Have an old analog synthesizer that doesn't work. Was told to replace the RC4558N and RC4558NB op amps. Tried looking at several online electronics parts places but no luck. Is there somewhere that I can look up a suitable replacement part for these? I assume that these parts are no longer produced.
Was also told to try replacing a couple of 1.8K thermal capacitors that are affixed to the top of some other ICs.
Any suggestions on where to find either of these components?
Thanks in advance.
Those are RCA part numbers, but I think they are replaceable by LM1458 and probably a host of others. The part is essentially a dual 741, without offset adjust. That makes it about the crappiest dual op-amp you can think of... almost anything you replace it with will be an improvement. TL082 or LF353 would be better choices, but if you want the LM1458 it's under a buck at Digi-Key.
I'm guessing by the 1.8K that you are talking about Q81 resistors, which have a special temperature coefficient that compensates for the thermal characteristics of the transistors used in the current source that drives the main VCOs. I can't imagine these things ever going bad, and they are probably expensive and hard to find... at least, they were expensive and hard to find back when the synth was made! I wouldn't worry about them until proven otherwise.
Best regards,
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
You could probably get away with anything pin compatible, but the MC1458 should be a near perfect match. 26 cents each in single quantity right here:
Sorry, I meant to say thermal resistors! It's a 1.8k thermal resistor that is affixed to 2 ICs.
"Bob Masta" snipped-for-privacy@yahoo.com
** The RC4558P ( 8 pin DIL) is currently made by Texas Instruments. ** Nope.RC = a Raytheon design.
** WRONG.The RC4558 is a far superior device to the 741 in terms of slew rate, input noise and bandwidth.
Uses PNP input transistors which reverse the input bias current too.
** WRONG !!** WRONG again !!!
There are upgraded versions, the 4559 and 4560 with more slew rate and even less noise.
** FET input types may not even function in the OP's application.A "analogue synth" uses VCOs and VCFs, likely to be very op-amp critical.
..... Phil
"BobG"
** Full output voltage swing is available to about 22 KHz.Not that hi-fi audio ever needs anything like that.
** So what ?????You must have swallowed all that audiophool crapology re "more is better".
** Only in the minds(?) of ratbag audiophools.** Horse poo.
** TL072s have considerably higher input noise than a RC4558.
Typically 18nV /rt Hz as against 8 nV /rt Hz
Makes the RC4558 * 7 dB * quieter in most circuits.
....... Phil
Yeah, you think you are smart, but you aint fast. I beat you to the keyboard, so all you can do is back me up. Have a nice day Phil.
** What an absolute Hoot !!!
I am ROTFLMFAO !!!!!
Someone with chronic diarrhoea is FASTER to the dunny too !!
Gotta get rid of all that shit ASAP !!
....... Phil
I really appreciate all the input on this subject so far, but I'm still not sure what my best choice is if I can't find the exact op amp (RC4558N) that I'm pulling out of this thing. Will this thing work for me:
Yeah, that'll work but its says its non stocked. You can use what I said... TL072, or use what Phil said, but he'll cuss at you for no reason if you talk to him funny, so I's recommend the TL072. I replaced all the 4558s in my Teac board with em and its still working fine 20 years later. Lets see if we can get Phill to cuss at us some more.
I was so foolish to do the same thing with my mixer, but I started with one channel only and compared it to the others first. Then I soldered the Raytheon chips back. Phil is in this case right on. Maybe you also read what Mr. Fields says about google.groupers.
-- ciao Ban Apricale, Italy
What's Fields problem? He doesn't like my reply? My newsreader has the whole thread in a tree. Its completely obvious what message was being replied to. I'm not going to do any work to fix a problem I don't have.
Well.. my response to that frame of mind is "Go fly a kite!"
-- According to my newsreader, this is the first time I\'ve replied to this thread. If you don\'t have a problem, why are you here?
** Go to Digikey:
Many as you like for $0.46 each.
The RC4558P is simply a RC4558N made by TI instead of Raytheon.
........ Phil
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