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Old 21st Oct 2019, 9:48 pm   #18
JUSTDAMO
Triode
 
Join Date: Jul 2019
Location: Hyde, Greater Manchester, UK.
Posts: 42
Default Re: Bush DAC90A - power but no sound

Thats sound advice and all noted.

this is the meter I have.

Quote:
Originally Posted by Sideband View Post
Without wishing to patronise, you really should become familiar with using a testmeter. Test instruments (of any kind) are only useful if the user knows how to use them. Best thing is to measure some resistors first and become familiar with how the meter reads the values. Low values, high values, intermediate values and check how the value of the resistor is read and which range to use for best accuracy.

Saying that 'the number 1.114 came up on the 2M range' clearly doesn't mean anything to you. The meter is in fact telling you that it (briefly) measured a resistance of 1.114 megohms (since you were on the 2 Megohm range) and then showed infinity (open circuit). Considering the resistance of the primary should only be about 500 ohms you should have been on a much lower setting resistance range (probably the lowest but depends on your meter). The meter would then probably have just read infinity (open) in which case the fault would have been more apparent.

I think we've established that the transformer primary is open and the reason for your no sound fault. It's a very common problem. DO NOT run the set with the transformer in this condition....it won't do the output valve (UL41) any good at all and these valves are now getting very difficult to find and also expensive. Next step is to either find a good transformer or have the existing one rewound by Ed Dinning. Ed will charge for his service (I've just had a transformer rewound by him) but it will be worth the effort.

While you are waiting for a transformer (either a replacement or a rewind), put the time to good use and get used to your meter, how it works and what the readings are telling you. If you are not sure....ask! Also you MUST replace the output valve coupling capacitor...it's probably one of the reasons why the transformer failed.

If you want to proceed with a rewind, I can PM you Ed's details.

Enjoy the hobby! We all started somewhere......
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