Technics SL-PG440A

[Chrisr3521]

I'm looking at refreshing my Technics sl-pg440a, with sensible simple upgrades. I will be replacing the opamp to the opa1642 on a soic8 to dip adaptor, capacitor wise, where should I be looking to put oscons, panasonic fc's etc? Please see service manual attached

 

[Chrisr3521]

So around the dac on the digital supply line I'm assuming this is a candidate to be changed to an Oscon cap?

 

[madis64]

I would start from sorting out the analogue output stage before doing anything with the digital part. Otherwise you would probably not hear any improvements.

Would you mind posting some photos of the main board - both from top and below?

 

[Chrisr3521]

Here's the pics, top and bottom

 

[madis64]

Some photos of a 770D (yes, dual dac but general layout is pretty similar) mod from ca half a dozen years ago.
The change was audible...

 

[Chrisr3521]

What would you do with the output stage?

 

[madis64]

What do you figure out from the photos that I did? 😉

 

[Chrisr3521]

Ah! Didn't see that, mks2 caps on output and change film caps around the dac to Wima as well?

 

[madis64]

Also replace the RCA sockets to ones isolated from the back panel. And remove C815/816 (1000pF from output to ground).

 

[Andersonix]

I think you're on the wrong track pursuing anything in the analog output. But it appears there is an empty spot for an optical output on the pcb, so do that?

I'm sitting on a SL-P370 also with an empty spot for Toslink TX...

 

[Andersonix]

Looking at a close-up of your pcb, can you add the Toslink transmitter and other parts needed to output digital?
This is the only Toslink TX I've found on the market that has 4 pins:
https://www.mouser.com/ProductDetail/757-TOTX1950AF

 

[niclasf]

I found my old PG440 at my mother’s place.
It had problems skipping forward randomly. It turned out to be a common problem in the CDM-module. A capacitor usually dries out.
Now it plays like a champ and it is really fast detecting the cd and changing tracks.

Now I have ordered parts to add toslink. Thanks for the tip @Andersonix
I hope the parts from mouser arrive to the Christmas break 🙂