#1
Just putting this here cuz i figure that poeple in the guitar gear section wont know about all the wiring and such:

So two days ago i did a complete marshall mod, when doing this i realized that c14 wasnt in there so i figured id try it with the capacitor in then just take it out if it sounds bad. well i played for about 40 minutes and all of a sudden i lost all my sound but got a little bit for a second when i flipped the standby switch, i turned the thing back on played for about 15 minutes it shut off a again so i took off the resistor plugged it back in and had no sound...upon looking around i found that both my tubes are shot, i burnt them up ( im pretty sure i ve never had a tube fail...i guess im lucky ). i took the tubes out and measured my voltages on pin 7 to ground and got 374 so i changed r10 to 2.7 k and now im putting out 379 at pin 7 (this is on the el84. I was wondering how to get this down and why it was that i burnt out those tubes, if i put some new ones in will they blow real quick too, note that i dont know what the voltage was with c14 in, i can reinstall it and see though. thanks for any help.
-caleb
#2
Hey man, what schematic are you using? How are your tubes shot... do they not glow anymore?

And as far as the plate voltage goes, a few volts isn't going to make any difference.
Last edited by Losenger at Oct 29, 2007,
#3
Why did you change r10? You should have been fine just changing tubes.
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#4
i changed r10 because i had too much voltage at the plate's and the tubes dont glow anymore and im pretty sure they re blown i ll see if i can take a picture of them. as for the schematic im using this http://www.sewatt.com/files/sewatt/sewatt/files/epv_jr._gold_part_s.xls cept for the 2.2 in r10...also the amp is only about 2 months old so the tubes shouldnt be blown alreaDy
#5
Are you 100% sure you used a 2.7k resistor? The Marshall mods call for a 1k 5w resistor, from all my research anyway.
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
#6
yah i originally had a 1k in there but i swapped it cuz i a) heard it soudned better and b) i heard it would lower my plate voltage
#7
i just put a 1k (not shure on the wattage but its at least 3 watts) in as a screen resistor and now i h ave even higher voltage at pin 7 ( its now 385 )
#8
Quote by mercinariesgtr
i just put a 1k (not shure on the wattage but its at least 3 watts) in as a screen resistor and now i h ave even higher voltage at pin 7 ( its now 385 )


You've made a mistake elsewhere then. Try undoing all your 'mods' and seeing if it works stock.
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
#9
no im not going back to stock cuz a) its a crap load of work and b) it sounds great how it is ( or it did) i put the 1k in the r10 spot and just for kicks i threw in a 4k as a screen resistor and the voltage is now down to 380...i dont get how its possible but thats what the mulimeter said
#10
The lower resistance, I'd have though would RAISE that plate voltage, but don't quote me on that.

But next time, don't go tearing into an amp with no idea of what you're doing.
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#11
well i know what im doing i just cant get the voltages down, i should have ben able to put a 1k in and have the thing be in a good area but instead it did nothing