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Post by prime on Apr 21, 2022 20:29:36 GMT
Hi I have a 474 and have it running great except for a low hum when playing a record. The hum is only there when the needle hits the record. I was wondering if that rules out the power caps? Im going to change the caps in the amp but did not want to change the large 1500 if not needed thanks pete
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Post by Ron Rich on Apr 22, 2022 0:12:48 GMT
Hi Pete,
Nope-- sorry, it does NOT rule out the filter caps-- It also does not rule out mechanical problems-- lift the tone arm while record is playing-- hummmm go away ??--mechanical problems-- Ron Rich
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Post by prime on Apr 22, 2022 0:43:07 GMT
I will test that.
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Post by prime on Apr 23, 2022 20:40:46 GMT
I recapped the amp which i find in most cases improves sound as it did in this case. Unfortunately I still have a low drone sound when record is playing. This does not sound like a ground issue but maybe im wrong, it is a very low sound audible only with the bass speakers, if i disconnect bass i cannot hear it. The sound stops when i lift the arm off of a record that is playing. On another note i am looking at putting this unit into free play, it has been suggested to me that if i strip back the blue/white, the black/grey and black wire going to the white connector on the credit unit, tie them together this will give free play. Any thoughts on this. Thankyou for your time pete
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Post by Ron Rich on Apr 23, 2022 21:29:57 GMT
Hi Pete Sounds like a mechanical issue, if the hum leaves when you lift the tone arm-- are the motor mount grommets new-ish-- and white in color -- IMHO ONLY "white" grommets may be used here ! As for the "free play"-- do you have a manual ? L@ k at the schematic-- If a mechanical type pricing unit-- see the above sticky Ron Rich |
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Post by prime on Apr 23, 2022 22:50:01 GMT
Hi Ron while checking out the motor grommets and listening to a record, i decided to switch from stereo to mono, to my surprise the noise is only in stereo, in mono it is perfectly quite...any thoughts on this? pete
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Post by Ron Rich on Apr 23, 2022 22:58:20 GMT
Hi Pete, Itz a ROCKOLA !
Me thinks, that maybe the capich-q-lator,needs re-capich-q-lating ?--or is that re-con-nor-dur-ing ? (in other words--I annagotz no clue !)  Ron Rich |
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Post by prime on Apr 23, 2022 23:36:08 GMT
Well this will be a challenge ..I think i will remove amp and look at what's connected to the stereo/mono switch. Maybe a bad resistor. pete
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Post by Ron Rich on Apr 23, 2022 23:39:05 GMT
Hi Pete,
I doubt a resistor is the cause--however, didja clean the switch ?? Ron Rich
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Post by jukenorman on Apr 24, 2022 13:09:49 GMT
Can you feed the signal into one channel at a time? If so, is the noise there on each channel? Something a bit weird going on though?
Norman.
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Post by prime on Apr 24, 2022 17:45:10 GMT
I can disconnect the wire going to one of the pre amps, i could try the balance knob and set it to one side, Im not sure how else i can eliminate a channel. Yes Ron the first thing i did was clean the switches, i also tried to minimize treble and bass to see if the sound would go away. Also i checked the feed going to the left and right channel of the cart , found very good contact and good ground all around. From what i can see mono and stereo each use the two preamps, the only difference is the stereo setting allows the feed to travel from left to right.
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Post by Ron Rich on Apr 24, 2022 18:09:52 GMT
Pete,
Can you swap the feeds ? If so, do it and see if there is any change-- ?? Ron Rich
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Post by prime on Apr 25, 2022 0:14:35 GMT
I can swap the feeds tomorrow but i have new info, it seems the relay on the tone board has either bad contact or the board has an issue, if I touch it the sound cuts out . Im going to reheat all solder joints and see if that resolves the issue, if not i may try another relay. pete
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Post by jukenorman on Apr 25, 2022 8:17:34 GMT
These Rock-Ola amps are very prone to poor solder joints, that's been mentioned a few times before.
Norman.
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Post by prime on Apr 25, 2022 11:58:24 GMT
Hi guys do too the cutting out while touching the relay, as mentioned i re flowed each connection(not sure about this term) after reinstalling i reconnected and played a record, unfortunately the sound level was so high it tripped the overload, i lowered the sound volume and waited a few minutes, restarted a record and have stronger and clearer sound, i was able to isolate each channel but the problem is on each one. I did notice something that may be an issue maybe even the problem. If i use the balance knob i cannot turn off left or right channel, it affects them some what. I feel this may be a faulty part. What are your thought on this.. . pete
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Ron Rich