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Old 18th June 2010, 10:03 PM   #1
rgo is offline rgo
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Default How to recover tuner memory

Have two Sony Hi-end tuners: St-s444 esII and ST-S550-ES that lose stored station memory when turned off. Does anyone know which specific capacitor's must be replaced in these models to restore stored memory?
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Old 18th June 2010, 10:47 PM   #2
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I suspect there is a lithium battery that needs replacement.
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Old 18th June 2010, 11:08 PM   #3
rgo is offline rgo
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There is a lithium battery in the s444 and I replaced it but that didn't cure the problem. I don't think the s550 has any battery at all.

Thanks for the reply..
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Old 18th June 2010, 11:53 PM   #4
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The site below does memory retention mods on a newer Sony and has links to others that do similar mods:

88108 MHz
Sony XDR-F1HD
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Old 19th June 2010, 07:35 AM   #5
rabbitz is offline rabbitz  Australia
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Default For ST-S550ES

There's a 0.1uF 5.5V super cap (also known as gold caps) used at C703 which can be found on the display / control PCB behind the front panel. I just replaced one with a 0.2uF 5.5V. Make sure of the correct polarity when installing.

They look like a squashed electrolytic..... like this:
SuperCap
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File Type: jpg s550es_backup.jpg (22.3 KB, 54 views)
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Last edited by rabbitz; 19th June 2010 at 07:38 AM.
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Old 19th June 2010, 09:36 AM   #6
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My STS-361 uses a supercap and still holds its memory for a month after >15years use.
Leakage has to be very low to last like that - your board must be clean with no conductive flux residue. If the charge goes very quickly, the ecap C701 in the above thumbnail is likely to have failed
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Old 19th June 2010, 10:37 AM   #7
Mooly is online now Mooly  United Kingdom
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Those "supercaps" have a habit of failing for sure.

Also... and be very very careful here, but I have had odd logic issues on equipment like this and the problem seems to be CMOS logic frozen in an invalid state causing strange behaviour. You can disconnect backup caps etc but it doesn't clear the fault. What does is first remove (disconnect) the backup caps and make 100% sure there is no stray voltage left anywhere and then press a piece of tinfoil over the PCB and short all the pins on all the IC's together. Leave for a while, then remove and power up.
Have fixed many faults that way over the years... there's no actual hardware fault... just an internal lockup within an IC.
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Old 22nd June 2010, 02:29 PM   #8
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The Philips I2C memory uses a normal cmos technology, with no wearout mechanism, unlike EEPROMs

I think that the (cheap) conventional electrolytic is more likely to fail the the supercap.
The supercap only stores power, the high esr and series resistors make them useless for supply decoupling. Faulty decoupling could cause logic lockups
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