Tube amp gurus, help please

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chameleon2112

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I turned on my 50 watt 5153 today and no sound. There was no pop and there is no burning smell. Checked fuse and it is ok. Put headphones on through headphone jack, nothing. Tubes are maybe 5-6 months old and I only play a few hours a week. Any ideas? Thanks!
 
chameleon2112":3u9l6fmy said:
I turned on my 50 watt 5153 today and no sound. There was no pop and there is no burning smell. Checked fuse and it is ok. Put headphones on through headphone jack, nothing. Tubes are maybe 5-6 months old and I only play a few hours a week. Any ideas? Thanks!
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I'm assuming all the tubes power up? Try swapping preamp tubes, if you don't have extras switch the present ones positions.
 
Found the problem somewhat. It seems to be the return jack on the effects loop. Will get some contact spray cleaner tomorrow and hopefully that will solve the problem.
 
chameleon2112":1kvd2wzl said:
Found the problem somewhat. It seems to be the return jack on the effects loop. Will get some contact spray cleaner tomorrow and hopefully that will solve the problem.
Click to expand...
If that doesn't work run a small cord from the send to return. Cleaning should work, needed to do that myself in some Jubilees I've had.
 
It could also be a shunting jack that just needs one of the legs bent slightly to make or break contact. I just had this problem on a Matchless and once I figured it out it was a simple fix.
 
Well I tried cleaning the jack, nothing. Took amp apart and pulled the jack out. Checked the legs on the jack and all looked in good order and held a tight fit to the plug. Amp plays while there is nothing hooked to the return jack, as soon as the plug goes in, no sound. Any other ideas? Thanks guys!
 
Find out which preamp tube affects the loop, swap that out for a different one. Not sure if that will work but its worth trying.
 
Had the same issue on my 50w. Turned out to be the return jack on this one...
 
I'm pretty sure the 50W head loop doesn't use a tube...

Here is Howard Kaplans (designer of 5150 50 watt) tube run down:
from the Gearpage (https://www.thegearpage.net/board/index. ... 59/page-32)

5150 III 50 watt Tube Functions
V1 - 1/2 for CH1/2; 1/2 for CH3
V2,V3, V4 - CH3
V5, V6 - CH1/CH2
V7,V8,V9 - Power Amp


5150 III 100W Tube Functions
V1 - 1/2 for CH1/2; 1/2 for CH3
V4,V5,V6 - CH3
V2,V3 - CH1/CH2
V7 - Effects Loop driver/buffer
V8 - Power Amp Phase Splitter
V9-V11 - Power Amp Tubes
 
I've gotta ask again because a lot of people don't know this - is it a shunting (switched) jack like this, or just a regular jack?

Switched_Jack.jpg
 
I had this happen on a MK III Boogie, it was a different jack than the one RL pictured, there are 2-3 different types of them floating around out there, but the contact had to be bent just a hair to complete the circuit as was stated before.
Maybe a pic of the particular jack you have would help?
 
Are you sure the cable you're plugging into the return jack is good?
 
rcm78":36jeiuqf said:
Are you sure the cable you're plugging into the return jack is good?
Click to expand...



Tried a few other cables and still nothing.
 
Rufus Leaking":21jhlyty said:
I've gotta ask again because a lot of people don't know this - is it a shunting (switched) jack like this, or just a regular jack?

Switched_Jack.jpg
Click to expand...

rT2ql0.jpg


l22jHI.jpg


The jack is similar to the second picture in that it is dual stacked, but each jack is shaped like the first picture that has 3 clips in the jack, if that makes sense.
 
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