Sansui QRX5500 receiver

Hi Lenny,

I have a schematic on fiche and while it's not the easiest thing to follow, we could probably figure out what's wrong. Do you have good signal coming into the driver board? Also, it looks like each channel has two 3.5A supply fuses. Let me know what you've found out so far.

--
David Farber
David Farber's Service Center
L.A., CA

I have a service manual with a schematic too but its a nightmare to try to follow. None of the sub assemblies are connected together and the points are so out of focus and illegible that its impossible to trace or put the blocks together. Also because its 4 channel SQ, I'm not exqctly sure what everything does. Maybe you have a better schematic than do perhaps. A conventional schematic where everything is connected together so that you could at least follow a signal path. That would help so much. The wiring goes through switches, tone controls over and under boards, etc. There are four audio paths of different colors. I have determined that the problem is in the yellow wiring but that is as far as I've gotten. Following it is another story though. Lenny.

follow,

coming

supply

I took a closer look at the schematic. You are certainly correct. If you have to trace signal from board to board, it's a nightmare.

It might be easier to trace back from the speaker output using a tone into the 2 channel tape monitor input. Is the signal distorted without a load? Is there a signal to the input of the driver board? My schematic indicates the signal comes into the F-1482 driver board at C01, C02, C03, C04 depending on which channel you're looking at. Those capacitors are 3.3uF at 50V. How does the signal look at the volume control? Is the distorted channel in the front or the rear?

--
David Farber
David Farber's Service Center
L.A., CA

First of all thanks for even getting involved in this headache. I really do appreciate it. I'm looking at my poor excuse for a schematic now. I believe that the driver and outputs are OK. because there is output from that channel when different modes are selected. The problem is that when you go to four channel synthesized the second two channels (left and right rear ) are supposed to be synthesized from the two fronts. In two channel with one set of speakers connected to the front or main it works fine. But in four channel syn. mode there is low output from channel C. the yellow sheilded cables. I'm not sure from this schematic what is next in line in the signal path. And the volume control is impossible to get at. I could locate ins and outs on these boards but I don't know how they're interconnected. This is truly your basic rats nest. I tried all the inputs including the tuner. They all have this problem. So it is common to everything but that doesn't help much. Lenny.

weak.

run

this

technical

into

load? Is

the

depending on

does

front

Hi Lenny,

I have a few more questions about what's working so far. Do the rear channels operate ok when you're not using synthesized mode? Do the rear channels even operate in normal mode?

My microfiche schematic is in black and white so if you mention colors, it won't mean anything to me.

Here's my interpretation of the signal path when the surround function switch is in the "QS SYNTHESIZER HALL" mode and the source is the tape 2-ch monitor:

From the 2-ch tape monitor inputs, it goes through the surround function switch, S702, and then into the F2048 board, pin 19 and pin 14. One of course is left, the other is right. The output of this board is at the collectors of Q12 and Q16. That would be a good test point to check signal.

I cannot seem to find the connection between the preamp output and the input to the driver board which is labeled, "9P6," and "9P8" It appears that this goes to a 9 pin "remote control terminal" and terminates there. The F-1484 board seems to be the likely candidate for the preamp output. If you can figure this part out, I think we can piece the signal together from beginning to end.

--
David Farber
David Farber's Service Center
L.A., CA

I'm going to try to follow your signal analysis and hopefully get some more infor mation on this set. I'll try to put some more time into it next week, after I do the paying jobs of course...I'll let you know. Thanks, Lenny.

I have a later model, the 9001, and the main problem is the mechanical switches. Many of them are multi pole push switches and I have no idea how to clean the conatcts. Otherwise the electronics seem to be OK. This was the last of the line, with IC's for all the Quad mode. Ken

text -

Hi all I'm new here and hope this makes it to all of you, Lenny, David and Ken. Just seen everybody's talk on the QRX5500. I think I have the same problem, in short when the function switch is in any of the QS or phase matrix positions the output levels drop way down. I found something awhile back that said if the voltage reg CCA F-1483 voltage is not set in its range of 25 V +/- .25V ? then the QS CCA boards will not function properly. Mine will not adj more then 18.5 volts and I have not been able to trace the cause down. One way I ck'd the regular 4ch outs (w/o QS as part of the issue) 2ch + 2ch is to connect an external source to the aux-1 inputs (4 jacks). Either in parallel or one at a time. Set the function switch to Discrete and look at each Spkr output. Each one should have the same Lvl with all balances at middle. If those are fine then this isolates the problem to either F-1483 Volt Reg, F-1488 connection interface, or F-2047/2048 QS Syn/ Vario CCA.

I am now at a stand still. No parts for V regulator. And no info for QS CCA. Like all of you the diagrams suck. I am trying to find how CCA are connected. The boards have terminal # on the diagrams but no info on where they go (I don't want to trace each wire in ea harness.

"Seems to be" is the operative term. These units are notorious for bad solder connections on the QS logic board.

quoted text -

Regarding the 25V output, do you have 44 volts at the emitter of TR04?

12volts at the emitter of TR05? Did you test the ESR of the caps in this circuit? What is the voltage drop across R17, 330 ohms? The schematic for this part of the circuit is fairly good even on my microfiche.

--
David Farber
David Farber's Service Center
L.A., CA

i have that reciever also and my problem is my left channel are distorted i clean the knob and dont work...so i connect one speaker to the A speaker and one speaker to B speaker channel and i only use the two channel and move the know to AB channel....i am not a stereo tech...but i work on electronic so i know how to read and use meters...any advice ?? left channel are distorted like a bad reception...even i play cd...

mechanical

idea

This

for

Repairing a receiver with distortion is not a beginner's project. On a set this old and complex, it will be a challenge even for an experienced stereo tech.

--
David Farber
David Farber's Service Center
L.A., CA