#121
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do you have a cap tester that can test for leakage at rated voltages?
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#122
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ok looking at the maggie schematic here it shows 140v 200v 270v 390v 405v plus for all voltages can i check these with the chassis out? because its nearly impossible to do this with this type of setup with a stero and tuner that has no plugs.
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#123
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these voltages were with no signal and i only have a dvom and i do have a cap checker and it measures NF and MF.
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#124
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if anything voltages should be higher since my line voltage is 122.9 v
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#125
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try replacing one of the .01 grid coupling caps for the difference amps, see if that changes the voltage reading on the grid of the 6GU7 diff amp tubes.
there are 3 of course, but you may as well only do 1 (say the blue) and see if there is a change. check to voltage before and after the change of the cap. think you said you were getting around +2v there, I show -2v should be there with no signal. if you can reach it, do a quick test, check each side of the 6Gu7 .01 diff amp grid coupling cap to ground. report back voltages on is behind one of the 6Gu7's the others are near the front of the board. Normally I would just test for leakage, but since you do not have the correct tester you need to replace or rig something up. Last edited by DaveWM; 02-12-2015 at 12:55 PM. |
Audiokarma |
#126
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what model number is that for?
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#127
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this is what you need to get. they are on ebay all the time.
https://www.youtube.com/watch?v=cjvCOhpVjYw |
#128
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i noticed every +140v source is at 121v , not good.
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#129
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if its a U45 you should be starting with 415v
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#130
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send me what you are looking at for a schematic
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Audiokarma |
#131
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i found a carbon resistor in the power supply that is a 3.3 k but tested at 40.5 k so i changed it dont know if it will make much difference. the +140 is low and the +270 is at 258v the difference between 258v and 270v is 12v and if that 12v is put to what i have on the +140 line at most its been was 120-125v seems to make up the loss on the +140. so is this 270v source used to boost up the +140 because the 270v comes in and goes threw a resistor just at the audio tube along with the +140v. what im not getting here is both 41 and 45 series schematics have the same setup in the power supply, resistors, so from the output of what looks like x2 it goes to a 1250 ohm 18watt resistor and pulls it down to what looks like supposed to be 270v but i only have 258v so this would suggest that 18 watt is bad so ill have to lift a leg and check. but checking it in the circuit its up around 1330 ohms. would this little bit pull it down to 258v from 270v ?
Last edited by timmy; 02-12-2015 at 04:28 PM. |
#132
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ok it looks like it is the 41 series and there is some difference in the 2 power supplys. so i lifted one leg of the 1250 ohm resistor and its 1398 ohms.
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#133
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dave im having problems here getting you the schematic i had got from davgoodlin
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#134
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is it at all possible to paralle a resistor with the 1250 ohm resistor to raise the voltage to see if this is the problem with the +140v and +270v being the 270v is fed right off the 1250 ohm resistor and it tests at 1398 ohms maybe the rise in ohms was enough to lower this source by 12v and if this 270v source is used together in the audio circuit with the stacked b+ to give +140v then this may be the fix. then there is what value resistor to try as the voltage cannot be that high but its for test purposes and if this does it ill get a new 1250 ohm resistor.
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#135
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odd, I thought it was a U45 all this time. if its not then everything I have been saying could be wrong.
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Audiokarma |
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