caliber 50 + issue

[user 7737]

hi everyone,

i got some problem with my cal 50+... on clean sound everything seem to be ok... on the lead mode and on the clean mode with my rat, the sound sizzling and crackling... when i'm on the lead mode and turn down the volume, even very low, the crackling is still there... so this is not my cab... the crackling is still there when i plug my guitar directly in the amp, and when i change my guitar and cables

settings
volume/gain at 5, master at 2

what do you think ?

 

[tetsubin]

Tubes (try the preamp ones first).

 

[user 7737]

Tubes (try the preamp ones first).

well... that's what i tought... but if it sounds ok on clean mode, this is not the tubes that drive the clean, if it crackling on clean mode with my turbo rat, it can't be only the tubes that drive the lead mode... do you know what i mean ? :?

 

[acorkos]

bad speaker...?

do you have another cab you can plug into? try a different speaker cable, too.

 

[user 7737]

bad speaker...?

do you have another cab you can plug into? try a different speaker cable, too.

i don't think it's the cab because when i turn down the volume very low the crackling is still there... but i'll check that as well... listen carefully in front of each speaker if the crakling is on every speaker or only one... i can't believe the 4 speaker are out...

 

[Vigo1999]

i had the same problem with a caliber that i had, it was really a pain in the *** to fix it. my amp tech said it was something with the octocouplers :?:

that was a thread here that another forumite was complaining about the same issue, seems that it is somewhat normal with the cal50+ :? , bad, cause it's a wonderfull amp.

 

[angelo]

Tubes (try the preamp ones first).

well... that's what i tought... but if it sounds ok on clean mode, this is not the tubes that drive the clean, if it crackling on clean mode with my turbo rat, it can't be only the tubes that drive the lead mode... do you know what i mean ? :?

I don't know for certain, but the V1 tube is the first "bad" tube to get noticed because any flaws it has are amplified many times over.

Replace that one and go from there is my advice for a cheap start.

 

[StephenF]

Just registered, so forgive the 0 post count up until now...

I have a .50 Caliber+ as well. Am also having some weird issues with the dirty channel. It looses its tone when lead channel is used, sound fades in and out when switched (which i believe to be normal due to using LDR's instead of switches..no pops, but get the fade in/out condition with those). And here's what I have found so far.

According to the schematic that I saw, the 50 cal's "overdrive/lead" channel injects an additional 12ax7 in the pre-amp stage, in front of the first tube on the clean channel. If this lead/overdrive channel tube is bad, since it is completely unique to that channel, any problems it might be having would only be heard when it's in use. There's also some feed back circuitry that this adds to the 2nd (primary on clean) 12ax7 in the circuit.

So far in mine, I have swapped all tubes (new owner, just got it about 2 months ago for $350 on craigslist....lucky me!). Just finished that about an hour ago. With the amp out of the case, I took a 3rd look over the circuit board.

I have found some soldier joints that need touching up, but I also found a resistor that's charred. And...oddly enough, the charred resister is in the preamp section, possibly before the first clean channel tube.

While replacing the tubes really cleaned up the sound of the amp, the dirty channel is still odd sounding. I am looking into this more.

Stephen

 

[user 7737]

i had the same problem with a caliber that i had, it was really a pain in the *** to fix it. my amp tech said it was something with the octocouplers :?:

that was a thread here that another forumite was complaining about the same issue, seems that it is somewhat normal with the cal50+ :? , bad, cause it's a wonderfull amp.

interesting... i'll tell that to my tech... caus' i really don't think it's the tubes...

yeah it's a really great amp with a amazing clean for a mesa...

 

[StephenF]

After my phone call with Mesa today...

The 330ohm resister in the LDR power supply should be checked (mine is charred), along with the 3300uf cap it's in series with (bubbled). Check the supply voltage here. Should be 1.6v with switch engaged (in overdrive), 7.6v without. As well as check the 680ohm resister that supplies this chain of devices (mine was changed out to a 2k resister by a previous tech, should be 680-1k, 2 watt, on left side near filter caps by effects loop taps).

The entire LDR switching depends on those 4 components. 680/1k - res/cap filter - 470ohm resistor. End of 470 ohm should read 1.6v with switch engaged.

Hope this helps!

Stephen
------------------
Update:

Replaced the 330ohm resistor and the cap which supplies the LDR's in my 50. Channel switching now works like a champ, or rather, a .50 Caliber.

 

[user 7737]

hop...

my crackling problem came from 2 components in the lead section of the preamp... 2 "condensateurs"... i don't know the word in english :?

 

[jamme61]

did you check V1 tube yet? Like others have said here, it could be that one preamp tube. It only gets switched on, with the lead channel, so give that a shot first.