Revox B285 blowing power fuse

[WhiteSE]

All of a sudden, The Revox is blowing the power fuse as soon as I plug it in...nice light show in the fuse and it dies.

Its a 5A, 250V slow blow little fuse...

Why would this happen all of a sudden?

 

[WhiteSE]

Eff It!! I am sending it to JM Technical Arts in TN...

 

[steerpike2]

Inside the transformer shroud, on the same board as the fuse, is a Rifa 0.1uF class X capacitor; they can go short circuit quite often, but it is usually a once-off event. After they've died, they go invsible and don't blow the fuse a second time.

More likely, one of the big 15000uF Frako cans has gone leaky. They are not cheap to replace - mainly because of their uncommon PCB style mounting pins.

 

[WhiteSE]

Inside the transformer shroud, on the same board as the fuse, is a Rifa 0.1uF class X capacitor; they can go short circuit quite often, but it is usually a once-off event. After they've died, they go invsible and don't blow the fuse a second time.

More likely, one of the big 15000uF Frako cans has gone leaky. They are not cheap to replace - mainly because of their uncommon PCB style mounting pins.

Thanks for the info...Its a great sounding unit, so I will fix.:thmbsp:

 

[steerpike2]

Thanks for the info...Its a great sounding unit, so I will fix.:thmbsp:

Replace all the Frako brand capacitors on the power supply board while you have it open. They will die and could do harm to other components when they do so.

Depending on the serial number, there was a sevice update to put clip-on heatsinks on the frestanding TO-220 style transistors UNDER the main big heatsink. These originally un-heatsinked TO-220's get very hot and the PC board gets cooked to the point of falling apart. The photo LOOKS like the extra heatsinks are present.

Its also worth replacing the two trimpots that set the power-amp idle current. They go intermittently open and this causes wrong basing & distortion.

 

[WhiteSE]

Replace all the Frako brand capacitors on the power supply board while you have it open. They will die and could do harm to other components when they do so.

Depending on the serial number, there was a sevice update to put clip-on heatsinks on the frestanding TO-220 style transistors UNDER the main big heatsink. These originally un-heatsinked TO-220's get very hot and the PC board gets cooked to the point of falling apart. The photo LOOKS like the extra heatsinks are present.

Its also worth replacing the two trimpots that set the power-amp idle current. They go intermittently open and this causes wrong basing & distortion.

I meant to say...I will send to get fixed...I shipped to JM Technical Arts...