hi,
i own Line Magnetic lm-219(monster amp), and lately i have been experiencing some problems with it, first it stopped playing on one speaker and soon after started blowing fuse after switch ON.
i know that those problems are often because either bad rectifier tube or bad power tubes.
in LM-219 case, there aren't any rectifier tubes so i would think that must be something to do with 845 output tubes.
first i pulled 845 tubes out and the amp powers ON without fuse blowing!, every other tube glows and seems fine ,...i used multimeter to check voltage in 845 tubes sockets and all seems to be fine so that shows that power supply is fine.
it measures :
anode~1000vdc
grid~147vdc
heaters 10vdc
i have some knowledge about tubes and etc. but i cant figure out what makes the fuse blow when i switch the amp ON with 845 tubes in it.
that would suggest the tubes are bad!,....i tried to insets each tube in just one socket and every time fuse goes!.
would it be possible both 845 tubes gone bad at the same time?!.
i checked the tube pins for shorts but all seems to be good.
...any suggestions?,...please let me know.
best.
K
i own Line Magnetic lm-219(monster amp), and lately i have been experiencing some problems with it, first it stopped playing on one speaker and soon after started blowing fuse after switch ON.
i know that those problems are often because either bad rectifier tube or bad power tubes.
in LM-219 case, there aren't any rectifier tubes so i would think that must be something to do with 845 output tubes.
first i pulled 845 tubes out and the amp powers ON without fuse blowing!, every other tube glows and seems fine ,...i used multimeter to check voltage in 845 tubes sockets and all seems to be fine so that shows that power supply is fine.
it measures :
anode~1000vdc
grid~147vdc
heaters 10vdc
i have some knowledge about tubes and etc. but i cant figure out what makes the fuse blow when i switch the amp ON with 845 tubes in it.
that would suggest the tubes are bad!,....i tried to insets each tube in just one socket and every time fuse goes!.
would it be possible both 845 tubes gone bad at the same time?!.
i checked the tube pins for shorts but all seems to be good.
...any suggestions?,...please let me know.
best.
K
that can be a lot but there is VERY little luck that the 845 failed at the same time.
however, look at the side of the bias circuit, it seems to be a fixed bias with a negative voltage circuit and also look at the side of the heating supply.
I wish you that this is not an output transformer that has failed because of too much current
however, look at the side of the bias circuit, it seems to be a fixed bias with a negative voltage circuit and also look at the side of the heating supply.
I wish you that this is not an output transformer that has failed because of too much current
sorry for a bad resolution but it's the only one i have got
check also the driver transformer (between 300B and 845)
An externally hosted image should be here but it was not working when we last tested it.
check also the driver transformer (between 300B and 845)
No fault in the output transformer can possibly cause the fuse to blow.
As bias voltages appear to be present at the sockets (i assume negative) all sensible venues appear to be covered.
Is it possible the replacement fuses are just the wrong rating or type?
I would suggest to test by applying filaments and bias without B+ and making sure the voltages are correct with the valve in the socket. Perhaps not easy to test with such a heavy amp.
hi,
good point it does have a delay start up,..but the fuse goes before that,..just after power ON.
...many thanks for your time and all suggestions.
i have done few more experiments with the amp.
i was usisng 2A fuse for last few days and all of them blow right away after power ON.
the LM company suggest to use 5A fuse with it but i diden't have any left.
i got some now and amp starts up/ powers ON, and i get a sound on right speaker but the left one hums/no sound.
i swapped output tubes ...and all remains the same,...sound comes out of the right speaker only.
that shows the output tubes are fine.
left channel hums,...and after 5 min. fuse goes again!
so before i used 2A fuse and it goes straight away,....but with no output tubes in sockets it powers ON.
with 5A fuse powers ON and plays on right speaker only...than fuse goes after 2-5 min.
???
i did open the guy up again,...tested all caps and and etc for shorts ...and no luck, all seems to be fine,...no smell inside or burned elements.
???
have no idea,
if you have any more suggestions please help me.
thank you all for your time.
best.
K
i have done few more experiments with the amp.
i was usisng 2A fuse for last few days and all of them blow right away after power ON.
the LM company suggest to use 5A fuse with it but i diden't have any left.
i got some now and amp starts up/ powers ON, and i get a sound on right speaker but the left one hums/no sound.
i swapped output tubes ...and all remains the same,...sound comes out of the right speaker only.
that shows the output tubes are fine.
left channel hums,...and after 5 min. fuse goes again!
so before i used 2A fuse and it goes straight away,....but with no output tubes in sockets it powers ON.
with 5A fuse powers ON and plays on right speaker only...than fuse goes after 2-5 min.
???
i did open the guy up again,...tested all caps and and etc for shorts ...and no luck, all seems to be fine,...no smell inside or burned elements.
???
have no idea,
if you have any more suggestions please help me.
thank you all for your time.
best.
K
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