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Old 13th Sep 2021, 12:59 am   #21
DMcMahon
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Default Re: Sony AV3670 Head motor starter capacitor

I have now seen the manual.

There is no mains frequency changeover switch, the changeover is done at the board that the dual capacitor fits into (C Board).

The wire connection at the 1.2uF goes back to function switch SW008 so does need to be left connected.

Page from the manual attached.

David
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Old 13th Sep 2021, 9:32 am   #22
Michael Maurice
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Default Re: Sony AV3670 Head motor starter capacitor

Quote:
Originally Posted by collisr View Post
oh and just to check , as there doesn't seem to be such a thing as a single 3.7uF start/run cap widely available, I am perfectly fine to wire my 2.5 and 1.2 caps (from post 4) together in parallel and solder the head drum motor across the combined replacement aren't I?
Actually no well not with the 1.2uF capacitor shown in the picture. That capacitor is not suitable as a motor run capacitor, not sure what would happen in the long run, but it isn't made to handle the sort of current you need.

I suggest you purchase a 3.6uF or 3.7uF capacitor
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Old 13th Sep 2021, 10:46 am   #23
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Default Re: Sony AV3670 Head motor starter capacitor

At Post 8 you measured 2.6uF at the dual capacitor terminals which should have been the paralleled combination (if measured at C Board with joining track not cut for 60Hz operation).

Have you measured (2.5 to C and 1.2 to C) on both capacitor sections since removing the dual capacitor ?

There of course is the possibility that the motor itself may have gone defective, less likely though.

David
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Old 13th Sep 2021, 11:05 am   #24
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Default Re: Sony AV3670 Head motor starter capacitor

Have you checked the 800mA fuse F007 at the FU Board, this feeds 100VAC from the power transformer to the main motor via the Shut off Tape in switch S007 & Stop switch S008 ?

David
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Old 14th Sep 2021, 4:09 pm   #25
collisr
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Default Re: Sony AV3670 Head motor starter capacitor

Hi all. Problem appears to be fixed now.

For all of you stating the UK 50Hz model needed a 3.6/3.7uF starter/run cap - you were correct.

So, the original Sony cap does appear to have failed. My confusion was how Sony "added in" the extra 1.2uF cap to the circuit. By assuming it was via the lead attached to the 1.2uF terminal it sent me down the wrong path.

Not clear - even on the attached pic here (of the board Sony provided in the original machine to connect the capacitor to the circuit) , there is a track joining the 2.5 and 1.2 terminals, thus creating a parallel circuit and the 3.7uF cap across the motor.

By joining the 2 replacement starter caps in parallel and connecting back up, the motor now starts to the correct speed everytime.

@Michael Maurice - I assume you are referring to my 1.2uF Fan Motor cap. This solution is working at the moment - and I can only see 3.5 or 4uF alternatives as a single cap. What is your concern as to what might happen?
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Old 14th Sep 2021, 4:26 pm   #26
DMcMahon
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Default Re: Sony AV3670 Head motor starter capacitor

Yes the board as shown in Post 21 attachment.

Do you have any data on your new 1.2uF fan motor capacitor ? I have no idea what your motor is like, i.e. is it fairly heavy duty ?

David
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Old 14th Sep 2021, 4:34 pm   #27
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Default Re: Sony AV3670 Head motor starter capacitor

If your fan cap has a voltage rating, make a note.

Then carefully measure the ac voltage across the caps when the motor is running.

If the latter is well below former, you should be fine.

John
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Old 14th Sep 2021, 4:39 pm   #28
collisr
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Default Re: Sony AV3670 Head motor starter capacitor

As requested,

The fan starter capacitor is rated at 450VAC.

The motor runs off 110VAC.

Do you think this capacitor (when combined with the 3.5uF starter cap from post 4) is indeed safe to use?

Many thanks all.
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Old 14th Sep 2021, 6:59 pm   #29
DMcMahon
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Default Re: Sony AV3670 Head motor starter capacitor

I would say yes.

The CBB61 are spec'd for continuous use as a motor run capacitor and are Polypropylene and the 450VAC rating is good (note the voltage across the motor split phase winding will be somewhat higher than the 110V supply (100V shown on schematic).

Some more inferior fan capacitors may not be that suitable.

I have used the CBB61 myself on tape recorder motors without issue.

David
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