Sansui QRX 6001 recapping questions

[Reed]

I progressed further with the recapping of my near dead Sansui QRX 6001 tonight and made some interesting discoveries.

First it is obvious that at some point a drink was spilled into this unit. The residue is obvious on the bottom of the circuit board for the fuses. This isn't really a problem, just a note of interest.

Second, I want to replace all the dial illumination fuse type bulb with LEDs, but I don't know what sort of LEDs to get or how to mate them with a resistor to make them work or how to mount the LED in the fuse bulb socket.

Finally, I found that factory service manual schematic for the F-1267 equalizer board had several of the capacitors completely mislabeled. C601 and C602 were labelled as resistors on the PCB but DID have caps in them. Coincidentally, R601 and R602 (located right next to C602 and C602) were labelled as caps but had resistors in them. Also, caps 601, 602, and 609-612 also all had the polarity reversed on the schematic from the polarity printed on the PCB and how the caps were installed in the PCB. I installed the new caps identically to how the old caps were installed, but it just worries me that there is such a huge discrepancy between the factory schematic and the PCB.

Questions:

(1) What sport of cleaning should I do to clean up the spilled drink, if any?

(2) Anybody have a link to a tutorial on how to replace the lamps in a Sansui X-001 with LEDs?

(3) Should I be worried about the discrepancies between the schematic and the PCB?

Thanks for helping an electronics neophyte out.

 

[Doug G.]

I can't specifically answer #2.

For the spilled drink, I would use a damp cloth and see if that cleans it up. Most liquids humans drink are soluable in water.

Always go by how components are mounted in the boards (if they are original) rather than by any documentation. Errors are common in printed matter for any given product. The departments which produce such matter aren't necessarily knowledgeable in the actual electronical side of things whereas the production areas generally at least know how the thing is put together.

Doug

 

[Reed]

Thanks for the response. I found a tutorial on how to replace Marantz bulbs with LEDs ( CLICKME ) so I figure I can adapt that method to the Sansui bulbs.

I am almost done recapping. The place I ordered all my caps form shorted me a bunch, so I need to make a tirp to my local Radio Shack to get the rest and get new fuses and the supplies to replace the burnt out bulbs. Maybe I will just do regular fuse lamps on this one and save the LEDs or the next.

 

[Doug G.]

I guess the only way I would replace the original style lamps with LEDs is if I could get an identical appearance. It would bug me if the unit didn't look the same lit up as it originally did.

I know it's inconvenient having to replace burnt out bulbs (boy do I know that with my Heathkits!) but I still think they should look original. Of course, if original style bulbs are unavailable, that's a different story but I would still try to get it as close to original as possible.

And I will NOT use the word "original" again in this post!

Doug

 

[Reed]

Both my units are really too far gone to worry about making them original. I do appreciate the desire to keep things original, but these two 6001s are past their prime and I am more concerned with just getting them functional. The unit I am recapping now has damage to the wood top, it was dropped so one of the sides has a big dent, and only about 1/3 of the functions work. My second 6001 is the one I am going to spend the time and effort on to really clean up nice.

I don't mind replacing the burnt out bulbs. They are actually easy to get to on the 6001. I just liked that the LEDs were brighter and I could change the color. However, I will save that project for a later day.

And the Pioneer qx949A will be a whole 'nother ball of wax!

 

[tracker-x]

Finally, I found that factory service manual schematic for the F-1267 equalizer board had several of the capacitors completely mislabeled. C601 and C602 were labelled as resistors on the PCB but DID have caps in them. Coincidentally, R601 and R602 (located right next to C602 and C602) were labelled as caps but had resistors in them. Also, caps 601, 602, and 609-612 also all had the polarity reversed on the schematic from the polarity printed on the PCB and how the caps were installed in the PCB. I installed the new caps identically to how the old caps were installed, but it just worries me that there is such a huge discrepancy between the factory schematic and the PCB.

Questions:

(3) Should I be worried about the discrepancies between the schematic and the PCB?

Thanks for helping an electronics neophyte out.

I've been reading up on the history of these units. Polarity being reversed on electrolytic (polarized) caps is a problem. I had an Akai M8 that smelled like burning transformer and one channel playing distorted. Upon opening it up, found a power supply cap installed backwards in polarity. Replaced it with a new one installed properly and it got a LOT better, but still the PST smelled like it was burning a bit, and sound down just a bit in volume. I replaced the PST and presto that brought it up to about 90% of the other channel. Then I finally changed the output choke and it was 100%.

anyway a reversed cap can degrade and damage the entire final output side of the channel, and the transformers. it DOES happen. Japanese assembly in the 1960-70's was not 100% foolproof. The set will still play with polarity reversed in some cases, and get through QC and then give some owner later a lot of headaches.

I've also found small components bent over on crowded SS PC boards that the leads touched each other and were shorting.

having said all this, the CAPS themselves in the Sansui 6001 are very high quality and hold their specs for 40 years no problem. Recapping is something one would should do to a 1960's or older set, not a 1970's and later set of this quality.

what does go bad on these sets are the final transistors, and driver transistors on the preamp boards. another issue with the Sansui driver boards, I've found a lot of lifted and damaged printed circuit board runs on them. if they had the small driver transistors changed the heat of soldering usually starts lifting the printed circuit board, eventually it breaks off at the solder connections and starts to open up. a circuit just hanging on by a few strands tends to heat up and blow out components at that intersection.

resistors do cook off the driver boards, due to a preamp driver transistor or final being shorted out.