i am new to the forum so let me start by introducing myself my name is wendell and i'm from arkansas i am a bass player but i play other instruments also. i was hoping someone here could help me with a problem i'm having. i have a acoustic g100t amp that quit on me it's dead no heater voltage. the heater voltage is present from the power trans but no tubes are lit. i found two rather large resistors burnt and figured after checking all the 6ls's that one of them was shorted and i think this is what caused the resistors to burn into or at least i hope it is this simple. but my problem is i cant figure the value of them as only one i could make outpart of the bands the other is completely gone. the one is a 1.01meg they are side by side on the circuit board. i'm not good at reading schematics so i took a couple of closeup pics of where they are on the circuit board hoping someone could help me idenify them. i realize that something had to have caused both of them to burn into and i'm hoping it's a tube issue but never the less i still have to replace the two resistors. anyway any help would be greatly appreciated. thanks, wendll.
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My guess is that those were R5 and R6 (and that you made a mistake reading one of them as 1.01M), and that they were taken out by a tube element shorting to a filament.
There's probably also a burnt up PCB trace or other wire between the transformer leads and the tube sockets.
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Originally posted by Euthymia View PostMy guess is that those were R5 and R6 (and that you made a mistake reading one of them as 1.01M), and that they were taken out by a tube element shorting to a filament.
There's probably also a burnt up PCB trace or other wire between the transformer leads and the tube sockets.
EricLast edited by icefloe01; 03-30-2009, 11:16 AM.
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Originally posted by tim View PostIf you're reading a color code as brown black black, that its a 100 ohm resistor. A 1.01 meg resistor would be a 1% resistor and I doubt there are any of those on there
Eric.
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You can see 5%, 10%, even 20% 1M resistors, but not 1.01M resistors. THOSE would be the 1% he mentioned. And not likely in a guitar amp.Education is what you're left with after you have forgotten what you have learned.
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Originally posted by Enzo View PostYou can see 5%, 10%, even 20% 1M resistors, but not 1.01M resistors. THOSE would be the 1% he mentioned. And not likely in a guitar amp.
Eric.
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you're right and I have egg on my face
10 ohm is brn blk blk. where was my head? I've been doing this for nigh on 40 years and I still screw it up sometimes.
I guess what I was really trying to get across is that if the resistor were a 1.01 meg, it would've had to of been a 1% resistor and I doubt that there is anything in that amp that is so critical as to have to use one of those in there. I have seen amps where a 10% was spec'd out but saw a 5 or even a 1% in there instead, probably because they got a good deal on several reels of the better parts
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I have a bunch of 1% parts, I got them either free or from surplus. They don;t need to be 1% for guitar amps, but they work just fine. I also have some odd values that are close enough to common values. Like 103k resistors. Those tend to be closer to 100k than many of the 100k carbon comps in the drawer. And 95uf caps are close enough to 100uf for me.
We used to know a tech who thought everything was rocket science. He went so far as to buy the same 4558 op amps from each factory, thinking somehow the 4558s that Peavey used were tested for god knows what and were different in some way from the ones that Fender or SLM used. We were always plotting on blowing this fellow's mind with such things as 1480 ohm resistors. Stick one in place of a 1500 ohm cathode resistor and watch the fun as he tried to rationalize why that part value must have been selected.Education is what you're left with after you have forgotten what you have learned.
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Originally posted by tim View PostI guess what I was really trying to get across is that if the resistor were a 1.01 meg, it would've had to of been a 1% resistor...
Eric.
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Originally posted by icefloe01 View PostYou're right on that and I failed to pay attention to that little detail in your original post. I'll have mine scrambled please. Did you happen notice what I was talking about with the parts list?
Eric.
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