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#1
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Need advice on Marantz scope diagnosis
Hi,
I'm trying to diagnois a non-working scope on a Marantz 150. Does any one know what the service manual means when they say to "short the collectors on both FET's " in order to center the beam to see if the vertical or horizontal amp is bad. There is a pair for each amp.(H905 & H906 and H907 & H908) I know that FET's don't have a collector but they are labeled that way on the board and schematic so that's not the question. The question is: Do I connect the two collectors together to short them or do I connect them to ground to short them? I was going to connect them together but a "tech" thought I should connect them to ground. Also, to test if both amps are out, can I short both pairs at once? Hopefully it won't come to that, so the first question is more important. More than one person responding would be good. Thanks |
#2
Posted to rec.audio.tech
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Need advice on Marantz scope diagnosis
On 30 Apr 2006 11:48:49 -0700, "tubedude"
wrote: Hi, I'm trying to diagnois a non-working scope on a Marantz 150. Does any one know what the service manual means when they say to "short the collectors on both FET's " in order to center the beam to see if the vertical or horizontal amp is bad. There is a pair for each amp.(H905 & H906 and H907 & H908) I know that FET's don't have a collector but they are labeled that way on the board and schematic so that's not the question. The question is: Do I connect the two collectors together to short them or do I connect them to ground to short them? I was going to connect them together but a "tech" thought I should connect them to ground. Also, to test if both amps are out, can I short both pairs at once? Hopefully it won't come to that, so the first question is more important. More than one person responding would be good. Thanks Without seeing the schematic it is hard to say, but from the sound of things you have a balanced, long tail pair amplifier. That being the case, you would equalised the drive on the two sides of the tube by shorting the collectors to each other, not to ground. d -- Pearce Consulting http://www.pearce.uk.com |
#3
Posted to rec.audio.tech
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Need advice on Marantz scope diagnosis
"tubedude" wrote in message ups.com... Hi, I'm trying to diagnois a non-working scope on a Marantz 150. Does any one know what the service manual means when they say to "short the collectors on both FET's " in order to center the beam to see if the vertical or horizontal amp is bad. There is a pair for each amp.(H905 & H906 and H907 & H908) I know that FET's don't have a collector but they are labeled that way on the board and schematic so that's not the question. The question is: Do I connect the two collectors together to short them or do I connect them to ground to short them? I was going to connect them together but a "tech" thought I should connect them to ground. To each other, I should think. |
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