is a MOS device, whereas the 1458(and equivalents such as the 4558) are bipolar, but would any circuit changes be required. Not having a scanner which will work with W10 I cannot post diagrams, but the circuit around the 1458 is conventional.

15th Sep 2016, 8:45 am	#2
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Can a CA3140E replace a failed CA1458? 741, 3130, 3140, TL071 etc are all single op amps. Another dual op amp is LM358, TL082. Last edited by Restoration73; 15th Sep 2016 at 8:48 am. Reason: Omission

15th Sep 2016, 8:50 am	#3
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,876	Re: Can a CA3140E replace a failed CA1458? Opamps are used in feedback circuits and those feedback loops have to be designed carefully to be stable. Without seeing the circuit and doing a few simple calculations I can't be sure substituting one dual opamp for another would work. The 1458 (originally Motorola MC1458) is a bread-and-butter dual bipolar. Nothing very special about it, while the CA3140 is a much more unusual part and a bit faster, though the 3140 was touted as capable of replacing 741s in almost all applications. If the pinouts match, give it a go. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

15th Sep 2016, 8:53 am	#4
mhennessy Dekatron Join Date: Jul 2007 Location: Evesham, Worcestershire, UK. Posts: 4,244	Re: Can a CA3140E replace a failed CA1458? No. The 1458 is dual; the 3140 is single. And the front end of the 3140 is rather fragile - I'd never fit a 3140 as a substitute - only when the original design calls for something particular about it. The 1458 is a dual 741 - about as "jellybean" as it gets. There are many dual 741-equivalents about. I use the 1458 in a simple project at work, but the National Semiconductor version. No particular reason - they're all the same - but I mention it because including LM1458 in your searching will bring more results. They're 63 pence plus the VAT from Farnell, for example: http://uk.farnell.com/texas-instrume...rfnonsku=false

15th Sep 2016, 9:08 am	#5
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Can a CA3140E replace a failed CA1458? David and Mark. Thanks for your replies. I should have checked before posting, as, since typing my query I've discovered that the 3140 is a single opamp. I've also checked CPC's website and have ordered 10 1458s for a few pence over £2.00 inc. Vat. from them Incidentally the fault in my Sig gen. was that, when switched to Stereo mode, the meter needle would swing fully to the right against the stop, with about 200mV being present at the meter's +ve terminal. By swapping 1458s (easy in this instrument as they are all inserted in sockets) a zero reading was obtained on the meter. The other functions (AM mod %, FM Deviation, RF o/p level) all function as designed, as this IC is only in use in the Stereo FM mode. Incidentally, in that mode the meter goes to FSD even with the internal modulation switched off!