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sam9 26th June 2002 07:38 PM

Upgrade/alternative to RC4136 ?
I'm trying to restore to life a 25+ year old piece of analog signal processing gear with the help of the service manual. I have strong reason to suspect that one or more of the op amps, (RC4136 quad opamp 14 pin DIP) needs replacement. The part is readily available and the cost is peanuts, but it occurs to me to ask here if after 25 years there are one or more functionally equivalant but higher performing replacements available. By higher performing, I principly mean noise.
The same unit uses a TIP3055 (that's a 2N3055 in a TO-218) package. This seems ok so far, but as long as I'm attemping surgery I'm open to suggestions about substitutions for this as well.

peranders 26th June 2002 08:50 PM

The 4136 (slightly better than uA741!) was at the time a rather low noise thing BUT the chip hasn't standard pinning!

A TL074 type will probely work but why don't you try a top modern OPA4134. Pay attention to the difference in pinning. Since the chip I suggest is much faster you may be forced to increase decoupling of the supply voltage. 100nF from V+ to GND and V- to GND if the OPAMP is feed with dual voltage, otherwise one capacitor from V+ to V- is enough.

The 3055 can much harder to replace without any knowledge about the circuit.

paulb 27th June 2002 02:19 AM

Here's a guy that wants to sell you an adapter board for the (expletive deleted) RC4136:
Seriously, there is some useful information there.
There may not be any reason to replace the TIP3055, if you have a schematic post it and you'll likely get a mittful of suggestions.

sam9 27th June 2002 03:26 PM

Surf Mount adaptor
I had also been told by some how to use a surface mount adaptor do do the same. Requires soldering skills and a very steady hand! Still I'm going to book mark the link. my vision and hand-eye coordination isn't what it used to be!

As for the 3055, it is used as a series pass transistor to regulate the power supply. Upgradeing it probably wouldn't accomplish anything. For now my task (I do this after work each day so it's a drawn out process!) to eliminate the more mundane problems on the unit. For instance the power switch seems to have poor contacts and is part of an assembly that I doubt is made any more.

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