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 Kreisler Baby Grand 11-157 Stereo Gram.
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 Return to top of page · Post #: 1 · Written at 12:34:28 PM on 28 February 2017.
Argenta's Gravatar
 Location: Nowra, NSW
 Member since 24 February 2015
 Member #: 1707
 Postcount: 12

Hi,

This is a 1974 (I think) solid state baby. Came to me with a massive 50Hz hum coming through the speakers. All components in the power supply were replaced, and the power transformer checked and pronounced quite sound. This circuit uses a LC Pi-filter on the output of the diode rectifiers, and the inductor is the component causing the hum. Would anyone have any idea on what I could use to replace that inductor. I don't have a value, the capacitors in the filter are both 2200μF, 25v. Someone did suggest two 1ohm 5watt resistors in parallel with each other, but I am uncertain that is a good option.


 
 Return to top of page · Post #: 2 · Written at 2:22:31 PM on 28 February 2017.
MonochromeTV's avatar
 Location: Melbourne, VIC
 Member since 20 September 2011
 Member #: 1009
 Postcount: 1136

I have the full service manual for the 11-157. It should have the value of the inductor in the parts list.

I'll check later when I'm at home.

UPDATE: L4 is listed a H.T. choke with a part number of 4048-025-02 but no other details.


 
 Return to top of page · Post #: 3 · Written at 7:18:34 AM on 1 March 2017.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 774

Try tightening the screws holding the inductor together and to the chassis. Or maybe a toothpick to insert between the wire coil and the lams.


 
 Return to top of page · Post #: 4 · Written at 11:26:29 AM on 3 March 2017.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2013

I recall looking for a hum in that model when it was new and under warranty.

It turned out to be not a fault with the power supply but something else that was affecting the amp's inherent hum rejection ability. Some sort of common-impedance issue with a ground return.

Sorry, it was a long time ago and I wasn't the one who found the fault. But at least I can assure you that it's NOT the filter inductor. The amp should be hum free with a couple of volts ripple on the supply.


 
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