Seeburg 222 now with a Whoop Whoop sound

Which amp do you have ??
Ron Rich

Jim, removing the 6BJ6 tubes should not cause a hum. Those are the variable resistance tubes, removing them causes the level to jump up if a loud record is playing. If a low, or no record is playing removing them should cause no change at all.

If you have one of the first two stereo amps (SHFA-1 or 2) the two selenium diodes only rectify the sampled audio AC for use in controlling the two 'BJ6s. I routinely replace them with any small signal diodes, usually 1N4001 or 1N4002.

This might be useful for future reference: http://www.diodes.com/datasheets/ds28002.pdf.

BTW: Does either this new hum or the old noises vary with the volume control?

Rob

So what was the solution after 1 year ? It took me this long to get back to the amp ! First I isolated the AVC circuit from the amp by removing the connections at C147 for Channel 2 and C108 for Channel 1. This got rid of the hum that had developed from the earlier whoop whoop sound. The amp now sounded louder but there was still significant problem with Channel 2, it was weaker in volume and very scratchy sounding. I found that some of the distortion was being generated by the cartridge, as it had a bit to much tracking force on the records. After adjusting the grams to under 4, things started to sound better, but when comparing channels there was still weak sound coming from channel 2. Ok, so I get out the volt meter and start measuring for the proper dc values as shown on the SHFA1 print, To do this I would play an "air" record by selecting a blank location to play. I found that channel 2 had a high voltage at the cathode of V109, print stated 90v, but I was measuring 135v, while Channel 1 V103 pin 8 was measuring 88v for comparison. I then started looking at the resistors in the vicinity of V109 pin 8. All seemed well, but I did find that R191 was supposed to be 100K, but was actually a 10K. I replaced this resistor, and my measurement now jumped up to 150v (wrong direction !}. Ok, I continued to check each resistor and finally I found that R201 (68k) was open. Once this was replaced my voltage dropped to 78v dc. Still not equal to Channel 1 value of 88v but closer. The sound was much better now and by using the balance I could get a fairly matched sound from both speakers. I then proceeded to tie in the Automatic volume control (AVC) circuit back in. The hum was no longer present, and the volume did drop somewhat with AVC in circuit. I don't pretend to fully understand exactly why the hum was present when R201 died, but it really sounds better. I assume that both Channel1 and Channel2 cathode should be closer to 91v, and expect the difference may be due to the resistor tolerances. Appreciate the input and Juke on.

Rob-NYC wrote:Jim, removing the 6BJ6 tubes should not cause a hum. Those are the variable resistance tubes, removing them causes the level to jump up if a loud record is playing. If a low, or no record is playing removing them should cause no change at all.

If you have one of the first two stereo amps (SHFA-1 or 2) the two selenium diodes only rectify the sampled audio AC for use in controlling the two 'BJ6s. I routinely replace them with any small signal diodes, usually 1N4001 or 1N4002.
Furst
This might be useful for future reference: http://www.diodes.com/datasheets/ds28002.pdf.

BTW: Does either this new hum or the old noises vary with the volume control?

Rob

Ron, it is the SHFA-1 amp, and yes Rob the new hum varies with the volume control.
About the diodes, I found this very interesting article. http://www.w3hwj.com/index_files/RBSelenium2.pdf

Cr1 & Cr2 diodes with meter on diode and resistance settings, which both indicate open of which I was sure had worked on a previous occasion. What is the proper substitute for these diodes ?

Jim, any silicon diode of 50Vpiv or greater will do.

Rob