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Problem with AU-919 MC phono input

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bebopdeluxe

Well-Known Member
Hello everyone - ghamilton suggested I repost this request here (duh - I should have known that);
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Hello everyone. After a LONG layoff, I am back listening to my rig - which means I am back to AK!

A question - I have an Echo Wars rebuilt (looks like he is not around these days) Sansui AU-919, with which I have always used a separate phono stage. As part of shaking the cobwebs out of the system, I discovered that my Wright Sound WPP-200 is not powering up (I am getting replacement tubes for the power stage - fingers crossed), so in the meantime I have finally plugged into the AU-919's phono stage. For now, I am using a Sanyo TP-1020 turntable (my backup, as I also am having issues with my Music Hall MMF-7 turntable's cueing level - aarrgghh!), with a new Denon DL-110 HOMC cartridge.

So the issue is this - there are two settings on the Phono 1 input for the 919 - for MM and MC. When I put the selector on Phono 1 MC, I only get music out of one channel, but when I use the Phono 1 MM, I hear it out of both speakers. Strange.

My question - for those who know the AU-919 - is this: is the MC setting on this amp simply a step-up transformer of the audio goodness of the amp's phono stage? To be honest, on the MM setting, things sound great...so good that I may actually reconsider whether I will get another outboard phono stage if the Wright is DOA after replacing the tubes. My guess is to get a outboard phono stage that will sound better than the 919, it might cost several hundred dollars (like, a Wright Sound level pre) - yes?

Thanks for the help!
 
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There is a ribbon cable with 6 wires connected to the MM board that is suspect. You will have to remove the covers to see this flat ribbon wire. Let us know when you have it exposed.
 
Perhaps I was not clear - the issue is the TT is plugged into Phono 1 - which has the option of either MM or MC. The input rotary switch at the top left of the unit goes (clockwise from bottom), "aux, tuner, Phono 1 MM, Phono 1 MC, Phono 2 MM"

When it is set to Phono 1 MM, it is fine, but when I turn it to Phono 1 MC, I only have one channel.
 
Each channel's MC head amp is comprised of a number of FETs in parallel, complete with their own simple but independent power supply. Do you have a scope and signal generator and a sensitive VOM? If you don't, best leave this to someone else, otherwise it is a straightforward matter of checking power supplies and tracing signals. The board you want to check for input to (possible switch or wire problem) and output from (on-board problem) is F-2833 and it carries both channels. The power supply for the MC head amp is on the board with the MM equalizer amp in its own corner of the board - that board is F2835.
 
I think this stuff (taking the lid off) is beyond my pay grade, and I am not sure I want to farm this out to just anybody. I remember how much of a PITA is was for Glenn (EW) to do the work back in the day.

To be honest, the MM output is pretty decent. Fortunately the DL110 is a pretty high-output MC, so other than turning it up a little more, it works just fine. I was just wondering if there is special pixie dust related to the MC aspect of the phono stage, because if all fixing that will do is increase the output of the signal, I can live with this.
 
If you don't want to take the top off then you will have to live with it unless you know someone that you trust to look into it.
 
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It could be dirty contacts on the selector switch. Still something that would need to be opened up to clean. I think the DL-110 does better with MM anyways.
 
lbcgav said:
It could be dirty contacts on the selector switch. Still something that would need to be opened up to clean. I think the DL-110 does better with MM anyways.
Click to expand...

I read that as well, and to be fair, it sounds really good through the MM input. I will probably just leave it alone for now.

Thanks, guys.
 
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