Firing up a Tube Amp after a Loooong lay off.

[FrettyMcgee]

Quick question for the tube experts. I've been eying up my Pitbull UL lately. But I've had it sitting for literally 4 years (don't judge me with your micro aggressions, I'm typing this from my safe place).

So...is there any sort of check list/ things to look for prior to sparking up the head? Can of air to blow any excess dust? Re-seat the tubes?

Relieve me of my ignorance.....

 

[MOvalve]

Best to bring it up slow on a variac if you happen to have one. The electrolytic solution in the power supply filter caps can dry up when they sit dormant for years. An honest tech would do it cheap for ya. That's not an inexpensive amp so I'd recommend playing it safe. If you're located anywhere near central NC I can help.

[gorch]

I would just switch it on and listen. You will be surprised how great it sounds.

[crunchee]

1 hour ago, MOvalve said:

Best to bring it up slow on a variac if you happen to have one. The electrolytic solution in the power supply filter caps can dry up when they sit dormant for years. An honest tech would do it cheap for ya. That's not an inexpensive amp so I'd recommend playing it safe. If you're located anywhere near central NC I can help.

Four years of sitting dormant in an indoor controlled-climate home environment isn't a VERY long time, but a trip to a tech couldn't hurt...it also depends on how old the amp (and it's components) is to begin with, too.

[HSB0531]

Electrolytic Caps Do have a shelf life whether in use hours  or stored hours.

Each electrolytic cap is stamped with a manufactured date code.

The cap starts aging from that point on, whether stored or in use.

That's important to understand.

The manufacturers' websites' spec sheets will give info on the expected operating life, so you can look that up.

Luckily caps are cheap and easy to replace.

Symptoms:

In power supplies you will hear more hum and get less sustained power output when they start to go.

In preamp circuits you will hear a popping scratchy noise when you turn knobs.

You can also experience fizzling, popping noises even when not adjusting any controls.

I literally threw out a vintage 4-band parametric Eq. because I thought these sounds were coming from the stacked pots (obsolete parts).

Turns out it was the dried up 25 year old electrolytics.

Notes: Always replace electrolytic caps with the same or higher DC working voltage of the original part.

If at all possible, if there is room to fit them, replace with a cap that can handle a higher DC working voltage.

The higher the VDC, the longer it will last.

 

 

[FrettyMcgee]

Guys, thanks for the replies. Very helpful. I may ask around the local music shop and see if they know a honest amp guy for a checkup.

I'm pretty sure sure things might be ok. I bought the amp new back in 2007, and it's probably got the lowest miles on it in the history of amplifiers.

HSB0531 - That's a particularly great response. When I was a lad of 14, I had a old (70s?) Ampeg G212. It had every symptom you listed, and sounded a lot like a old clangy oil furnace when I wasn't cranking a guitar through it, haha. But when the buzzing and pops aligned properly and the reverb (that only worked periodically) kicked in, it sounded awesome.    

[Culhain]

Clean off the dust and fire it up in standby for a few minutes to warm the tubes before kicking it on and playing.

[tomteriffic]

At only four years, I'd go ahead and, maybe blow any dust out then fire it up. Obviously you'll then be listening for any of the symptoms HSB0531 noted, but really, 4 years isn't that long and those VHT amps are seriously, seriously built.

[MOvalve]

On June 5, 2016 at 9:36 PM, tomteriffic said:

At only four years, I'd go ahead and, maybe blow any dust out then fire it up. Obviously you'll then be listening for any of the symptoms HSB0531 noted, but really, 4 years isn't that long and those VHT amps are seriously, seriously built.

Yes VHT amps are built well and honestly the odds of that amp letting the magic smoke out upon fire up are pretty low. But......if nothing else just firing it up without some measures to reform the power supply caps could severely limit their lifespan. It's really up to Fretty as to how he wants to play that hand. I'd caution against it but it's not the end of the world either.

[Caddie]

On June 5, 2016 at 3:06 AM, crunchee said:

, but a trip to a tech couldn't hurt...it also depends on how old the amp (and it's components) is to begin with, too.

That kind of thinking is how the amp tech at the guitar shop earns his keep.  Yep, it always needs a new set of matched tubes, a blow job to get all the dust out, biasing, and "I found & replaced a couple of leaky caps".

[Armitage]

Electrolytic Caps shelf life is shorter when NOT in use then when they are... which makes people selling N.O.S. more then suspect...

[Dave Scepter]

Well?.. did you fire it up and did it work?

Variac is the best way however, I always plug it into a switched Outlet strip, put on some safety glasses "just in case" then turn it on, use your senses... & if you see or smell anything...  quickly hit the off switch of the outlet to keep the rest of the amp from damage~

[FrettyMcgee]

To update:

I cleaned out anything remotely dust related and made sure the tubes were all seated. Fired it up on standby with my eyes and nose at full alert, and my hand on the power plug, ready to pull it, haha. I let the tubes warmup for about 20 minutes, and then turned off the standby.....

....BOOM! The amp exploded.

 

 

 

Well, not really. Damn thing sounded perfect, switching through all channels. No doubt the long lay off has reduced the caps life, but I'll burn that bridge when I come to it.

Thanks again guys!