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[noynek]

My Park G10R practice amp stopped working. Specifically, the amp turns on, and if I turn up the volume, I can hear a buzz. However, when I plug my guitar into the amp, no sound comes through.

I know almost nothing about amps, but I figure the amp is worth less than the cost of a repair shop looking at it.

Here are shots of the internals. Is there anything you can see that might help me debug?

Thanks.

[J M Fahey]

1) does any of the controls affect buzz?
what happens when y6ou put everything on 10?
And when you lower treble or gain 1 or gain 2 or master or reverb?
do you hearthe spring noise if ypu kick the reverb tank or brush the springs with your fingers? (obviously, with reverb and master on 10).

[noynek]

Thank you, J M Fahey.
I can cause buzz in the following configurations with the volume always at 10:

• turn up Gain 2
• Turn up Reverb

With Gain 2 on, all of the other knobs affect the sound, so it appears they are all working.

I hear the reverb echo when I bump the amp.

Thanks.

[J M Fahey]

Your amp seems to be working, but you probably have problems with the input jack.
It may have its leaf contacts bent/worn/weak/dirty so they don't touch your plug properly or maybe you yanked the cable (it happens all the time) and some solder cracked or a track in the PCB did the same.
With the amp unplugged from the wall (it's not enough to turn it off) pull knobs, then jack and pot nuts and pull the PCB so you can look at the solder side.
Have a close look under good light , retouch suspect solder points adding *a little* solder, don't make a mess out of it; you can buy a new jack and replace it.
If lacking practice, get a friend who has already built something lend you a hand.
The basic idea is that the guitar signal does follow a path along that board; you  must find where it's interrupted.

[noynek]

Thank you, again.

I couldn't find a replacement jack, but luckily the headphone jack is exactly the same. I de-soldered both jacks and switched them. I am able to get some sound through, but it's spotty.

For example, I have to turn the amp up quite a bit to get much sound out of it. Then, I get pops and occasionally full volume will break through, but just for a second.

Possibly related: when I turn the gain knobs, I hear popping as well.

I'm tempted to scrap the amp since it's not worth much, but I'm also enjoying learning. Please let me know if you think it's worth further investigation.

Thanks!

[J M Fahey]

Of course it's worth repairing !!
Specially since the amp *does* work properly, but has some "mechanical" problem (cracked solder pads/tracks, dirty or cracked pots)
Tap it (lightly) in different places (as in everywhere) with a chopstick or plastic pen until you find a point which when pressed or pushed makes the sound come back, check and redo soldering points there.
Consider it homework in "Electronics 101". 

If possible, post a couple pictures both sides of the PCB and a close up of the underside in the input area.

[BigPolishJimmy]

I'm going to add this  "Check and then double-check your cords and your guitar's input jack by playing through another amp".    Yes, I am being captain obvious, but this has happened to me about a year ago.  I thought the problem was the input jack of my amp, then i was sure the problem was a cord.  After I shortened and re-soldered the ends of my cord, and played through another amp, I found that it was the input jack of my guitar.  Later I found that the input jack on the amp really was going bad, but there was a combination of things going bad all at once.

Good luck and let us know how it turns out.

[noynek]

Thanks for the ideas. I'm in the process of tapping the board to see if I can trigger any change. I noticed one interesting thing: when I turn the power off, I get full sound for half a second as it powers down. I'm not quite sure what that means, but I figured it might suggest something pretty obvious to someone more experienced.

[noynek]

Here are photos of the front and back. I tapped all over the place and couldn't cause any change. The only things that seem interesting are:

• If I strum my guitar very loudly, I get a pop from the amp
• As I turn the amp off, it sounds fully loud for a brief moment

I'm also now in a state where I burn through fuses. Every other time I turn the amp on, it blows a fuse. Maybe my fiddling made something loose. I'm also wondering if the wrong fuses could be the problem. I picked up some 250v .315 Fast Acting fuses, but I'm wondering if they shouldn't be fast acting.

[joecool85]

Build yourself a Light Bulb Limiter so you stop blowing fuses, then track down the problem.