Op Amps

[gilligan]

I have a vintage ( early 70's ) Ampeg V-6b solid state bass amplifier that has a bad op amp. They are obsolete now, and I can't find them. I would like to upgrade the op amps to a more modern one. I was wondering what are some good choices? These have 14 legs, but they aren't all used. It is a 240 watt rms amp head.
Thanks,
Ron

[Enzo]

It would have been helpful to identify the part.

If it is a dual op amp in a 14 pin DIP, compare its pinout to that of a standard 8 pin op amp. You will find the legs are in the same order, there are just unused pins added in each row. You can insert a modern op amp like the TL072, 4558, etc at one end of the leg pattern with a couple pins bent outwards. then tack small wires from those flying pins down to the old holes. You should be able to do this with just 2 or 3 wires, with most of the pins on the 8-leg going to appropriate holes already.

One old trick is to mount a DIP socket on the board. Now take another DIP socket to mount the new op amp into. Add the flying wires and tack solder them into this socket. Once this second socket has been turned into an op amp converter module we plug this socket into the one mounted on the board. Yes, two sockets stacked. The second socket has been turned into a plug. of course you can always hard wire if you like, but I'd use the sockets.

I don't recall if RG has this trick on his site, but it is the sort of thing he would.

Any modern op amp will work fine - TL072, 458, 4560, 4565, 4580, 5532, 2068, or your other favorites. It is not like there will be a wrong choice. Guitar amp is not a critical application for an op amp, we don't need anything cosmic.

I would replace the one chip, but would not bother with the rest. They are just as likely to last another 30 years.

[gilligan]

Thanks Enzo, I think I can handle that.