• Check out the Annual AK Secret Santa exchange Program, signup before November 23rd in the AK Charities & Christmas forum!

My first QS-500 project

matjo

matjo

Member
This week I started on a really beaten-up Sansui QS-500. I bought it without the wood case, and covered in dust. Since I had no idea in what "electrical" state it was, I hooked it up on my Variac and Dim Bulb Current Limiter. And YES, it was still working, sound came out the speakers I connected. So, I decided to do a full recap of capacitors and transistors.

It took me 2 nights of research which transistors are the right replacements; there are a few used that I've never seen before (for example: the 2SC959-2SA606 pair). Fortunately Mouser could deliver 99% of my needs. And they delivered quick! Within 4 days to The Netherlands.

The QS-500 has 3 prints that are easy removable (like the 555a I've been working on already many times).

I'm not finished yet; some capacitors need to be replaced on the backside of the unit, but I am so excited about this project, I wanted to share the results so far.

A big thank you for Audiokarma and the posts by Overundr1 and Leestereo (who else) for their contributions; I took a lot of info from these posts.IMG_1012.jpeg
 
Register to hide this ad
After receiving the needed parts; I started working on the easy prints; the F-1388 (Synthesizer); the F-1357 (oscillator) and the F1180 (driver)

The F-1388 before:
IMG_0955.jpeg IMG_0983.jpeg
and after:
IMG_0987.jpeg IMG_0986.jpeg
I've replaced the 1uF's with film types; the XA495BL transistors with ZTX694B's and 2SC1000's with KSC1845's.
 
The driver F-1180 was a bit more work; I've also placed the suggested Baxandall diode mod as recommended by LeeStereo.
I've decided to let the 2SC959-2SA606 pair in place; although the oxidation is severe; the 2SC281 that is connected to the 2SC959 with a copper plate has a metal cover; I was not sure what the effect would be if I would replace this transistor with a SC1815 for example; perhaps someone can give me a good suggestion?

The 2SC458LG has been replaced by KSC1845's; the 2SC627's were replaced by MJE1532G

I also had difficulties finding the right multi-turns. Either the pins did not align with the holes on the board, or the size was incorrect or the adjustment-screw was located at the wrong position. Anybody with a good suggestion is welcome!
IMG_0988.jpeg IMG_0989.jpeg IMG_0990.jpeg IMG_0991.jpeg IMG_0992.jpeg IMG_0993.jpeg
 
KeithD said:
I have a QR-6500, which uses the F-1180C driver board, so not sure if it is equivalent. The trimmers I used for replacements on the two driver boards are:

View attachment 2896031
Click to expand...

Thank you KeithD for your input! Much appreciated! I was also looking at the same trimmers; I thought by looking at the way they are shaped that it would not fit on the board. But if you managed to do it; I will not hesitate to order some.
 
I detailed my refurb of the QR-6500 in this thread. Description of what I did on the driver board with pictures are in posts 19 and 20 of that thread. Enjoy!
 
Well done. The new case looks especially nice, properly designed and built. I am curious though at the lack of venting in the top. these have a rear channel power amp, and the factory cases had slots routed in them to allow heat to escape.
 
Sansuiman said:
Well done. The new case looks especially nice, properly designed and built. I am curious though at the lack of venting in the top. these have a rear channel power amp, and the factory cases had slots routed in them to allow heat to escape.
Click to expand...
Thank you for the compliment! I must say, with building the case I had help of colleagues on board of the ship I work; the veneer I did myself. Still work in progress; I still have to make the ventilation; looking into the best way to do it without ruining the case (lack of woodworking equipment is a major problem in my case).
 
Now all ya gotta do is figure out how to set the balance on the thing ... luck wit dat, eh! I actually had to RTFM to figure that out.

Nice unit tho ... pre- vario matrix, but I always liked the synth on that better than the newer versions for non-encoded stuff.

** BONUS - My version of "where's Waldo" ... find the QS500! <G>

qs500-system-july20.jpg


You want "different" ... currently driving the front channels in holographic matrix using the Carver C4000. Ain't blowed up yet!

PS - just noticed your location. Please to send me a wheel of Leyden ... BEST ... cheese ... ever!!!
 
Last edited:
sKiZo said:
Now all ya gotta do is figure out how to set the balance on the thing ... luck wit dat, eh! I actually had to RTFM to figure that out.

Nice unit tho ... pre- vario matrix, but I always liked the synth on that better than the newer versions for non-encoded stuff.

** BONUS - My version of "where's Waldo" ... find the QS500! <G>

qs500-system-july20.jpg


You want "different" ... currently driving the front channels in holographic matrix using the Carver C4000. Ain't blowed up yet!

PS - just noticed your location. Please to send me a wheel of Leyden ... BEST ... cheese ... ever!!!
Click to expand...

You are so right about the Leiden Cheese! It is delicious! I've also read your posts regarding the QS-100 and learned a lot.
I have the NTE129MCP matched PNP-NPN replacement on stock but still confused what exactly to replace; the schematics mention that the SC959 and SA606 is considered a pair; but the locations on the board are NOT the ones connected with a piece of copper (that would be the TR803/TR804 and the TR808/TR809). So I am confused.......
 
and this is the result so far. Audiokarma member ARGOU showed in his QS-100 post that he also managed to replace the MODULES 905/907. Sounds interesting! I will give this a try too....
When I will be back from my next term on board (mid July), I will start cleaning the amp and creating a proper ventilation in the wood case.
IMG_1011.jpeg
 
You must log in or register to reply here.
Back
Top Bottom