Rockola 470

I have a Rockola 470 which has developed crackling crom the speakers when not playing records and is even louder when playing records, i have disconnected both pre amps and the crackling is still their, I have had all the covers off of the PSUs and amplifiers and have tapped everything thinking I would find a loose wire but the crakling doesnt change, its not mains hum its just the sort of noise you would get from wobbling a loose wire. Could this still be a capacitor problem in the PSU Has anyone got an idear of what it could be.
2. I want to connect a blue tooth receiver to the microphone socket, it looks like its 9 pins with the top 3 pins wired and 2 pins at the bottom, anybody know what each pin does.

Hi Robert,
If the mute circuit is working ( touch the needle while "at rest"), I would assume the problem is in the output section(s). If it's doing it's "thing" on both channels, I would guess the power supply is causing it, if the two channels "share" the supply. If only happening on one channel, I would look at that channel-- in any case, it could be almost "anything"--bad cap, resistor, transistor--? Ron Rich

Ron Rich wrote:Hi Robert,
If the mute circuit is working ( touch the needle while "at rest"), I would assume the problem is in the output section(s). If it's doing it's "thing" on both channels, I would guess the power supply is causing it, if the two channels "share" the supply. If only happening on one channel, I would look at that channel-- in any case, it could be almost "anything"--bad cap, resistor, transistor--? Ron Rich

Hi Ron, thanks for that, as i say i disconnect both pre amps and still makes loads of crackling/poping on both channels, If I remove the mute relay the noise gets louder, it sounds like the noise you get when turning an sold volume pot that hasnt been used for a long time. so I guess the only common point is the PSU, as its not a mains hum im assuming I can forget the very large capacitor, can the old ceramic resistors cause noise, I have had a fuse in a PCs sound circuit create loads of noise so im guessing they can as well. I need to get hold of the PSU and amplifier cuicuits to see how this lot intergrates i guess. It does seem odd I cant add to the crackling by knocking each connection point thoughout the amp or PSU.

Hi Robert,
Yes, as I wrote above--"anything" can cause this--Please read all of the above posts, and purchase a Service Manual Package.
Ron Rich