Leslie Combo PreAmp II Circuit Breaker

[Tim Abraham]

I just bought an old Leslie Combo Preamp II. Used it for 5 minutes and the fuse blew.

They're not supposed to have a fuse, but a circuit breaker, so it appears that someone in the past replaced the circuit breaker. The problem is, there is no marking on the little fuse at all to let me know how many amps it is, so I'm not sure what to replace it with.

There are schematics available on the internet, but I don't know how to read them.

Does anyone know how many amps the original circuit breaker would have been?

Thanks,

Tim

[Minion]

Originally Posted by Tim Abraham

I just bought an old Leslie Combo Preamp II. Used it for 5 minutes and the fuse blew.

They're not supposed to have a fuse, but a circuit breaker, so it appears that someone in the past replaced the circuit breaker. The problem is, there is no marking on the little fuse at all to let me know how many amps it is, so I'm not sure what to replace it with.

There are schematics available on the internet, but I don't know how to read them.

Does anyone know how many amps the original circuit breaker would have been?

Thanks,

Tim

If this is a Preamp then it probably doesn"t have very high power consumtion so a 250mA Fuse should be good but if that Blows try a 500mA fuse but if that Blows I would suspect that there is a problem of some sort that is causeing it to Blow....
You might also try replaceing the Circuit breaker which should be in the Schematics so if you post the schematic then maybe someone could look at it and tell you what type of Breaker to use to replace it with.....

PS: You might also look into getting a "Slow Blow" Fuse which aren"t as sencitive to blowing as standard fuses.....


Cheers

[Tim Abraham]

Originally Posted by Minion

If this is a Preamp then it probably doesn"t have very high power consumtion so a 250mA Fuse should be good but if that Blows try a 500mA fuse but if that Blows I would suspect that there is a problem of some sort that is causeing it to Blow....
You might also try replaceing the Circuit breaker which should be in the Schematics so if you post the schematic then maybe someone could look at it and tell you what type of Breaker to use to replace it with.....

PS: You might also look into getting a "Slow Blow" Fuse which aren"t as sencitive to blowing as standard fuses.....


Cheers

Thanks for the reply. I'm wondering if the fuse might need to be beefier since the preamp supplies power to the Leslie cabinet.

I'm unable to attach the schematic I have, but if anyone is inclined the schematic is available here:

******//www.captain-foldback.com/Lesl...s/cpa2_man.zip

If anyone can take a look at the schematic, and let me know what the fuse should be, I'd appreaciate it.

Cheers,
Tim

[Wavebourn]

Unfortunately, no information in your documentation about power consumption of speaker motors and power supply that supplies the pedal. The pedal itself draws a little current, most current goer to the speaker rotating motor. You may read what the label on it says.

[Tim Abraham]

There is a fuse on the Leslie (Model 825), so I'm not sure if the circuit breaker in the pre-amp is for the pre section only, or for the Leslie power supply (Is this apparent in the schematic?).

If it helps, printed on the back of the preamp is the following:

117V 50/60hz
400 Watts 4.0 Amps
Maximum

Also, the fuse that was in the preamp has printed on it:

BUSS MDL1

and on the other end:

250V

But no amp marking.

Any ideas anyone?

Tim

[cornutt]

Originally Posted by Tim Abraham

Thanks for the reply. I'm wondering if the fuse might need to be beefier since the preamp supplies power to the Leslie cabinet.

It does, including the motors. I can see that in the schematic. I'd try a 4A or 5A slow-blow; motor starting currents will probably blow a regular fuse. Or replace with a 5A CB.

Be very careful with the connection between the preamp and the cabinet. There is line voltage on several of the pins. Needless to say, don't unplug the cabinet while the preamp is on.

[Minion]

Well the "BUSS MDL1 fuse" is a 250v 35amp slow blow Fuse which seems like it is "REALLY HIGH" as most breakers in a house are only 15 to 30 amps.....

So it seems pretty strange to have a 35amp fuse in a device that can not possibly draw that much power, Hell a 35 amp Transformer would be about 3 times the size of the Preamp it"s self and weigh about 50lbs and there probably isn"t an outlet in your house that could supply that much power....

It seems very strange to have a Fuse that big and even stranger to blow a Fuse that big......

Good luck

[Wavebourn]

You need 4 amp fuse. Since there was a circuit breaker, sometimes starting the motor it draws higher peaks.

[Tim Abraham]

Originally Posted by Minion

Well the "BUSS MDL1 fuse" is a 250v 35amp slow blow Fuse which seems like it is "REALLY HIGH" as most breakers in a house are only 15 to 30 amps.....

So it seems pretty strange to have a 35amp fuse in a device that can not possibly draw that much power, Hell a 35 amp Transformer would be about 3 times the size of the Preamp it"s self and weigh about 50lbs and there probably isn"t an outlet in your house that could supply that much power....

It seems very strange to have a Fuse that big and even stranger to blow a Fuse that big......

Good luck

This is what I thought today when I looked up the MDL1 on the internet and saw that it was 250V / 35amp. The fuse definitely is a BUSS MDL1 (it's printed on the fuse, and the picture on the net was identical to it).

Hopefully when it blew, nothing else fried. I may just replace it with a new MDL1 and see if the thing works...

[cornutt]

Originally Posted by Tim Abraham

Hopefully when it blew, nothing else fried. I may just replace it with a new MDL1 and see if the thing works...

I would not put in anything bigger than a 5A slow-blow. If it blows that, it's got problems. The 35A (if that's what it really was) may have been a standard fuse, someone's way of working around the motor start surges. If so, it's a crappy way. Replace it with a slow-blow of the proper amperage, or a new CB.