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Old 5th January 2013, 09:25 PM   #81
srinath is offline srinath  United States
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For good measure I am going to pull c463, 464, and c462 and see if the voltage improves @ pin 2.
Cool.
Srinath.
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Old 5th January 2013, 09:30 PM   #82
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Hi,
I agreed 100% with you. A 12 volts AC transformer will do the job.
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Old 5th January 2013, 10:08 PM   #83
srinath is offline srinath  United States
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There has to be a dead CD player round here somewhere ... Let me find it and see what it says.
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Srinath.
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Old 5th January 2013, 10:12 PM   #84
srinath is offline srinath  United States
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Would this baby work ?

MR16 60Watt 60W Low Voltage Halogen Transformer 120V 12V MR16 | eBay

I think those leads give me the flexibility - LIke I can test it without having to remove the board and then get it off the board, etc etc.
Cool.
Srinath.
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Old 6th January 2013, 09:10 PM   #85
srinath is offline srinath  United States
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OK - liberated from a cassette deck, a 10.2 0 -10.2 v ac transformer. 50 watt capacity. And 2 x the size, but I think it should fit in the spot sideways. Or I can mount it outside of the board on top of the power transformer.

Anyway, I measured 13.4v to ground from the output leg of the original transformer.
Doesn't that mean its 13.4 - 0 -13.4 ?
Of course the original transformer doesn't have a center tap. Its center is the ground post of the diode bridge D454-D456 and c463 - c464.

The diode d453 in the 1 leg is used as a 1/2 wave rectifier, the resistor cuts down the amperage, then the cap, zener and resistor gets a proper 5v - can I get that 5v with a 10.2 - I think so - 10.2 with full wave will give ~15v dc, 1/2 wave should be ~7, I suspect the zener and cap should smooth it out ... it may lack the amperage, maybe I can take that 4700 ohm guy r453 down to say 3500. Anyway I think the first try I should leave it as is.
Then the 7806 circuit - I think it should work just fine running 10.2 0 -10.2 to 6v. Just the same as it did with 13.4.
That leaves the third leg - the ones feeding the relays 12v - 10.2 0 -10.2 should work fine there too, unless there is something is going to cut it down more.

Cool.
Srinath.
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Old 6th January 2013, 09:46 PM   #86
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Hi,
If the original transformer read 13 volts it will give you 13 x1.4 = to 18 volt DC. If the CD transformer read 10 volts then it will give you 10 * 1.4 =14 volt DC. I will not worry about the voltage going to PIN 2 connector since it goes thru the 4700 ohm resistor. Did you check Mouser to see if they have a transformer close to the one use in your amplifier? They may have one. No exactly but one that you can install inside of the cabinet.
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Old 6th January 2013, 09:55 PM   #87
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Before you replace the transformer make sure you do a good visual check to the PS board for crack tracers or bad solder joints. If it is possible use a magnifier glass to check for trace cracks etc etc.
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Old 6th January 2013, 10:30 PM   #88
srinath is offline srinath  United States
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I will inspect it for sure, but I have looked at it like crazy, I think the short I had - R456 to C478, I dont have that any more, it may have happened a long time ago, or when I pulled it apart one of these many times when working on it before it went DOA - anyway that may have been what killed the trafo.
Now there is no 18v anywhere in this board, 5v, 6v, and 30v. The 30v may have the main power transformer powering it.
Cool.
Srinath.
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Old 12th January 2013, 10:40 PM   #89
srinath is offline srinath  United States
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I swapped out transformers ... and still no relay click.
The transformer I pulled out made 13.4 volts ac. Its primary side tested like a capacitor. The one I put in made 10.4v ac. It tested like a resistor.
I think something else is blown up on it.
I will be poking around on it tomorow.
And follow the other points in this thread.
Cool.
Srinath.
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Old 12th January 2013, 11:09 PM   #90
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Hi,
If it read as a capacitor the primary it is open. Now What it is the DC voltage with the new transformer ? Do you still have 2 volt at the connector CP458 pin 2? To be able to close the relays you need a positive signal at the CP458 connector pin 1. Also what it is the voltage at the CP458 connector 4? Do you have 6 volts?
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