First real soldering attempt - SUCCESS

bbill335

First of all, I would like to thank everyone who helped me pick out an Antex soldering iron. The one recommended by @Gagaryn is so much better than the Aldi middle aisle special iron I've used in the past, plus he sought out a site that what selling them really cheap. The only way he could have been more help would be to personally put it in my hand.

For my first project, I thought I would pull out the guts of a cheap guitar and replace them with full sized pots and, if it went back together and worked, I'd invest in some good pickups and install them myself. It is back together, it works, but going from 10-9 on the volume pot is a very big change. This might be to do with the pot I chose, but I fucked up the wiring a couple of times and had to move wires round a fair bit, including soldering/desoldering to the back of the volume pot.

It's a CTS "modern audio" taper. Have I borked it?

Funkfingers

Not sure exactly what "modern audio" taper is. Logarithmic, extremely logarithmic, whatever?

If almost all of the volume change happens in the very last fraction of pot rotation, either you have chosen an unsuitable resistance value or you have connected something wrongly.

Further remote diagnosis will require photographs of your actual wiring and a link to the schematic diagram that you were following.


EDIT: One other consideration. Are either you or the modified guitar left-handed?

bbill335

Funkfingers said:

Not sure exactly what "modern audio" taper is. Logarithmic, extremely logarithmic, whatever?

If almost all of the volume change happens in the very last fraction of pot rotation, either you have chosen an unsuitable resistance value or you have connected something wrongly.

Further remote diagnosis will require photographs of your actual wiring and a link to the schematic diagram that you were following.


EDIT: One other consideration. Are either you or the modified guitar left-handed?

Nope, righty. This was the diagram I followed 
But just for one pickup, it's an SG and I just junior'd it for now. 

impmann

Whats the value of the pot?

bbill335

500k

Veganic

Sounds like you have the pot wired back to front.

(But then it should work back to front...hmmmm)

Funkfingers

In these schematic diagrams, the convention is that the pots are illustrated as viewed from below. i.e. The orientation in which you would see them in situ in a Gibson/Epiphone control cavity.

Have you performed any soldering on the output jack socket? 

Going to need photographs.

ICBM

What taper was the old volume pot? If it was Linear (B taper) - many far-east guitars use them - then a Log pot will have an unexpectedly large drop-off from 10 down to 9.

If the new pot works smoothly throughout its range from full down to zero, and it sounds 'normal' when it's up full, it's unlikely it's damaged.

Another possibility is a partly shorted tone cap - with the 50s wiring, that produces a much steeper volume cut as you roll down, because the tone control is connected to the output not the input. Does turning the tone control all the way off sound normal (ie same volume, but dull), or unusually/extremely muffled or quiet?

JoeHenry

This circuit diagram is perhaps confusing you Bill as it looks as though all three pins of the pots are shorted together. So you might have a mistake in your wiring as the diagram isn't very clear. The usual suspect for unusual effects is a bad ground connection. If you're new to soldering - the back of the pot sinks a lot of heat and it might be that you have a dry joint on the body of the pot. A bad (partially shorting) capacitor is a bit of a strange idea - but this should only have an audible effect on high frequency roll off - not the output volume (to any great extent).

I'd wager that you've got one of the following  issues.

1. A bad ground (solder joint) on the back of one of the pots
2.  You've connected all three pins of the tone pot together (as the diagram is confusing) 
3. You've connected the wrong side of the capacitor to the output jack (i.e. gone from the tone pot rather than the volume)
4. You've got an earth connection going to the wrong place

These components are pretty difficult to destroy or fry - you don't have anything like enough voltage in a passive guitar circuit  to fry a volume pot. Good luck.

JoeHenry

One other thing to try - try unsoldering the tone cap at one side and see if you still get the same effect.  Cheers Joe

bbill335

I'm thinking it's just the taper of the pot, the wilkinson p90 actually sounds fuller and clearer with the improved pots (I kept the original output socket). Plan is to ditch the p90 for a firebird pickup when funds allow.

ICBM

JoeHenry said:

A bad (partially shorting) capacitor is a bit of a strange idea - but this should only have an audible effect on high frequency roll off - not the output volume (to any great extent).

No, a partially shorted tone cap will roll off volume as well - because it's no longer a block to low frequencies, ie it has developed a resistance (fairly low) in parallel with its capacitance. It's rare, but I've come across it a few times, usually when the cap has been overheated. It can also be completely shorted, and then turning the tone control right down will mute the output.

Also check nothing is touching the shielding paint - again this tends to cause a partial short and heavy tone suck/volume loss rather than a dead short. I can't see anything obvious, but check the leg of the cap that goes to the volume pot is not touching where it's bent down.

Another rare but known possibility is a partially shorted jack - this can happen with cheap far-east ones - like that one. Best to replace it with a proper US Switchcraft really.

bbill335

ICBM said:

Another rare but known possibility is a partially shorted jack - this can happen with cheap far-east ones - like that one. Best to replace it with a proper US Switchcraft really.

I'll definitely do this when I get a decent pickup in there.

streethawk

Soldering looks nice and shiny. I usually bend the ground lugs to the back of the pot.
CTS pots are really solid, no way you fried it.

Why are you going off a 2 pickup diagram? (the lugs are all wired together too!?).

How many wires coming of that pickup?

JiJoe

ICBM said:

JoeHenry said:

A bad (partially shorting) capacitor is a bit of a strange idea - but this should only have an audible effect on high frequency roll off - not the output volume (to any great extent).

No, a partially shorted tone cap will roll off volume as well - because it's no longer a block to low frequencies, ie it has developed a resistance (fairly low) in parallel with its capacitance. It's rare, but I've come across it a few times, usually when the cap has been overheated. It can also be completely shorted, and then turning the tone control right down will mute the output.

Also check nothing is touching the shielding paint - again this tends to cause a partial short and heavy tone suck/volume loss rather than a dead short. I can't see anything obvious, but check the leg of the cap that goes to the volume pot is not touching where it's bent down.

Another rare but known possibility is a partially shorted jack - this can happen with cheap far-east ones - like that one. Best to replace it with a proper US Switchcraft really.

I'm an electronics design engineer by trade ICBM - no such thing as a 'partial' short. If you mean that the dialetric has broken down and its now just a low value resistor - fair enough - the circuit is just a voltage split now and both tone and vol pot will adjust volume as you said. No such thing as a partially shorted jack either - but f***k it - on you go. 

Gagaryn

bbill335 said:

First of all, I would like to thank everyone who helped me pick out an Antex soldering iron. The one recommended by @Gagaryn is so much better than the Aldi middle aisle special iron I've used in the past, plus he sought out a site that what selling them really cheap. The only way he could have been more help would be to personally put it in my hand.

Glad it's working out for you. Soldering looks good in those pics. :-)

Funkfingers

The problem is the way that you have made the connections on the tone control pot.

Looking at them top to bottom;
The capacitor connection is correct.
The middle contact is where everything goes wrong.
The lowest contact is correctly unused.

All of the cables currently connected to the central terminal on the tone pot should be relocated to the chassis of the tone pot.

You then need to make a new connection between the central terminal of the tone pot and its own chassis. It maybe advantageous to use insulated cable for this. 

bbill335

Ok, I know it's weird to ground a lug that way but I was hedging my bets because I really suspected to mess it up. I thought it would be easier to fix using bits of wire instead of bent lugs. 

@streethawk that was the first diagram I found that didn't seem to leave out something that I (as a novice) needed to see clearly explained. I think it was easy enough to just ignore half of it? I think it's a 4 wire stacked coil p90 (w9skb) with only two wires actually used from the factory. All I know is I don't like it very much.

@Funkfingers so nothing connected to the mid lug tone, a single wire from the jack sleeve to the back of the vol pot?

streethawk

@bbill335 ;
Gotcha, what's that black wire coming off the centre lug (not the one going to the jack)?

Veganic

Not OP but that looks like the ground from the pickup?
And the blob of solder is bridging to the tone pot body?

Looks like a mystery to me.

Edit: ignore me I can't keep up.

streethawk

Veganic said:

Not OP but that looks like the ground from the pickup?
And the blob of solder is bridging to the tone pot body?

Looks like a mystery to me.

Edit: ignore me I can't keep up.

I can see one little wire popping out of the insulation to the back of the pot and another shiny black thing soldered to the centre lug that looks like it's coming off the pickup too. 

.