Technics 1520 motor help

[Tim]

Damaged coils in the motor could cause the symptoms.  And I'm assuming you are correct when you say the flywheel spins freely (is not binding or impeded).

The RS-1500 series often has bad solder joints on the circuit board plugs.  Re-solder the capstan motor connector (the section of the plug that is soldered to the circuit board)

I have a RS1500 in my shop for repair.  When I have time, I will determine the order of the motor washers.  That may not be your defect, however.  Try the re-solder job first.

[sk8ter]

ok will do thank you

[sk8ter]

ok reflowed all the joints on the circuit board...no luck...

[ironbut]

Regarding the wiring of the multipin connector;
There were slight differences from machine to machine, even within the production run of RS1500 models.
I'm not sure if you have a RS1520 manual or not but there is definitely some differences between 1500 and 1520.
The bottom line is;
If the machine was working fine with the connector wired the way it is, don't change it. It may be for model changes in IC's etc..

It's probably time to get out a multimeter and make sure the correct voltages are arriving at the motor. Could be a broken conductor within the wire that you can't see.
Sometimes, if you're lucky, you can fool around with the wires where there is a bend or other obvious strain points and get it to make enough contact so the motor will turn for a second.
Just be sure and have the machine set up so it will turn when contact is re established (use some tape to hold down one of the tensioners).

[sk8ter]

ok more updates...thanks guys I really appreciate  all your time and help...

ok so i did start to check test points....no voltage at TP910 its suppose to be about 10 volts or so..i get .8volts ..something i dragging down the voltage I check with an DVM the transistors involved no shorts or anything ...suggestions...my thoughts are I will have to isolate the various transistors(desolder) one end of the feeding resistors...and see if they still bring down the voltage...

if you have some  easy way ..please help

Lawrence

I still need to know the correct orientation of the washers in the motor 

[ironbut]

You mentioned that you'd replaced some caps.
Test the power supply voltages and work your way toward the "control board". It may be a bad solder joint or even a defective cap (it happens). Also, some of the caps are polarized and it could be that one is in backwards.
As you check your voltage paths, pull each of the multipin connectors, clean the pins and reinsert them. Those connectors can get a little iffy and while it might not solve your problem, it might head off any in the future.
While you're at it, "work" the speed and timer start buttons. They are a common source of problems too.

You should always test the machine as a whole after replacing a few caps. I know it's a pain! But unless you're used to doing a lot of troubleshooting (like Tim is), it will minimize the number of things you need to check.

[Tim]

You said you resoldered capstan drive board connector H.  Also resolder the other connectors (I, J,L).

I'm assuming you have proper DC power going to that board (connector I)?   With ground on pin 1, you should have 5V, 21V and 15V on pins 4,5,6.  Also check DC on D906 (one end is ground).

Are any caps on that board leaking?  Often it's a green fuzz.  Very common defect.

Clean all switches on that board.

There are 8 coils in the motor.  Check that all have continuity.  pins 1/8, 12/9, 12/10, etc.

[sk8ter]

ok sorry scratch my last post i forgot that the capstan motor plug has  a jumper from
pin 1 to pin 2....this is what bring in the 21volt off of pin 5 on the power supply connector....

but I did check and resolderd all the connectors..this is not the issue...I also checked and rechecked all the capacitors...there was an error.... that when the unit was built they installed the wrong cap! c924 and c923 should be 33uf caps in series ...my board had a .22uf in c924 spot... so i replaced it with the correct 33uf cap...

it still may be still in the motor ....any luck or could you post the pinout so i can ring out the motor windings..my schematic is not correct or something..

Thank you

Lawrence

[ironbut]

As I mentioned in a previous post, the info in the manuals isn't correct for all versions/production runs of the 1500 (which I'm more familiar with).
If the machine was running correctly with the .22uF cap and now it isn't with the 33uF cap, I think that switching the cap back is worth a try.
I haven't had a chance to look at the schematic so this is just a guess.

[Tim]

You need to put that .22 cap back.  You said the motor worked perfectly prior to you taking it apart. Correct?  Also, the board typically has the correct values (rather than the schemo).

The schemo has 12 pins for connector H.  Connector H has 15 pins, so ignore pins 1-3.   Pin 1 of the schemo starts at pin 4 on the connector.  Check all coils now.  Should range between 7.5 ohm and 25 ohm.

You did not tell me connector "I" DC power supply voltages.  Are they correct?

Are there any leaking caps?

You said the motor worked after you replaced the capacitors.  Correct?  It only stopped working after you took it apart. Correct?

[sk8ter]

Tim yes all the voltages on connector I are correct the 15volt measure 14v but the rest is fine...

no the motor did not work after the recap of the main control,capston and reel  motor and tension control boards were redone but i cannont fine issues with them..

I did the main power supply first and everything worked fine..until i took the motor apart and or recap those boards...

I hope i answered and gave you enough to go on...

[sk8ter]

ok no connection on pin1 and 8 brown and grey wires ....ok so this looks like the problem....suggestions please

[Tim]

At first, you said the motor stopped working after you took it apart and re-assembled it.

Are you now saying the motor stopped working after you replaced the caps and took the motor apart?  Big difference, BTW.  You need to tell us the whole story.

[Tim]

Pins 1 and 8 should be 29 ohms..    It's 3 coils in series.  They are called the primary position detection coils.

There are 6 small coils on the inner ring of the motor.  3 of those are the coils in question.  Likely a wire going to those coils was damaged/broken. If the coil wires look intact, start at pin 1 and keep testing with ohm meter until you find the break.

[sk8ter]

ya Tim I found the problem and attempted to fix/solder them tiny wires...but they are just not long enough....so the question is where can i find a pair of the detection coils?
they look like they are just glued can you help

Thanks for everything..