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Anyone heard of STC 51SB24T Relays?
Anyone heard of STC 51SB24T Relays?
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Old 18th January 2008, 09:34 PM   #1
johnm is offline johnm  United Kingdom
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Default Anyone heard of STC 51SB24T Relays?

Hi - hopin someone out there might be able to help me.

I have a DPA PDM One - Series 2 DAc which I still love, and rate very highly even today.

Unfortunately the relay which clicks when a digital signal is detected is starting to become more and more unreliable i.e. sometimes there is a dirty white noise before the music starts.

I need to replace all three STC 51SB24T relays, but I haven't a clue what with, and cannot find any data sheets on these items.

Does anyone out there have any idea's of a high quality replacement?

Many thanks.

- John
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Old 18th January 2008, 10:14 PM   #2
JohnW is offline JohnW  Hong Kong
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Hi John,

Sorry to say, itís not going to be the relay at fault, the relay only Mutes the audio output - and cannot cause "White Noise".

White noise is indicative of corrupted digital data stream / clock recovery error.

Hard to say where I would recommend to start fault finding, however maybe the Tantalum capacitors around the input receiver chip (presuming a clock recover / PLL error).

Check the PSU supply voltages on the digital chips - you will need to find the data sheets - they should be 5V.

If youíre unlucky, it could be the SAA7350 failingÖ However its VERY common to see the UA9637 input receiver failing (from Static / Earth Leakage damage) - mind you I've only seen them fail completely (dead unit), however its easy to imagine ESD damage causing "temperamental" performance - due to excessive current draw - if it's hot to touch, a certain sign of a damaged device.

So, try the 9637, Itís the 8 Pin DIL devices "Surface mountedĒ to the PCB near the Coax input first. Check for 5V on the PSU pins (Pin1 +5V, Pin 4 Ground) - if Low (say less then 4.7V then the device is dragging down the PSU rails due to internal damage).

Good luck

Time is my worst enemy!
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Old 19th January 2008, 09:10 PM   #3
johnm is offline johnm  United Kingdom
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Thanks for your informative reply John

Upon further investigation I think it's because I'm using the PC as source, running a USB SPDIF output into the DPA.

I reinstalled windows from scratch yesterday as my PC had been slowing down and so far so good no glitches, so perhaps it wasn't the DAC to blame afterall. I'll keep an eye on it though

Thanks again for your help.

- John
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