you might need a cap job if?

[rectofried]

might need a cap job if your amp sounds like what? what are some symptoms, generally speaking

 

[94Tremoverb]

Hum, ghost notes - apparently out of tune frequencies when playing notes around Bb (US) or Ab (Europe) on the low E string at high volume - excessive sag or mush when playing hard, or erratic changes in volume or tone. These can be caused by other things too, like bad tubes, but if you've tried changing tubes and the same problem exists it may be time for a cap job, especially if the amp is over 20 years old. Modern caps do have a much better life expectancy than they did years ago, so I wouldn't generally suspect them until at least that amount of time, but you can still get random failures much sooner.

If the amp is over 20 years old and one cap goes, change all of them. If it's under 10 years old I would just change the failed one. In between... use your own judgement as to whether the cost of a complete job warrants it.

 

[rectofried]

thanks 94T, that helps a lot. im talking about the same ole 96 recto thats been giving me fits. another tech and still the same response..noting wrong with it.? amp sounds great when first turned on but after about 10/15 min of playing tone sounds harsh and top string sounds fuzzy and mushy as you said. fully retubed twice and have the HG+ chinese in v3/4. when it starts doing this in channel 2 modern i notice the clean channel loses head room and starts to become slightly distorted as well.

 

[94Tremoverb]

That doesn't really sound like a filter cap problem (although I won't rule it out completely - and it could be a *bias* filter cap, which may make the amp run too hot), but it should be relatively easy to find - monitor the voltages at all the tube connections before and after the fault develops and it should be fairly obvious what's changing - or at least where in the circuit it is. If there is a definite time interval after turn-on it sounds more like a resistor that's gone badly out of spec and is overheating.

 

[rectofried]

fantastic ! thanks for that info.. i will test it in the next day or so and post back...thanks again

 

[clutch71]

From what I was told when a cap goes you'll know it. It will stink up the whole house with a pungent odor.

 

[94Tremoverb]

Very unlikely. That can happen in very rare cases, but it's extremely unusual even if the cap fails outright. Normally, it either makes the amp hum loudly (cap fails open-circuit) or blows the fuse (cap fails shot-circuit) with no other apparent symptoms. And that's even for an outright failure - usually, caps simply degrade with time and don't perform as well as they used to, without causing any major problems or even being really obvious they have done... until you re-cap it and hear the difference.

 

[rectofried]

well, after turning the amp on and playing it hard i got a steady 24ma from all tubes from the bias tester. nothing changed in that department. the amp just sounds very flat got bass set at 9'oclk anything higher sounds like musy garbage..presence at 10oclk and high at 1'oclk anything higher on those it sounds very harsh and not cutting like its supposed to (compared to my other rectos). mid at noon. so bass makes it sound fuzzy and distorted and highs or pres. make it sound very harsh.. please note my clean channel sounds pretty good although breaks up way to early.

 

[94Tremoverb]

OK, so not a bias supply fault...

Sounds like the next thing you need to do is get inside and measure plate, grid and cathode voltages on all preamp tubes. Are you experienced enough to do this safely? If not, please don't...!

 

[rectofried]

i guess im just gonna have to unload the amp, i have had it looked at 3 times and everybody tells me nothing wrong with it.. most techs dont wanna spend the required time to track down a problem..if its not obvious like something burnt or broke.im gonna cut my losses. thanks for the info.

 

[mikey383]

It honestly sounds like you have a bad solder joint somewhere. When the amp heats up, the joint loses contact.

I'd take it to a Mesa certified tech. Look on their website for one in your area.

 

[rectofried]

all the techs were mesa service centers... i thought about sending it to voodoo or fja.. but i got too much money spent on it already.