General valve amp care and operation

AlanRatcliffe

General valve amp care and operation

Turn on the main power switch and wait at least 60 seconds (preferably more) before turning on the standby switch. This will help extend your valves lifespan. It is also a good idea to shut off the standby switch first before turning off the mains power switch.
Make sure that a speaker is always plugged into the amp. Valve amps need to see speakers plugged in at all times and will blow very quickly without a speaker connected
Make sure that the amps impedance switch is set to the same impedance as your speaker cabinet. The wrong impedance can also blow the output transformer and more
Take a little extra care in transporting them. Have a padded surface to put them on when you transport them. A car seat is ideal, but if it's in the back of a truck or bakkie the Polypropylene camping mattresses are great
Make sure that there is proper ventilation for the valves. Valve amps run hot – especially class A models. Don’t cover the ventilation holes with anything and also don't put the amp right against a wall so that there is no air circulating to the vents. Some players recommend keeping a fan on some hot running amps like AC30s
Change the power valves about once year, more often if your amp is very high gain, like a Mesa/Boogie or is used hard or every day. If you only play the amp occasionally and then at low levels, your valves should last two years or more.
Do not move the amplifier immediately after shutting it off. Let the amp cool down for a few minutes before moving or transporting it. This extends valve life.
Never play on a wet or damp floor or wet wooden stage! Some valve amps have internal voltages exceeding 600V! Never take your amplifier apart, even when turned off, as there are capacitors which store current for a long while after you have shut it off. Leave all amplifier work up to your trusted technician.

aja

Thanks for the tips!

Is it bad to leave the amp on standby for long periods?

AlanRatcliffe

It won't be a problem AFAIK. The valves will wear a little when they are hot, but nowhere near what they do while it is in use.

Cannon

Got a vintage 1969 valve amp. I've changed the tubes a few times but I've heard that u should change the power caps too....is this true and if so....how the hell does one get hold of these rare caps.
C.

matta

Cannon wrote: Got a vintage 1969 valve amp. I've changed the tubes a few times but I've heard that u should change the power caps too....is this true and if so....how the hell does one get hold of these rare caps.
C.

Yes, indeed! Electrolytic caps only tend to last 10-15 years, their dielectrics break down over time and tends to lead to a loss of bass, hum and eventually cap failure. I'd not only change the power caps but ALL the polarized caps as the same time and be done with it.

I'm also of the opinion you should rather pay ONCE for QUALITY caps that will last another 10-20 years, like Sprague Atoms. I've JUST ordered in a set from the USA for my 67' Bandmaster, and set me back around $50+ USD for all the lytics.

Cheers

Matt

AlanRatcliffe

Yup - The filter caps are most important, but you should change all of the electrolytics every 15 years or so. Ideally, you should try and get someone to go through and check other components for value drift beyond original spec too. That's all the kind of stuff I prefer to let a pro amp tech like Karel handle though - there are lethal voltages in and around the filter caps.

EDIT: Matta beat me to it...

Cannon

Thanx guys....sounds like a lot of work...THANX!!! ☹

Wizard

Slight thread hijack.
I built a hi-fi amplifier once and needed a 10uF electrolytic capacitor.
The schematic called for 35v tolerance and I found an available capacitor without checking too carefully (rated 10v).
It was one of the more dramatic, loudest bangs I've ever heard.
I ended up with an ear that didn't work for a while, bits of electrolytic everywhere ... found the casing a few days later on top of a cupboard way across the room.

matta

Cannon wrote: Thanx guys....sounds like a lot of work...THANX!!! ☹

It isn't too bad. Valve amps have FAR fewer lytics than Solid State ones, totally number in my 40W '67 Fender Bandmaster/Bassman is a whopping 11, LOL. So an hour or 3 of labour for any proficient tech.

BUT as Alan said... these voltages stop hearts and life itself... get it done by a serviceman/tech, not worth loosing your life over.

Cheers

Matt

zappa

Thanks to Al for all the advice, it's really handy.

I have a Messa Boogie lying around which I bought second hand from TOMS back in '93.

I think that they are no longer agents, anyone know who will service this amp in JHB?

TIA

AlanRatcliffe

http://www.guitarforum.co.za/amps-speakers-and-valves/valves-and-good-amp-techs-in-gauteng/

zappa

Thanks again!

Danny-B

Question:

If I'm playing, and take a break for an hour or so, is it better to leave it on standby or turn off mains?

nick

Alan Ratcliffe wrote: General valve amp care and operation

Turn on the main power switch and wait at least 60 seconds (preferably more) before turning on the standby switch. This will help extend your valves lifespan. It is also a good idea to shut off the standby switch first before turning off the mains power switch.

Weirdly enough the Classic 30 has no standby switch so its on and 20 seconds before its at full volume[/list]

AlanRatcliffe

Vox amps and and similar designs do not need a standby switch as the rectifier tube powers up the circuit relatively slowly, which protects it from a sudden current inrush.

Danny-B

Sorry, I didn't phrase my question correctly.

What I meant was, is it better to leave it on stanby for an hour, or return and turn on the mains again? Which preserves valve life more efficiently?

FenderBender

I would leave it on standby for such a short time. Initial voltage surge ages components faster than anything else under normal operating conditions.

AlanRatcliffe

I also prefer to leave them on if it's less than an hour or so. The valves stay all nice and toasty and the amp settles down nicely.

Cannon

Yup I agree! Leave it on.....and even more so in winter!

aja

JP Le Roux (an amp tech) told me it is best to switch off whenever not in use and that the standby thing is just to prevent the tubes getting hit hard with voltage from the solid state rectifier when switching on initially, and that leaving it on standby still reduces tube life.

???