# Riddle me this: Amp works outside of cab, not in?



## StevieMac (Mar 4, 2006)

This one has me baffled. I've had my PR clone working flawlessly for some time now. Loaded it into a combo cab, tightened the mount bolts, and...nothing. Well, not exactly _nothing_. No pilot light and ONLY the recto tube will light up. Pulled it out and plugged it in and get the pilot & all tubes working again. Did this 3 times (mounted & tightened then unmounted) and results were identical i.e. amp funtions fine outside the cab ONLY. I even tried not tightening it so much but results were the same. 

So, my question: WTF???


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## WCGill (Mar 27, 2009)

Bad connection or solder joint on your heater CT or one of the legs. My wild guess.


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## epis (Feb 25, 2012)

It must be mounting bolt(s) are touching something inside, I would try removing one at the time and see what's going on. Cheers :smile-new:


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## greco (Jul 15, 2007)

I can't help...but I'm sure this thread is going to be fun to follow.

Hope you can solve this mystery soon StevieMac.

Cheers

Dave


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## Lincoln (Jun 2, 2008)

epis said:


> It must be mounting bolt(s) are touching something inside, I would try removing one at the time and see what's going on. Cheers :smile-new:


that one mounting bolt runs very close to the back of the pilot lamp......that would do it


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## StevieMac (Mar 4, 2006)

Lincoln said:


> that one mounting bolt runs very close to the back of the pilot lamp......that would do it


Hmm. Lincoln & epis, you may be on to something. I'll try that tomorrow and report back...


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## StevieMac (Mar 4, 2006)

Update: Pulled the mount bolts one at a time and then all 4 and still nothing but the recto tube lighting up. Pulled the chassis and there's no obvious spots where the bolts touch anything anyway. Plugged the chassis in outside the cab and it is not working now (other than recto tube). Finally, I also noticed the PT is getting warm (not hot though) rather quickly when just the recto is lighting up.


Other suggestions?


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## GuitarsCanada (Dec 30, 2005)

Certainly odd. I am interested in the final solution though


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## nonreverb (Sep 19, 2006)

Got a pic. of the guts Steve?


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## loudtubeamps (Feb 2, 2012)

WCGill said:


> Bad connection or solder joint on your heater CT or one of the legs. My wild guess.


 My guess would be the same.If a mounting bolt was shorting chassis components to ground you would think it would have popped the fuse.:Smiley-fart:
A bad connection somewhere..............? Is it an open chassis or does it have a lid?Do u have a shielding mesh screen or foil on the underside of the cabinet top? 
Try flexing the chassis and see if U see any signs of life back.:sFun_dancing:


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## StevieMac (Mar 4, 2006)

I removed the screen earlier, just in case something was touching.

I think I fixed the amp, though not entirely sure how. I changed two things: 1) one of the resistors off the pilot light/heater wires looked like it may have been grounding out against another lug so I moved it away from that lug; 2) less obvious was that the connection of the OT's brown wire to one of the output tubes looked a little sketchy so I resoldered it. It's also possible it was touching the wire beside it off the output tube so I made sure to move it away as well. Seems to be running fine now.

Expert explanations of what I actually did to fix it?


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## keto (May 23, 2006)

Probably you flex the chassis enough to make one of those connections ground out when you screw it into the cab. By moving them, you now allow for that flexing. SWAG.


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