Rock-ola 474 Sybaris

[Ron Rich]

Hi Pete,
Didja clean the pot ?-- May be dirty, not faulty ? Also-- is that relay cleanable ? Ron Rich

[jukenorman]

Hi Pete,
I'm not sure that the balance pot kills each channel, if I recall correctly? Is your phono cartridge wired in phase, are you getting lots of bass? It's very strange that the noise vanishes when you select mono - which it would if the cartridge was picking up some noise and the channels were out of phase, then the noise would be cancelled out in mono.

Norman.

[prime]

Ok like always i am not precise enough, when i switch to mono the low drone is low enough that i could live with it, i errantly stated it was gone. So it is present just hard to hear. I will clean the pot. I have very good base that is controlled well with the switch. I did clean the contacts on the relay but since i reflowed all of the solder connections on the board, i am having no issues with the sound, i mean if i touch the switch it does not cut out any of the music. pete

[prime]

I cleaned the pot and have found if i turn the pot to the right, the left is muted but if i turn it to the left it doesn't change balance but it increases base which in turn increase the drone low sound, pete

[jukenorman]

The balance control pot is on the tone control board. Does the problem occur for all settings of bass and treble? Maybe a failed component?

Norman.

[prime]

When i set the bass switches to minimum, and the treble on maximum a few things happen, the problem sound almost completely goes away, still the balance switch will cut out the left speaker when turned to the right, but not only does turning completely to the right have sound in both speakers, it also increases the bass some, not as much as the switch on max more like med.

[prime]

Ive decided i will remove the balance pot and test to see if there is an issue, if that doesn't confirm anything i will jump the two connections and try the board with no balance. pete

[prime]

Hi Norman, i have been looking back at the posts and your statement about the cart being wired out of phase, i looked in the manual for proper wiring to connect cart to tonearm , i just either missed it or it is not in there. Do you have the correct wire to pin info so i can confirm someone prior has not made a mistake. thanks pete

[Ron Rich]

Pete,
That info shood-outtbe on the amp schematic ! No ? Ron Rich

[jukenorman]

Probably the issue is that the large fold-out schematic is required for the amp diagram. Below is a copy from a 478 where the cartridge is wired the same.



Norman.

[prime]

Thankyou and yes i dont seem to have the fold out. Pete

[prime]

I think this may just be unsolvable, checked wiring to cartridge, as per schematic, I removed the tone board, tested balance pot, when turned fully to left got 115 ohm on left ,7.8 ohm on right when turned fully to right got 115 ohm on right and 8.7 ohm on left. I know the pot is listed at 100 ohm but im sure this pot is working correctly. i also tested at the left and right pin and got 7.8 ohm and 8.7 ohm so the tone board seems to be ok. My only question i have now is it possible it is a defective cart? pete

[Ron Rich]

Pete,
Carts do 'zero" work here-- all the "work" done in most mag carts. is done inside the needle enclosure-- do you have a gen-u-whine Shure needle / Do you have another needle to try ? Didja read the coil's two resistance readings ? If close, it's good ! Ron Rich

[prime]

After i got the jukebox and heard the issue i purchased a needle from needles4jukebox , i do think its genuine. I will look at the resistance. pete

[prime]

Checked resistance about 618 ohm left and right. I guess i can rule that out... I just have trouble understanding that the balance pot works well but only the left can be silenced when i turn to the right but the right is not reduced when turning to the left. pete