Peavey VB-2 Why is my Tube Amp Humming/Buzzing? - Replace the Power Supply Filter Capacitors!
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- Опубликовано: 24 апр 2022
- My apologies I was not able to take more video showing the process of replacing the capacitors. I have specialized tools I use in many of my electronics projects to make the process easier than with regular soldering tools. Recapping a tube amplifier should NOT be done by any novice. There are dangerous high voltages inside the amp that can KILL you, or at the very least give you one hell of a shock!
Doing work on my Peavey VB-2 All Tube bass amp. I had changed out all of the valves inside a few months ago and it really brought this amplifier back from the dead. I quickly realized that I was getting a nasty 120 hertz buzzing that I could not get rid of with the volume knob. Being that the amplifier is over 15 years old at this point I should have replaced all the power supply capacitors when I had it apart a few months ago.
The 120 hertz buzzing I immediately knew that the filter capacitors were starting to wear out to the point of failure. I ordered an entire set of Nichicon caps to replace the old Illinois Capacitors this amp came stock with.
The final results speaks for itself. Very happy with how it turned out. The minor buzzing noise left over is not filter capacitor noise but a design flaw of the amp.
The effects loop is passive and not buffered by opamps. The master volume is also not driving an op-amp, instead it goes directly to the phase inverter valve. as a result of the high impedance of the master volume knob when set to 5 (middle of its travel) this can pick up the buzzing sound that you hear. its called High Impedance Coupling effect
The solution is to use an external buffer on the effects loop to keep the impedance from the preamp to the PI tube of the power amp low. This will prevent the circuit from picking up the noise.
"Don't do it half way!"
I just did it half way. I re-capped a 1985 Peavey Audition 20, and replaced all but the two large capacitors in the power supply circuit, because I didn't have the other two on-hand. Plugged it back in and... still buzzing. Order placed for the missing caps from Mouser...
Its great advice. Its always Murphys Law not to change every single cap, even if only one has failed. Take apart once, cry once lol
Great video! Was wondering what made the buzz and pop
Thank you for watching the filter capacitors were well over 15 years old at this point. They have a finite service life and as they start to dry out inside they allow some of the ac voltage to leak through causing buzzing but at 120 HZ or double your mains frequency
Did I just find Jeff Daniels' secret RUclips account?
Nope!
I just bought this same model amp, it is sofa king noisy it sounds like an old radiator style heater, it really sounds like an old heater, and I'm really concerned that it's going to cost me an arm and a leg to get it right. But at least I've got your videos to show my tech guy and hopefully that will put him on the right path.
Is this the kind of maintenance that a big tube bass amp regularly requires?
@@leebodean1493 yes. Electrolytic caps have a limited life span of 10-15 years as they dry out. Some have said to me they can go longer, but I wasnt going to chance it. $45~ in new caps was worth it.
@@Bassguitarist1985 I'm going to have everything done for my amp, that you have done to yours in both videos. I'd like to know about how much you spent on parts and about how much time it would take a knowledgeable tech to get it done?
@@leebodean1493 about $45 for all new caps, $10 for two fuse holders and standard 5x20mm fuses to fit instead of the solder lead 5x15mm.
Figure 30-45min labor to disassemble amp, and say another 45-60 min ( could be longer depending on the tools he uses) to install caps/adhesive and fuse holders. Add another 30-45 to reassemble.
A matched sexet power valves plus two 12ax7s and one 12AT7 can vary. EHX ones are $$$$$. Setting the bias to 26mA/valve with a probe is a 15-30min procedure.
I don't know what the going rate is for Amp technician services these days. Assuming the amp does not need anything else repaired while he's in there this is what you can expect to pay.
@@Bassguitarist1985 thanks man, you've been super helpful.
Do you remember the capacitator order nr/brand/type? For the big ones.
Send me an email and I can give you a parts list from Digikey.com. the large 350V 470úF caps are below. Nichicon is the brand I used, but if you match the physical dims of the cap you can cross it to another reliable brand.
www.digikey.com/en/products/detail/nichicon/LLS2V471MELB/2549000
i got a 50hz buzz in one channel not effected by volume
Filter caps I'd say
You can also smell them when the fail
True! Thankfully i caught it just in time! Otherwise I would have been really swearing at it and if it took out the new set of tubes in addition to then things would be thrown haha
What do you mean smell them what do they smell like I’m not trying to be rude or funny I’m having trouble with a Peavey Ultra Plus 3:12
You might as well have said muffler bearings lol!
Apologies! This is one of my pet projects I've been itching to complete. I was ready to go all technician on the video comparing schematics and all that fun stuff but I know that I would have lost most of my audience watching after the first two minutes.