Question on how to remove the cover from a Pioneer protection relay

dbayles

New Member
On my Pioneer SA-7500 II, I'm experiencing something that seems eerily similar to what's been described as protection relay "break through". There will be very low output out of one channel then when the volume is raised sufficiently high, the amplifier will suddenly begin to behave normally. I've cleaned the regular switches and potentiometers with Deoxit, and treated the potentiometers to some fader lube; however, the problem is still persisting, so my next thought was to clean the protection relay contacts. Can anyone provide some advice on how to remove the clear relay cover without breaking the cover? On my unit, there's not a lot of room to work in, which is making it hard to figure out how the cover is held in place. I'd also benefit from any advice you may have on safely cleaning the contacts. I've seen comments regarding the use of ultra fine emery paper or some cleaning paper with alcohol. Thanks for chiming in!
 
Don't bother trying to burnish the contacts. They'll just carbon up shortly afterwards and you'll have the same problem again as the plating has been burned off. REPLACE the relay.

Unmount the relay from the chassis with the 2 screws. Then with a couple of very thin narrow dental picks, work the upper case away from the bottom plate along the sides. There is a tab on each of the sides. Pull the side out enough to clear the tab, and repeat on the other side. Lift up and remove the upper case.
 
Thanks for the information Larry. I don't see any screws holding this relay onto the PC board. It looks like its only held in place by the eight solder connections used by the relay. I do see the tabs you mentioned and I think I can see how to pry the sides with my picks to release the cover. What would an acceptable replacement be (the OEM part is an ASR-023-A according to what's written on the relay cover.)
 
That's Pioneer's PN and tells you Jack about what you need for a replacement. But...the service manual foil pattern seems to indicate a MY4-style relay, and the schematic shows 34.5V at the top of the coil (with a dropping resistor in the emitter leg of the relay driver), so these indications seem to point to it being a 24V relay, which would mean an Omron MY4-02-DC24.

FYI, dirty switches can do the same thing as you describe.
 
To get the cover off, the relay needs to be desoldered from the board.

At that point replacement of the relay becomes almost a moot point.

BUT if you want to give it a shot, after the relay is off the board, a few "sliders" cut from a polyester pop bottle or an aluminum can (CAREFUL) can be slipped between the case and the body to allow the bump to clear the hole.

Then use mild abrasive to get a TEMPORARY fix. The damaged contacts WILL oxidize sooner, especially if the plated layer that was the contact material has been corroded, burned or abraded away.

This will hold you until a parts order is made and received.

BTW, to preserve contacts of good relays, go to zero signal before switching speakers or power.
turning down the volume control can be a pita, but throwing a tape monitor to an unused input accomplishes the same thing.
 
Last edited:
Mark's idea is awesome. I used to utility blades when I replaced mine. Again watch the sharp edges if you use the blades. I like the dental pick idea as well
 
Thanks for the information folks. As EchoWars noted, the part number isn't necessarily as informative as needed. For reference sake, the cover also has "Type MS4U" and "24 VDC". The Omron MY4-02-DC24 does look to be a correct replacement part (Mouser part No. 653-MY4-02DC24). I have to agree with markthefixer, if I need to take the unit out to clean or to replace, then there's little point in trying to clean it. As an update, to eliminate the switches and potentiometers from the list of candidate problems, I did a second round of cleaning the potentiometers and switches with Deoxit and then lubricated with fader lube. That seems to have improved things, so I'm going to monitor the relay's performance over time and if the problem persists, I'll replace the relay. Again, many thanks for your assistance.
 
I found this thread during the cleaning of my new to me SA-7500 II. I was having the exact same issue. I removed the cover, and deoxit seems to have fixed it for now at least. My unit was used in a garage, and had greasy dirt/dust liberally applied through the inside. Here are a few pics.

Last pic is the relay under discussion. I can post a picture of my crude relay cap remover if anyone wants.
 

Attachments

  • uploadfromtaptalk1430966153511.jpg
    uploadfromtaptalk1430966153511.jpg
    56 KB · Views: 64
  • uploadfromtaptalk1430966172216.jpg
    uploadfromtaptalk1430966172216.jpg
    47.2 KB · Views: 80
  • uploadfromtaptalk1430966190094.jpg
    uploadfromtaptalk1430966190094.jpg
    44.7 KB · Views: 108
Problem returned. I am going to replace the relay. Here is the digikey part number.

Z2634-ND
 
Never mind... It is better again. This is goofy. I guess I will hold off until it acts out again.
 
Back
Top Bottom