Howl from Seeburg B

While listening to a song, the juke will develop an overwhelming howl that is deafening. Shutting it off it will go away. It seems to do develop the howl after it has warmed up. Looking at the trouble shooting guide I purchased from a reputable dealer listed here, I am directed to see diagram on page 4044. The problem is the manual I received only goes to page 4042 and pages 4043 and 4044 re not there. Would appreciate if anyone could send me a copy of those two pages?

As the howl usually becomes evident the longer the phono is on I suspect that a tube may be defective. Is there any tube that is prone to causing this issue?

I also see that this can be caused by loose parts or faulty part in amplifier, no idea what part they mean by ?faulty part"?

Best
Darrell

Hi Darrel,
On the MRA's that's usually caused by the 1st tube in the chain--the 6J7. Look at it, very carefully--if "Wolf Brand"--toss it out ! If not, check the connections to it including the top one--does it still have the shield ?? If all appear OK--swap it, and I think your problem will disappear-- ( you might also check that the ground connection at the RCA input plug is good--tight--AND that the " B+ Jumper" on the speaker plug is tight---)-Ron Rich

Darrell, the first thing to determine is whether this is acoustic feedback or electronic oscillation.
Does the noise go away when you lift the stylus off the record? Does the noise change/go away with a lower volume setting?

As Ron points out, tube microphonics in a high-gain stage are where this sort of thing can occur. Try opening the backdoor and also, try holding the 6J7 tube to stop vibrations. Tapping tubes to see if a noise results can be helpful.

Rob

Ron

Thank you so much. As usual, you are the man. The 6J7 tube was not seated properly (apparently came loose from being moved around too much) and the top connection was somewhat loose. The shield is in place and it is a Rayethon tube. Howl is now gone and life is good again.

Best
Darrell

Rob

Thank you for the sage advice. It was the 6j7 tube.

The noise did not go away when stylus lifted off record or when volume was changed.

Best
Darrell