QRX 8001 - blown chip or bad connections?

[asyd7]

I just picked up a Sansui QRX8001. It did not seem to be decoding correctly, due to the fact that when switched to VARIOous modes, I would have to compensate heavily with the balance on both front and rear. I took it in to the local high-end/vintage repair shop and they believe that it needs a new chip.
Questions:

How do I figure out if it is really the chip?

Where/When/How much can I get a chip?

Are there suitable replacements?(from other receivers)?

Any other info would be great.(QR*500 series vs QRX)
Thanx for all of your help.

 

[QuadBob]

Welcome aboard Asyd7!

I could answer your questions........but I'm long overdue for a policy that I've wanted to institute. Why should I spend the time and effort to try and help you if you can't even take the time to fill out your profile here? Your public profile is the best way the rest of us have to "meet" you and understand a little about what your experience level is.

So, please take a few minutes and fill out your profile! Then, I'll be happy
to spend a few minutes looking it over.......and answering your questions!:sun
You'll find we're really just a great bunch of guys trying to keep our old gear going and performing at its best! I'm really not trying to give you a hard time, its just everytime someone joins and asks a question........the first thing I do is look at their profile to see "who they are"...........when its blank, I have a hard time getting my mind in gear to write anything!

 

[QuadBob]

Ok,

Now that I've got that out of my system in my last post.....I'll go ahead and try to help you out (presuming that you will fill out your profile!), just to show I'm not really a jerk!

I just picked up a Sansui QRX8001. It did not seem to be decoding correctly, due to the fact that when switched to VARIOous modes, I would have to compensate heavily with the balance on both front and rear. I took it in to the local high-end/vintage repair shop and they believe that it needs a new chip.

A) It's not a "chip". I've probably got more experience with these receivers
than anyone except the original factory. In over 10 years of dealing with
them I've found exactly ONCE that a decoder IC was bad.....and in that
instance I'm pretty sure it was blown by the owner "messing" with it, rather
than it going bad on its own!

B) The fact that your "local high-end/vintage repair shop" THINKS thats
what the problem is.......reflects poorly on them, both as to their experience
level with the QRX series receivers, and diagnosing the fairly complicated
circuitry found in them!

Of course, they probably just used that as a means of bailing out on the
repair......and pointing you towards something new and cool. In which case,
they could almost be forgiven for at least not sucking you into a massive
repair that they didn't want to do.......and you wouldn't want to pay for!

Questions:

How do I figure out if it is really the chip?

Where/When/How much can I get a chip?

Are there suitable replacements?(from other receivers)?

You really can't without some intense troubleshooting through the circuits.
However if you spend a little time to research previous posts here, you'd see that most likely the source of your problem is the "cold solder pass through joints" on the function select pcb. This IS NOT simple repair, gaining access to the joints and repairing them correctly is very time consuming and difficult.

The ICs are found in all the QRX-*001 series receivers...so you could buy another one. I'm about the only place I know of that "stocks" them, but I don't normally just sell parts as I use them for restorations. And, there's
an extremely high probability that there is nothing wrong with the chip anyway!

Any other info would be great.(QR*500 series vs QRX)
Thanx for all of your help.

You're comparing first generation Sansui decoding against second generation "vario-matrix" IC decoding. A major difference!! Again, do a search here through the back posts and you'll find lots of great info comparing various models and the development of Sansui Vario-matrix decoding!

ps; I'll bet you could have filled out your profile quicker than I could write this post!

 

[JonUrban]

"Easy on the newbie's, Bob!" :slap:

 

[QuadBob]

"Easy on the newbie's, Bob!" :slap:

Buuuuuuuurrrrrpppppp!

Excuse me............pet peeve stuck in my throat!:smack:

 

[Obbop]

And the crowd :wave goes wild

 

[ClarkNovak]

Hey Bob,

I've read various of your posts on fixing the pass-through joints and you mention "pinning" them during the restoration process. Do you mean that you actually put a pin through the joint and solder it in, attaching the components then to the pin's ends?

Color me curious.

Clark

 

[ss9001]

I just picked up a Sansui QRX8001. It did not seem to be decoding correctly, due to the fact that when switched to VARIOous modes, I would have to compensate heavily with the balance on both front and rear. I took it in to the local high-end/vintage repair shop and they believe that it needs a new chip.

asyd7 - Welcome to the forum!

QuadBob restored my QRX9001 last year. He's on target about the cold solder joints. I purchased my 9001 new in '78-79 and started having intermittent channel dropouts and channel level imbalances in the early '80's. By that time, quad was dead. I took it to the local authorized Sansui repair shop in Cincinnati in the mid to late 80's (can't remember when - getting older), they told me repairing it would be cost prohibitive and "chips" weren't available anymore. They encouraged me to go with a new Dolby Surround receiver. They also confirmed that cold solder joints were a problem and that mine looked like small hairline cracks in them. They replaced the relays on the 2-4 channel selection & relays on speaker outputs which helped with one of the problems I was having, but channel imbalances continued. I compensated by using the balance controls.

So fast forward to the 90's: by '93 or so, the 9001 would be "dead" with no sound output until it had warmed up. By '02, no sound at all. Luckily, I found a web page by QuadBob discussing restoring the QRX series. All the things he talked about accurately described mine's history. I finally had QB restore mine early '03 and we're back into quad! Chances are there is nothing wrong with the decoder circuitry. Bob will replace caps, repair and improve all the cold solder joints, remove the problematic 2X power stereo relays, install preamp outputs, calibrate voltages to factory specs and clean all the controls. His restoration is not cheap, but it's better than letting the repair shops "hack" at it. Ive talked to Bob extensively about the Sansui's and I'm convinced he's probably one of the few people left who really understand the guts of these receivers. I've seen digital pics he took of the circuit boards and Sansui's design was very complex for its day. This is exactly what the Cinci shop told me in the '80's: that the PCB's were complicated and a lot of labor is involved to dismantle the receiver and get to them.

Sansui had one of the best decoders in their VarioMatrix. What QS Synth can do to create quad from stereo is what appealed to me. It works really well. To my ears, the effect is not the same as using Dolby ProLogic on stereo. On certain recordings, the synth is as good as quad encoded.

Good luck!

 

[Quadzilla]

I am glad to see that there are so many people who are knowledgeable about the x001 line of receivers. It would be a shame for this fine equipment to die. I have a question for one of you. I have heard that the QRX-7001 is less prone to these issues as the 8001 or 9001 because it is a lot simpler design. Is this correct?

I am currently using a QRX-6500 in a small bedroom system with a Sony DVP-NS500V as it's only source. I like the 6500 for synthing 2-ch CDs, but I have been thinking about replacing it with a 7001 for the better Variomatrix. I am not concerned with all of the other functionality, and I don't need the extra power, so if the 7001 will require less TLC, do you guys think that this is a worthwhile upgrade?

Thanks to Cai, I have a QSD-2 in my main system that was expertly recapped and tweaked by his quad-guru buddy in Japan, so I know the benefits of the latest decoder design, but since the QRX-6500 works well, I am reluctant to get into a 7001 if it is going to be a hassle down the road.

Cheers, Mike.

 

[QuadBob]

Hey Bob,

I've read various of your posts on fixing the pass-through joints and you mention "pinning" them during the restoration process. Do you mean that you actually put a pin through the joint and solder it in, attaching the components then to the pin's ends?

Color me curious.

Clark

Basically Clark the process involves cleaning out the old solder from the joints, then scraping a small "landing" on the runs on either side of the pcb. You then insert the "pin" (actually a small piece of solid wire about 1/4" long, I use the leftover "legs" that are cut from the new caps installed) through the pass through joint and solder it directly to the run on each side. Then I seal the whole joint in solder just like the original (it ends up looking the same, only slightly larger) joints. This pretty much permanently solves the joint problem as what causes them to fail is the heating/cooling cycle inducing expansion/compression in the pcb itself. Over time.....the original solder joints crack and separate from the runs on either side of the pcb. (this is what SS9001 was talking about in his post).

Through the combination of using high-grade silver solder (which is softer than regular solder) and the "U" shaped pins soldered directly to the runs on either side, both the silver solder itself and the pins allow the board to flex minutely without degrading the conductivity of the joints. Thus.....they pretty much should last forever!

It is however just about the single biggest "pain in the a#@" in doing a restoration on an 8001/9001. As there are 54 joints in the function select pcb to be done, and you end up soldering each joint 3 times......one side, the other side, then fill. Besides the pin preparation and placement while you do it!

Later production 9001s received rivets passed through the joint to attempt to solve the problem. However, the rivets are less flexible than the pins, and the production solder still cracked.......only then it cracked around the rivets instead of within the joint itself.

More than you wanted to know?

 

[QuadBob]

QuadBob restored my QRX9001 last year. Luckily, I found a web page by QuadBob discussing restoring the QRX series. All the things he talked about accurately described mine's history. I finally had QB restore mine early '03 and we're back into quad! Chances are there is nothing wrong with the decoder circuitry. Bob will replace caps, repair and improve all the cold solder joints, remove the problematic 2X power stereo relays, install preamp outputs, calibrate voltages to factory specs and clean all the controls. His restoration is not cheap, but it's better than letting the repair shops "hack" at it. Ive talked to Bob extensively about the Sansui's and I'm convinced he's probably one of the few people left who really understand the guts of these receivers. I've seen digital pics he took of the circuit boards and Sansui's design was very complex for its day. This is exactly what the Cinci shop told me in the '80's: that the PCB's were complicated and a lot of labor is involved to dismantle the receiver and get to them.

Thanks Steve! About the only thing you might add is how your 9001 stacks up against your Denon 5800 HT receiver.....does it hold its own for sound quality?

 

[QuadBob]

I am glad to see that there are so many people who are knowledgeable about the x001 line of receivers. It would be a shame for this fine equipment to die. I have a question for one of you. I have heard that the QRX-7001 is less prone to these issues as the 8001 or 9001 because it is a lot simpler design. Is this correct?

I am currently using a QRX-6500 in a small bedroom system with a Sony DVP-NS500V as it's only source. I like the 6500 for synthing 2-ch CDs, but I have been thinking about replacing it with a 7001 for the better Variomatrix. I am not concerned with all of the other functionality, and I don't need the extra power, so if the 7001 will require less TLC, do you guys think that this is a worthwhile upgrade?

Thanks to Cai, I have a QSD-2 in my main system that was expertly recapped and tweaked by his quad-guru buddy in Japan, so I know the benefits of the latest decoder design, but since the QRX-6500 works well, I am reluctant to get into a 7001 if it is going to be a hassle down the road.

Cheers, Mike.

A complete restoration on a QRX-7001 (or 6500) takes about half the amount of time that a 8001/9001 restoration takes. Thus, the cost to restore one is considerably less. The 7001 is built on an entirely different chassis (shared with the 6001), and though the decoder pcbs are the same.....their mounting and function select interface are completely different. There are no passthrough joints on a 7001/6001, and the total "cap" count is 198 vs. 243 in the 9001.

I am nevertheless seeing more and more of the "trusty, reliable" 7001s failing now.....simply due to their age. The same is true for the QRX-*500 series too, simpler designs........but age catches up with all of us. You already can compare the first generation (6500) decoding vs. the second generation (your QSD-2).....so you pretty much know the difference. Eventually, you'll either have to restore or replace the QRX-6500 anyway....without even taking into account the "sound/performace" quality of running an unrestored 25+ yr. old receiver. A testament to their design......that they're still running at all!