• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

QRX-7001 Demodulator board W. T. actual F?

tabpat

tabpat

Member
I am working on my Sansui QRX-7001. One of the issues that its had for longer than I've owned it (around 20 years) is the CD-4 demodulator has never worked. The phono stage is OK, but it's never properly demodulated CD-4 albums. I can't remember if the light comes on or not, but it's been a dud. Anyway, I opened it up and quickly discovered that someone has been all through this thing. The capacitors are not original and they are of no-name quality. The soldering was horrific. But, there is an addition on the back of a transistor ( that coincides with where TR603 is marked on the other side) with a capacitor and three resistors - one of which has what looks to be a diode strapped across it. On the component side, there is a transistor that has two legs going through and the third leg is soldered onto a resistor (R610). There is no reference to this transistor being there in the schematic. I can't imagine it coming from the factory like this...but I also can't imagine the numb-nuts that did the capacitor replacement being smart enough to attempt a new circuit design. Anyone got a photo of theirs or any ideas???
20170323_220212584_i_OS.jpg

bodge.jpg
 
Register to hide this ad
Looks like your board is a different version than mine. The traces are laid out differently, but seem to have all the same components. That appears to require yours to have C-606 on the underside. Plus mine has TR-04 where yours has it labeled TR-03. Yours (apparently) has TR-04 on the underside. I don't have a clear readable schematic. I wish I did because this 7001 I have had been butchered up too.
 
Please post the serial number for the database. Click on the link in my signature block.

- Pete
 
I'd have to get it back out but I'll try to get it. Oddly enough, the demodulator started working once it was all put back together and I gave up on it. "Working" is a loose term, however. It's terrible and slips in and out of CD-4 mode at the drop of a pin. It partly be a shielding issue as that's the only thing that changed - i.e. the metal cover...
 
Do you have a good clear schematic? If you do would it be possible for me to get a copy of it? The scan I have is not readable. I would really appreciate it.
 
You must log in or register to reply here.
Back
Top Bottom