Just got an SQ-W

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SQLGuy

Member
Joined
Mar 22, 2016
Messages
48
Location
Colorado Springs, CO USA
Hi folks,

I was thinking of building an SQ decoder, but had a number of disruptive things come up, and, the other day decided to see what was on eBay. There was a guy with an "as found", only known to light up, SQ-W. I negotiated and bought it for $220 + $18 shipping, rather than the $350 + $18 he was asking. Sadly, but not surprisingly, it's not working. No sound in most modes, pass-through discrete gives a pulsing bass thump with a lot of noise. And the power lamp seems to have lasted only long enough to light up once.

Opened it up and found a bad solder joint on the main capacitor, but resoldering it didn't help. First look at voltages didn't look right... will take another look at that.

The good news is that it's in good shape - doesn't look like anyone has worked on it before - physically just a couple of scratches and missing feet. The other good news is that all the components are generic, discrete, devices, with the exception of the four prehistoric ICs. They are Motorola SFC6043 devices... which I couldn't find anything about... but the schematic says, "MFC6043 or MFC6040." The MFC6040 does have some info online, and those seem to be available from eBay. Apparently, they're not exactly op-amps, but voltage-controlled attenuators.

So, first question is whether anyone has experience repair or overhauling these. The electrolytic caps are all Matsushitas. I've have very good experience with their caps, but these ones are still 44 years old. I'm thinking to pretty much shotgun the caps in favor of some 21st century Nichicons. Any ideas on a suitable 6.3V lamp for the power indicator?

Any other ideas on what else typically goes bad in these things?

Thanks,
Paul
 
OK. Took a closer look. The voltages are definitely wrong. Looks like the voltage regulator (transistor) is shot. Obsolete, but an MJE181G looks like a valid currently-available replacement. Where there should be 35V, there's about 12V... and it goes downhill from there. Doesn't look like a downstream short - the 51V on the collector of the regulator stays there after you switch it off.

My guess is that that bad solder joint on the main filter cap led to some pretty lumpy DC being fed into the regulator, and, eventually, it couldn't take it anymore.

I'm certainly happier to see a pretty much open regulator than a shorted one.
 
Hi folks,

I was thinking of building an SQ decoder, but had a number of disruptive things come up, and, the other day decided to see what was on eBay. There was a guy with an "as found", only known to light up, SQ-W. I negotiated and bought it for $220 + $18 shipping, rather than the $350 + $18 he was asking. Sadly, but not surprisingly, it's not working. No sound in most modes, pass-through discrete gives a pulsing bass thump with a lot of noise. And the power lamp seems to have lasted only long enough to light up once.

Opened it up and found a bad solder joint on the main capacitor, but resoldering it didn't help. First look at voltages didn't look right... will take another look at that.

The good news is that it's in good shape - doesn't look like anyone has worked on it before - physically just a couple of scratches and missing feet. The other good news is that all the components are generic, discrete, devices, with the exception of the four prehistoric ICs. They are Motorola SFC6043 devices... which I couldn't find anything about... but the schematic says, "MFC6043 or MFC6040." The MFC6040 does have some info online, and those seem to be available from eBay. Apparently, they're not exactly op-amps, but voltage-controlled attenuators.

So, first question is whether anyone has experience repair or overhauling these. The electrolytic caps are all Matsushitas. I've have very good experience with their caps, but these ones are still 44 years old. I'm thinking to pretty much shotgun the caps in favor of some 21st century Nichicons. Any ideas on a suitable 6.3V lamp for the power indicator?

Any other ideas on what else typically goes bad in these things?

Thanks,
Paul
I don,t want to be smart after you have spent you cash
But have you heard of the surround master
It is a 3 band SQ decoder as good or nearly as good as the Tate
and a 3 Band QS decoder as good as the QSD1
Not much more than you spent
And it is new
Sorry
Ron
 
I don,t want to be smart after you have spent you cash
But have you heard of the surround master
It is a 3 band SQ decoder as good or nearly as good as the Tate
and a 3 Band QS decoder as good as the QSD1
Not much more than you spent
And it is new
Sorry
Ron

Yes, I had heard of it. When I looked last, they didn't have the factory seconds for $400, so the SQ model was $500.

Supposedly, the SQ-W is second only to the Tate and also quite good at QS in Composer A mode. It also has the advantage of four channel discrete through, so I can daisy chain my CD-4 unit if I want.

If I had known that the Surround Master was that good and had been reduced in price, I probably would have considered it.
 
Yes, I had heard of it. When I looked last, they didn't have the factory seconds for $400, so the SQ model was $500.

Supposedly, the SQ-W is second only to the Tate and also quite good at QS in Composer A mode. It also has the advantage of four channel discrete through, so I can daisy chain my CD-4 unit if I want.

If I had known that the Surround Master was that good and had been reduced in price, I probably would have considered it.

Hi. SQLGuy

Yes rustyandi is right about the Surround Master ,but the SQ-W as you say is very close to the Tate 101a I bought one a couple of years ago and I got mine totally recapped and recalibrated to the spec of the service manual and it sounded fantastic in all respect good luck in restoring your unit.
Bill.
 
Some of us like the legacy equipment and it is a sense of accomplishment to get it working properly again.

Doug
 
Some of us like the legacy equipment and it is a sense of accomplishment to get it working properly again.

Doug

Parts have been ordered. Knowing Mouser, I expect to see them by Thursday.

I did go ahead and order all new electrolytic caps. I may just fix the power supply first, though, and then decide whether to swap the audio path caps as well. One thing that surprised me is that the little caps (1/50, 4.7/25) are still the same size for modern audio grade ones (5x11 mm), but the big ones, like 470/50, are much smaller physically in modern offerings. A new, high current, high temp, Nichicon 470/50 is about half the size of the original cap that's in there.
 
Parts arrived today. I just quickly installed the replacement lamp and the replacement for the regulator. The old regulator definitely was bad, and the unit does work now. A JKL 2180 is a suitable replacement for the indicator lamps.

Probably will try it out a bit before going back in and replacing the caps.

Anyone know where I can get some wav files or a CD of SQ calibration tones? Looks like what I need is some 2KHz signals encoded for each of the positions.
 
Parts arrived today. I just quickly installed the replacement lamp and the replacement for the regulator. The old regulator definitely was bad, and the unit does work now. A JKL 2180 is a suitable replacement for the indicator lamps.

Probably will try it out a bit before going back in and replacing the caps.

Anyone know where I can get some wav files or a CD of SQ calibration tones? Looks like what I need is some 2KHz signals encoded for each of the positions.

Hi. SQLGuy

I think that's going to be hard to come by because I think Audio tech general have test equipment and follow the procedure from the service manual, calibrating the unit correctly does bring everything back to spec and does make a big difference, if NOT done right it could muck thinks up???
I don't know if this file will help much.
 

Attachments

  • SQTones.mp3
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Parts arrived today. I just quickly installed the replacement lamp and the replacement for the regulator. The old regulator definitely was bad, and the unit does work now. A JKL 2180 is a suitable replacement for the indicator lamps.

Probably will try it out a bit before going back in and replacing the caps.

Anyone know where I can get some wav files or a CD of SQ calibration tones? Looks like what I need is some 2KHz signals encoded for each of the positions.

might a needledrop of this SQ-encoded LP be any use in calibrating?
PM anytime.

c0KwMpG.jpg
 
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