Marshall TSL602 Blowing HT Fuses

[radcochran]

My Marshall Tsl602 keeps blowing HT fuses. I thought maybe one of the power tubes had died, so I replaced the tubes with a matched set, and the fuse will still blow as soon as the amp is turned on. It all started when I was practicing yesterday, and the amp just quit in the middle of a song. No hum, or any type of sound. It is dead silent. Maybe the transformer went out?> I have no experience testing transformers, but would like to test it myself. Any advice would be greatly appreciated. Guess it could be another problem also. Any suggestions or ideas about my problem would be great. Thanks

[Enzo]

Why would we think it was the transformer?

Does the HT fuse pop when you turn the amp on, or only when you ALSO turn the standby switch on?

Are you using the proper type fuse? Most Marshall HT fuses are SLOW BLOW. A fast blow will often pop on power up

[radcochran]

Fuses

The fuse blows as soon as the amp powers up. I never have to take it off of standby for it to pop. It is a fast blow fuse though. Though, the original fuse that blew the first time it happened was a slow blow. I have not tried a slow blow since the new tubes were installed.

[Enzo]

Well it should be a slow type. If that does not solve the problem, there are only a few places left to look. Possibly a shorted rectifier diode, D9-13. Possible shorted filter cap, C29, C35. Not much else.

The uncharged power supply caps cause a stiff current surge at power on. The slow blow fuse can withstand that.

[radcochran]

Thanks a ton.

Thanks man!! The slow blow fuse (the correct fuse!! LOL) and the new tubes corrected the problem. Guess it was a failing power tube to begin with. Thanks a lot.

[goldtop5]

Hello,

I've been having the same problem with a JCM 600. Never thought to install a slow blow fuse. I thought it was something in the circuit or maybe the tubes were causing it.

[Enzo]

It says T500ma right over the fuse holder. T means "time delay" which is the same thing as slow blowing.