Sansui QRX 9001 question

[Quadmanfinally]

First let me start off and say Hi!!! I am new to Quad's I did have one in '75 that my dad gave me as a Christmas present. And from what I remember it sounded great.
So now fast forward 36 years and I have my second one. It is a lot better then my first, though this one probably cost 20 times more. So no real comparison.
Well my question,
I have this QRX 9001 that when I play in SQ, QS, Surround and Hall some SQ records and some songs on FM stereo sound distorted,muddy. Especially from the rear speakers, but if I switch to CD-4 it gets louder and clearer.

Could this be my Decoder board?

Is the CD-4 decoder board separate?

Does this sound like I have to do a QRX 9001 up grades and The Holy Grail alignment?
All and any help needed and will be appreciated. I want to really hear how Quad is supposed to sound like.

Richard

 

[JR Hearne]

Hi Richard, and welcome to QQ. All of the decoder boards and all of the matrix and the CD-4 switches are connected to the 2-sided circuit board sometimes call the Quad Board. This is were i think your troubles began. This is the board in my opinion gives theses receivers the most trouble. The 9001 has it's own separate CD-4 board located under the 9001. But it runs most of it connections through the 2-sided circuit board especially for the 2 channels you would be using for stereo if you are planning to play records for SQ or QS decoding. There are a lot of users on this board who know more about the 9001 than i do and hopefully they will give you more information about it. You can also search the board for more information about this and what has to be done to solve your problems. I hope this helps. Jay

 

[Quadmanfinally]

Hi Jay and thanks. I was wondering if that infamous decoder board problem could be related. I have read and read about these boards and now you have clarified that the CD-4 runs through it. Now if I was going to do the upgrades I know what resistors to use, but what caps would you guys recommend and for my speakers.(I restore Pre War radios as a hobby and they are not finicky on what caps you use.) I want to replace the ones on my CS-63DX crossover. They are out of tolerance yet sound good and clear up front when on two ch., but I know they can sound better! Also does anyone have the location of the signal path caps that are the lucky receivers of the poly bypass caps? Thanks again,

Richard

 

[Gimme 4]

I have this QRX 9001 that when I play in SQ, QS, Surround and Hall some SQ records and some songs on FM stereo sound distorted,muddy. Especially from the rear speakers, but if I switch to CD-4 it gets louder and clearer.

Could this be my Decoder board?

You say "some". Not too unusual for a matrix type decoder to put existing source distortion in the back channels. They will put the difference in the L and R audio channels into the back channels, so if there's distortion, it will likely wind up in the back channels. Switching to CD-4 with no CD-4 input signal puts the same L and R in the front and back channels, 4 speaker stereo, no matrixing going on.

 

[Quadmanfinally]

Thanks Gimme4, I now know why it gets loader and clearer when switched to CD-4. I can play two or three songs off one album and they sound distorted and then one or two songs can play on the same album and they sound better not great, but clearer. Especially the Columbia QX 31403 An Introduction To The World of SQ Quadraphonic Sound. Now that blew me away. Must of caught the receiver in a good mood. It was simply amazing. Yet I tried it again for the family to hear(they think I am nuts for spending all this time and money on this set up for Quad sound. Yet they haven't heard what true Quad sounds like, then they will understand) and it sounded nasty. I want to get it running

I notice last night it is getting more distorted and I am loosing bass. I turn the bass up and it sounds awful. It is more of a rumble then pounding. I tried switching around my speakers and they all sounded a like. Just a little subtle differences, but close enough to figure it is the receiver.
Also FM, some stations seem to sound as if in 4 ch. fills the room while others seem flat. Do they still broadcast in 4 ch. matrix (if that is the terminology. Still learning)?

Richard

 

[Gimme 4]

Being as this is a 33 year old or so QRX-9001 and they do have the well known problem with feed-thrus on the boards, and the usual electrolytic capacitors that fail with age, I wouldn't be surprised if there are problems like you describe. I remember back in the '80s a friend's 9001 developed the feed-thru problem, when the receiver was less than 5 years old.

 

[Quadmanfinally]

Well a recap and up grades are, I guess in order. What caps do you guys recommend? Also for speakers, I might as well recap them. They are as old as the receiver. I can do that it is the calibration part afterwards that has me nervous. I know the voltage is vary important and right now it is at 25.04v. So after changing and soldering the feed thru will this change much? And the 4 pots need tweeking. That is why I preyed it would be different and work with out all that, but it looks like I am going to learn the calibration. Maybe it is not as hard as it sounds.