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Discussion in 'The Workbench' started by Force235, Nov 28, 2020.
WIll it work?
You need a heater fuse for a 6100?
Isn’t a fuse with a “t” a slo-blow?
please use the fuse the amp calls for
You are correct..T means timed, as in slo blow. Any fuse I have ever seen with a T in the prefix is a slo blow fuse.
Thanks, a fuse is not a fuse, is not a fuse, I ordered some better quality fuses to make sure the supposed slo-blo I'm using is really a "timed" fuse. The fuse I'm using, works for a few days then blows, it says its a T, but just looks like a regular single filament fuse.
This is for my JTM-60
If the fuse says T it's a slo blow. Perhaps your heaters are drawing too much current for some reason, I assume it was working for some time before it blew that fuse, why did it blow to begin with, with the original fuse?..that may be indicating a problem in the circuit itself. I have never worked on the jtm 60 so I don't have experience with it, or the schematic handy, but amps I have worked on that repeatedly blew heater fuses had rectifed heaters, and failing bridge rectifiers..not saying that's your issue here, but it may not be just a fuse problem.
heater rectifier is a common point of failure (among many others) of that series. usually leaves behind a nice scorch mark on the board when the underspeced rectifier bites the bullet
Bridge rectifier tests out good, even removed it and tested it. The original fuse lasted 25 years, then it died. I replaced it with a fuse I got from a cheap fuse kit from Amazon (China), I am suspect of the quality of the fuse, so I just ordered some higher (hopefully) quality fuses.
Good luck, hope that fixes it.
Testing a bridge rectifier cold will not prove your point, if you are not sure replace it, with the correct type of course.
You have the ohms set right on the amp? Put a meter on your cab to verify what it is. Wrong ohms will pop a fuse eventually even if its the right fuse.
Yes, I tested the bridge rectifier in and out of the amp, tested good, but I might replace if it keeps blowing fuses. The speaker is correct, fyi.
Can I assume it wouldn't hurt to use a slo-blo (same rating) in a position that only needs a regular fuse?
won't hurt the fuse but will likely hurt the amp
you may wish to find yourself a good local tech because you seem bound and determined to damage your amps
Definitely bound and determined to look into it myself - carefully... Last question was dumb agreed...
Can't find a good gut pic but does that use spade connectors in the heater string?
Referencing the JTM60/600 schematic, measure R142 & R143 (100ohm balancing resistors)...and this is a 20-25 year old amp? If around that timeframe, take an LCR meter to C134, C135, C143, C144...large deviations in a reading indicate they likely need replaced. Look for typical cap swelling, etc. Might be causing a bit of extra current pull. ?
A, not sure what you mean but here is a good pic of the area in question, the fuse that keeps blowing is behind the large blue cap on the left.