rich
Newbie
Posts: 7 
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Post by rich on Oct 7, 2016 20:00:23 GMT -5
Purchased amp head used last April(2007 model). Everything sounded fantastic until recently. What would cause the amp to make a loud pop when I change channels,never done this before. Plus the thing is making popping noises when just sitting there. Did the usual unplug everything,guitar straight in. Changed power tubes and pre.etc. thanks.
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Post by gtrjunior on Oct 7, 2016 20:12:33 GMT -5
The only time I've gotten popping noises from any amp I've had is due to power tubes. At least when it's idling anyway. Are you 100% sure it's biased properly?
The changing channels popping is strange...maybe the foot switch cable is bad?
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Post by splawndude on Oct 8, 2016 10:09:07 GMT -5
Also, popping like that can sometimes indicate that a preamp tube pin is arcing with the socket connection or board itself. If that is the case, I usually tell people to spray the tube pins with some Dioxit contact cleaner and work the tube in and out of the socket to clean all the contacts real good. Then, make sure all the tubes are seated down real snug.
When you say you changed the power and preamp tubes are you saying you literally bought all new tubes and it still does this?
Also, leave the foot switch unplugged for awhile - if it still pops then plug it back in but clean the 1/4 sockets with contact cleaner. Don't spray into the hole, spray the jack and then work it in and out.
If it still pops after all of this - then contact Scott or an amp tech.
Good luck
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Post by briman on Oct 12, 2016 19:51:37 GMT -5
Good advice Splawndude.
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Post by splawndude on Oct 12, 2016 20:30:31 GMT -5
Thanks Briman (sorry you couldn't get to the mothership)
If the popping still persists and you are pretty sure it is not the footswitch and you've removed all pedals etc and have guitar going straight into amp, another thing you can do is take all the preamp tubes out. If popping continues then you've ruled out the preamp tubes. Obviously, you wouldn't want to try that trick with power tubes - those need to stay in. Also, you can plug the guitar into the FX Return jack. If popping goes away then it may indicate a preamp problem.
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rich
Newbie
Posts: 7
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Post by rich on Oct 16, 2016 18:13:48 GMT -5
Thanks for all the advice! I went to turn it on last night to show a buddy my amp. It powers on but NO SOUND!Tubes glow and everything, I freaked (lol)! Definitely taking it in hoping its nothing major.
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shaja
Junior Member
Posts: 74
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Post by shaja on Oct 17, 2016 10:05:24 GMT -5
If power tubes and phase inverter tube(4th 12ax7 looking from behind) are glowing, but no power in the other pre tubes, and no lights in the footswitch, you need to replace the bridge rectifier on the channel switching board inside the amp. I've had the same problem, nothing serious, but you should contact Scott.
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rich
Newbie
Posts: 7
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Post by rich on Oct 17, 2016 18:31:32 GMT -5
I contacted Scott via email and he replied that if all the tubes are glowing and foot switch lights up, it isn't the bridge rectifier. The new tubes were not the problem, because it sounded (tone-wise) better. I sold my '81 JCM 800 2204 head so that I had something a little more "current" and more versatility for this one. Major bummer...
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Post by gtrjunior on Oct 17, 2016 18:38:14 GMT -5
Did he have any suggestions for you to check out?
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Post by briman on Oct 17, 2016 20:53:17 GMT -5
I changed power tubes one time with my 2007 Competition and after a while, i got popping noises and then volume swells. Then a very loud pop and one of power tubes was bright red like it wasbon fire!!
I turned off amp immediately and returned tubes for new ones and everything was fine after i installed them.
You could have defective tubes like i had.
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rich
Newbie
Posts: 7
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Post by rich on Oct 18, 2016 16:34:28 GMT -5
Scott replied back and told to check the HT fuse. Looks blown,going to radio hack. Looks like a Bad power tube.previous tubes were el34 and the ones I replaced them with were el34b. Would this make a big difference? Also, if I wanted it run half power, which power tubes would be working (inside 2, outside 2) Thanks.
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Post by gtrjunior on Oct 18, 2016 17:16:37 GMT -5
El34...34b...it's all good. IIRC half power uses the two inner tubes. splawndude....is that correct? |
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Post by splawndude on Oct 18, 2016 20:29:47 GMT -5
Yes
And make sure you drop your power load to your speaker cab in half. So you if you are normally set to 16 ohms for a 16 ohm cab you want to set your amp to 8 ohms.
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rich
Newbie
Posts: 7
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Post by rich on Oct 19, 2016 10:31:51 GMT -5
Fuse changed. Works! Still a loud pop when I still switch channels via foot switch. How are the splawn tube sets in the website?
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Post by gtrjunior on Oct 19, 2016 15:48:27 GMT -5
I'm currently running the Splawn power tubes. They are good enough. They are a Chinese made tube. When the amp needs a retube I'm going to try something different though. I was thinking either Tung-sol or Electro-harmonix.
Keep in mind that if you do not have the dropB+ option you may want to consider a tube that can handle high voltage applications. Ruby makes some...the BHT model IIRC
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