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Post subject: Hum after replaces Master Volume Potentiometer
Posted: Sat Mar 03, 2012 10:19 am
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I didnt like the twitchy MV on my Hot Rod Deville 410 so I got a tapered potentiometer and replaced it. Well, I guess I didnt do such a great job as now I have a hum (no guitar plugged in). The hum increases the most with the reverb pot. Since I didnt care too much for the new volume pot, I pulled it apart again and put the old potentiometer back in. It still has the same hum, not super loud so I can play it fine. However, I figure it shouldnt have much hum at all with nothing plugged in. The pots that affect the hum the most are treble and reverb. I double checked my solder work, it was ugly but Im not seeing any crossed wires and the continuity checks out on each post of the MV potentiometer. Im guessing that I have a bad ground or corrupted circuit but I dont know what to check. The hum is on the clean channel too, I have the master volume and drive turned off.

It was stupid of me to do this since I really liked the clean channel and used my full-drive overdrive pedal for distortion. I really didnt need to mess with the drive channel, but so many raved about this "simple" repair. Im sure I must have done something bad, just not sure where to look.

Anyway, if someone has some tips for how to locate which circuit I screwed up when I did this solder work, that would be great. I only messed with the Master Volume pot.


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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sat Mar 03, 2012 11:05 am
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"Ugly" solder work, i.e., cold solder joints will cause noise and hum. Reflow all the joints you made so they are nice and shiny and I bet the hum will go away.

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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sat Mar 03, 2012 12:55 pm
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Thanks for the suggestion, I bet you are right. One or two of the traces got slightly torn and lifted off the board, but seem to solder back up and checked out with a multimeter continuity check. Part of the problem is I am using a pistol type gun with a "bulky" tip. Is there a special solder gun or tip that I can get for my gun that would work well here? Maybe I just need a smaller tool with pointed tip.


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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sat Mar 03, 2012 2:02 pm
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I use this for guitars and amps:

http://www.acehardware.com/product/inde ... 4975445704

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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sat Mar 03, 2012 8:04 pm
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Also use a high quality solder - if your going to go for broke and use a Silver based solder you will need a fairly high watt soldering gun..


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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sat Mar 03, 2012 8:23 pm
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stanglx wrote:
Also use a high quality solder - if your going to go for broke and use a Silver based solder you will need a fairly high watt soldering gun..


Silver solder serves no useful purpose. 60/40 tin/lead rosin core solder is all you need. Stay away from lead free solder at all costs.

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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sun Mar 04, 2012 7:49 am
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If after re-soldering the hum is still there, consider using wire from point-to-point. Look for any cracks in adjacent solder runs and/or cracks anywhere on the board.

Definitely get a soldering iron...40W at most.

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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sun Mar 04, 2012 9:56 am
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Im going to get some small wire and do just that if one looks suspicious. I ordered a 30w pencil type iron with pointed tip and got some 60/40 thin solder. I will check the schematic to see which one's are ground and since reverb is affected, and its the pot right next door, it must be that connection. Yes, I should put a wire between the two since I know that pcb trace got corrupted. Any idea on what gauge? I'm thinking 20ga or smaller.


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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sun Mar 04, 2012 11:25 am
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Tuco314 wrote:
Im going to get some small wire and do just that if one looks suspicious. I ordered a 30w pencil type iron with pointed tip and got some 60/40 thin solder. I will check the schematic to see which one's are ground and since reverb is affected, and its the pot right next door, it must be that connection. Yes, I should put a wire between the two since I know that pcb trace got corrupted. Any idea on what gauge? I'm thinking 20ga or smaller.


22 gauge is used to wire up my Weber 5F6A Bassman clone that I built.

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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sun Mar 04, 2012 2:31 pm
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Thanks for tips everyone. It looks like from the schematic that all pots are grounded thru the pot brackets and this board is then grounded to the chasis. Im guessing that the ground connection from the Master to the reverb and or the ground from master to the middle pot got corrupted and causing the hum. In a few days I will have the tools and time to do a more careful job. I will post back with the results...fingers crossed!


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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Sun Mar 04, 2012 2:41 pm
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Just a thought, but did you remember to reconnect the green ground wire from the pc board to chassis?

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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Wed Mar 14, 2012 8:48 am
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I cleaned up all the connections, but there is still a hum when using too much reverb. If a keep the reverb down to about 3 or less, the amp sounds good. I dont think the problem is a ground issue, i think I might have damaged a part when I messed with the amp. Well, I wont be doing that again!

Does anyone know if replacing the entire circuit board is expensive? Are these parts available?


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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Wed Mar 14, 2012 12:00 pm
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have you tried disconnecting the reverb?

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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Wed Mar 14, 2012 3:38 pm
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Tuco314 wrote:
Does anyone know if replacing the entire circuit board is expensive? Are these parts available?


Circuit board plus all the parts? Do you even have to ask? :lol:

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Post subject: Re: Hum after replaces Master Volume Potentiometer
Posted: Tue Mar 20, 2012 5:23 pm
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okay, I wouldnt bother replacing the board. It really sounds great, the buzz is not as loud as Im probably making it out to be.

have you tried disconnecting the reverb? Im not sure how to do this


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