Problem with Sony tuner memory

Lourens · 17th July 2005, 11:12 AM

When I disconnect my old Sony ST-S770ES tuner from the mains for longer than a few minutes, all stored information has gone.
I guess some cap has to be replaced, but I am not sure which one or where to look. On the ‘control board’, near of the printed indication ‘back up’?

I don't have a service manual, so any help is greatly appreciated!

Thanks
Lourens

Miniwatt · 17th July 2005, 07:03 PM

I GUESS the back-up battery is dead, but I know next to nothing about tuners.

Elso Kwak · 17th July 2005, 07:32 PM

Hi, It is ususally the large capacity backup electrolytic and/or the diode in the supply line to it.

Lourens · 18th July 2005, 10:05 AM

Thank you for your replies.

Miniwatt,
there is no (detachable) back-up battery like I know them from computer motherboards.

Elso,
could you be a bit more specific, please: how large is 'large', for instance? There are several 330-470uF 'normal' ones located around the psu, one 'huge' (in my perception

63V/2200uF (labeled 'Negative Black') and 2x 'big' 63V/1000uF.
On the control board (near the microprocessor, with RAM i presume?) 2x 'small' 50V Elna's (3,3 and 10uF), plus a much bigger Elna 5,5V/0,1uF (hxw=6x12 mm).

BTW, i tried in vain to detect some standby voltage supplying the suspected back-up electrolytic in off-position, assuming this voltage should be present because as long as the tuner is connected to the mains, he never forgets anything.

Wish i had a digital camera at hand, or a schematic... still hoping this helps to get some more advise

groeten
Lourens

karma · 18th July 2005, 11:14 AM

if it has a display in the front. it would be a small flat round blue or green cap on the back of the pcb or under the display. this cap would be not to far from the display chip .

DigitalJunkie · 18th July 2005, 01:16 PM

"plus a much bigger Elna 5,5V/0,1uF (hxw=6x12 mm)."

Are you sure that larger cap isn't 5.5V 0.1F(arad)?
That sounds kinda like a memory back-up cap to me.

Lourens · 18th July 2005, 01:40 PM

You're right... it's 0,1 Farad! Sorry...
It is located near the display and uP, on the 'Control' pcb.
It definitely looks very different from all the other lytics, but optically in good condition.
Any hints to make sure it's broken? Or should I just replace it?

Elso Kwak · 18th July 2005, 06:50 PM

Hi Lourens, Just replace the cap. Yes it is in Farads not µF. Also replace the diode in the supply line feeding the cap. The diode is for preventing the cap becoming empty into the supply when power is off. Usually the diode gets leaky by the large inrush current when power is applied. Replace by an 1N4004 type regardlkess what Japanese type is used. I replaced many of these caps and diodes as a repair technician.
If you have trouble finding a cap like you need www.conrad.nl has them.

Lourens · 18th July 2005, 07:45 PM

OK, i'll do that. Thanks Elso, and all others for your kind advise!

groeten
Lourens

17th July 2005, 11:12 AM	#1
Lourens diyAudio Member Join Date: Dec 2003 Location: Utrecht NL	Problem with Sony tuner memory When I disconnect my old Sony ST-S770ES tuner from the mains for longer than a few minutes, all stored information has gone. I guess some cap has to be replaced, but I am not sure which one or where to look. On the ‘control board’, near of the printed indication ‘back up’? I don't have a service manual, so any help is greatly appreciated! Thanks Lourens

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17th July 2005, 07:03 PM	#2
Miniwatt diyAudio Member Join Date: Nov 2004 Location: Den Haag	I GUESS the back-up battery is dead, but I know next to nothing about tuners.

17th July 2005, 07:32 PM	#3
Elso Kwak Banned Join Date: Dec 2001 Location: Zamboanga, City of Flowers, Mindanao	Hi, It is ususally the large capacity backup electrolytic and/or the diode in the supply line to it.

18th July 2005, 10:05 AM	#4
Lourens diyAudio Member Join Date: Dec 2003 Location: Utrecht NL	Thank you for your replies. Miniwatt, there is no (detachable) back-up battery like I know them from computer motherboards. Elso, could you be a bit more specific, please: how large is 'large', for instance? There are several 330-470uF 'normal' ones located around the psu, one 'huge' (in my perception 63V/2200uF (labeled 'Negative Black') and 2x 'big' 63V/1000uF. On the control board (near the microprocessor, with RAM i presume?) 2x 'small' 50V Elna's (3,3 and 10uF), plus a much bigger Elna 5,5V/0,1uF (hxw=6x12 mm). BTW, i tried in vain to detect some standby voltage supplying the suspected back-up electrolytic in off-position, assuming this voltage should be present because as long as the tuner is connected to the mains, he never forgets anything. Wish i had a digital camera at hand, or a schematic... still hoping this helps to get some more advise groeten Lourens

18th July 2005, 11:14 AM	#5
karma diyAudio Member Join Date: Feb 2003 Location: hamilton,ontario	if it has a display in the front. it would be a small flat round blue or green cap on the back of the pcb or under the display. this cap would be not to far from the display chip .

18th July 2005, 01:16 PM	#6
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 3	"plus a much bigger Elna 5,5V/0,1uF (hxw=6x12 mm)." Are you sure that larger cap isn't 5.5V 0.1F(arad)? That sounds kinda like a memory back-up cap to me.

18th July 2005, 01:40 PM	#7
Lourens diyAudio Member Join Date: Dec 2003 Location: Utrecht NL	You're right... it's 0,1 Farad! Sorry... It is located near the display and uP, on the 'Control' pcb. It definitely looks very different from all the other lytics, but optically in good condition. Any hints to make sure it's broken? Or should I just replace it?

18th July 2005, 06:50 PM	#8
Elso Kwak Banned Join Date: Dec 2001 Location: Zamboanga, City of Flowers, Mindanao	Hi Lourens, Just replace the cap. Yes it is in Farads not µF. Also replace the diode in the supply line feeding the cap. The diode is for preventing the cap becoming empty into the supply when power is off. Usually the diode gets leaky by the large inrush current when power is applied. Replace by an 1N4004 type regardlkess what Japanese type is used. I replaced many of these caps and diodes as a repair technician. If you have trouble finding a cap like you need www.conrad.nl has them.

18th July 2005, 07:45 PM	#9
Lourens diyAudio Member Join Date: Dec 2003 Location: Utrecht NL	OK, i'll do that. Thanks Elso, and all others for your kind advise! groeten Lourens

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