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Post by jukenorman on Jun 7, 2021 18:45:52 GMT
Hi Rick,
Ignore my previous post, I was getting myself a bit confused with where readings were taken! When the record is playing, yes you will get -33V at the wire from the micro switch going to the mute relay. When the gripper is active you should be getting zero volts there because the micro switch is switching ground - so the micro switch must be faulty!
Norman.
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Post by rockolarick on Jun 7, 2021 19:36:03 GMT
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Post by Ron Rich on Jun 7, 2021 20:02:33 GMT
Mez comfuzzed two ! When the gripper is running, is the relay energized, or relaxed  ? There are three spade lugs on a MicroSwitch-- Are all three being used on this one ? What does the schematic show ? Ron Rich |
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Post by jukenorman on Jun 7, 2021 20:07:47 GMT
You need a dual 741, the item you've linked is a single!
Norman
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Post by Ron Rich on Jun 7, 2021 20:10:56 GMT
On the "op-amp"" I would assume a 741 op-amp, to be a 741 op-amp-- do you have a data sheet-- is there any difference between a -1 and one without the -1 designation ? If they are,in fact, the same, or interchangeable, I would once again, assume that something else on that board is failing ?? Ron Rich
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Post by rockolarick on Jun 7, 2021 20:58:49 GMT
I attached the schematic of the process of the gripper placing the record back. The mute relay is energized when the gripper is moving. the only time it is not energized that I saw was when the music was playing. Reading the voltage/vdcs during this process, below is a chart postimg.cc/CBY7pVD7________________Black/Orng Orange/Grn Home_____________0_________0 Magazine moving____0_________-26 Gripper moving_____0__________-26 Record playing_____-31_________0 Gripper moving_____0__________+ reading moved all over Magazine moving____0_________-31 While gripper moving, If I connect red lead to Black/orange spade and black lead to another ground on the box, then that's where I get less than 6 vdcs. I did find it interesting that when the gripper was placing record back (static the loudest) I was getting a + reading on the orange wire. Seems like I should be getting 0 or neg on that wire. Trying to find out if the switch is bad as I have done 2 trials that proved that the switch works. I have taken the wires off and manually contacted them together at the right time and I have tried another switch. Same results as what it is doing now. |
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Post by jukenorman on Jun 7, 2021 21:11:22 GMT
Strictly speaking, I think a 741 is a single op amp - the dual 741 package carries the number 1458 (eg MC1458P or CA1458 depending on manuafacturer).
Norman.
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Post by rockolarick on Jun 7, 2021 21:37:10 GMT
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Post by Ron Rich on Jun 7, 2021 22:05:15 GMT
Remove the input wire(s) from the amp-- still get noise when gripper runs ? Ron Rich
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Post by rockolarick on Jun 7, 2021 22:52:10 GMT
I removed the 3 prong plug that leads to the cartridge from the amp and yes still get noise.
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Post by Ron Rich on Jun 8, 2021 2:38:27 GMT
OK-- check all grounds going around / to the motor, including those in/on plugs. Have you looked at the motor-- what is the condition of the brushes ? Ron Rich
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Post by jukenorman on Jun 8, 2021 8:17:32 GMT
Hi Rick, Yes that LM1458 should be fine.
Norman.
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Post by rockolarick on Jun 9, 2021 18:18:58 GMT
Thanks Ron and Norman. Ron, I checked all the grounds on this circuit and it all seems to be ok. Lastly, I took the gripper motor off and opened it up. See attached. There is a lot of debris, but as far as the brushes go, they seem to be ok? I didn't see any breaks or burn marks. Is there something else I should be looking at? Is there a way I can clean these? I tried checking the FAQ and didn't see anything about cleaning brushes. Can I clean the contacts in there to see if I can get a better connection to see if that gets rid of the noise out of the speakers? postimg.cc/LYZ04rQCThanks again |
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Post by Ron Rich on Jun 9, 2021 18:33:55 GMT
On this type motor, one should remove the brushes-- do not loose the springs ! Remove the armature, wash it with a safety solvent, and wash the motor housing, with that solvent too. Clean the armature "slits" with a toothpick, ONLY. File the brushes so that most of the "curve" is gone, before re-installing them-- Lubricate the bearings with 20 wt. oil-- grease as/if needed, in the gearbox. Do not "add grease" to the gearbox- if grease is needed, old grease must be totally, removed, then replaced ! Ron Rich
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Post by whammoed on Jun 9, 2021 18:50:24 GMT
Rick,
Is that a gear on the shaft of the motor? If so is it almost worn down to the nub? Not sure how that's supposed to look. |
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? There are three spade lugs on a MicroSwitch-- Are all three being used on this one ? What does the schematic show ? Ron Rich 
