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Author Topic: Park G10 Turns On, but No Sound  (Read 6589 times)

noynek

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Park G10 Turns On, but No Sound
« on: April 14, 2012, 10:53:11 PM »

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.


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J M Fahey

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Re: Park G10 Turns On, but No Sound
« Reply #1 on: April 16, 2012, 12:56:34 AM »

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).
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noynek

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Re: Park G10 Turns On, but No Sound
« Reply #2 on: April 16, 2012, 10:39:03 PM »

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.
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J M Fahey

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Re: Park G10 Turns On, but No Sound
« Reply #3 on: April 17, 2012, 06:08:06 AM »

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.
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noynek

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Re: Park G10 Turns On, but No Sound
« Reply #4 on: April 19, 2012, 01:28:24 AM »

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!
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J M Fahey

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Re: Park G10 Turns On, but No Sound
« Reply #5 on: April 19, 2012, 07:13:44 AM »

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".  :dbtu:

If possible, post a couple pictures both sides of the PCB and a close up of the underside in the input area.
« Last Edit: April 19, 2012, 07:15:01 AM by J M Fahey »
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BigPolishJimmy

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Re: Park G10 Turns On, but No Sound
« Reply #6 on: April 19, 2012, 09:07:57 AM »

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.
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noynek

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Re: Park G10 Turns On, but No Sound
« Reply #7 on: April 19, 2012, 08:58:51 PM »

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.
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noynek

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Re: Park G10 Turns On, but No Sound
« Reply #8 on: April 19, 2012, 11:13:42 PM »

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.
« Last Edit: April 19, 2012, 11:38:34 PM by noynek »
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joecool85

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Re: Park G10 Turns On, but No Sound
« Reply #9 on: April 20, 2012, 01:14:20 PM »

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

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Re: Park G10 Turns On, but No Sound
« Reply #10 on: February 26, 2018, 11:39:24 AM »

l own a park g10r amp i came across in early 1990. most of pots were either frozen or scratchie. sprayed all inside wiper arear and also at the shaft male female seams. still scratchy but got more movement when using wd40 lithium grease spray on shaft seams. still scratchie. will change em all out for same value audio where i can slowly dial in sounds iam looking for.but will continue to upgrade the amp in which i love the clean sound i love. the reverb has been a on and off project over the years swapped out cheap belton reverb tank for a 17 1/2 hammond acoutronics sounded great but too large for cabinet in which i knew but was curious. So i spoke to a engineer @ acoutronics and gave em the belton tank numbers and told em was looking for a better sustain and more larger sound. they sent me a med decay 9 1/4 tank was better but still was set on finding real spashy wet dripping surf reverb. so i went with a modkits with a long decay 8BB3C1B and never looked back. it sounds like a fender princeton or a fender stand alone reverb unit. i know i could have bought another amp bla bla bla. but i love this amp cause of its tone and cause its portable.  now i want some input advise as how to install a effects loop and line output. please help.
what are the best chip mods i can use for the jrc4558dd 8 pin ic i have four of them would  TL02 ic be best for all of the 4558DDs to make it less hiss and quiet and bright. what about the power transistor with the heat sink. please open to suggestions thank you Indian Mike
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phatt

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Re: Park G10 Turns On, but No Sound
« Reply #11 on: February 28, 2018, 07:07:41 AM »

If you want an FX loop just break the circuit before the master volume and wire up 2 sockets in the back panel.

I doubt there would be much benifit from swapping chips.
Any hiss is likely circuit design and little to do with the chips used but try out LM833 if you want but your hiss might get worse.
It's a gamble. xP

If you want more treble then raise the value of the slope resistor in the tone stack. (I can't read the value on the schematic I found)

And/Or lower the value of C25 which is 470pF,, try 150pF ~ 220pF.
Of course more treble will mean MORE hiss.

Power chip ,,, forget that idea.  :loco
If you want more wattage then you need a bigger power transformer.
smarter to buy another amp.
Or slave a larger power amp and speaker from the FX loop which can work as line out.
If you want more detail then track down a clear schematic for folks here to help you. :tu:
Phil.
« Last Edit: February 28, 2018, 07:08:58 AM by phatt »
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indianmike

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Re: Park G10 Turns On, but No Sound
« Reply #12 on: March 01, 2018, 01:03:03 AM »

If you want an FX loop just break the circuit before the master volume and wire up 2 sockets in the back panel.

I doubt there would be much benifit from swapping chips.
Any hiss is likely circuit design and little to do with the chips used but try out LM833 if you want but your hiss might get worse.
It's a gamble. xP

If you want more treble then raise the value of the slope resistor in the tone stack. (I can't read the value on the schematic I found)

And/Or lower the value of C25 which is 470pF,, try 150pF ~ 220pF.
Of course more treble will mean MORE hiss.

Power chip ,,, forget that idea.  :loco
If you want more wattage then you need a bigger power transformer.
smarter to buy another amp.
Or slave a larger power amp and speaker from the FX loop which can work as line out.
If you want more detail then track down a clear schematic for folks here to help you. :tu:
Phil.
thanks and i contacted park and they are looking into getting me the schematics for both park g10 and park g10r. try to up load them to this site for you to view. Hopefully will be able to offer advice based on what values are present. thanks for your help Phatt
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indianmike

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Re: Park G10 Turns On, but No Sound
« Reply #13 on: March 04, 2018, 11:10:15 PM »

If you want an FX loop just break the circuit before the master volume and wire up 2 sockets in the back panel.

I doubt there would be much benifit from swapping chips.
Any hiss is likely circuit design and little to do with the chips used but try out LM833 if you want but your hiss might get worse.
It's a gamble. xP

If you want more treble then raise the value of the slope resistor in the tone stack. (I can't read the value on the schematic I found)

And/Or lower the value of C25 which is 470pF,, try 150pF ~ 220pF.
Of course more treble will mean MORE hiss.

Power chip ,,, forget that idea.  :loco
If you want more wattage then you need a bigger power transformer.
smarter to buy another amp.
Or slave a larger power amp and speaker from the FX loop which can work as line out.
If you want more detail then track down a clear schematic for folks here to help you. :tu:
Phil.
If you want an FX loop just break the circuit before the master volume and wire up 2 sockets in the back panel.

I doubt there would be much benifit from swapping chips.
Any hiss is likely circuit design and little to do with the chips used but try out LM833 if you want but your hiss might get worse.
It's a gamble. xP

If you want more treble then raise the value of the slope resistor in the tone stack. (I can't read the value on the schematic I found)

And/Or lower the value of C25 which is 470pF,, try 150pF ~ 220pF.
Of course more treble will mean MORE hiss.

Power chip ,,, forget that idea.  :loco
If you want more wattage then you need a bigger power transformer.
smarter to buy another amp.
Or slave a larger power amp and speaker from the FX loop which can work as line out.
If you want more detail then track down a clear schematic for folks here to help you. :tu:
Phil.
thanks and i contacted park and they are looking into getting me the schematics for both park g10 and park g10r. try to up load them to this site for you to view. Hopefully will be able to offer advice based on what values are present. thanks for your help Phatt
swapping out all the pots all making scratchie noise. there is one that clearly says 2.2k (2 period 2k )located on mid control. i cant read the schematic is it a misprint value for this is it 22k if not what other value could i use instead.
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indianmike

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Re: Park G10 Turns On, but No Sound
« Reply #14 on: March 21, 2018, 02:29:16 AM »

swapped out the 4558 ics for texas instrument TL072 type very well controled far less hiss iam very please all pots were replaced with audio type just got in a 2.2k audio. I dont know if its the mod tank but reverb seems a little smaller sounding even at full up. the eq seems to be working ok. any change due from swapping from linear to audio on some of the pots. what i mean should some of them be linear than all audio maybe in the eq section. any and all suggestions considered.  On this how can i enhance the tone maybe different caps vintage type if so would bring out more hiss white noise ect. please let me know. thanks mike.
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