Interesting QSD-1 just acquired

Sansuiman

I like big amps and I can not lie!
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Today, a QSD-1 I purchased at a good price showed up. It has some cosmetic issues (scratches, outer volume knob misisng) but what is most interesting is that it appears to be a very early unit, almost like an engineering sample. It has serial number 7407010. That's no typo, only 7 digits. I interpret that as unit 10 , July 1974 on line 7. If anyone has further thoughts on the odd serial number, please chime in here.

Now, where the differences are really evident is per the following list:

1. Absolutely no markings on back panel identifying it by make, model, or voltage input (the typical ID plate present on most Sansui gear). The back panel is screen printed with the markings for all the ins and outs, and shows the fuse rating at 1A 250V at 100V. Those are all the markings present. No UL or other certification stickers, though it has a standard two prong north American plug fitted from the factory.

2. The rear panel has two holes punched where the ID plate would be secured with screws or rivets. Nothing was ever attached there, black paint still present all the way through the holes to the inside surface. The serial number sticker is located here.

3. All internal circuit boards are single sided - including the backplate board - and lack green conformal coating on the foil side. No silk screening at all on either side of any board.

4. On the two front most boards, F-2462 and F-2466 (these markings are present as voids etched in the foil, not screen print) there are several mods added with caps and resistors hand assembled to the solder side of the boards in point to point fashion.

5. Front panel legends are all screen printed in black, including the QS insignia. On my later QSD-1, the front panel is engraved (black fill on all legends) and the QS insignia is a separate silver on matte black badge that attaches to the aluminum panel. Also, the "on" and "off" legends above and below the power toggle are not present, just the word "POWER".

6. The power transformer is marked with the Sansui logo, T-8496 and "43 7" on it top surface. I suspect this is configured for 100V. Interestingly, it has two primary input leads. Orange, soldered to one pole of the power toggle switch, and red which is capped with a rubber boot. Suspect the red may be a 120V in, but not sure. Could be a 220V primary as well.

Anyway, anybody run across one like this before? There aren't many QSD-1 around, but this is the first instance I've seen of this variant. Will try to get some pictures up here in a bit.
 
Pictures please! A serial number doesn't follow the standard Sansui format can indicate the unit was built by a subcontractor. I've added your serial number to the next database update.

- Pete
 
Ok, several pictures here. Shown are the front panel (screen printed legends, no engraving) and note also the screws that hold the panel in place are stainless hex head. Later units had round knurled stainless screws, not hex head type.

Next is top down view, note the backplane board has no screen print legends on the component side. Next is the transformer and power supply board (also with no legends present).

Then a front on view of the pluggable circuit boards, also lacking any screen printed legends. Followed by the rear panel and serial number sticker. The sticker is of the standard type for Sansui, done with the same sort of number stamp but having only 7 digits rather than 9. Note the holes on either end of the sticker where the ID plate would normally be attached. None was ever present as the holes are untapped. There is nothing to indicate the input voltage, the power consumption or the model number present on the rear of this unit.

Also note the lack of the standard disclaimer stating that there are no user serviceable parts inside. This is screen printed on later units. There is also no round "passed' sticker or voltage sticker, nor is there the sticker normally present on most Sansui quad gear listing the applicable patent numbers under which it was made. This latter sticker is usually on the left side near the rear on the QSD-1.

Final picture is of the F-2466 board foil side showing factory mods (capacitors and resistors added to foil side of board). This isn't all that unusual in Sansui gear, but taken with all the other oddities here I thought it interesting.

All in all, a very strange find. First time I've had my hands on any Sansui component that had boards with no legends at all. Green conformal coating is not used on any of the boards. While this was common for Sansui in the late 60's and early 70"s, by 1974 everything they made - that I've seen and had apart - usually had it.

One more notable detail, all the audio signal wiring from the board to the RCA jacks on the rear panel is standard single conductor, not shielded two conductor as normally found in Sansui gear.

This almost looks to me like a pre-production prototype that was rush-jobbed either as a demo or evaluation unit given the rather unpolished state of the boards and lack of proper ID plate, especially. I also just now noticed the wiring bundles where secured together use nylon wire ties, not the rubber tubing that was notably used to tie off wire bundles.

Regarding the input voltage, I have decided that it must be set for 110V in. Normal setup in multi voltage Sansui gear typically has orange as a 110V primary input and red as a 100V primary. This is borne out by looking at several service manuals for other gear I own, and they all follow this color code.
 

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The earliest QSD-1 we have on file is from November '74. We have three from that month's production. It looks like the next batch was run off in November and December '75. There are none on file between November '74 and November '75. Then a couple in April and September '75 then none until a larger group in March and April '76.

Looking at the serial number on yours it uses the type face that Sansui used during that era. That may support your theory of this being a prototype. Nice find.

- Pete
 
Pete, my other QSD-1 is a later unit, normal production with engraved panel and all other attributes as expected (compared to the one under discussion). Serial number on that unit is 215110040, November 75. It is multi voltage (100 to 240, selectable by normal pin plug on back panel under the ID plate).

Not sure what to make of it, especially with the short format serial number. The only way I can see to read it that makes sense is July 74. If it were a pre-production prototype, I'd not expect it to have any serial number, and to be marked as a sample unit by some means. Conversely, If it were regular production, even if very early in the process, I'd expect it to have gotten a regular 9 digit number in the standard format of the time.

And yet, I'd be surprised if Sansui sold a unit that was lacking the id plate, warning and patent notices and so forth. That leads me to speculate that this was from a small early batch of units used for evaluation, and maybe originally supplied to a magazine reviewer, record label, or other industry professional for live testing purposes.

Even the earlier serial numbers Sansui used (pre 1972 or so) had 8 digits, and I have some gear so marked, most notably speakers. So, for the moment, this one remains a bit of a mystery. I was hoping someone would see this thread and chime in that the short number was something seen before on engineering samples or evaluation units and may have other examples to support that theory.

This is a fully functional unit, but is in a rather unpolished state with the internal boards and such appearing to be rushed into assembly without the screen print and green mask. They are otherwise standard production boards near as I can tell, but look to be entirely hand soldered on close examination. The chassis and enclosure is regular production save for the absent screen printing of some items on the rear, and the screen printed versus engraved front panel.

If anyone has further insight on this - even if based upon a different model - I'd like to hear it. Given the rarity of the QSD-1, I'm not expecting to find a litter mate to this one amongst the members here, but maybe someone will surprise me.
 
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