2nd Sep 2019, 12:22 pm | #81 |
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Re: Shaftesbury 519 amplifier
I'm losing the plot here. Have the smoothers now been reformed using a diode resistor combo?
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2nd Sep 2019, 1:09 pm | #82 |
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Re: Shaftesbury 519 amplifier
Graham.
I was checking that the transformer was good to go first. Now I will endeavour to reform the caps. Best regards |
2nd Sep 2019, 1:43 pm | #83 |
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Re: Shaftesbury 519 amplifier
The heaters will most likely drop to about 6.5 volts with the valves in so it should be OK.
It looks like time to reform the caps now. |
2nd Sep 2019, 1:46 pm | #84 |
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Re: Shaftesbury 519 amplifier
I have just connected across pins 7 to 3 and switched on.... Immediate buzzing sound. That can't be correct??
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2nd Sep 2019, 1:47 pm | #85 |
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Re: Shaftesbury 519 amplifier
I hope that was not with a solid wire.
It should be with the resistor and diode. |
2nd Sep 2019, 1:59 pm | #86 |
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Re: Shaftesbury 519 amplifier
With 200kR 2watt and 1n4007 in series?
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2nd Sep 2019, 2:05 pm | #87 |
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Re: Shaftesbury 519 amplifier
That is right.
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2nd Sep 2019, 2:07 pm | #88 |
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Re: Shaftesbury 519 amplifier
Should it buzz though?? Am I better off starting with a lower voltage through a variac?
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2nd Sep 2019, 2:09 pm | #89 |
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Re: Shaftesbury 519 amplifier
It will buzz with a short circuit across the rectifier diode and it is also likely to damage the transformer.
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2nd Sep 2019, 2:10 pm | #90 |
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Re: Shaftesbury 519 amplifier
What I am doing incorrectly?
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2nd Sep 2019, 2:16 pm | #91 |
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Re: Shaftesbury 519 amplifier
You connected a solid wire where the diode and resister should have been.
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2nd Sep 2019, 2:20 pm | #92 |
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Re: Shaftesbury 519 amplifier
You misunderstand, I did use a diode and resistor in series between pins 7 & 3. I'm now at a complete loss what has happened.
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2nd Sep 2019, 2:54 pm | #93 |
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Re: Shaftesbury 519 amplifier
Oh dear, its now buzzing without any connections across the rectifier at all.
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2nd Sep 2019, 2:58 pm | #94 |
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Re: Shaftesbury 519 amplifier
Have you got the rectifier the right way round?
The 'cathode' (the band end) Must point to the pin 3. (It does not matter if the diode or resistor goes to pin 1/7 as long as the band points to pin 3.)
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2nd Sep 2019, 3:02 pm | #95 |
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Re: Shaftesbury 519 amplifier
It wasnt buzzing before I connected the diode/ resistor. So it appears something has now shorted out...... Where to start!
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2nd Sep 2019, 3:12 pm | #96 |
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Re: Shaftesbury 519 amplifier
You had the transformer shrouds off, were the bolts tightened properly when you re-assembled it?
Lawrence. |
2nd Sep 2019, 3:14 pm | #97 |
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Re: Shaftesbury 519 amplifier
I think I will have to take it apart again to make sure nothing is shorting out inside... What a pain!
Interesting point thought, it not tripping out my laboratory super fast rcd though?? |
2nd Sep 2019, 3:44 pm | #98 |
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Re: Shaftesbury 519 amplifier
One matter never resolved is the resistance of the primary winding. What does it measure?
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2nd Sep 2019, 4:40 pm | #99 |
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Re: Shaftesbury 519 amplifier
Across the 2 purple primary cables.... 78R
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2nd Sep 2019, 5:01 pm | #100 |
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Re: Shaftesbury 519 amplifier
What an idiot..... Shrouds were loose, I'd not tighted them fully. It's not buzzing now so shall I try the resistor/diode again?
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