Hum from my Rockola 445

Hello again:

There's always been a noticeable hum emanating from my Rockola 445 when it turns on and plays records. It's not so bad that it drowns out the sound of the records, but it is noticeable. I think the right lower speaker is contributing to the hum; I checked the other three speakers (lower left and two upper speakers) and it is clearly the lower right speaker from which the hum is emanating. The louder the volume and the higher the treble setting, the more noticeable the hum is.

I can hear the hum even when there is no record playing. Recently I touched the tonearm cartridge to see if it was contributing to the hum, and interestingly the hum decreased slightly when I pushed it in, so I'm not sure if it is the tonearm that is the cause, the speaker, both, or something else.

The sound has never been crystal clear on the jukebox. I've always compared it's sound to that of AM radio; AM radio is not as clear as FM radio, and nor is the jukebox as clear as my component stereo system. I've always assumed that the jukebox was never meant to be an audiophile-quality device. However, is there a way that I can remove or decrease the hum I am getting and improve the sound quality/clarity?

Any advice would be greatly appreciated.

Jeremy

Jeremy,
While not "audiophile" quality, it was good when new ! The amp probably needs to be rebuilt,--all caps should be changed and all resistors checked for spec. at minimum. There is one other thing on some model RockOlas--I don't know if your model has it or not--but search around for a common ground lug, with several wires connected to it--all must be clean, the nut holding the wires should be brass, and tight ! If not in that condition, a "hum" will exist !
Ron Rich

Ouch. An amp rebuild sounds complicated (and expensive!)...especially for someone not electronically-inclined like myself. Sounds like a job for a service technician...

I was hoping that it may be something simple for me to check/troubleshoot. I will check for a common ground lug, as you've suggested, and see if there is any problem there.

I'll keep you posted.

Thanks again,

Jeremy

Ron:

Further to my last email, do you have any idea where I might find this common ground lug? Would it be inside the amp or power supply cabinets, or outside of these - attached to the floor of the cabinet, back wall, side wall, etc.?

Thanks,

Jeremy

Jeremy,
RockOla usually used large(r) green/yellow wires for this function, and they will be ALL over the phono--
This varied by model, and sorry, I do not re-call what was done in that model--sometimes a bare thicker, silver colored, wire was used--
Ron Rich

Ron:

I found those large green and yellow wires; they are all over the place. There are three connected together in one spot on the power supply cabinet. I checked all connections, and all seem pretty secure. While I didn't loosen any, there is no observable corrosion on any of them...so I assume all is fine.

Playing around with the amp cabinet switches, I notice that switching the Phono volume switch from position #1 to #4 seems to cause the hum to decrease. Maybe I just need to play around with some combinations and see what sounds the best.

Any other (simple) things I could try?

Pay a "pro" to fix it --- you will pay now, or pay later--Hum indicates a problem, which if allowed to become worse, usually also becomes more costly ---
Ron Rich

Good point. Thanks for the advice.

Jeremy