How to make Sony SQR-8750 real SQ? + something else...

[furui_suterioo]

The document on hifiengine is the same for sqr-4750, 6750, and 8750 talks about the decoder:

There is a more detailed document for the sqr-4750 also on hifiengine:

 

[Soundfield]

The document on hifiengine is the same for sqr-4750, 6750, and 8750 talks about the decoder:
View attachment 57372

TRANSLATION- we wanted to make this stuff cheaper and our poor AGC circuit causes such terrible pumping effects it was an easy thing to throw away. But never mind – if you feed this version from an over compressed FM station it will still sound as bad as the original!

 

[MidiMagic]

In many cases in repair jobs, I would find wires like that on circuit boards where either a trace on the circuit board was bad or damaged, where a plated-thru hole didn't plate, or where a design change was made after production started.

 

[MidiMagic]

I would prefer SQ with just Variblend and no F-B logic.

 

[CZmok]

You always mention SQ but do the other decoder functions work? RM and 2-4. Did you check the back speakers on the working front channels?

@par4ken - If I say SQ decoder I mean all the decoder section (red lined on pic bellow). So nothing which goes through the decoder block (2+4, SQ, R-MTX) is playing. If I choose pure 2CH, it plays because it bypassed the decoder block (green line on pic bellow). Maybe DISCRETE inputs will play correctly but I cannot try it, I have nothing to play from. But from the diagram, it seems it goes somehow through the decoder also.

Yes, I checked speakers. All are fine.

 

[CZmok]

The document on hifiengine is the same for sqr-4750, 6750, and 8750 talks about the decoder:
View attachment 57372
View attachment 57373
There is a more detailed document for the sqr-4750 also on hifiengine:
View attachment 57374iscreteiscrete
View attachment 57375

@furui_suterioo - wow!! Is possible to provide me the pics in higher quality somehow, mail, personal message? I believe it will help another service man to repair it. Thanks a lot!

 

[furui_suterioo]

The file is too large to upload, here is the link:
https://www.hifiengine.com/manual_library/sony/sqr-4750.shtml
It is free to make an account and also worthwhile, there is a lot of useful documents on here. The sqr-4750 might not have the same layout as the sqr-8750 but the documents seem to indicate that the decoder circuits operate the same way.

 

[CZmok]

@furui_suterioo - I forgot I've already registered 22 weeks ago on hifiengine when I was finding right device for me... I got the documents. Thanks for advice.

 

[CZmok]

btw how is possible fact that on HifiEngine is more than service manual? Sony inc clearly told me those informatioans are not available to customers. Or this was some kinf of exception (new circuit?) or some kinf of leak from Sony?

 

[furui_suterioo]

btw how is possible fact that on HifiEngine is more than service manual? Sony inc clearly told me those informatioans are not available to customers. Or this was some kinf of exception (new circuit?) or some kinf of leak from Sony?

I would assume these were distributed to servicers many years ago, luckily some were kept, scanned and eventually uploaded.

 

[Soundfield]

I would assume these were distributed to servicers many years ago, luckily some were kept, scanned and eventually uploaded.

Yes, exactly, they were only released to the trade and never published. Back in the day if you spoke very nicely to the manufactures you could occasionally get hold of them - some manufacturers were more helpful than others - I managed to get the service manuals for Panasonic and Revox quite easily for example. Most manufactures won't have copies of service manuals for equipment they stopped making forty or more years ago - why would they? Interestingly I don't think they produce manuals like this for most modern equipment - there aren't any repairmen left and everything is considered to be disposable! The majority of stuff that fails under warranty just gets replaced and if it fails outside of warranty you're stuffed!

 

[MidiMagic]

@par4ken - If I say SQ decoder I mean all the decoder section (red lined on pic bellow). So nothing which goes through the decoder block (2+4, SQ, R-MTX) is playing. If I choose pure 2CH, it plays because it bypassed the decoder block (green line on pic bellow). Maybe DISCRETE inputs will play correctly but I cannot try it, I have nothing to play from. But from the diagram, it seems it goes somehow through the decoder also.

Yes, I checked speakers. All are fine.

View attachment 57387

If you have only a 2-channel source, you can test the discreete part two channels at a time.

If that is the SQ part, where are the R-matrix and the 2-4 parts?

 

[par4ken]

btw how is possible fact that on HifiEngine is more than service manual? Sony inc clearly told me those informatioans are not available to customers. Or this was some kinf of exception (new circuit?) or some kinf of leak from Sony?

Information is not available because of the equipment's age. You can still find manuals online for sale but they are pricy. It's possible that Sony won't supply service manuals for newer equipment, as someone else said the new stuff is throw away! The information on HifiEngine is just a blurb about the new decoders that use the Sony chipset.

 

[CZmok]

If you have only a 2-channel source, you can test the discreete part two channels at a time.

If that is the SQ part, where are the R-matrix and the 2-4 parts?

If I understand the question the answer is: in the decoder block on the right site, there are the swithers of 2+4, SQ, R-MTX if I understand well the schema.


@furui_suterioo , @Soundfield , @MidiMagic , @par4ken - thanks for advice and comments.



Today I gave the amp to service man with all information I know about the amp. Old guy is really enthusiastic about old devices and I hope the reparation of my machine would by vase and honor for him.

 

[MidiMagic]

Try Sams Photofacts.

 

[Circular Vibes]

Try Sams Photofacts.

They only have a lower model listed.

 

[CZmok]

Hi there,

my amp has changed little bit. SQ decoder is bypassed but all channels are working properly. Bulbs are replaced by LED belt with warm color cover.

https://photos.app.goo.gl/yUbFb8s3dVZZ27sc9
Few more things to solve:

Antena - do You please suggest siutable type?
Phones - there are two outputs of phones: back anf front. How should that work?

Thanks

 

[par4ken]

Hi there,

my amp has changed little bit. SQ decoder is bypassed but all channels are working properly. Bulbs are replaced by LED belt with warm color cover.

https://photos.app.goo.gl/yUbFb8s3dVZZ27sc9
Few more things to solve:

Antena - do You please suggest siutable type?
Phones - there are two outputs of phones: back anf front. How should that work?

Thanks

Quadraphonic headphones have two plugs, one plugs into the front jack (usually the top one) the other is for the back the other plug. For stereo headphones use the front jack only. Modern phones need an adaptor 1/8" to 1/4".

 

[CZmok]

Thans a lot @par4ken !

What about Antena? Today I can buy for example this 300 ohm antena with coax:

https://www.datart.cz/antena-pokojova-gogen-da-918p-pasivni-cerny-da918p.html
But how to connect it to 2 (or 3 connectors) of antena 2 pieces + ground? Do I have to some hoe strip the cable?

----

One more thing...

If everything works fine and I listen for example stereo radio and turn SQ function on. What sound goes out from 4 speakers, quadro or 2+2 stereo?

Thanks

 

[gvl_guy]

Thans a lot @par4ken !

What about Antena? Today I can buy for example this 300 ohm antena with coax:

https://www.datart.cz/antena-pokojova-gogen-da-918p-pasivni-cerny-da918p.html
But how to connect it to 2 (or 3 connectors) of antena 2 pieces + ground? Do I have to some hoe strip the cable?

View attachment 59819

----

One more thing...

If everything works fine and I listen for example stereo radio and turn SQ function on. What sound goes out from 4 speakers, quadro or 2+2 stereo?

Thanks

I'm not sure about the antenna. Radio near me us pretty worthless so I don't bother anymore.

As far as turning on the SQ, you'll get a bit of fake quadraphonic sound. The decoder will try to find some phase shifts in the recording and try to decode that. It won't sound great, but it won't be double stereo either.

Does your receiver have any other quad mode? Maybe a RM for regular matrix? That might be better for a fake quad sound from a stereo source.