i'm going insane - amp Fizzle when ringing out...

[JohnnyC]

Noticed that my amp/speaker cab is having a fizzle out/slight cracking when chords and/or certain notes are played to one after the other and cascaded/let ring out.
It happens on both humbucker and single coil guitars and the amp/speaker cab has never done this before.

Amp is a 30W EL84 Framus with matching 2x12 (greenback and V30)
its driving me nuts now as im fixated on this fizzle out. Its not noticeable when youre actually playing lead/rhythm…only on ringing out.
Ive gone through the process of elimination and nothing seems to resolve the problem…so far

- replaced preamp tubes in all positions (several different ones…ranging from fairly new/to 1year old…mullard NOS,EH,JJs,Penta,Tungsol) and also tried 12AT7 etc

-replaced power tubes (only had old ones but still no change…JJs,Sovek) amp is cathode-bias

-replaced all cables (instrument and speaker cable
-removed pedals from chain (including fx loop)
-removed THD hotplate
-removed speakers/rotated and not overly tightened or loose
-tried amp in different room/power outlets
-tried different guitars
- tried framus with diffrent cab...fizzle still there.
-tried diffrent amp (jet city) with framus speaker cab...dont think its the cab...but havent ruled out the possibility either

the fizzle happens on the gain channel at all gain levels, but its much more noticable at lower gain. clean channel sounds fine.
the fizzle is also present if i use pedals for gain/distortion on the amps clean channel.

the only thing I haven’t tried is changing the rectifier GZ34 tube…I have a spare sovtek one…somewhere.

driving me insane!

Any other suggestions???

even my wife's ears notice it...

 

[glpg80]

sounds to me like a cap problem.

open that fucker up and look for any electrolytic capacitors with blown tops or leaking bases. do not touch them even when the amplifier is off and unplugged.

look at the actual tube sockets and see if you can notice any visual solder points that have come unsoldered.

my best guess - bad capacitor, or cold solder point somewhere in the channel.

basically its tech time in my opinion if you dont have any electronics background. you covered all of the other bases - and as long as the speakers check out - i wouldnt see anything else that could be causing it.

 

[Ancient Alien]

I was gonna suggest a cap job too.
Very well can be the culprit, especially running an EL84 amp with a hotplate.
That thing has to get hotter than hell

 

[JohnnyC]

yeah it does get hot...i open the back up.
but i dont use the hot plate to dime the amp and squash it down either...only use it sparingly and have the volume/master as close to noon as i can get it.

will have a look see later tonight.

 

[JerryP]

Get a new set of power tubes. EL84's are known for shit like that. Chances are if you gently tap them the amp will make all sorts of noises. I hate EL84 amps.
Jerry

 

[JohnnyC]

im hoping its just a simple power tube replacing.
i normally replace them around this time of year...just never had this issue before.

fingers crossed.

 

[glpg80]

im hoping its just a simple power tube replacing.
i normally replace them around this time of year...just never had this issue before.

fingers crossed.

i was under the assumption you already replaced them with known good tubes?

if thats the case, i agree with Jerry 100% - get EL84 tubes that you know are not deffective or overly used/old.

with the mentioning of a hotplate - that wears them out pretty fast.

 

[Ancient Alien]

im hoping its just a simple power tube replacing.
i normally replace them around this time of year...just never had this issue before.

fingers crossed.

i was under the assumption you already replaced them with known good tubes?

if thats the case, i agree with Jerry 100% - get EL84 tubes that you know are not deffective or overly used/old.

with the mentioning of a hotplate - that wears them out pretty fast.

+1

 

[JohnnyC]

i mentioned that i "replaced power tubes (only had old ones but still no change…JJs,Sovek)"
so theyre not fresh.

it is around that time of year that i normally would replace them anways (man this years gone fast)
ill have to get some more electrical contact cleaner too.

 

[JohnnyC]

so after trying another set of tubes and contact cleaner...with no luck.

im starting to think it may be the speakers/cab.

ive heard that overtightening the screws may cause the speaker frame to warp/be the issue?

since ive already loosened hte screws and rotated the speakers...think it may be worth a tighten?
i hand tightened them and then use an allen key to do a 1/4 to half turn in x pattern...

should i go tighter?

 

[cyndicate]

I had something similar happen when I was hacking up my Metro Superlead.. one issue was a cold solder joint at the pins of the preamp tubes.. or a cold solder at another part in the preamp section.. check all solder joints and see if they are okay.

 

[guitarslinger]

I had a bad resistor make this happen in my 2150.

get out your multi meter.

 

[jet66]

What's the best way to test a cap to see if it's good or bad? Aside from bridging the leads across my tongue... (My dad, such a kidder.) I've got a Peavey XXX Super 40 combo that's on the fritz. Went from the fizzle at the end to fizzling off and then dead. I've got a good digital meter, as well as a good analog meter, but no scope or knowledge of how to use one even if I did. I've bled the caps on other amps I have worked on (bad screen/grid resistors) so I'm fine on the safety part. I'm capable, just not well-versed when it comes to amps.