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Post subject: FM65R volume drop issue
Posted: Tue Jul 16, 2013 4:43 am
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Hello.
I have an 2003 Fender FM65R amp, and it has a major problem. Volume drop. I'm playing it and suddenly the volume drops to almost none, and even when I use 10 gain and 10 volume, it's still low volume.
ometimes I need to stop playing, shutting the amp off, wait and turn it on again (sometimes the volume is low again, sometimes it's ok for few minutes and then again low volume).

Please tell me what is the cause for this, maybe the Resistors as I've read on the internet. I dont know...

The problem is on both channels. Volume drop.

Thanks!


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Post subject: Re: FM65R volume drop issue
Posted: Tue Jul 16, 2013 1:00 pm
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Hi chipikk,

Very likely a solder joint issue, with the input jack(s) being a good place to start looking. Have you tried the other input jack? It is a good idea to check all solder joints while you are in there.

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Post subject: Re: FM65R volume drop issue
Posted: Tue Jul 16, 2013 1:39 pm
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....or guitar cable or guitar output jack .


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Post subject: Re: FM65R volume drop issue
Posted: Tue Jul 16, 2013 2:16 pm
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Both inputs are fine, cables are fine with any other amp and guitars. I'm pretty sure that something is loose somewhere, but I have no idea what and where.


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Post subject: Re: FM65R volume drop issue
Posted: Tue Jul 16, 2013 3:08 pm
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That's what I'm suggesting, something is loose, such as a solder joint. How did you determine that both inputs are "fine", did you check those solder joints already?

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Post subject: Re: FM65R volume drop issue
Posted: Wed Jul 17, 2013 2:19 am
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While the guitar was in each input I was 'screwing' around with the input, you know, moving it, inserting in and pulling out etc... both inputs, nothing suspicious.


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Post subject: Re: FM65R volume drop issue
Posted: Wed Jul 17, 2013 6:50 am
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chipikk wrote:
Please tell me what is the cause for this, maybe the Resistors as I've read on the internet. I dont know...


This statement leads me to beleive that you really have no idea how to test or repair an amp even if we are able to suggest something that might be wrong such as shimmilou did. Is that a true statement? If so, I suggest you take the amp to a tech for evaluation and possible repair.

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Post subject: Re: FM65R volume drop issue
Posted: Wed Jul 17, 2013 7:32 am
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bluesky636 wrote:
chipikk wrote:
Please tell me what is the cause for this, maybe the Resistors as I've read on the internet. I dont know...


This statement leads me to beleive that you really have no idea how to test or repair an amp even if we are able to suggest something that might be wrong such as shimmilou did. Is that a true statement? If so, I suggest you take the amp to a tech for evaluation and possible repair.


I have a basic idea of how amp works, my dad knows the electronics etc... . I will check the inputs again but im 99.9% sure their aren't the problem.
Any other suggestions ?


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Post subject: Re: FM65R volume drop issue
Posted: Wed Jul 17, 2013 7:57 am
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chipikk wrote:
bluesky636 wrote:
chipikk wrote:
Please tell me what is the cause for this, maybe the Resistors as I've read on the internet. I dont know...


This statement leads me to beleive that you really have no idea how to test or repair an amp even if we are able to suggest something that might be wrong such as shimmilou did. Is that a true statement? If so, I suggest you take the amp to a tech for evaluation and possible repair.


I have a basic idea of how amp works, my dad knows the electronics etc... . I will check the inputs again but im 99.9% sure their aren't the problem.
Any other suggestions ?


The chassis needs to be removed and look for anything that could be loose. Check all the connectors, solder joints on the jacks, ribbon and spade connectors etc. It could even be a bad volume pot. If you haven't a clue as to what you're looking at, I'd take it to a tech. You can potentially do more damage messing with stuff you know nothing about. :wink:

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Post subject: Re: FM65R volume drop issue
Posted: Wed Jul 17, 2013 10:19 am
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[/quote]The chassis needs to be removed and look for anything that could be loose. Check all the connectors, solder joints on the jacks, ribbon and spade connectors etc. It could even be a bad volume pot. If you haven't a clue as to what you're looking at, I'd take it to a tech. You can potentially do more damage messing with stuff you know nothing about. :wink:[/quote]

I have removed the chassis before and everything seems to be ok, but tomrrow I will take pictures and post them.


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Post subject: Re: FM65R volume drop issue
Posted: Wed Jul 17, 2013 10:25 am
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shimmilou wrote:
That's what I'm suggesting, something is loose, such as a solder joint.


+1

Check solder joint in Power Supply section ; More current = heat = desorldering resistor or printed circuit.


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Post subject: Re: FM65R volume drop issue
Posted: Wed Jul 17, 2013 7:17 pm
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Try the wooden chopstick test. It may help locate the faulty component or solder point. Just be careflu, as you'll be working with a live amp.


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Post subject: Re: FM65R volume drop issue
Posted: Thu Jul 18, 2013 1:27 am
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BMW2002Ti wrote:
Try the wooden chopstick test. It may help locate the faulty component or solder point. Just be careflu, as you'll be working with a live amp.


Excuse me lol but what is Wooden chopstick test ? How does it work ?


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Post subject: Re: FM65R volume drop issue
Posted: Thu Jul 18, 2013 1:41 am
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Get one All-WOODEN cheapo chopstick (such as given in a Chinese takeout). Amp on stand with guts facing you. Speakers connected, no inputs, little-to-moderate volume.

WITH ONE HAND ON the chopstick, (keep the free hand far from amp) probe the solder points, caps, resistors, input jacks, tube socket (if this amp has any), wiring lugs, etc. You are listening for "pops" and "scratchy" noises indicative of a bad component or cold solder point.

Ground points are notorious for being cold---especially star ground points soldered directly onto the chassis. Go from the front-end input to the output section tapping each component and solder point.

Good hunting.


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Post subject: Re: FM65R volume drop issue
Posted: Thu Jul 18, 2013 2:25 am
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BMW2002Ti wrote:
Get one All-WOODEN cheapo chopstick (such as given in a Chinese takeout). Amp on stand with guts facing you. Speakers connected, no inputs, little-to-moderate volume.

WITH ONE HAND ON the chopstick, (keep the free hand far from amp) probe the solder points, caps, resistors, input jacks, tube socket (if this amp has any), wiring lugs, etc. You are listening for "pops" and "scratchy" noises indicative of a bad component or cold solder point.

Ground points are notorious for being cold---especially star ground points soldered directly onto the chassis. Go from the front-end input to the output section tapping each component and solder point.

Good hunting.


Will do ! Thanks. Results will be posted soon.


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