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Old 28th April 2011, 12:43 PM   #1
ivog is offline ivog  Latvia
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Default Tuner doesn't remember saved stations

Hi, I recently bought tuner in ebay and faced with problem. This is a quite good digital tuner - Onkyo T-4511 and works perfectly ... but when I switch off the tuner and switch on after 15 minutes memory is completly erased and all porgrammed stations are gone...
Since I'm not a newbee in electronics I tried to solve the problem bu myselves but I didn't find any backup battery inside or capacitor, well there are couple of small electrolytic caps on display board but they are not responsible for memory backup.
Could you help me please with ideas - how to find and solve the problem!
Many thanks!
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Old 28th April 2011, 12:54 PM   #2
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Most of these types of tuner used a supercap - a 1F or so capacitor which looks very like any other electrolytic cap. Try looking for one that is only 5V or so.
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Old 28th April 2011, 01:28 PM   #3
Mooly is offline Mooly  United Kingdom
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They look like this,
PANASONIC|EECF5R5U105|CAPACITOR, 1F, 5.5V | CPC
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Old 28th April 2011, 02:07 PM   #4
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Mooly has shown you the modern equivalent. Some older supercaps were slightly taller, I've got a couple of NOS 1F 5.5V caps which are about 30mm tall. They were prone to failing.

Just check that the previous owner hasn't removed a leaking Ni-Cad battery. You may just spot where it ought to be located.

Older TVs used to use Ni-Cad batterys for just this purpose before supercaps became commonplace.
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Old 28th April 2011, 07:29 PM   #5
ivog is offline ivog  Latvia
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Thank you! But I can't find any cap like that... here is shots of tuner boards
FOTKI.LV - Lietot?ji / I / ivog / Onkyo
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Old 28th April 2011, 09:49 PM   #6
miklos is offline miklos  Canada
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The pictures are to small, but check the blue cap to the right of the display.
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Old 28th April 2011, 09:53 PM   #7
miklos is offline miklos  Canada
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I don't have the schematic of the T4511, but the T4711 has the super capacitor on the display board. On that tuner it is called C703 and has a value of 0.1F.
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Old 28th April 2011, 10:21 PM   #8
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I would take a close look at the capacitor on the tuner board next to diodes D751 & D753. Diodes are often used to charge the super cap with out letting it discharge the same way.

C753 is next to diode D752, but it is not the shape I am used to seeing, but look closely at it also. The other C next to it also could be one.

On the main board next to IC101 are two similar capacitors and a diode so check them. One other likely is next to IC201.

The IC's at the back of the main board are FM demodulator and stereo decoder so it is unlikely a super cap would be there.
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