Marantz 250M relay replacement help.

[gogofast]

I'm in the process of recapping 250M. Was able to troubleshoot one channel out and loud hum. Now, all it needs is a recap and possibly a new relay.

I've read every thread in AK and other forums regarding 250/250M relay mod using the MY2. None of the links and videos are still alive.

Anyone with detailed information regarding this relay replacement? Whether modding the relay itself or the circuit board?

Thanks in advance.

 

[wlhd1610]

I have been carefully modifying the Omron MY2-02 relays successfully for years now.
I first saw it on Chrismarantz's Faultlineaudio site which is no longer active.
I just did one yesterday for a client's 240 amp.
It's delicate work but beats some of the High School Science Fair jobs I've seen on eBay where they silicone it on sideways and add a bunch of wires or some Mickey Mouse outboard circuit board.

I'll attach a few pics


Here's the relay after modifying.
You have to reverse the coil wires and the movable armature wires.

I carefully unsolder the white wires and move them out of the way temporarily.

The older relays in the Faultline Audio tutorial had flexible wires connecting the coil wires to the pins making it much easier but Omron changed to a solid coil to pin connection about 4 or 5 years ago so now you have to carefully cut the metal strap out between the coil wire stud and the pin.
Once this is done I solder a insulated jumper wire from the coil wire stud over to the middle pin which in the 1200/240/250/250M relay circuit board is the coil feed.

Then I solder the white armature wire to the back pin and repeat on the opposite side of the relay.

Put the cover back on and you have a brand new unobtainable relay!

To make it fit the board properly you have to slightly skew the pin holes so the smaller footprint relay will fit the existing holes.

The only difficult part is taking your time and being very careful not to touch anything else with your soldering iron while working in the close confines of the relay.

The finished look is well worth it!

Bob

 

[gogofast]

Wow, thanks for posting the procedure.
I'm not really familiar with the relay internals. I believe the below is the MY2-02 pin out. What pins am I swapping internally?

 

[wlhd1610]

9&13
12&14

The coil feeds are pins 9 & 12 in the Marantz 1200/240/250 and 250M which use the Shrak(sp?) relay.

Pins 1 & 4 are not used and just get in the way so I snip them off.

Bob

 

[gogofast]

9&13
12&14

The coil feeds are pins 9 & 12 in the Marantz 1200/240/250 and 250M which use the Shrak(sp?) relay.

Pins 1 & 4 are not used and just get in the way so I snip them off.

Bob

Ah, I get it now.
This will help me and others looking to do the same in the future.
Thanks again!

 

[MBuras]

Thanks so much to Bob @wlhd1610 for detailing this relay modification. I'm in process of rebuilding a 1200 and although the current relay is serviceable I wanted to challenge myself with soldering some small bits. It went quicker than I expected and I'm happy with the result. Glad I always save bits of scrap wire for times just like this.

 

[catrafter]

I have been carefully modifying the Omron MY2-02 relays successfully for years now.
I first saw it on Chrismarantz's Faultlineaudio site which is no longer active.
I just did one yesterday for a client's 240 amp.
It's delicate work but beats some of the High School Science Fair jobs I've seen on eBay where they silicone it on sideways and add a bunch of wires or some Mickey Mouse outboard circuit board.

SNIP!

Bob

Thanks for documenting this, I was afraid it was lost when Chrismarantz's site went away.

Tom

 

[Ed Torres]

Thank you all for the detail information on the relay replacement. I followed the instructions and my 250 worked flawlessly for about a week and then the same leg of the replacement relay burnt. Any suggestions and what to look next, obviously something is burning one leg of the relay , however when i look at the schematic, both legs are switched by the same transistors , so why is only one burning?

 

[ChrisMarantz]

It's good to see that the Relay Modification lives on - Chris

 

[catrafter]

Thank you all for the detail information on the relay replacement. I followed the instructions and my 250 worked flawlessly for about a week and then the same leg of the replacement relay burnt. Any suggestions and what to look next, obviously something is burning one leg of the relay , however when i look at the schematic, both legs are switched by the same transistors , so why is only one burning?

I suspect that one amp module has a problem. It could have high DC offset and/or be oscillating. If the relay tries to open or close, the large current fries the contacts.

Tom

 

[Ed Torres]

Left amp is burning the relay blades contact, I adjusted the DC offset as close to 0 mV (more like 30 mV) on that channel and it worked for a day and burnt the relay again. How do i check for oscillation? or any ideas or what to look for next? Thanks.

 

[catrafter]

To test for oscillations, an o'scope or AC voltmeter with sufficient bandwidth would work.
The O'scope would let you 'see' the problem.

I don't know if the 250M is as temperamental as the 250, @wlhd1610 would know.

Tom

 

[wlhd1610]

I don't know if the 250M is as temperamental as the 250, @wlhd1610 would know.

I have found that the 250M is no where near as tempermental as the early production 250 amps were.
There were 3 production changes to the 250 amp board.
The earliest 250's with the "block" type bias transistor were notorious for failure due to runaway bias issues and extra special attention has to be paid to the Technical Service Bulletin regarding transistor matching among other things.
Later 250 variations had the same style 220 bias trasistor as the 250M and were more stable.



Bob