Tubes, heat and cooling fans

[bleakanddivine]

Hi

I need to put in a replacement fan in my 60/100 MkIIB, and it's got me thinking about it.

Tubes are built to be run pretty hot, right?, and they contain a vacuum, so blowing air over the outside of them is not going to change the operating temperature much, is it? Presumably the purpose of an amp fan is more to protect the other components from the heat the tubes produce in a small space. The standard Boogie combo fan seems to blow cooler air from the bottom of the cab up over the tubes, where it is heated and then into the top of the cab, where it can't easily escape from, so you'll just get warm air (and dust?) going round and round the chassis. I usually run my amp tilted back, so it seems to me that all the hot air is just going to collect at the top front of the amp, rather than escape out the opening in the back of the cab which is directly below that area.

Would it be better to mount the fan upside down so that the warm air from the tubes is sucked down away from the chassis components? Or even vertically, so that the warm air in the cab is blown straight out the back of the cab. Is there then enough ventilation in the top of the cab to allow cooler air to be drawn in to replace the warmer air forced out?

Any thoughts/experiences?

Thanks
Jonathan

 

[igfraso]

The only Mark that doesn't need a fan is the Mark I.

 

[Dude2Dude]

Not sure that the fan is in there to save your tubes. Have you felt the underside of the chassis after you've been playing (w/o the fan) for a while? It gets damn hot.

I had mine unplugged for quite a while; after doing some recording with it, I forgot to plug it back in. Probably not too bright.

 

[screamingdaisy]

Your Mark IIB has been functioning just fine for around 30 years.

If it ain't broke, don't fix it...

 

[stevenhugg]

Not sure that the fan is in there to save your tubes. Have you felt the underside of the chassis after you've been playing (w/o the fan) for a while? It gets damn hot.

I had mine unplugged for quite a while; after doing some recording with it, I forgot to plug it back in. Probably not too bright.

Dude is right, you must follow him..for heating and cooling of fans.

Cheers!

 

[johnwood]

Don't worry brother, the only issue is the "fan". just make it right and problem will be resolved.

 

[MrMarkIII]

Hot air rises. It won't "stay" anywhere if there is an escape route. The entire open back of the amp is a huge escape route. The fan is constantly circulating air. The tubes heat the air, the fan blows the heated air away. Heated air constantly being supplied/removed/supplied/removed = circulation. It's the circulation more than the coolness of the air that counts.
Unplug the fan and them suckers will get purdy dang warm, which can actually be good if the ambient temp is cold. My Mark III sounds a lot better warmed up.
Science!

 

[megavoice]

My Mark III sounds a lot better warmed up.

Yes, difinitively. But too much heat seems obviously to be bad for him.

I've recently asked MESA for removing or not removeing the fan. And they clearly replied: "No!" - and even NOT in the Class-A modus with two tubes only working.

 

[MrMarkIII]

In Class A the inner pair of tubes is still "on" and generating heat, their outputs are just not connected to the circuit.

 

[megavoice]

Yes, but I've taken them out completely. Why should they heat for anything ....

 

[igfraso]

The only Mark that doesn't need a fan is the Mark I.

I think I heard that 60 Watters don't need a fan either.

 

[MrMarkIII]

Yes, but I've taken them out completely. Why should they heat for anything ....

Yeah, I only make left turns, so I took the tires off the right side of my car to save on tires... Car runs funny somehow.

 

[bgh]

Yes, but I've taken them out completely. Why should they heat for anything ....

Can this be safely done on any Mark running in class "A"?

 

[MrMarkIII]

Yes, but I've taken them out completely. Why should they heat for anything ....

Can this be safely done on any Mark running in class "A"?

Safer than leaving them in? Doubtful.
What are you trying to do? Extend tube life on the tubes removed?
You're more likely to damage the tubes removing / replacing / removing / replacing / removing / replacing, etc.
You're also more likely to break something when somebody accidentally hits the Simul-Class switch, turning on all four tubes when there are only two installed.
Murphy's Law.

 

[megavoice]

I've played now for 26 years for about 95% in Class A modus with the both 6L6 stored outside safely. The amp is sounding better than ever. Never had problems.
The 15 watts are enough for big open-airs. The only concern is to avoid killing people .
If I like to put in the 6L6, I need about 15 seconds for. So why should I wear them down, when I don't need them ? Why should I heat up the chassis and the rest ?
The Class A is fantastic to cover bands like D.P., SAGA, Genesis, Yes, U. Heep etc.
Great guitar-players used the first and A/B for in my former bands. It's just like driving Cadillac or Chevrolet.
There did not anything break ever when removing or putting them in again.
Switching A/B on unwillingly with the 6L6 outside ? Anything happens. Only A/B doesn't work,.....that's it.

 

[mark2boogie]

The only Mark that doesn't need a fan is the Mark I.

There is no fan on my MKIIA too, and doesn't get hotter than my SF Twin Reverb. Maybe one day I will put one, a silent 80x80mm 12VDC model for PCs...

A+!

 

[Rick Mark2A]

I know back in the day the 60 watt Mark amps didn't come with fans. My original cyclone fan has become somewhat noisy and I'm now looking for a suitable replacement. My amp tech suggested I might want to try a 220 volt fan hooked up to 110 volts. It would supposedly be a lot quieter than a 110 volt fan since it would be running at half speed, and would still provide nice cooling.

 

[mark2boogie]

My amp tech suggested I might want to try a 220 volt fan hooked up to 110 volts. It would supposedly be a lot quieter than a 110 volt fan since it would be running at half speed, and would still provide nice cooling.

Yes, Rick Mark2A, It's a simple idea to try - that we cannot do, us Europeans !

I remember nonetheless having done this test with a Variac : not all the 220-240 fans would accept to run on 110-120V, and some of them were not so less noisy under half voltage. Junky fans ? Not necessarily, so have a sorting try !

Otherwise, it would be easy to find a very silent DC fan in any size, and powering it with a small compact variable PSU (117 / 0-12VDC, 3-5W power) discreetly installed somewhere in the cabinet, the whole being connected instead of the usual Boogie AC Fan. It would be the solution that I would use, personally.

A+!

 

[rw4951]

The only Mark that doesn't need a fan is the Mark I.

I think I heard that 60 Watters don't need a fan either.

I'm a Mark I fan. I've noticed that 60 watters have no heat sink. 100 watters do. Are Mk II/III's the same with the heat sinks?

 

[Buster Leggs]

I know back in the day the 60 watt Mark amps didn't come with fans. My original cyclone fan has become somewhat noisy and I'm now looking for a suitable replacement. My amp tech suggested I might want to try a 220 volt fan hooked up to 110 volts. It would supposedly be a lot quieter than a 110 volt fan since it would be running at half speed, and would still provide nice cooling.

I've got a 220 volt fan in my Mark lll (DRG) combo. Gotta say it's much quieter than my 110 volt fans. But it seems to me like it's not pushing enough air, not even close. I get that it's running at half speed but unless mine's defective, it's not cooling properly. It looks fairly new so I've no reason to think the fan is function improperly under the circumstances. I'm putting a 110 volt back in the lll as soon as I get a chance. I know their louder but fan noise doesn't bother me as long as it's not being picked up when miked which so far isn't happening. If someone could recommend a quiet 110 volt fan, I would go with that rather than the 220 volt fan IMHO. Also I brought it up to Mike B. at boogie when talking to him about other things and he said HE didn't recommend the 220 volt fan in place of the 110 so that's all I needed to hear.

I JUST REALIZED MY FANS ARE 115 VOLTS NOT 110, I GUESS THATS BASICLY THE SAME THING. BUT THE ONE IN THE MARK 3 IS 220