Oberheim keyboard

496dart · 02-03-2007, 12:22 AM

A friend gave me a Matrix-6 keyboard to try and fix. Doesnt power up . Before the transformer is a small board . It has a fuse(good) , 3 caps , and an inductor?
the caps test `ok on my multimeter , but is there a basic test for an inductor? This one has 4 connections. Anyway, i dont have any voltage coming out of this board.

The trans is a Bando EP-55 . The primary has 4 taps so i dont know which 2 to apply 120v -

David Schwab · 02-03-2007, 04:41 AM

I don't know the answer, but here's a site with the schematics and service manual.

http://www.tcapp.com/pub/synths/ober.../matrix6/docs/

I own a Matrix-6.

Enzo · 02-03-2007, 05:54 AM

Your inductor is two coils around the same core. Each leg of the mains runs through it on into the circuit. It is just a filter. The two halves have contonuity or not.

496dart · 02-03-2007, 10:48 PM

looks like i have continuity at the coils. I still dont have any voltage coming out of that first board. I assume one of the caps is bad? even though my meter reads ok .

Also ran 120v into the trans . O volts coming out of it. This is with the trans completely out of the keyboard.

Enzo · 02-06-2007, 04:48 AM

Well THAT is your problem, not caps.

496dart · 02-06-2007, 07:15 AM

Enzo the board is Before the trans. Shouldnt it have 120v coming out of it ,TO the trans?

Enzo · 02-06-2007, 01:10 PM

Well yes, but if the tranny is bad...

Flip the little board over and follow the traces, either with 120 applied or wuth an ohm meter and the board cold. if a little noise cap is open, it won't stop the 120v, and if one is shorted, it will either make the chassis hot or it will blow the wall breaker. Any caps on the incoming mains power board should not stop the 120 from getting to teh PT.

496dart · 02-06-2007, 10:29 PM

ok, the board is putting out 120v, i guess i didnt check it right the first time..

now to try and find a trans for this thing .

02-03-2007, 12:22 AM	#1
496dart Senior Member Join Date: Jun 2006 Location: iowa Posts: 122	Oberheim keyboard A friend gave me a Matrix-6 keyboard to try and fix. Doesnt power up . Before the transformer is a small board . It has a fuse(good) , 3 caps , and an inductor? the caps test `ok on my multimeter , but is there a basic test for an inductor? This one has 4 connections. Anyway, i dont have any voltage coming out of this board. The trans is a Bando EP-55 . The primary has 4 taps so i dont know which 2 to apply 120v -

02-03-2007, 04:41 AM	#2
David Schwab Pickup Maker Join Date: May 2006 Location: Montclair, NJ Posts: 4,974	I don't know the answer, but here's a site with the schematics and service manual. http://www.tcapp.com/pub/synths/ober.../matrix6/docs/ I own a Matrix-6. __________________ www.sgd-lutherie.com www.myspace.com/sgdlutherie www.myspace.com/davidschwab

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02-03-2007, 05:54 AM	#3
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 9,266	Your inductor is two coils around the same core. Each leg of the mains runs through it on into the circuit. It is just a filter. The two halves have contonuity or not.

02-03-2007, 10:48 PM	#4
496dart Senior Member Join Date: Jun 2006 Location: iowa Posts: 122	looks like i have continuity at the coils. I still dont have any voltage coming out of that first board. I assume one of the caps is bad? even though my meter reads ok . Also ran 120v into the trans . O volts coming out of it. This is with the trans completely out of the keyboard.

02-06-2007, 04:48 AM	#5
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 9,266	Well THAT is your problem, not caps.

02-06-2007, 07:15 AM	#6
496dart Senior Member Join Date: Jun 2006 Location: iowa Posts: 122	Enzo the board is Before the trans. Shouldnt it have 120v coming out of it ,TO the trans?

02-06-2007, 01:10 PM	#7
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 9,266	Well yes, but if the tranny is bad... Flip the little board over and follow the traces, either with 120 applied or wuth an ohm meter and the board cold. if a little noise cap is open, it won't stop the 120v, and if one is shorted, it will either make the chassis hot or it will blow the wall breaker. Any caps on the incoming mains power board should not stop the 120 from getting to teh PT.

02-06-2007, 10:29 PM	#8
496dart Senior Member Join Date: Jun 2006 Location: iowa Posts: 122	ok, the board is putting out 120v, i guess i didnt check it right the first time.. now to try and find a trans for this thing .

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