Page 1 of 1
Calling All Amp Techs
Posted: Wed Dec 09, 2009 4:26 am
by LJay942
As per my thread yesterday:
http://forum.metroamp.com/viewtopic.php?f=15&t=29128" onclick="window.open(this.href);return false;
I have come to my wits end with this amp. I am now interested in sending it to someone to diagnose and fix. I simply do not have the time or patience to continue trying to fix it. I will cover all shipping expenses, parts and labor. If you are interested in this please contact me via PM or e-mail LJay942 at gmail.com (replace at with @).
Thanks again,
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 9:04 am
by jcmjmp
You're asking a lot here. I wouldn't expect this to work out for you by New Year's Eve, especially with the shipping delays.
Static can be a real b*tch to get rid of. I assume that you tried different tubes?
One thing I do to isolate the problem is remove one 12AX7 tube at a time, starting at V1. When the problem dissapears, you've isolated to the problem somewhat. If that doesn't work, or in conjunction with this method, try grounding the signal path at incremental spots starting at the input jack. If nothing gets rid of the noise, you can move on to the power supply.
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 12:18 pm
by LJay942
jcmjmp wrote:You're asking a lot here. I wouldn't expect this to work out for you by New Year's Eve, especially with the shipping delays.
Static can be a real b*tch to get rid of. I assume that you tried different tubes?
One thing I do to isolate the problem is remove one 12AX7 tube at a time, starting at V1. When the problem dissapears, you've isolated to the problem somewhat. If that doesn't work, or in conjunction with this method, try grounding the signal path at incremental spots starting at the input jack. If nothing gets rid of the noise, you can move on to the power supply.
I think your right about the New Years Eve. I have removed that portion.
Can you explain this grounding the signal. I would being grounding the green wires using a pair of jumpers by V1, V2, and V3 correct? I'm still learning.
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 12:50 pm
by jcmjmp
LJay942 wrote:
Can you explain this grounding the signal. I would being grounding the green wires using a pair of jumpers by V1, V2, and V3 correct? I'm still learning.
I ground the green wire (input grids) on V1 to V3 to see where the problem stops. If its a signal path issue, this should definitely help in narrowing down the problem.
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 2:32 pm
by LJay942
jcmjmp wrote:LJay942 wrote:
Can you explain this grounding the signal. I would being grounding the green wires using a pair of jumpers by V1, V2, and V3 correct? I'm still learning.
I ground the green wire (input grids) on V1 to V3 to see where the problem stops. If its a signal path issue, this should definitely help in narrowing down the problem.
Went through and did what you mentioned.
No effect on static
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 4:13 pm
by jcmjmp
<edit> Removed bad advice... <edit>
my guess is a power supply problem. If you have a scope, you could check what it looks like.
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 5:01 pm
by paulster
Don't try grounding the grids on the power tubes, as that'll leave them with no negative bias voltage which is a very easy way of killing the tubes.
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 5:31 pm
by LJay942
paulster wrote:Don't try grounding the grids on the power tubes, as that'll leave them with no negative bias voltage which is a very easy way of killing the tubes.
I only did the pre-amp section I left power amp un-touched.
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 6:47 pm
by Mars Hall
PM sent.
Re: Calling All Amp Techs
Posted: Wed Dec 09, 2009 8:03 pm
by LJay942
Mars Hall wrote:PM sent.
PM replied to
I think that would be the way to go, as I'm not too far from Hinsdale.
Re: Calling All Amp Techs
Posted: Fri Dec 11, 2009 1:29 am
by Drifting
I'd try it with a different guitar, and at another location too, to make sure your house isn't part of the equation. Maybe what I've said isn't the cause, but it is simple and easy to rule out, before you want to pay someone to check it out for you.
At my local music store for example, one of the neighboring shops around it has some generator or appliance that affects certain amps very negatively, regarding noise floor. It only goes on after 5 or so, and is incredibly noticeable. It is important to not forget outside factors, since your guitar and amp are grounded correctly.
Re: Calling All Amp Techs
Posted: Fri Dec 11, 2009 4:06 am
by LJay942
Thanks for all the replies!
Mars Hall recommended a local tech so I went ahead and dropped it off at his shop. We tested multiple guitars there is something going on. He said he should have it taken care of by Tuesday.
I'll let you guys know what he says.
Thanks again,
Re: Calling All Amp Techs
Posted: Wed Jul 06, 2022 7:26 pm
by uiovbged332