How to Repair a THR10 Guitar Amp Power Plug

I found out the hard way that the Yamaha THR10 guitar amp has a fragile power plug. Mine fell off a table, the cord yanked, and the power plug shattered. My favorite travel amp was dead. Here’s how I fixed it.

Purchase Replacement Plug

The internal power plug is hard-soldered to an internal PCB. It’s not hard to replace, but it was a little tricky to find the right plug. This is a power plug with an internal switch. The act of plugging in the AC cord automatically disconnects the battery compartment. After some online detective work, I found that it’s Yamaha P/N V5095000, which is a relabeled SMK P/N LGP7031-0300.

I bought it from Full Compass, here’s a link to the purchase page I found:

http://www.fullcompass.com/prod/241489-Yamaha-V5095000

Here’s what it looks like:

Repair Process – Step by Step

Click to enlarge photos

Remove the four chrome hex nuts in the front.

Remove the four chrome hex screws

Remove the four black screws from the base.

Remove the USB Screw.

Remove the three black screws connecting the top and bottom of the amp.

Remove the three black screws connecting the top and bottom of the amp.

Unplug the two connecting cables between the top and bottom of the amp.

Unplug the two connecting cables

Remove the nuts and washers from the input jack, power switch, and all the knobs.

Remove the three PCB hold-down screws.

Carefully unplug the connection cables shown here and disassemble the boards to access the old power plug.

The liberated board on the bench.

The liberated board on the bench

Remove the old power plug and prep the holes for the new plug at location JK 501 on the PCB. 

First, I used nippers to carefully break apart the old plug. Then I nibbled away until I could cut the leads close to the PCB.

Location JK501

Next, I used solder braid to wick away the solder and clean the holes. I’m out of practice, there’s a lot of extra flux and it looks a little nasty. It still worked.

JK501

Solder in the new plug.

JK501 installed

While I had the amp apart, I decided to make one additional fix.  While researching this power plug issues, I ran across an article at pickroar.com. They report an interesting bug in the design of the THR10:

The Yamaha THR10, THR10X and THR10C are fantastic little practice amps, but they have a design flaw. When some of the wires inside get too close together, their signals interfere and a nasty high-pitched whining, squealing or ringing sound results.

My amp didn’t have this problem, but I did their simple fix anyway to prevent any future issues. Check out the full instructions at pickroar.com.

Once I had that item fixed as well, I reassembled the amp. Success!