Posts: 70
Threads: 17
Joined: Jan 2006
City: Newbern
State, Province, Country: Tennessee
Working on a 570. For years had the intermittent problem of working or just squealing. Never knew what you were going to get. Gone over and over to no avail. Now it just makes this loud rumble. All resistors and capacitors are in specs. I isolated to the second detector tube. If all tubes are out except 80 and 47 its quiet. the moment I put the 2nd detector in it starts. Remove it and place all the other tubes in but not that one, its still quiet. Found the voltage to the plate and screen grid high way out from what Philco says. At a loss. Any one else had this problem?
Posts: 15,816
Threads: 554
Joined: Oct 2011
City: Jackson, NJ
Stupid question: do you have the multitube shield in place?
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 70
Threads: 17
Joined: Jan 2006
City: Newbern
State, Province, Country: Tennessee
Posts: 1,402
Threads: 70
Joined: Oct 2007
City: Linn Creek, MO
Could be any component associated with the second IF transformer through the detector. If you short the grid of the detector to ground, does the noise stop?
Steve
M R Radios C M Tubes
Posts: 70
Threads: 17
Joined: Jan 2006
City: Newbern
State, Province, Country: Tennessee
yes if you ground pin 3 grid it stops also pin 4 . but not grounding cap.
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
