Sony SQD-2020 servicing

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Sergeauckland

New member
Joined
Apr 19, 2013
Messages
7
Location
Suffolk, United Kingdom
I've been playing with my newly acquired SQD-2020 unit, and it seems to be working fine.

However, it IS some 40 years old, and may not be working to spec. My inclination is towards the 'if it ain't broke....' approach, but having read the manual, and seen the number of adjustments for separation, I wonder about how stable those are.

I can build the SQ signal generator, it's only two transistors and some switching, and I have all the other test gear necessary, but my question is whether it's necessary to tweak, or best leave it alone as it seems to work fine.

Does anyone here know how stable the SQD-2020 logic is? Do the pots generally need tweaking to maintain performance, or are they likely to be still in spec? I've checked common parameters like THD and noise, and they seem OK.

Thanks for any guidance.

S
 
i don't have any experience of this unit but if you don't have the disc already i can help out with a drop of the CBS Labs SQ Test Disc which may be some help in calibrating your setup just let me know
 
What you need is the Popular Science SQ test record and a good turntable with a quality cartridge and stylus. The test record is PR 401 SQ. It also comes as PR 401 CD4. Make sure you have the correct one for SQ. E-bay is your friend.:) PR 401 SQ.jpg
 
What you need is the Popular Science SQ test record and a good turntable with a quality cartridge and stylus. The test record is PR 401 SQ. It also comes as PR 401 CD4. Make sure you have the correct one for SQ. E-bay is your friend.:)View attachment 31136

Yes thanks. I have bid on those before, but lost out. Might try again.

I'm however interested in whether setting up the SQD-2020 according to the Service Manual is necessary, or only needed if something's obviously wrong. At the moment, nothing obvious is.

I've been very kindly sent the CBS test LP, so will give that a try.

As to turntable, will an EMT948 with TSD15vdh do?

If it won't, I also have an AEG TRS9000 with V15V SAS

:)

S.
 
Oh Yeah :D Those might just work. Keep in mind that the SQD 2020 is capable of discrete separation in all four channels when using the test record. Both of mine do when using the Popular Science record.

Without the proper test equipment it is not recommended to mess with any of the pots.
 
Oh Yeah :D Those might just work. Keep in mind that the SQD 2020 is capable of discrete separation in all four channels when using the test record. Both of mine do when using the Popular Science record.

Without the proper test equipment it is not recommended to mess with any of the pots.

I've had a brief play with the CBS Test LP, and the only test that doesn't give me the full spec separation is Centre-Front to Centre-Back and Centre-Back to Centre-Front. Both are only a few dB, not the 15dB+ I would expect. All the individual RF, LF, RB, LB and diagonal are all around the 20dB level, so seem OK, it's just the CF-CB ones that are off. I'll do some more tests to make sure I'm not fooling myself...easily done at my age!

I'll have to build the Sony SQ generator as per the Sony manual before I start fiddling. I have all the other bits of test gear necessary, I was just hoping not to have to build anything as I've got a fair bit of DIY on.

S.
 

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Just thought I would provide an update to this thread.

I built the SQ Tester, and went through all the adjustments in the SQD-2020 according to the manual.

The Tester works OK, (mostly) but has a very peculiar response on Rb, as that comes out as something else, but Lf, Rf, Cf, Cb all work OK (not sure about Lb. I've checked the circuit three times, and can't see what's wrong, so assume an error in the manual. I did find at least one other error in the manual, so this could also be one.

No matter, I got the SQD nicely set up.
One interesting thing, the F-B and B-F separation controls can provide more than the stated separation, but if set to the max, which is what I did first, and >20dB has to be better than 15db, hasn't it? resulted in unpleasant pumping, so I went back to the recommended 14-16dB. I expected that all the controls were to some extent mutually dependent, so it took a couple of iterations for the line-up to be complete.

Using the CBS Test LP SQT1101, which I downloaded as a FLAC file, and I send my thanks to the downloader, all is fine, and I'm, happy my decoder is working as well as it can. Not bad for a 40+ year old product.

Having built the Tester, I checked my DIY decoder, and realised it's pretty poor!
Next project is to find out why, and make it usable. It may not be as good as the Sony, but it has to be better than it is!

I'm now enjoying my growing albeit still modest SQ LP collection, and will exhibit at Kegworth 2018 (nee Scalford) https://hifiwigwam.com/forum/forum/...ggest-hifi-enthusiasts-show-17-18-march-2018/ to show the modern world what we all missed when Quadraphonics went away.

S.
 
Hello Everyone!

I've been a looky-loo for years, I'm from that "quad" era in time. Quad was beyond my finances
but I was always fascinated & interested. This site is my reference/touchstone to that time.

Anyway...

I've accumulated several SQ decoders over the years, I want a method to check decoding operation.

I'm a semi-retired engineer and can understand/follow good information/instructions. I'm looking for a
consistent SQ encoded signal source to feed the 2-channel (stereo) inputs of these decoders. I have
the SONY SQD-2020 Service Manual and could construct the "Signal Mode Selector" circuit, if need be.
There was, previously posted, info in this thread which indicates that circuit has issues. True?

I do have a sealed copy of "CBS SQ Test LP SQT 1100". Currently I don't have a good setup to digitize this LP.
My idea is to transfer this LP to CD (keeping the SQ encoding intact) and use the CD (convenience) as a stereo
input signal source for testing SQ decoders. Has anyone done that successfully/cleanly?
Does the quality of SQ encoded information suffer? Recommendations?

There are on-line businesses that offer LP to CD services, input on any of them? Recommendations?
On the other hand, I have access to numerous SQ LPs, if I decide to procure equipment and digitize
these LPs myself, Recommendations?

Hello Again & Thanks,
Tom Q.
 
Hello Everyone!

I've been a looky-loo for years, I'm from that "quad" era in time. Quad was beyond my finances
but I was always fascinated & interested. This site is my reference/touchstone to that time.

Anyway...

I've accumulated several SQ decoders over the years, I want a method to check decoding operation.

I'm a semi-retired engineer and can understand/follow good information/instructions. I'm looking for a
consistent SQ encoded signal source to feed the 2-channel (stereo) inputs of these decoders. I have
the SONY SQD-2020 Service Manual and could construct the "Signal Mode Selector" circuit, if need be.
There was, previously posted, info in this thread which indicates that circuit has issues. True?

I do have a sealed copy of "CBS SQ Test LP SQT 1100". Currently I don't have a good setup to digitize this LP.
My idea is to transfer this LP to CD (keeping the SQ encoding intact) and use the CD (convenience) as a stereo
input signal source for testing SQ decoders. Has anyone done that successfully/cleanly?
Does the quality of SQ encoded information suffer? Recommendations?

There are on-line businesses that offer LP to CD services, input on any of them? Recommendations?
On the other hand, I have access to numerous SQ LPs, if I decide to procure equipment and digitize
these LPs myself, Recommendations?

Hello Again & Thanks,
Tom Q.
You could digitize the LP, or use a program like Adobe Audition to generate test tones, as I recall 90 degrees is Right Back and 270 degrees is Left Back and of course in phase is front centre and 180 degrees is centre back. Why pay someone for something you can do yourself (digitize a LP), you just need a computer with a sound card and a turntable and pre-amp, check eBay for deals!
 
You could digitize the LP, or use a program like Adobe Audition to generate test tones, as I recall 90 degrees is Right Back and 270 degrees is Left Back and of course in phase is front centre and 180 degrees is centre back. Why pay someone for something you can do yourself (digitize a LP), you just need a computer with a sound card and a turntable and pre-amp, check eBay for deals!

Hello par4ken,

Thanks for your response! It's all helpful.

I understand the mechanics of digitizing an LP: Turntable/RIAA preamp/Analog-Digital Converter/Software.
My issue is the hardware I have currently available. I would only want to do this or have the transfer done
using the best equipment $practically$ available to me. Most USB turntable solutions (with their built-in preamps
and ADC's) look unpredictable.

I'm looking for a piece of equipment (or signal source) that can output a definite discreet signal on any one of the 4 outputs
with little or no crosstalk/bleed between channels from an SQ encoded stereo source.

Hope that helps clarifies my post.

Regards,
Tom Q.
 
First of all, I'm new to this forum, and I'm happy to be accepted as a member.

I have gone through a Sony SQD 2020 restoration project and I thought it would be good to share my experience, also because I found a few errors in the Service Documentation that is available at various places on line.
When my SQD 2020 came in it wasn't working properly at all: signals completely off balance in SQ mode and loud intermittent noises occurring at random moments.

After reading about this online, I soldered through all connections on the B-board (the large PCB with all the trim pots on it) where pins make connections between the top and the rear of the PCB. (There are many of them and make sure you don't miss one.) In my case this even turned out to be necessary to do this on both sides of the PCB. I also cleaned the SYSTEM switches. After this the SQD 2020 worked much better and the intermittent noises were gone.

In the SQ-mode, however, there were still problems. The channel separation was bad, and the rear speakers 'pumped': they sounded as if some kind of dynamic expander active.
I therefore decided to go through the calibration procedure as explained in the Service Manual.

On page 18 it is explained that you either need the SONY SQ CHECKER (which of course I didn't have) or build a Signal Mode Selector based on the diagram in figure 3-1 on the same page.
However, after many unsuccessful attempts to calibrate my SQD, I came to the conclusion that there is a serious mistake in that diagram!
Based on the attached files I will explain what this mistake is.

1_SQD_2020_diagram_3-1.jpg


I analysed the main signals in the diagram (the ones that go to the switches and then to the input of the SQD 2020) as follows: in step 4 (left-back + right back) the phase relation between the left and the right signal should be 180º. Therefore, the blue signal must be 0º and the yellow signal must be 180º. In that way, step 1–4 are like this:

Step 1: 0º on left channel, nothing on right channel
Step 2: nothing on left channel, 180º on right channel (why this is 180º is a mystery to me, but since there is no signal on the right channel it doesn't make a difference)
Step 3: 0º on both channels
Step 4: 0º on right channel, 180º on right channel

At position 5 of the switch (left-back), the phase relation between left and right should be 90º, so since the 0º (blue) is connected to 5 at the left channel, the signal at 5 on the right channel must be the 90º phase (yellow).
Then at position 6 (right-back), the phase relation should be -90º. However, looking at the diagram, the 90º signal is connected to the left channel, and the 180º signal to the right channel. The resulting phase relation is then +90º, and not -90º as it should be.
This explains why Sergeauckland wrote that "The Tester works OK, (mostly) but has a very peculiar response on Rb".
I corrected the diagram in the next image, so that in step 6, the 180º signal goes to the left channel and the 90º goes to the right, resulting in a phase relation of -90º.
In this way the Signal Mode Selector works correctly throughout the whole calibration procedure.

2_SQD_2020_diagram_3-1_corrected.jpg


Something else that I would like to mention regarding the Service Manual, is that on page 22, it says that measurements should be made by touching the collector of several transistors on the B-board. This is actually not necessary at all, since at least in my SQD 2020, there are measuring points on the PCB next or close to the transistors Q811, Q804, Q815, Q817 and Q910. This makes measuring the currents at these points much easier.

Then on page 23, there are two more mistakes!

At point 4 of the procedure under 3-11, RV801 and RV802 are swapped. While measuring the level at Q811, RV802 should be adjusted, and while measuring Q815, RV801 should be adjusted.

A similar mistake can be found at points 2 and 3 of 3–12. At point 2, RV907 should be adjusted, whereas at point 3, it should be RV906.

After having gone through the whole procedure, my SQD 2020 works wonderfully!

I hope this was helpful.
 
Commendable, Kees!!

There is joy in fixing vintage equipment, but IMHO much more opportunities for disappointment. But this research makes me wish I had a 2020.

My preamp is motherboard-based, very difficult to fix and even to upgrade. That is somewhat sad.

You should make a YouTube video about this. Check the work of xraytonyb, blueglow electronics, Mr. Carlson Lab and others.
 
Many thanks Kees, sorry it's taken so long to reply, but better late than never!

I have had a haitus from my HiFi for several months due to building works at home, and have only just been able to get my HiFi operational again, and started looking at this forum again.

Today, I made the changes to my SQ generator as Kees suggested, and it works perfectly. It's also helped me understand how it worked rather better, so a double win for me.

My SQD-2020 does all the right things now using the generator.

I also picked up the other errors, more by trial and error, but yes, the Sony manual could never have been properly checked when it was written.

I suppose I'd better change my Avatar!

S.
 
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It's so easy to generate test tones with a program like Audition that I wouldn't bother building the tester. I have a SQD-2010 which uses the Sony chips rather than the all discrete 2020. I had a problem with mine that pointed to a defective chip, but tuned out to be a crack on the PC board. I then did a quick adjustment setting separation to max and as reported that causes the unit to pump excessively so as to be unalienable. I'll have to realign it when I get the chance. I purchased a couple of the Involve evaluation modules and put the Involve QS board in the 2010 case wired to the discrete input, this allowed me to compare the built in RM decoder to the Involve. I also have the SQ board, I think that I'll swap boards, then properly adjust the 2010, then I can easily do a quick comparison between the two.
 
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Many thanks Kees, sorry it's taken so long to reply, but better late than never!

I have had a haitus from my HiFi for several months due to building works at home, and have only just been able to get my HiFi operational again, and started looking at this forum again.

Today, I made the changes to my SQ generator as Kees suggested, and it works perfectly. It's also helped me understand how it worked rather better, so a double win for me.

My SQD-2020 does all the right things now using the generator.

I also picked up the other errors, more by trial and error, but yes, the Sony manual could never have been properly checked when it was written.

I suppose I'd better change my Avatar!

S.

Great to hear that you got it working Serge.

Kees
 
It's so easy to generate test tones with a program like Audition that I wouldn't bother building the tester. I have a SQD-2010 which uses the Sony chips rather than the all discrete 2020. I had a problem with mine that pointed to a defective chip, but tuned out to be a crack on the PC board. I then did a quick adjustment setting separation to max and as reported that causes the unit to pump excessively so as to be unalienable. I'll have to realign it when I get the chance. I purchased a couple of the Involve evaluation modules and put the Involve QS board in the 2010 case wired to the discrete input, this allowed me to compare the built in RM decoder to the Involve. I also have the SQ board, I think that I'll swap boards, then properly adjust the 2010, then I can easily do a quick comparison between the two.
If it is "so easy to generate test tones with a program like Audition", it would actually be nice if you could explain how you do that. For instance, how do you deal with the +/-90 degrees phase shift and how do you compensate the resulting levels?
I actually tried to do something similar in Pro Tools, but I find the tester's 6-position switch very convenient.
 
In Audition 3.0 you open the program in edit view, click on Generate,Tones, for sample frequency and bit depth it doesn't mater what you select, 44100 and 16 bit is fine. Then you see the Generate tones panel. Simply put in the test frequency you want and the phase shift you want between the two L&R outputs. Hit preview and your sound card will output a perfect test tone. Make sure the Levels are set equally in my example -6dB. Hit Preview again and the tone will stop. If you hit OK the tone will be saved to edit view in Audition. It`s so easy to toggle on and off different test tones this way, for Lf and Rf I just unplug the opposite channel cable, or you could adjust the level sliders (turn R all the way down for L test signal, and boost L by 3 Db. I like to use an oscilloscope to check the output levels.
AuditonGenerate.png
 
Thanks a lot! I happen to have Audition, and although it is version CC 2019 and the interface is different, it is indeed very easy to generate tones, set the phase relation between left and right, and save presets.
 
Hello,
I have a SQD2020 and wondered if anyone had ideas on why the pots on the speaker levels would be having differing effects on the signal level as indicated by the VU's? On Mono everything is the same and can be adjusted the same. On SQ it goes a bit haywire with just the fronts showing any kind of level. I think the rear input level pot is a but jumpy as this has and odd effect on the signal every now and again. Also on turn on this section of the decoder shows quite a bit of change in signal level depending on which way the winds blowing. I've changed the Push switches and done the main board through hole connections. Discrete Input works fine with only a slight level difference on the right channel. I'm only a hobbiest, so please write slowly so I can follow.... :)
Many Thanks
Joe
 
If you are playing stereo through the SQ mode the rear outputs will always be rather low. Try decoding an SQ encoded program and the outputs should be much better balanced. Pots should be deoxed/cleaned as well.
 
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