MESA BOOGIE shit fan removal

[Colas LeGrippa]

Hi !

Mesa Boogie on the bench next to me...client says amp is blowing fuses....on test since 2 hours with a 2A fuse ( instead of 3 ), still plays. Possible fan too dirty consuming to much power ?

What about fan removal ????????? Model MARK III

Thanks guys I love you all !

Colas

[kagliostro]

Hi Colas

Many years ago an italian automotive magazine reported this

One man had a strange problem with the oil pressure warning lamp

the lamp lighted also if there was enough oil on the engine

the solution given by a repair man was to put a piece of patch in front of the lamp



Why do you think that the problem is the fan ?

K

[super&plexi]

I used to get terrible eye pains from drinking coffee.........................many people gave advice.....................still no relief.............."the caffeine, the sugar, the soap you wash the cup in, everybody had a thought-remedy........... until someone watched me make it, pour it, drink it....................forget those BBguns...............man watch out for the spoons!.   

[floyd]

I used to get terrible eye pains from drinking coffee.........................many people gave advice.....................still no relief.............."the caffeine, the sugar, the soap you wash the cup in, everybody had a thought-remedy........... until someone watched me make it, pour it, drink it....................forget those BBguns...............man watch out for the spoons!.    

What are you talking about ?!!

[stratele52]

1- What is the working current need for the fan ?

2- When starting electric motor need 175 % of is normal working current : this is the fuse current .

3- Fuse must be a time delay too .

4- Wiring must be the right size too and Good connexion . Too many people use too small wire


Is your fuse and wiring are like that ?

[PRR]

> Possible fan too dirty consuming too much power ?

The cooling fan is MUCH-MUCH lower power than the tube-amp it cools.

Even on a house heater, where the fan must blow through skinny ducts to the far corner of the house, the fan is less than 10% of the total power (electric+oil) into the heater. (60,000BTUh of oil is 20KW, blower is 0.8KW.)

Also the power input to a fan can't rise a whole lot. (Yes, my heater's 0.8KW fan can pull 4.8KW if I grab the motor shaft with a wrench; but that is not the same as blocking the outlet or barnacles on the blades.)

Also: if you think the fan is dirty, you can clean it? Old paint-brush, or air-compressor?

> client says amp is blowing fuses....on test since 2 hours

Don't just sit there--- BEAT IT! High power amps flow a lot more current when ROARING than they do sitting idle. (Idle your car for an hour- very little gas and low chance of the engine breaking. Roar the highway for an hour at 200KPH- burn a lot of gas and you might throw a rod.)

[phsyconoodler]

signal generator-dummy load-full volume=finding issue. Idling is useless in finding fuse blowing problems.

 A fan cooled dummy load is the best way to find issues.I call it the torture chamber.What mesa boogie model is it? Some have issues that are well known that are easy to correct.

[Willabe]

Model MARK III

[Colas LeGrippa]

ok thanks !

[Jack1962]

A dirty fan won't blow fuse's a fan that is locked up may. plug a signal into it jam it up to 8 and run it for awhile with the proper fuse size and type . my money says it's probably the power tubes . is the schematic I have attached the amp on our bench ?

[Colas LeGrippa]

yeah that's the messy crappy schem. All tubes are brand new JJ's. Bias is fine, heaters too. Never blown a fuse here on my bench, even a 2A slo blo. I suspect voltage too high at the amp owner's place.

Colas

[kagliostro]

Ciao Colas amico mio

I suspect voltage too high at the amp owner's place

My son had a similar problem at the rehearsal (try room - I really don't know how to translate this) that his group had at a friend's house, due to problems of instability of the line

K

[stratele52]

yeah that's the messy crappy schem. All tubes are brand new JJ's. Bias is fine, heaters too. Never blown a fuse here on my bench, even a 2A slo blo. I suspect voltage too high at the amp owner's place.

Colas

JJ"s are not as good they where before for output tube '. I don't use them any more , better to use Wingeg C.

The fuse , I though you talking about the fuse in line with the fan . I understand is the amp fuse you are talking about .

I will  always put a fuse in line with fan motor . A short in fan must not shut down the amp , just the fan.

[Jack1962]

yeah that's the messy crappy schem. All tubes are brand new JJ's. Bias is fine, heaters too. Never blown a fuse here on my bench, even a 2A slo blo. I suspect voltage too high at the amp owner's place.

Colas

JJ"s are not as good they where before for output tube '. I don't use them any more , better to use Wingeg C.

The fuse , I though you talking about the fuse in line with the fan . I understand is the amp fuse you are talking about .

I will  always put a fuse in line with fan motor . A short in fan must not shut down the amp , just the fan.

It's the only schematic I have , I haven't had time to contact Mesa to get one yet , but anyway , yes I was talking about the mains fuse. As for JJ's I guess if a person likes them buy them I have had nothing but bad luck with these tubes , whe n I install EL34 and 84's I used Sovtek , 6L6 or 6V6 I used Ruby(yeah I know they are rebranded) . A fuse on the fan is a great idea. If you have turned the amp up and played thru it for a hour or so at , at least 50% volume and the fuse hhas not blown most likely yes it is the line voltage at the customers place recommend a furman power conditioner.

[stratele52]

IMO we don't need a power conditioner for tube amps .This is not a "fragile "electronics like Plasma TV .

Bias must be "colder " than hot. If you crank the amp a bias at 70 % idle ( AB class ) can easely go to 125 %  and more . But I'm shure you know . How JJ's will react at these power ?

[Jack1962]

IMO we don't need a power conditioner for tube amps .This is not a "fragile "electronics like Plasma TV .

Bias must be "colder " than hot. If you crank the amp a bias at 70 % idle ( AB class ) can easely go to 125 %  and more . But I'm shure you know . How JJ's will react at these power ?

I was actually talking about plugging the entire amp into a furman .  Oh yes I do know how JJ's will react or should I say not react , because most of them are bad when you get them 

[stratele52]

I was actually talking about plugging the entire amp into a furman .  

That is what I read. Tubes amps don't kneed power conditionner .

[Jack1962]

I was actually talking about plugging the entire amp into a furman .   

That is what I read. Tubes amps don't kneed power conditionner .

I have always used them with mine and had very little problems due to voltage issues . If it hooks up to my equipment it's goes thru a furman .

[stratele52]

I was actually talking about plugging the entire amp into a furman .   

That is what I read. Tubes amps don't kneed power conditionner .

I have always used them with mine and had very little problems due to voltage issues . If it hooks up to my equipment it's goes thru a furman .

You can't fix the problem in the room's electrical circuit ?