Noisy 434 during lead in and lead out groove on records

[jwday]

I recently got a Rock-ola 424 Concerto. it has a 132 replacement cartridge and a new replacement needle. 

I constantly get what sounds as a turntable rumble during the lead in groove and the lead out groove. I replaced the turntable bushings but I have read about tone arm bushings )where the tone arm pivots up and down. I have decreased the pressure on the tone arms and this appears to help some. Also the tone arm appears to be loose in the back is that normal?

In addition the 45/33 intermix seems to be very tight I assume it needed oil to work probably because it appears that even when the prongs are pressed down, it wants to still play at 33.

The last question is I have the speaker panel from 424 that has the speakers along with the 45 display (which the 434 only has the 45 display) I see the connection for the speakers on the amp, but unsure how these are bolted on as the cabinets are the same. are there bolts behind the amp.

I have orders the owners manual for this machine.

Thanks,

Jim

[Ron Rich]

Jim,
If you lift the tone arm at the start of a record, do you still "get it" ? Ron Rich

[jwday]

No sir, it stops. Only get it once the needle touches down.

[robnyc]

Jim, if the test Ron suggests results in no noise when the arm is lifted off a record it will confirm the problem is mechanical not electronic noise.

The problem you describe is typical of these machines due to several factors.

The cartridge you installed has significantly higher output than the original. You must now set the internal gain controls lower.

In this sort of circuit there is an inherent compromise between allowing the AGC to fully compensate for even the lowest level record vs. having this burst of rumble at setdown.

To explain: since ROck-Ola used an unconventional method of normalizing the levels between records via thermistors. There is no provision for applying a squelch voltage to set the internal AGC gain at a low level at the start of a record. Thus the circuits ahead of the volume control start out at full gain and this gets pulled down and set by audio signal from the record.

Finally, these turntables are barely one step above portable and kiddie phonos of their time. You will never get the kind of signal-to-noise ratio you can expect from a higher quality table using direct or belt drive. It is what it is.

Look for the two gain controls. They are either on the face of the amp near the input or on the side facing down. They adjust with a small screwdriver.

RobNYC

[jwday]

Thank you, I will give that a try.  It is clear that this machine was not loved for a long period of time and it has been a work in progress. I thought that the cartridge might have been dragging by my tech (Paul from Pinball Paul's) has adjusted this on one of my other rockola's and it made a big difference in sound quality

Best,

Jim