WOPL 400 Build Problem!

nadude98

nadude98

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#81
Gepetto said:
A good way to do welding :)
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Yep, they were pretty big rods on the end of a long wooden handle.... of course the caps were about a foot wide by a couple of feet high.. They were in the transmitter section of the AN-FPS 27A I was assigned to. Only had to do that a couple of times, when we either had to replace the Klystron tube or the transformer that provided the plate voltage.... IIRC

Made me glad I was in the receiver section!!! :toothy5:
 
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Gepetto

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nadude98 said:
Ok, well I had an order to get from mouser to recap a Pioneer A60, I added a couple of those to the order and it'll be here tomorrow. Maybe I should replace since there was an issue with +15v side
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The TL431 and the OPA134 devices are both sensitive to damage by static electricity so be very careful to discharge yourself before handling these prior to being installed in the circuit card.

The bipolar transistors are as well but much less so than the integrated circuits are.
 
nadude98

nadude98

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I came back from leave one time and my crew chief..a transmitter guy, had a hole in his elbow the size of a dime... forgot the golden rule of always having one hand in your pocket when working in the high voltage room... ouch!
 
nadude98

nadude98

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Okay, I powered everything up and I have the correct voltages at the correct spots.... I did replace VR1 with a new one...... I am going to go ahead and replace the pico fuse at this time.
 
nadude98

nadude98

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Here is where it stands as of now... the amp sounds better to a degree but there is definitely something amiss. It has to do with with bass response and it is being caused by the left channel...! If I have my balance all the way to the right channel and turn up the bass on the left channel (carver c4000 I can do that) it starts distorting the right. The left channel when I do that sounds like poop!

All voltages are correct as far as test points are concerned.
 
nadude98

nadude98

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Yes, and like I said, all voltages are good at the test points... with a scope I think this would be easy to track down..... but it's sounds okay until the input get above a certain level.... I went over the 14_20 board with a magnifying glass looking at the solder joints.. all the diodes test good. Well, I can't test D5 and D6 without pulling them out of the board. Just for poop and giggles I swapped out the op amp with a new one..... didn't help.
 
nadude98

nadude98

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Hey, I'm using the original twisted pair from the inputs.. shouldn't cause a problem should it? I know it's not ideal..
 
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laatsch55

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That won't affect an output signal, old wires don't do that. Yes a scope would show you what you are hearing. Due to the feedback present in this amp a scope can't tell you where the problem originates, but Joe has talked me through problems like this when using a scope based on the scope image. I am not that good yet. He can see a scope image and tell you WHY it looks the way it does.

Where you had a short between the collector and a heatsink, that can affect quite a bit, from the backplanes to the driver board. Does your offset voltage climb as your output goes up?
 
nadude98

nadude98

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laatsch55 said:
That won't affect an output signal, old wires don't do that. Yes a scope would show you what you are hearing. Due to the feedback present in this amp a scope can't tell you where the problem originates, but Joe has talked me through problems like this when using a scope based on the scope image. I am not that good yet. He can see a scope image and tell you WHY it looks the way it does.

Where you had a short between the collector and a heatsink, that can affect quite a bit, from the backplanes to the driver board. Does your offset voltage climb as your output goes up?
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Nope, offset stays the same. The driver board wasn't connected when I had that short.. the unit only had the four bottom outputs and and i was putting in the row nearest the output terminals. The short wasn't at full charge on the caps. So the short was on the right channel board. Shouldn't have had any affect on left channel.

Right now it's back to where it was initially.. dang. I believe it is also heat related. Could be a component breaking down under stress.

I used to be that good with a scope...lol. 40 years away from it... it's not quite like getting back on a bike... :tongue4:
 
Gepetto

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I am not seeing the 2 enameled secondary center tap wires from the transformer coming into the copper bus bar between the caps. The picture is truncated so it is difficult to tell in the rectifier area.
 
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