fuse issue

[marinebassplayer]

i have blown f4 3 times over the past month. i have checked the bias of my tubes and everything is normal, and the tubes are all under 6 months with little use on them. is there anything that i could check to make sure that nothing bad is gonna happen down the road.

 

[Jaded Faith]

I can't recall what fuse this is off the top of my head. I do assure you if the same fuse is repeatedly blowing, something is wrong. You should probably have a qualified tech look at it and follow the lines back from that fuze to locate the issue. If not, it will eventually lead to a much bigger and more expensive problem than a blown fuse.

 

[marinebassplayer]

happened again. contacting the repair man tomorrow. i think i have read it somewhere but a 10amp fuse is ok for the tube power supply fuse located close to slot 3 (f3/f4) and is slow blow ceramic fuses ok or should i use the glass ones?

and rob is it ok that i share your contact info if things get crazy?

 

[Jaded Faith]

Sorry for the delayed reply here. I'm available 9-5 to help if your tech needs help.

Assuming these fuses are in an RM100, F3 & F4 should be the low voltage supply off the power transformer and are 5A 250V fuses. The schematic doesn't indicate if they are delayed or not, but I think the are Slo-Blow (a T prefix on the fuse will confirm this). Do confirm that the replacement fuse you are trying to use is a 250V type, as they sell a lot of 125V at stores like Radio Shack and it's an easy mistake.

If this fuse continues to blow, I'd be suspicious of either BD1 (the bridge rectifier right after the fuse) or U1G (the 12V regulator) a little further downstream.

Good luck and I hope this helps!
Rob

 

[marinebassplayer]

well still waiting for my amp. and my bayou mod is to be delivered today. i called once and the tech said there is something intermittently causing my heartache. oh poor me. sorry i just need to vent.

 

[marinebassplayer]

i have kt66s and 5881s in the mail. i was gonna try the kt66s on the outside and the 5881 on the inside sockets. what i found that the 5881s would be biased around 28-32mv but what about the kt66s?

is there any rhyme or reason to socket placement?

 

[Corium_AZ]

i have kt66s and 5881s in the mail. i was gonna try the kt66s on the outside and the 5881 on the inside sockets. what i found that the 5881s would be biased around 28-32mv but what about the kt66s?

is there any rhyme or reason to socket placement?

This was answered in the post just below yours:

http://mtsforum.grailtone.com/viewtopic.php?t=19380

 

[marinebassplayer]

34-36mv. got it. thank you corium_az

 

[marinebassplayer]

this information is spread all over the forum. i wonder would it be possible to create a sticky that would have all the recommended bias settings and that way nuggets like me won't have to dig and dig...

 

[Corium_AZ]

The Rm100 (and I'm sure the other Randall/Egnater MTS products) manual has the bias range for most popular tubes, and it's frrely available as a .pdf. Just do a Google search. Not sure about KT66's. But, yeah, a sticky with all biases would be quite useful. It might bring some new folks into the MTS world via google searches too, as I'm sure people ask this all the time in-general.

 

[Jaded Faith]

I'm sure people ask this all the time in-general.

If you only knew! :lol:

 

[Caine]

Just looking at old "fuse" related threads. I read on another thread the it's okay to use a 400mA fuse

http://www.parts-express.com/littelfuse-400ma-gma-fast-blow-fuse-5-pcs--071-808

supposedly "Bruce said" it was okay. What does Rob say? Ever hear of that?

http://mtsforum.grailtone.com/viewtopic.php?t=14955&highlight=fuse

 

[Jaded Faith]

A 400aA fuse is just fine.