Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: smilch on October 27, 2018, 05:42:33 pm

Title: High pitch sequel or low frequency hum with Feedback circuit off
Post by: smilch on October 27, 2018, 05:42:33 pm

Just finished building a blues JR from the Hoffman kit . the amp was sounding pretty good and then I noticed I forget to hook up the feed back circuit . Thats when trouble arose . When the pot is turned off there is a high pitched squeal  coming from the speaker . turning all other pots switches make no difference , except the meat pot As soon as the pot is turned half way or more up the noise goes away . I checked connections and found a bad ground at the 4.7K resistor in the circuit going to the Meat Pot ..

Im sure someone has run into this . Just looking for some starting point suggestions .

Title: Re: High pitch sequel or low frequency hum with Feedback circuit off
Post by: sluckey on October 27, 2018, 05:46:53 pm

Swap the OT primary plate leads.

Title: Re: High pitch sequel or low frequency hum with Feedback circuit off
Post by: smilch on October 27, 2018, 09:52:48 pm

That was easy . problem fixed