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Question: Is it normal to hear substantial background noise on a Philco 70-A ? and what are the options to eliminate this problem.

Symptoms: Background noise is present even with the volume control completely turned down and the antenna lead has been physically disconnected.

Set known characteristics: Canadian model & has no AVC.

Performance: Although there is background noise, this set will received well on the AM band with plenty of volume.

The only occurrences where the background noise completely disappears are:

• When the 2nd detector tube is physically remove from the set;
  
• Plate voltage disconnected from the 2nd detector tube; and
  
• The coupling audio capacitor .1 uf is disconnected.

I have tried the following option: the background noise can be significantly be reduced by altering the 2nd detector tube overall gain performance. To achieve this goal, the suppressor Grid bias capacitor .09uf has been temporaly disconnected, which will reduce the 2nd detector tube overall gain with the result of significant reduction of background noise.

I currently ran out of troubleshooting options.

Any advices on how to remedy this set will be most welcomed.

Recepteur