Test setup for SQ decoder alignment

[Techfixer]

Hi All,
I have 2 SQ decoders and I’d like to be able to properly align them to spec. However both service manuals say to use a SQ encoder.
I don’t have one can’t find one and so far haven’t found a circuit to build one. I do have a CBS SQ test record, is it possible to use that?
How do you align your decoders?

Techfixer
Sony SQD-2020
Lafayette SQ-W

 

[monarchee]

This may be of help for you.

https://www.quadraphonicquad.com/fo...and-amplitude-correct-sq-qs-test-tones.15859/

 

[Techfixer]

Hi Monarchee,
I have the test tones (not really long enough to do an alignment, I guess I could copy/splice) and I actually have the CBS quad tast record. All the service manuals refer to a hardware test set. They don’t offer alternate ways of calibration using tone or record. I don’t want to make things worse. Has anyone calibrated theirs using tone or record and if so what was your procedure?

Thanks in advance,

Techfixer

 

[Bonzodog]

You can make an SQ encoder from two non-logic SQ decoders. They should be identical.
I made mine from a couple of Sony 1000 decoders.
They used to be cheap and plentiful, but the only one I saw on Ebay was $100 with shipping. Used to go for around $20.

http://www.4channelsound.com/encode.htm

https://midimagic.sgc-hosting.com/encodsqd.htm

 

[Monkeyboi]

Hi All,
I have 2 SQ decoders and I’d like to be able to properly align them to spec. However both service manuals say to use a SQ encoder.
I don’t have one can’t find one and so far haven’t found a circuit to build one. I do have a CBS SQ test record, is it possible to use that?
How do you align your decoders?

Techfixer
Sony SQD-2020
Lafayette SQ-W

Make yourself a simple test circuit using just 2 transistors and a handful of basic components as shown in Sections 3, page 18 of the Sony SQD-2020 service manual. You will need a 2kHz +/- 1% test tone applied to its input which you can source from an audio oscillator which most techs would have as standard on the bench or generate it from your PC's soundcard.

I have built this circuit and successfully aligned many Sony SQ decoders using this method. The only precision parts required are a 33k resistor at 1% and a 2.4nF capacitor (suggest MKT type) at 2%. Any small signal NPN Si transistors can be used. I made my test rig up with a couple of BC547 as these were what I had on hand. Powered by 18 volts (2 x 9v batteries) it requires only a few mA of current.

Cheers,
Alan R.

 

[Soundfield]

Make yourself a simple test circuit using just 2 transistors and a handful of basic components as shown in Sections 3, page 18 of the Sony SQD-2020 service manual.
I have built this circuit and successfully aligned many Sony SQ decoders using this method.

Interesting. Another member has already posted about the errors in the SQD-2020 manual and in particular that the suggested test circuit did not work properly. He explains the flaws and changes he had to make in order to be able to use it.
See his post - SQD-2020 servicing

 

[Monkeyboi]

Interesting. Another member has already posted about the errors in the SQD-2020 manual and in particular that the suggested test circuit did not work properly. He explains the flaws and changes he had to make in order to be able to use it.
See his post - SQD-2020 servicing

I built mine from the circuit diagram that appears in the SQD-2010 service manual. I better pull out the paper copy SM and check if there are any differences with the same (similar) diagram in the SQD-2020 SM from which I copied and pasted in my post and referenced the page as I assumed the OP had the SM for the 2020 model.

I might have modified mine. It's been some decades back.
Thanks for the link to the thread. Most appreciated.

Cheers,
Alan R.

 

[par4ken]

The easiest way to generate test tones is with an audio program such as Adobe Audition info here Sony SQD-2020 servicing