Need Help - Issues w. Pot Replacement

[joel_ostrom]

Hey all - so a bit of background for you: I'm refurbishing an old Fender M-80 1X12 amp. The pots were all extremely scratchy and staticky when you'd turn them, sometimes signal would cut out completely so I opted to replace them instead of cleaning them out (tried deoxy cleaner, didn't work).

Right now i'm in the middle of replacing the pots. Now these are the kind of pots that were originally installed[img:514:600]http://www.guitar-parts.com/sites/defau ... /37596.jpg[/img]

but i'm installing standard alpha pots. I understand that because the snap in pots have 4 pins to ground I will have to jumper the ground terminals on the PCB with hookup wire (which I have done, no problem).

My problem comes with the first pot that I installed. It works just fine, no scratchiness or static when turned but - the taper is backwards. When I turn the pot counter-clockwise, the volume goes up. Clockwise, it goes down.

Do I have the wrong pot for this?

I purchased the pots from Small Bear Electronics Online
I acquired the pot specs from the layout and schematic of the amp itself that I got from Fender.

Here's a shot of the work i have so far:
[img:768:1024]http://i277.photobucket.com/albums/kk50 ... G_0167.jpg[/img]You can see how i've soldered all the jumpered ground points to the 1st terminal on the pot and the hot leads to the 2nd and 3rd.

The Volume Pot (Clean Volume) that i'm having the problem with read 30C50K. As I understand it, this means that it is a 'C' type taper. I have read from THIS ARTICLE that 'C' was the old code, and is now referred to as 'A' taper.

Did I wire this up wrong?
Or do I just have the wrong tapered pot?

Any info you guys can give is greatly appreciated.
Thanks,
Joel

Attached is the PDF file for the layout and schematic of the amp, if this helps you with any info needed to answer my question

[Reeltarded]

You have the ground side hot and the hot side as ground. Swap the outsides with each other.

[joel_ostrom]

You have the ground side hot and the hot side as ground. Swap the outsides with each other.

I'll try that for sure. Are you talking about swapping the outsides on the POT or on the circuit board. Not sure if you can tell from the picture, but there's 3 holes on the PCB that were previously soldered to the terminals of the snap in pot. Going left to right, the first on the left I have soldered to the 3rd terminal on the Pot. The 2nd hole in the PCB is wired to the 1st terminal on the Pot (ground). The 3rd hole in the PCB is wired to the 2nd (middle) terminal of the Pot.

Which am I switching? My soldered connections on the Pot or the PCB?

Just wondering, if I had the ground improperly soldered, wouldn't that cause problems when I turned on the amp? Like incredible amounts of noise?

Thanks!

[Reeltarded]

No, not at all. There is a way you could wire it backwards and the signal is grounded that might or would make noise. You just have the wires to the opposite terminals. It's all good! Go fix that and be happy! I swear it.



If the pot ever operates backwards, it's the terminals are swapped.

[joel_ostrom]

No, not at all. There is a way you could wire it backwards and the signal is grounded that might or would make noise. You just have the wires to the opposite terminals. It's all good! Go fix that and be happy! I swear it.



If the pot ever operates backwards, it's the terminals are swapped.

Ah very cool, thanks so much!

Cheers!

[Reeltarded]

You can swap at the board too, but the pot is easier and the board is delicate and not something easy to repair if it gets melty.

[LeftyStrat]

Just wondering, if I had the ground improperly soldered, wouldn't that cause problems when I turned on the amp? Like incredible amounts of noise?

Thanks!

It's properly soldered as far as the pot is concerned. Just backwards for those of us who insist clockwise is more.

[Reeltarded]

Also you can buy pot almost anywhere. No reason to replace it with something else.

That was a deliberate drug reference.

[joel_ostrom]

Just wondering, if I had the ground improperly soldered, wouldn't that cause problems when I turned on the amp? Like incredible amounts of noise?

Thanks!

It's properly soldered as far as the pot is concerned. Just backwards for those of us who insist clockwise is more.

Haha, yes my OCD will not accomodate this...

[joel_ostrom]

Also you can buy pot almost anywhere. No reason to replace it with something else.

That was a deliberate drug reference.

[joel_ostrom]

I have one other question:

For the rest of the pots to be replaced, how can I determine which hole from the PCB is the outgoing signal (to go INTO the pot) and which is the signal that will flow OUT of the pot?

I have the schematic, but i'm not educated enough on reading them to understand which is which.

Thanks again!

[Reeltarded]

If you leave it backwards you can tell people to shut up when they tell you to turn it down.

Turn it down!

I did.

[rp]

If you leave it backwards you can tell people to shut up when they tell you to turn it down. Turn it down! I did.

I'm confused, so instead of 11, it goes to -1?

[Reeltarded]

Possibly. I am a theoretical arithmetician.