Test setup for SQ decoder alignment

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Techfixer

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Nov 5, 2016
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Boston MA USA
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

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Joined
Jan 10, 2007
Messages
38
Location
Edinburgh UK
This may be of help for you.

 

Techfixer

New member
Joined
Nov 5, 2016
Messages
6
Location
Boston MA USA
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
 

Monkeyboi

New member
Joined
Mar 12, 2010
Messages
4
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.
 

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Soundfield

701 Club - QQ All-Star
Joined
Dec 29, 2011
Messages
788
Location
Essex, UK
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

New member
Joined
Mar 12, 2010
Messages
4
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. :p
Thanks for the link to the thread. Most appreciated. :)

Cheers,
Alan R.
 
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