It’s Fixed!

Replacing the RC4558 op-amp solved the no signal (at all) problem.

A big, “Thank You!” to, “The EH Man,” (a Big #1 response to you my man!), for helping me troubleshoot, diagnose and remedy the issue with my ’81 era Small Clone!

And to Kartoonhead for “spiritual advice” and the handy audio test tool, I couldn’t have figured it out w/out it, or w/out both your help!

A few notes,…

I managed to source a MC4558CN op-amp from a local sound gear joint after all (OK, I’ll give ’em some props, it was Sound Source in Rochester NY). Their tech said that there would be no noticeable difference between the two op-amps.

The original op-amp part number in my ‘Clone was a RC4558N. From what I was able to research, the RC4558P is the exact same op-amp, but just by a different manufacturer.

I have an RC4558P on order,… just to get closer back to the OE spec components

From what I can tell on the product data sheets, there are a few differences between the op-amps, but not much. The biggest thing that caught my eye was the voltage gain differences with the RC4558P being about 3dB higher than the MC4558CN. Perhaps The EH Man can shed some light on if there is/will be a noticeable difference between to two op-amps for this application?

As I am going to be swapping the MC4558CN op-amp out for the RC4558P, I installed a socket so that I don’t have de-solder/re solder the parts and ravage the board any further (the traces are rather brittle on this old, brown, board,…).

Thanks again!

PLU,

Neil

Thank you Ron!

Shall I:
1.) Post a reply to this thread when I install it and it works/doesn’t work?

2.) Post a new thread giving the results?

3.) Just shut up and play my guitar?

All the best,

Neil

Kartoonhead and Ron,

So, I made the audio tester and started probing around looking for where the signal craps out.

I get signal up to pin 3 (1IN+) of the RC4558N op-amp, but that is as far as it goes (battery installed with switch/LED “on”).

So far, my guess is the RC4558N op-amp is dead.

In my search on this problem so far, I have seen no mention of the RC4558 op-amp going bad. Any advice please?

From scouring the ‘Net for “RC4558N” I think I have found that a suitable replacement is Mouser PN: 595-RC4558P (supposedly the RC4558N made by TI, rather than Raytheon).

I’d love to hear from you before I order/replace this part, as it’s surface mounted, so more difficult to replace than the socketed IC’s/op-amps,…

Thanks much!

Neil

Ron and Kartoonhead,

Thanks for the speedy replies!

Thanks, Kartoonhead, for the easy plan to make a test lead. I’ll have to source the 0.1uF 50V cap and make it.

By the sounds of it, according to Ron, I’ll need to be getting another cap in there anyway. Gotta love one stop shopping,….

Ron, is the cap you are referring to a 10uF 18V (Reeken?) blue, “can,” type? There are three on the board that I can see. They all look good from the outside.

You said when it’s bad you get a weak chorus sound. While I am getting a weak chorus sound, I’m not getting any guitar signal at all, just the weak wobbling sound on whatever is coming through on the ether.

I think I may have just had an, “Ah Ha” moment while I was looking at that cap through a loop ,… :freak: (<- what the cap saw) On the solder side of the board the legs of the cap may be touching the next resistor. The legs stick through the board and appear to be bent over. I’m not sure how that would have happened sitting in a box for years on end. Gremlins? I’ll test this find with my meter. If it’s shorted, I’m going to try lifting/cutting the legs in that area short and see if I get this to work. If that doesn’t do it I’ll build the audio tester and replace that cap (after I hear that I have identified the correct cap, please!). Any other advice gents? Like I said, I’m getting no signal at all,… Best Regards, Neil