Sansui AU-X11 Restoration

[Ronito6]

https://www.nidec-copal-electronics.com/e/catalog/trimmer/rj-13.pdf

Copal RJ-13

TOCOS (Tokyo Cosmos) G12X

Most on AK prefer multi-turn ones though.
25 turn the most prefered.

 

[SanthoshA]

https://www.nidec-copal-electronics.com/e/catalog/trimmer/rj-13.pdf

Copal RJ-13

TOCOS (Tokyo Cosmo) G12X

Are these better than the bourns, or is there something in particular i need to consider.
Edit, i just noticed that the multi turn ones are preferred,in AK.
Any preferred/recommended models to consider.

 

[Ronito6]

Are these better than the bourns, or is there something in particular i need to consider.
Thanks for your reply.

Not better if using the same materials and wattage.

Amp8 ones use cermet (ceramic-ize cement). Fantastic quality and certainly an upgrade.

Copal has multi-turn too. Same quality with multi-turn ability.

Bourns are very good but for me they have a weakness, the legs / leads. The ones on Bourns tend to be soft. Copal's legs are way more stouter and strong.

More expensive, but I prefer Copal.

The down side of the Copals used by Amp8 is that the middle leg is set back. So if you look carefully at his installation of those Copals, he usually drills a hole for the middle leg and then bends it forward to solder it to the pad that it should contact. Bending the middle leg (and insulating it) and the back legs so that they go into the original through holes is another way to go with those Copals. Either way, using those Amp8 Copals can be fiddly extra work.

 

[Hyperion]

Bourns are very good but for me they have a weakness, the legs / leads. The ones on Bourns tend to be soft.

Can I just say here that you need to remove your baseball gloves when installing Bourns trimmers.

The Bourns leads are a little soft - but to me that means less mechanical stress transmitted to the inside of the pot when installing or in use.

 

[Ronito6]

Can I just say here that you need to remove your baseball gloves when installing Bourns trimmers.

The Bourns leads are a little soft - but to me that means less mechanical stress transmitted to the inside of the pot when installing or in use.

There was quite a bit of stress on me when the Bourns 3296 trimmers I originally installed on the EQ boards on my X1 kept bending away when I tried adjusting them.

No issue like that with Copals.


Bourns legs are rather less substatial

 

[Hyperion]

I tend to agree regarding the Bourns ones, chosing the right orientation/leg pattern is key to success with them, those Copal ones look rather nice Ron.

 

[SanthoshA]

I tend to agree regarding the Bourns ones, chosing the right orientation/leg pattern is key to success with them, those Copal ones look rather nice Ron.

I did also go through couple of models from Copal, what i noticed is that the middle pin is not in a flat line , as compared to the Bourns.
I have almost check all models from Copal and can see that the ones with side adjustment, have the middle slightly misaligned from the other two pins.
Whereas the top adjustment ones from Copal are fine(pins aligned correctly),but they are not a suitable match for the bias adjustment potentiometers, because of the vertical driver board pcb arrangement.

Probably as Ron discussed in couple of posts earlier we would have to drill a hole in the PCB, or another way is to bend the middle leg and insulate it.

 

[SanthoshA]

Going through the driver board schematics of the AU-X1, i can see voltage measurements at certain points of the driver board, marked with a red circle.

For a reference ground should we consider pin 8 or pin 5 or pin15 marked as ground on the driver board schematics, or can we just pick any other ground point on the driver board.
Will be grateful if any one can help me .

Attached reference driver board picture of the AU-X1, sourced from its service manual.

Thanks in advance.

 

[smurfer77]

Going through the driver board schematics of the AU-X1, i can see voltage measurements at certain points of the driver board, marked with a red circle.

For a reference ground should we consider pin 8 or pin 5 or pin15 marked as ground on the driver board schematics, or can we just pick any other ground point on the driver board.
Will be grateful if any one can help me .
View attachment 1049677
Attached reference driver board picture of the AU-X1, sourced from its service manual.

Thanks in advance.

Any ground will do.

 

[SanthoshA]

Thank you smurfer77, for the reply.

Update: The bias measurement pins have arrived, i dont think they are going to be a direct fit for the bias test points in the AU-X11, it has two small lines of grooves around the plastic female connectors, probably a mod to remove this grooves will help.



On a side note, i was also considering to replace the AC Filter capacitors, the 10,000uF 80V capacitors that produce the rail voltage.
I managed to measure the rail voltage across the positive and negative side, and it measures to around 68.3volts across both sides to be precise.
I believe or assume the power supply/transformer section to be fine for now, as it produces the same voltages as given in the manual for the Sansui AU-X1.

I am in a dilemma, thinking whether to replace the AC power filter capacitor's or not . I have also placed an order for the Peak Atlas ESR70, and the DCA75 tools, from U.S.A.
Plan to check the ESR values across power supply capacitors before considering a replacement.

There are few 10,000uF capacitors available in mouser, rated at 80v, since the rail voltage measures around 68.3volts the 80v capacitors will be more than sufficient.
The dimensions matter though, let me do the ESR test and then make out if they really need a change.


Based out of India, sourcing parts from abroad in a big pain, and it takes couple of weeks to months to get them in my hand.

Any one heard of element14, i see that they supply parts without customs charge in India, not sure how genuine it is compared to Mouser or Digikey.

Apart from this i see amp8, replaced two polystyrene or styrol capacitors in his restoration thread, any one ever found a need to replace them ?

These capacitors are labelled 332J, credits to Mr.Am8 for the above picture, this picture can be seen in last pages of his thread where he has showed, in a tray the components that he has removed for the work.

Now sure where Mr.Amp8 removed these capacitors from in his restoration thread, i have been doing a/b comparison,with pictures of before and after removal in his thread finding out where these capacitors were actually removed from , but i have tough luck figuring this out.

 

[slimecity]

Any one heard of element14

Yes - they were formerly Farnell - I guess that makes them UK-based?

I get stuff from them all the time. The only problem I have with them is when ordering, nothing on the site tells you if an item is out of stock - so after ordering you then get an email advising of lead times - if you are out of luck - they will make you wait days or weeks until the order comes in. Not ideal - and every other major supplier tells you up front if the item isnt in stock, so you can order something else.

Otherwise, they are fine, reasonably quick delivery.

 

[Hyperion]

Apart from this i see amp8, replaced two polystyrene or styrol capacitors in his restoration thread, (These capacitors are labelled 332J), any one ever found a need to replace them ?

No, although they can easily be heat damaged, solder re-flow enthusiasts beware! - note also that they are 'polystyrene' types the very best capacitor dielectric for sound quality.

 

[SanthoshA]

No, although they can easily be heat damaged, solder re-flow enthusiasts beware! - note also that they are 'polystyrene' types the very best capacitor dielectric for sound quality.

I will take care of it when i work on the driver boards, thanks for letting me know.
By the way i also read somewhere that you have replaced the ac filter capacitors in AK, forgot the exact thread as i was going through lots of stuff.
Were the clamps remade, or did they fit directly for you, just interested to have your opinion on the same too.

Thanks in advance for your reply.

 

[Hyperion]

By the way i also read somewhere that you have replaced the ac filter capacitors in AK

Yes, I did replace the 8 main filter capacitors, with same diameter 40mm 100V, 12,000µF replacements, and also re-stuffed the 2 auxilliary supply filter capacitors. The 8 old filter capacitors tested ok, so I didn't really need to change them, as they would have been Ok for another 5 or so years at a guess. But I am very much aware that some components are becoming increasingly difficult to find, and was therefore pleased to change them anyway for future proofing reasons. The 2 re-stuffed capacitors did need to be done, so I am glad that is 'done' and out of the way as well.

Here is the thread, I didn't post as many pictures as I could have done.
http://audiokarma.org/forums/index.php?threads/it-feels-like-i-am-in-heaven.792718/

 

[smurfer77]

I tend to leave the silver cylinder polystyrene caps alone as they are long-lived and sound great. That said, I have replaced them when restuffing boards completely, replaced with other good film caps, like polypro. There may be specific reasons for him replacing certain caps beyond standard procedure, like a failed component nearby taking out some caps, and we will never know by looking at his photos...

 

[Ronito6]

I will take care of it when i work on the driver boards, thanks for letting me know.
By the way i also read somewhere that you have replaced the ac filter capacitors in AK, forgot the exact thread as i was going through lots of stuff.
Were the clamps remade, or did they fit directly for you, just interested to have your opinion on the same too.

Thanks in advance for your reply.

Kale suggests clipping heat shunt to the leads of those polystyrene caps when soldering near them.
He said heat traveling up the traces could damage them.

Easy on the X11 as Sansui stopped mounting them flush to the PCB as they did on the X1.

Bit of a struggle to heat shunt those leads on a X1.

 

[SanthoshA]

Update: The first order shipment from Mouser has arrived, this consists of all electrolytic capacitors from Nichicon FG series, for the Flat amp board, and the driver amp board alone, and also two pair's of OnSemi MJ21193G and MJ21194G as i already of 4 them available with me.
I have ordered the black flag replacements locally here, and am currently waiting for them to reach my place.
I did not notice that the C0G's are better than the silver micca capacitors, until i went through our fellow member Willy6's restoration thread.

I also made a mistake and sourced the Wakefield Kapton TO-3(greaseless) insulator's instead of regular micca insulator.
https://www.mouser.com/search/ProductDetail.aspx?r=567-175-6-310P
Can any one suggest if the Kapton TO-3 insulators are good enough, or provide reviews of the same, the link to the product ordered in mentioned above.

Worst case scenario, i will have to re-order the TO-3 insulators from Mouser again, as these of good quality are not locally available in my place.

 

[Hyperion]

Can any one suggest if the Kapton TO-3 insulators are good enough, or provide reviews of the same, the link to the product ordered in mentioned above.

They are fine - but strictly speaking they are a 'one time use' item (use once then discard) - whereas the Mica ones you can use over and over again. Thus if you only fit the OP transistors once and don't blow any OP Tr's up then the Kapton ones are fine.

 

[SanthoshA]

They are fine - but strictly speaking they are a 'one time use' item (use once then discard) - whereas the Mica ones you can use over and over again. Thus if you only fit the OP transistors once and don't blow any OP Tr's up then the Kapton ones are fine.

Another small help John, i am also looking for the potentiometers from Bourns, but i cannot find the exact series with proper pin out's matching the AU-X11's DC bias and offset adjustment potentiometer.
In case you have replaced them in yours, do you have the exact series and model numbers that you had ordered?

I almost went through all the series from Bourns, and find that the center pin is always slightly misaligned. Basically looking for a potentiometer that requires no mods/bending of pins to fit in the driver board, not sure if one exists from Bourns, or i am missing something.

These are the ones which i have already checked, and they have misaligned pins.
3250p
3252p
3262P
3266P
3290P
3292P
3296P
3299P

 

[Hyperion]

3296P

This is what you are looking for, they are 'side adjust' and have 3 pins (wires) arranged in a triangle - perfect for mounting in place of the originals.

If you have been looking at the pictures online in the Mouser catalogue, often they put a generic picture up - which is confusing - you need to check the data sheet for the series you need. Which in this particular instance is the 3296P - for DC offset and for Bias pots on the AU-X1/11 driver boards.

NB: the pins or wires are pretty flimsy as has been previously mentioned - I alleviate the tendency for the wires to bend by mounting the trimmers above the board (very often no room 'on' the board), using ceramic beads. The beads support the trimmer body above the board, and you get almost no movement of the trimmer body (when adjusting) as a result.