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Post subject: 65 Twin Reverb Reissue Reverb Hum
Posted: Fri Apr 25, 2014 9:21 am
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I've recently had a problem with my reverb humming. If I turn the Reverb all the way down, hum goes down. Reverb up, hum goes up. I believe its either my preamp tubes or the tube socket itself. I took the tube out, cut the amp on and it had no hum. Swapped the tubes around and hum came back. Swapped them around agian and the hum is still there just not as heavy. Could it be I have a few "bad" preamp tubes or could it be the tube socket? Before I had this problem I let my brother borrow the amp for a gig and he said it gave him trouble so he was going to let one of his "technician" friends look at it. His friend fixed whatever problem he had but when he was putting the tubes back in the amp, he put a 12at7 preamp tube where a AX7A was suppossed to be. So after I got my amp back I noticed static noise so I checked the tubes and found he had put one in the wrong spot and I put them back in the correct order. Could that wrong tube being in that socket affect that socket? Like I said before, if I take that tube out and power on the amp, there is zero hum. Thanks for any input.


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Fri Apr 25, 2014 10:38 am
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Any 12XX7 tube in the socket can't damage amp socket or other unless you are very bad lucky and bend tubes 'pin and damage socket connectors. If tube's pin look ok , socket might ok .

Check for the good tube ; V3 = 12AT7 , V4 = 12AX7 .

V6 is a 12AT7 too , you could use for test . All other are 12AX6

Hum ; check wires between reverb tank and amp for damaged. Dirty RCA connectors , bad ground at the wires. You can use any HI-Fi wires with RCA connectors.


If you only have hum with reverb / no hum with reverb channel volume at 0 . It must be one of the thing I write . Or the reverb tank is too close from the speaker !!! It screw on the cab bottom.....
You must know how to check cable and rca connector..

Good luck


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Sun Apr 27, 2014 5:01 am
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I had the same problem with my Twin. Does the hum go away when you switch off the reverb? If so, then I would guess it is the reverb tank that needs to be replaced.
Kenny V


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Sun Apr 27, 2014 5:35 am
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Kenny V wrote:
I had the same problem with my Twin. Does the hum go away when you switch off the reverb? If so, then I would guess it is the reverb tank that needs to be replaced.
Kenny V



It could be many things .

I fix many reverb trouble , I never need to replace the tank . But this may happened , few tests to do before as I write .


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Sun Apr 27, 2014 8:11 am
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Good point stratele52. I am by no means an amp repair guy. I wish I was. Turned out that was what was wrong with mine, of course I am going to have to pay for it. It's is currently being fixed. Glad to see people who have amp knowledge are on this form.
Kenny V


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Sun Apr 27, 2014 10:27 am
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Kenny V wrote:
Good point stratele52. I am by no means an amp repair guy. I wish I was. Turned out that was what was wrong with mine, of course I am going to have to pay for it. It's is currently being fixed. Glad to see people who have amp knowledge are on this form.
Kenny V



We are here to learn , some more than other . :)


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Sun Apr 27, 2014 5:54 pm
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Well I talked to a tech and he recommended cleaning the tubes sockets and RCA cables going to the Reverb box. After I cleaned it the hum was still there but after about 15 min of playing, the Reverb just cut out. I've swapped the tubes twice and still no reverb.


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Sun Apr 27, 2014 11:58 pm
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Pull the cables out & run some compressed air into the female side. Work the cables in-&-out a few times (starting to sound like a sex therapy session, eh? :lol: )

Now, try the reverb. You should dry all excess contact cleaner from surfaces before use.

Good luck! Tell us how it worked out.


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Mon Apr 28, 2014 7:01 am
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I dunno... My Supersonic 112 works perfectly and sounds sweet, but it has always had the exact same reverb hum problem that you describe. I also have a silverface tube reverb unit that works perfectly and is dead quiet. I replaced the tubes in the Supersonic with tubes from the reverb unit, and the Supersonic reverb still hummed. I plugged the Supersonic's reverb in and out cables to the tank in the reverb unit and the Supersonic reverb still hummed. So, I figure it isn't the tubes and it isn't the tank. I assume it's something in the amp itself. I know the Supersonic is a loud amp (as is your Twin) and I wonder if a loud amp played quietly is just going to have a hum problem with the reverb(?)


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Mon Apr 28, 2014 8:18 am
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Redfarfisa wrote:
I wonder if a loud amp played quietly is just going to have a hum problem with the reverb(?)



No it should be quiet

Did you try the tank outside the cab ? Far from the speakers magnets ?


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Mon Apr 28, 2014 1:00 pm
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I've tried cleaning the tank and I've played it outside the cab


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Mon Apr 28, 2014 3:34 pm
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I've also tried unplugging the tank from the amp and the hum is still there. The hum is pretty strong so it's definitely not normal


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Mon Apr 28, 2014 3:40 pm
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Mattblackwell wrote:
I've also tried unplugging the tank from the amp and the hum is still there. The hum is pretty strong so it's definitely not normal



So the hum is coming from inside the amp . Not from the tank or cables

The hum may come from the foot pedal jack ( or the foot pedal itself )

Remove V4 ; any hum ?


Last edited by stratele52 on Mon Apr 28, 2014 4:00 pm, edited 1 time in total.

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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Mon Apr 28, 2014 3:57 pm
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I believe so but I'm no technician. And like I said if I take the V4 tube out, there is no hum at all. I've tried every ax7 tube in that socket and there is still a hum


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Post subject: Re: 65 Twin Reverb Reissue Reverb Hum
Posted: Mon Apr 28, 2014 4:01 pm
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Mattblackwell wrote:
I believe so but I'm no technician. And like I said if I take the V4 tube out, there is no hum at all. I've tried every ax7 tube in that socket and there is still a hum



This is not the output jack . Check 220K resistor at pin 2 of V4 check it is good and solder at ground , one end.

V4 pin 2 is a input , if no tube ;no output/ output because no tube . With tube, pin 2 with no /or defective 220K act like antenna and tube is an amplifier for the noise ( hum ) from pin 2 .

So check pin 2 , something there IMO


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