<!-- from fixya rte -->Why do the fuses keep blowing - Fender Passport 150 PRO Portable PA System

The fuse rating should be printed on the panet right by the fuse holder. If there's still a question about values, you're best bet is to contact Crate customer service.
Here's the link-
http://www.crateamps.com/support
However, if you're meaning that you keep blowing fuses and therefor think you're instaslling the wrong value, you may have a short in the amp that's casuseing the fuses to blow. In that case, it needs to go to the shop. If you're not a tech, don't poke around inside it. You can make the problem worse, or even get a nasty shock.

Blowing fuses, was caused by many thing.
Short of rectifier,resistor,elco,tube heater,tube pin, and also trafo itself (primary or secondary winding). It must check step by step.
CAUTION :
THIS IS HIGH VOLTAGE AREA.
RISK OF ELECTRIC SHOCK THAT CAN KILL.
DON'T DO THIS IF YOU ARE NOT TECHNICIAN OR NOT FAMILIAR WITH VACUM TUBE CIRCUIT. THE CIRCUIT MAY STILL CONTAINS ELECTRIC SHOCK EVEN IF IF THE AMP IS NOT POWER PLUGGED.

The simple steps (see picture) are:

1. Disconnect all connection from secondary of power trafo (PLV,PDCH,PACH and PHV).
   Power ON the amp. If fuse is not blowing,trafo is good.
2. Power OFF the amp. Unplug the cord.
   Connect PLV1-PLV2-PLV3 (this are Bias voltage,+/-15VDC and Backlight PCB voltage) to power trafo.Power ON the amp. If fuse is not blowing,PLV circuit is good.If fuse blowing,there are parts is damage (dioda,elco,7815/7915,resistor) in this PLV circuit.
3. If step 2 is good,go to next step.
   Power OFF the amp. Unplug the cord.
   With PLV circuit stay connected,connect PDCH 1-2 and PACH 1-2 to power trafo. Power ON the amp.
   If fuse is not blowing,PDCH and PACH circuit is good and all tubes heater/filaments are lights after a few seconds.
   If fuse blowing,there are parts is damage (dioda,elco,tube heater pins) in this PDCH/PACH circuit.
4. If step 3 is good,go to next step.
   Power OFF the amp. Unplug the cord.
   With PLV,PDCH,PACH circuit stay connected,connect PHV 1-2 to power trafo.
   Power ON the amp. CAUTION: HIGH VOLTAGE AREA is ON.
   If fuse is not blowing,PHV circuit is good.
   If fuse blowing,there are parts is damage (dioda,elco,tube pins) in this PHV circuit.

.
Notes:

• Steps had to be done sequentially from 1 to 4, not upside down.
• If tube/heater pin is short,it can't be repair. The tube must be replacing.
• PDCH circuit is voltage for V1-2-3-4 heater/filaments.
• PACH circuit is voltage for V5-6-7 heater/filaments.
• Always replace fuse with same type.

Be sure the capacitor was replaced with the correct polarity?
in the beginning of my tech career I have replaced caps back words on accident. ..

Like all the past answers, make sure everything is clean and lubricated expecially on the Lesley if it's a motorized rotating speaker, the slow blow fuse is telling you there is a problem ?

Blowing a fuse means that it has a dead short. The fuse does its job by protecting the other components while the circuit fails. Something is definitely burned out inside.

I suggest either replacing these OR taking them to a professional to be serviced. Fuses blowing are a sign of serious malfunction and inexperienced DIYers should not attempt to induce the Darwin Effect

Any unit that blows fuses needs to be serviced. Do not keep putting in fuses only for them to be blown again. Each time you put in a fuse and it blows, it will create more damage to the amplifier.

You are either trying to: (A) push it too hard, (B) using the wrong type of fuse -- should be a "Slo-Blo" type, or (C) it has internal shorting or voltage modulation and requires service.

there could be something wrong with moisture. I had a drink spilled down the back of mine and I had to clean the board cause it kept blowing fuses.

Try running the amp with no speaker cables connected. If it doesn't blow the fuse you know it's either your Speakon cables or the speakers themselves that are to blame (it's usually the cables)

If it still blows then there is a more serious problem with the power section.