Friday, June 28, 2013

How not to troubleshoot an electronics issue with a new guitar

I have a story to tell. It should feel familiar.

So I finished wiring up the prototype Multiscale (RedStar II) and strung it up. I was excited to hear the multiscale pickups for myself. I have built around 10 sets but never been able to use them in a multiscale guitar. (The pickup mule is a 6 string)

Upon plugging up the guitar I get sound and microphonic feedback. And I am thinking great I F'd up the pickups and I am going to have to build a new set... let me check the cable first. Grabbed my 25 year old 23' Pro-Co Excaliber (used to be 25' but had to fix it a time or two over the years). Still making noise... not as bad but still. Maybe it is the wireless headphones and the RP-150 running into the mixing board. Over to the ADA-MP1 and the vintage AKG 240s.

Quieter but still noise...  Cartoon Network Adult Swim NTSF:SD:SUV  comes on in the background. I wished it was Auqua Teen Hunger Force but whatever I have to figure this thing out.

Disconnect the pickups from the switches one wire at a time hoping this thing will all the sudden shut up. I get them all disconnected and it shuts up.

Of course it shut up because no load... I touch the ground on the switch and NOISE. It must be a bad switch. I had grabbed this one from somewhere I don't remember. Prototypes are built from spare parts. I disconnect the switch with a pair of side cutters. I have now successfully ruined a beautiful wiring job.

By now the second episode of NTSF:SD:SUV  is playing on the TV and I still can't watch as I am seriously befuddled by what is the actual problem.

Wondering if the ground that runs to the bridges is bad I cut it loose. Noise continues.

The only thing left hooked up to the input jack is the Bourns push/pull pot. It was brand new. I have never had one of these go bad. I do have a customer who is crazy and says they get scratchy after a while but he is just obsessive about volume swells.
I touch the volume pot on its ground wire and there is NOISE. It must be a bad volume pot. I proceed to remove it from the chain with side cutters and the noise stops.

Now at this point had I any brains I would have checked the input jack. Instead I decided to use alligator clips and run the pickups straight of the tip of the Pro-Co cable. Mainly because I really needed to hear this thing and I wanted to make sure it wasn't the pickups.

Great news it wasn't the pickups. The thing sounds great except the pickups are too low and the prototype HBs have tabs that are too small and screws that are too short. I will fix that later. It isn't the pickups.

Still haven't checked the input jack. Eagle Heart is playing on the TV. What a silly show full of retards.

Since I have the alligator clips out I decide to put the volume pot back in the signal chain. It is easier to use the wires from the input jack than to alligator clip straight to the cable so I twist the volume pot wires to the input jack leads and alligator clip the bridge pickup back in. NOISE!!! Horrible mind numbing microphonic noise...  I tap on the switch and it gets worse, I turn it up and down all effecting the tone of the NOISE but not eliminating it.

Feeling pretty frustrated and not really getting the "Your pretty face is going to hell" show I finally check the input jack. Accidentally.

I hooked the input leads to the pickup without anything else in the chain and the NOISE is horrific. Finger nails on a chalk board. Now I pull the input jack out, hook it to the Pro-Co outside the guitar and alligator clip the leads to the pickup and NOISE.

It was a brand new switchcraft 1/4" input. I am using the Electrosocket jackplate on this one and plain 1/4" input jacks. A $1.25 part was killing me. Never would have suspected the part with the least amount of mechanics in it to cause so much noise.

I didn't even fix it. I just went to bed. 

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