JCM 2000 TSL Blowing Both fuses

[Kyuss]

Right, here goes, I have a JCM 2000 TSL, when i bought it, i tried it through a standard 4X12 cab, everything worked fine.
I got it to the practise room, plugged it into my 4X12 and my 2X12 cabs and switched it to 4ohms (as both of my cabs are 8ohms) thus running my head knowing that in impedance is down to 4ohms.

First time it blew it took the first fuse out which is a TA2 as i recall ( the first fuse on the back of the head) when we cranked it too much,
then the next try it took the TA1 out which was the second fuse compartment as soon as we tried a pedal through the clean channel,
the next time it took the TA2 out again when just switching off the standby..
All this happened while both speaker cabs were connected with the right ohmage...

Iam asking if any of you have had the same problems? if im doing anything wrong? or there maybe something else?
Any feedback would be awesome,
We are gonna try getting more fuses, plugging it in a different place with one cab and go from there...
Much appreciate any knowledge...
Thanks

[Jazz P Bass]

If, and that is a big if, the 4 ohm winding is bad, that very well may be the issue.
Try the amp on a different output secondary setting.
Oh, and make sure that you install the correct fuses.

[Enzo]

First, make sure the fuses you install are what is printed by the fuse holder.

T1A means "timed 1 ampere" fuse Timed is another word for "slow blowing" or "slo-blow"

If you use a fast blowing fuse ( also called Normal) instead of a slow blow, it will often pop when you flip the switch.


Depending upon your Marshall, the two fuse holders hay also be labelled mains and "HT" The mains fuse is for the incoming power from your wall outlet. The HT fuse means high voltage inside the amp for the tubes.

In any case, blowing fuses on a tube amp usually point to failed power tubes.

[Kyuss]

Ok man nice one for the quick response, we will in a few hours be trying it in the 8ohm position, with a 8ohm speaker attached, that'll cancel out any faults there.. if it works that way then you may very well right..
Thanks very much

[Kyuss]

Yeah, thanks also man, gonna make sure that the exact fuses are used and they were the exact ones when i took them out after they had blown, i was thinking that the mains coming in was either too strong or not regulated enough for a tube amp to handle as in my experience they dont like it at all power that is not constant, obviously our other amps work fine as they are all solid state and dont need as much 'constant' or 'regulated' power as much and cope alot better with that.
Thanks for your replys, i will keep you up to date in a few hours as to how things have gone with my above 'trails'

[Enzo]

Having your speaker impedance off a notch should not blow fuses.

And I have to say, in my experience of several decades, I have never found tube amps to be sensitive to mains voltage variation.

Blowing fuses generally points to a circuit failure, not some environmental variance.

[Kyuss]

Ok thanks Enzo, gonna go try it with one cab in the 8ohm position to see if that keeps it good, will post back my findings...

[Kyuss]

Works fine now, in the 8hm position, with 1 cab attached, need to take it back to the rehearsal room and fire up both cabs...

[g1]

Suggest you test the other cab and it's cable alone first, then try both.