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Technics 1210 turntable internal fuse keeps blowing

Crick

Jun 12, 2012
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Hi all! Looking a bit of help with a 1210 repair i'm pretty stumped with. The 250mA internal fuse keeps blowing and i can't find what's causing it and i've went through 5 fuses so far testing it.

So far i've checked Q1, !2 and Q3 (removed from board and tested with DMM). Also removed D1 and tested it. All tested OK.

Also checked C1 (removed from board and tried powering up with a new fuse and it still blew). Done the same with C3 and C108 with another blown fuse.

Another thing i checked was the lamp. I disconnected the lamp connector from the main PCB and powered it up and it blew another fuse.

I was mainly taking this info for testing from a thread on diyaudio.com. Can anyone guide me on this one?

Edit - Also, just to add. The adhesive between D1 and the two caps beside it (is that C5 and C6? Haven't got it infront of me at the minute) seemed to have came unstuck. Thinking back now, i suppose i should've checked those caps first…but still, any info will be appreciated!

Cheers!
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Some photos would be good.

My first suspect would be the power supply, or an excessive load on the power supply. But it would be really good to see what we're talking about.
 

KrisBlueNZ

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Nov 28, 2011
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So you have a service manual and/or schematic? How about uploading them and posting a link so we all know what we're talking about?
 

Crick

Jun 12, 2012
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Sorry folks! Can't believe i forgot to post up the schematic! Check out page 4 and 5 of the pdf i've uploaded for the schematic. You can see the power suppy circuit at the top of both pages. Then the image shows the top of the PCB. I stole this from the internets but its the same circuit. The two fuses on the power supply circuit are outlined in red, my problem one is the one on the right. D1 can be seen just to the right of these with two caps right beside it on the left.
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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That looks like F1, the 1.2A fuse in the 30V secondary of the transformer (and shown on the top of page 18 of the PDF). Does that sound right?

Can you take an image of the power supply board from the top and bottom, from directly above the board and large enough so we can read everything that's on the board.

Also please post a photo of a blown fuse (I want to see how it has blown)
 

davenn

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Sep 5, 2009
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your pic of the circuit board shows 2 fuses ,.... the PDF shows only one fuse. a 1.2A fuse
there's obviously differences between your unit and what the service manual covers

is that 250mA fuse on your board on the mains side of the transformer ?
 

Crick

Jun 12, 2012
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Yeah, i think there's two different types of turntable. One's an international version and the other's US or Japanese or something. That must be what this service manual's for but I can't find one for mine unfortunately. This one i have must be the international one. It has a voltage selector switch (110/240V). Its definitely the 250mA fuse that's dead. (The one I took out was 250mA anyway).

I'll add more info to this in a minute but I've attached images of the fuse and the underside of the board. Can't really make out the fuse too well unfortunately. I'll stick a better pic of the power supply circuit in a minute.
 

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Crick

Jun 12, 2012
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Here's the topside of the PCB and yes, the fuse looks to be on the mains side of the transformer. You can see it's on the same tracks as the AC in part of the board if you look at the image of the underside of it
 

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davenn

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OK remove the 1.2 Amp fuse and see if the 250mA fuse still blows
if so it is inferring that the transformer is faulty
 

Crick

Jun 12, 2012
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Took out the 1.2A fuse and the 250mA one still blows. So if this suggests the transformer is faulty, what would be the best way to confirm this
 

Crick

Jun 12, 2012
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davenn

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Took out the 1.2A fuse and the 250mA one still blows. So if this suggests the transformer is faulty, what would be the best way to confirm this

the transformer probably has a shorted turn(s) in the primary winding

I also disconnected the supply to the main pcb and tried powering it up and it blew the fuse again. Problem has to lie in the power supply pcb then.

you have already proved this fact by the previous test ;)
 

Crick

Jun 12, 2012
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Yeah, I realised that after I posted lol. Was hoping nobody picked up on that!

Thanks for your help!
 
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