Welcome to Australia's only Vintage Radio and Television discussion forums. You are not logged in. Please log in below, apply for an account or retrieve your password.
Australian Vintage Radio Forums
  Home  ·  About Us  ·  Discussion Forums  ·  Glossary  ·  Outside Links  ·  Policies  ·  Services Directory  ·  Safety Warnings  ·  Tutorials

Tech Talk

Forum home - Go back to Tech talk

 Kreisler Baby Grand 11-157 Stereo Gram.
« Back · 1 · Next »
 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


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.

« Back · 1 · Next »
 You need to be a member to post comments on this forum.

Sign In

 Keep me logged in.
Do not tick box on a computer with public access.