Universal Replacement for Speaker Protection Relay

[pa_200]

My family uses several Pioneer (SX-727, 737, 750, 828) and Yamaha Receivers (CR-600, -800) and nearly every Model has a different speaker protection relay.

So I got the idea, why not exchange the original one with a universal relay if they need replacement. These are all general purpose relays, so I would order two types, depending on the original relay, either with 12 vdc and 24 vdc coil voltage and at least 5A or 8A. 6 Pin (max 8 pins) should work as well, these type has got a bigger contact surface.

I had once seen a solution with a solid socket and a plug in relay was used, unfortunately I cannot find this page right now.

My question to you, what do you think about that plan. Has anyone done this before and if so, what type of relay and socket did you use?
The main aim will be, to minimize the oxidation on the contacts inside the relay, as long as there is no sound deterioration.

What would you recommend? Maybe a sealed relay?

 

[merlynski]

The biggest issue with Protection relays is the DC break current, once an arc starts (even at low voltages) the hot plasma continues to conduct current (and dissipate the max power the source can produce) until the voltage drops, or the arc path length increases enough that it cools down and quits. The contacts, under normal conditions, close after power on, usually before the music starts, so there is little risk of damage then, because no significant current flows. Also, Look at the datasheet, closed (undamaged) contacts usually have resistance in milliohms or less. Basic Ohm's Law: low resistance = low power dissipation = little or no contact damaging heat. I like the socket idea, but I have seen others here, with more experience than I, say it introduces another failure point. Under NORMAL operating conditions the relay should never open under power. The relays purpose is to protect the Speakers and (maybe) Output transistors, which are usually more expensive than a relay. The point of all this is that the relay is sacrificed rather than the speakers. If you are repeatedly replacing relays you are probably abusing your amp: get a more powerful amp that can handle the listening levels you desire.
Small current signal (sealed) relays are designed for a different purpose. Once again, maybe TMI, .

 

[pa_200]

Actually my listening level is very low, otherwise it’s calling for trouble with my wife. I never can us the full power level without annoying the neighborhood.

My SX-828 has most likely a relay issue. A few minutes after power on, the sound is fading between the channels like a stereo station out of tune, but I have it as well with phono selected. To solve it I just have to turn up the volume for a few seconds, then the fading stabilizes on both channels and stays at the normal stereo level even if I reduce the volume again to a very low level.
One other vintage owner told me, that this issue is probably caused by oxidized relay contacts.

 

[merlynski]

Actually my listening level is very low, otherwise it’s calling for trouble with my wife. I never can us the full power level without annoying the neighborhood.

My SX-828 has most likely a relay issue. A few minutes after power on, the sound is fading between the channels like a stereo station out of tune, but I have it as well with phono selected. To solve it I just have to turn up the volume for a few seconds, then the fading stabilizes on both channels and stays at the normal stereo level even if I reduce the volume again to a very low level.
On other vintage owner told me, that this issue is probably caused by oxidized relay contacts.

I agree with your other vintage owner, replace the relay (or burnish the contacts for a temporary fix). I have the same 'Volume Acceptance Factor' with my wife when she wants to get some sleep. My main system is in the basement, so I don't have problems with the neighbors. Now the system in my shop will 'entertain' the neighbors.

 

[dly66]

The few times I have seen relay problems are much like control pots and switches, it is oxidation of the contact surfaces over time. The oxidation can often depend on the history of the unit. Some of mine sound great even at very low volume nothing has been done with the relay in a 45 yr old unit.

Some I have had issues with. Sherwood that looked like it had been stored in an attic, garage, or the like for a very long time the contacts were so bad what got through was barely audible at max volume. If you have a fine touch, if the trigger coil is not open, can de-solder them, pop the clear case off, and burnish the contacts with fine sandpaper or the like, then put the case back on and reinstall. Rubs off the oxidation. Cheap fix that often works, and good for old relays modern ones don't exactly fit. Just don't want to bend the contact strips so be gentle. In the case of that Sherwood 45-50 years later the same relay with the same model number was still available, though stocking was limited at Mouser or Digikey. Old Brumfield and Potter, was part of AMF then, now its Tyco. Many times you can get a modern relay that fits where the old one did. Omron still around, might still find some people selling a stock of old Fijitsu.

I had that kind of issue with a Yamaha amp (CA-610II), listening at low volume the left channel would keep dropping in and out, I noticed it seemed a certain volume level was the on and off point. Turn it up a bit and no dropping out. Read about relay resistance so I took out and burnished the relay contacts after that no issues at low volume any more. Has old Fijitsu. I first tried to get an Omron that looked close in pin layout and dimensions, tried to bend the tabs a little to fit board holes but one broke off so I just burnished the contacts on the old one with find sandpaper and put it back in. As long as it works will probably leave it in there.

 

[pa_200]

@dly66, have done this trick on my CR-600 and worked perfect.
But I just wanted to see and read, if there are some other smart ideas around here at AK to that subject.

 

[dly66]

I flushed it good with some contact cleaner over a catch tray before I put it back together and reinstalled. Don't want any fine metallic debris causing trouble over time.