Popping noise

[TheRazMeister]

Hey guys...searched but couldn't find a satisfactory answer. Lately, my ROV combo (JJ E-34L's) has been popping and crackling when I turn the amp on. It even made a horrible screeching noise at one point. It pops whenever I flip the standby switch before I power down also. AND there seems to be a faint hum that was never there before. Is this a tube issue?
This, right after I bragged about how trouble free and quiet my ROV was.

BTW, I'm note sure I've noticed a loss of tone or anything, but I also haven't cranked the amp lately.

 

[Boogiebabies]

Tool requirements - 1 Chopstick - Do not touch anything with your hands
unless you know how to discharge your filter caps. Hence, the Chopstick.
Put one hand behind your back and keep it in your back pocket. The stick is not made of 98% water, but you are.


1. Visual Inspection of the circuit board - Look for burnt spots
2. Look for leaking yellow goo from the big blue filter caps
3. Clean all switchs internally with De-Oxit or a good contact solvent - Lube with Cai-Lube
4. Clean all pots with De-Oxit and follow with Cai-Lube to re-lube
5. Check the speaker for damage. I use a 9 Volt battery and look for movement.
6. Clean all tube socket pins with De-Oxit and follow with Pro-Gold
7. Power Tubes ( if not fresh)
8. Pre-amp Tubes ( check even if they are new )
9. Have a cup of coffee
10. Smoke a Cigarette
11. Clean input and speaker jacks with contact cleaner and sand.
12. Clean loop jacks. I use 12,000 grit sand paper so they shine.
13. Clean and dust the entire interior and exterior
13.25 Play test. Also try another speaker or cabinet to be sure

****WARNING - THE FOLLOWING IS FOR ADVANCED TECHS ONLY ****
13.5 Check Screen Grid resistors with ohm meter - Blown ones show 0
14. Check negative voltage at pin 5-DOCUMENT -57V
15. Check negative voltage at bias supply caps - DOCUMENT -57V
16. Check Plate Voltage at pin 3 of every PT - DOCUMENT
17. Check Bias with a Bias Meter
18. Ask yourself why you are doing this
19. Re-Assemble and playtest.

Outer sockets may show a lower negative voltage due to Simul-Class
Plate Voltage should be within 1-2 Volts
Bias Meter will determine what % of MPD you are at
Bias supply at supply caps should be equal at -57V
Document any wide variances. And read up on amp maintenance.

This is where I start when I look at an amp. I have been known to Q-Tip for hours and check resistors and capacitors for drift. Some need to be taken out of the circuit to be read, especially when coupled with a resistor.

 

[TheRazMeister]

Phew, I saw your suggestionson another thread and I'm not sure if I'm brave enough to do all that, especially since my amp is still under warranty and I wouldn't want to chance voiding it.

I'll add that it's fine for about 30 seconds, then a pop/crackle while I'm playing followed by a constant slight hum. I was able to re-create the SCREEEEECHHHHH noise by turning my standby off and on 3-4 times...

Tool requirements - 1 Chopstick - Do not touch anything with your hands
unless you know how to discharge your filter caps. Hence, the Chopstick.
Put one hand behind your back and keep it in your back pocket. The stick is not made of 98% water, but you are.


1. Visual Inspection of the circuit board - Look for burnt spots
2. Look for leaking yellow goo from the big blue filter caps
3. Clean all switchs internally with De-Oxit or a good contact solvent - Lube with Cai-Lube
4. Clean all pots with De-Oxit and follow with Cai-Lube to re-lube
5. Check the speaker for damage. I use a 9 Volt battery and look for movement.
6. Clean all tube socket pins with De-Oxit and follow with Pro-Gold
7. Power Tubes ( if not fresh)
8. Pre-amp Tubes ( check even if they are new )
9. Have a cup of coffee
10. Smoke a Cigarette
11. Clean input and speaker jacks with contact cleaner and sand.
12. Clean loop jacks. I use 12,000 grit sand paper so they shine.
13. Clean and dust the entire interior and exterior
13.25 Play test. Also try another speaker or cabinet to be sure

****WARNING - THE FOLLOWING IS FOR ADVANCED TECHS ONLY ****
13.5 Check Screen Grid resistors with ohm meter - Blown ones show 0
14. Check negative voltage at pin 5-DOCUMENT -57V
15. Check negative voltage at bias supply caps - DOCUMENT -57V
16. Check Plate Voltage at pin 3 of every PT - DOCUMENT
17. Check Bias with a Bias Meter
18. Ask yourself why you are doing this
19. Re-Assemble and playtest.

Outer sockets may show a lower negative voltage due to Simul-Class
Plate Voltage should be within 1-2 Volts
Bias Meter will determine what % of MPD you are at
Bias supply at supply caps should be equal at -57V
Document any wide variances. And read up on amp maintenance.

This is where I start when I look at an amp. I have been known to Q-Tip for hours and check resistors and capacitors for drift. Some need to be taken out of the circuit to be read, especially when coupled with a resistor.

 

[Boogiebabies]

Check the pre's first. I have had more than enough amps pass my way that sqeal or fart when the filter caps discharge on power down. Most of the time a pop on power up is a tube or a dirty switch contact. If it's under warranty, you do not want to drop $ 50.00 to ship it back for a preamp tube problem. Mesa has written many manifesto's on the subject. Do the simple stuff first.