Sony Amp

[Digital Steve]

I have a Sony DE 875 Amplifier which is giving me some problems. When I turn the amp on, it emits a loud cracking sound through the speakers even if the volume control is turned down.

I did some research and it appears that this is a common problem with these amps. The suggested repair is to check for cold solder joints especially around the final outputs. I went ahead and re-soldered any cold solder joint I could see, however the problem still exists.

Once the receiver is on it works fine so that leads me to think that it could be a relay problem. Here is my question. There are 3 relays in this amp ( OSA-SS-212DM3). I ordered new relays online, however they sent me (OSA-SS-224DM3). When I contacted the seller they assured me that these relays would work fine.

The coil resistance on the factory relay is 270 ohms and the replacement is 1100 ohms. Does this matter?

https://www.te.com/usa-en/product-5-1419124-6.html?q=OSA-SS-212DM3&source=header#pdp-docs-features
https://www.te.com/usa-en/product-5-1419124-9.html?q=OSA-SS-224DM3&source=header#pdp-docs-features

I appreciate all help.

Steve

 

[Les Jones]

The voltage rating of the coils is different. The data seets do not directly give the coil voltages but from the coil power rating (540 mW) and the coil resistance. (270 ohms for the 212DM3 and 1100 ohms for the 224DM3) you can work out the coil voltages. For the 212DM3 V = Square root of 0.54 x 270 = square root of 145.8 = 12.07 volts. For the 224DM3 V = Square root of 0.54 x 1100 = square root of 594 = 24.37 volts. So it looks like the 12 and the 24 part of the part number is the coil voltage rating. The 22DM3 part will not work as it will not pull in with 12 volts across it's 24 volt coil.

Les.

 

[unclejed613]

is the problem in one channel, or more than one?

 

[tomizett]

Sounds unlikely to be relays. Have you tried tapping round with a plastic pen to see if you can make it worse or better? Could still be a bad solder joint, but they're always in the last place you look for them.

 

[Nigel Goodwin]

Presumably the relays are the speaker switching ones?, for speaker protection and 'anti-thump' - these can't cause crackling with the volume at minimum, as there's no signal. All they could cause is the audio to go ON and OFF, if the contacts were poor.

So I wouldn't be changing the relays anyway.

 

[Digital Steve]

is the problem in one channel, or more than one?

Both channels.

 

[Digital Steve]

Presumably the relays are the speaker switching ones?, for speaker protection and 'anti-thump' - these can't cause crackling with the volume at minimum, as there's no signal. All they could cause is the audio to go ON and OFF, if the contacts were poor.

So I wouldn't be changing the relays anyway.

Yes, they are the speaker protection relays.

 

[Nigel Goodwin]

Yes, they are the speaker protection relays.

Not the relays then, from your initial description.

 

[unclejed613]

is the model DE-875, or STR-DE875? the reason i'm asking is the STR-DE875 is a surround receiver with more than two channels, and the service manual for that one keeps coming up.
is the crackling simultaneous in both channels, or is it present in both channels but not identical timing of the pops and clicks?

 

[Digital Steve]

is the model DE-875, or STR-DE875? the reason i'm asking is the STR-DE875 is a surround receiver with more than two channels, and the service manual for that one keeps coming up.
is the crackling simultaneous in both channels, or is it present in both channels but not identical timing of the pops and clicks?

It is the STR-DE875. The crackling seems to be simultaneous in both channels, although it is hard to tell. It is very loud. Maybe I will find a cheap set of headphones and give that a try. This one is hard to diagnose because once the amp is on it works fine.