Sansui AU-101 Restoration, advise a novice

[SansuiSushi]

SANSUI AU-101

'Complete' Restoration Project

 

Hello all, I by no means claim to be knowledgeable in the world of hi-fi audio equipment, but

I can solder. I wish to restore this amp to be the absolute best it can sound using modern components without 'ruining' the sound.

And so I am looking for advise from knowledgeable types on component selection, technique and practices. I am wanting to learn,

in return I will blog, and photograph the process the progress for your viewing. 

 

Somewhat of a draft sort of, I am looking and putting together a parts list and have included photos of its current state.

If anything stands out in the photos to you let me know, I am not sure if it has been fiddled with or not from 'factory'.

 

1: Replace mains cable + plug which is currently 1.5 foot in length (see photos)

2: Recap the F-1302 amp and the tone board

3: ... pending

 

So far I have read the following threads to attain some information and understanding, some is a little over my head.

 

Great post start here....

https://www.audiokarma.org/forums/index.php?threads/recapping-and-tweaking-of-a-au-101.341428/

 

Another recap

https://audiokarma.org/forums/index.php?threads/sansui-au-101-amplifier-recap-before-and-after.432354/

 

 

 

 

 

 

 

Edited July 31, 2021 by SansuiSushi

[muon*]

Nichicon KG for power supply and output caps, and Elna Silmic ll for the rest of the polar capacitors, you can up the capacitance by around 20% for the power supply and output caps, maybe go to 1500uf/35v for the output caps which is 50% greater than the original 1000uf/35v output caps.

 

The Alt scan of the schematic is the clear one on hifi engine.

https://www.hifiengine.com/manual_library/sansui/au-101.shtml

 

For caps 10uf or lower try replacing with poly caps, and electrolytics that are under 25v (like 16v, 10v ect') replace with 25v caps.

 

@pete_mac might be able to help.

 

Edited July 31, 2021 by muon*

[BLAH BLAH]

Magnificent thread...have a great fondness for the Sui-101...sweet lil amp! 

[SansuiSushi]

11 hours ago, muon* said:

Nichicon KG for power supply and output caps, and Elna Silmic ll for the rest of the polar capacitors, you can up the capacitance by around 20% for the power supply and output caps, maybe go to 1500uf/35v for the output caps which is 50% greater than the original 1000uf/35v output caps.

 

Hey @muon*I read a few posts of people putting as high as 4700uf 63v in the power supply cap C001 if I am not mistaken? Mouser have two at that spec LKG1J472MESBAK LKG1J472MESCCK, size and "ripple current" being the two differences, I have no idea which is better for this application. Why might someone go as high as 4700uf? I watched a YouTube video of a guy saying it can put strain on the transformer?

 

Output caps are C817 & C818 on the schematic if I understand it correctly? 

 

Hope to see @pete_mac to hop in

 

Maybe getting ahead of myself but I had a question about how do I bias it if I don't have variable resistor pots on my early board (the first one by the looks of it)

 

[muon*]

I like to be conservative when I don't know what is following those caps.....I'm not a tech' just a part swapper with a little bit of knowledge so it pays for me to be a tad conservative especially where it comes to giving others advice..

 

Yes, I hope Pete has time to pop in too.

 

Isn't it in one of the service manuals? Hopefully Pete or John or someone can help there.

[SansuiSushi]

Like me then Ian, learning in progress, thank you for your input and I'd say very sensible advise. Have you owned a Sansui 101?

[pete_mac]

It's been a while since I have worked on an AU-101!

 

Your amp has already had all of the small capacitors on the main board replaced with generic capacitors. I'd suggest replacing them in due course. The large red capacitor is also non-standard. I also noticed that the output transistors on the right channel have died at some stage and have been replaced with TIP-31As, and likewise the other transistors have also been changed in this channel. You can see the physical difference between each channel when viewed from above in your photos.

 

There are some suggested components and tweaks in this thread:

 

 

 

@sloper is a bit of an AU-101/AU-505 guru these days and may have further suggestions based upon his experience.

 

 

Edited August 2, 2021 by pete_mac

[audiofeline]

If you were OK taking away from standard, you could update the RCA sockets and put in some binding posts to connect speakers. 

[sloper]

Geez Pete you are too kind.

 

l Do have a Au505 on the bench at the moment.

Will be cascading the coupling caps  and power supply as l do in the AU101 as well.

 

So as for the AU101 and 505, Poly cap on the power supply main cap of about 8 to 10uf, with a 100pf as well.

The coupling caps get a Poly cap 6 to 10uf and a 100pf as well.

Found this really lifts the detail of the amp on a whole, and makes the amp sound up there with Sansui"s best.

1uf film caps on the signal path of the tone board.

l do do all the transistors on the tone board as well, l use KSC1845 as l have heaps.

Just remember they are about face.

Tend not to do the main board unless there's a problem.

Dont be afraid to reflow a lot of joints.

 

There are also some other mods to lower the noise floor, although l have not needed to do them this amp will get them to see what it sounds like.

 

And once your finished, your hooked the AU505 sounds nicer than a 101 in my opinion but its  a great introduction to Sansui goodness.

l have cut down to just 2 AU505's now as l am trying to fund a Alpha.

The AU70 and AU717 are keepers.

 

regards Bruce

 

 

[SansuiSushi]

@sloper Thank you for joining in, would you be kind enough if you have the time to, work with me on a parts list? Some of that went over my head, being the lowly amateur that I am! Your suggestions sound great though and I would like to implement them. 

 

XML (Excel) file of a list from another thread in the ether.

https://drive.google.com/file/d/1I4uYAiG5i8ju3wGpT1blOu7XNyAqNLpy/view?usp=sharing

 

@pete_mac Thank you also for joining in, I've seen many posts by yourself in the past regarding the AU-101 will look at your suggestions in the other threat you linked.

You say they had been replaced with generics, I suspected such, can you suggest a GOOD replacement make / type?

 

Looking to order all the parts in one go so need to form a list. and give it a good go over a day or two. Looking forward to it!

 

@audiofeline Certainly would update the connections a little wouldn't it, I'll consider it once I have the internals complete, also looking at making new (keeping the old) cheeks in black zebra wood to go with the fascia. See sample below.. brings out the gold and works with the black.

 

 

Thank you all.

 

Edited August 2, 2021 by SansuiSushi

[SansuiSushi]

Did anyone have an answer to biasing this amp once its recapped etc, seems I have the original v1.0 without any trimmers...

 

Answer : Replace R-823,

R-824 with 1/4W 200 Ohm variable resistors (VR-801, VR-802 on F-302-1 onward. Correct me if I'm wrong)

 

Mouser 858-64YR200LF

Edited August 3, 2021 by SansuiSushi

[SansuiSushi]

On 02/08/2021 at 8:44 AM, sloper said:

1: Poly cap on the power supply main cap of about 8 to 10uf, with a 100pf as well.

 

2: The coupling caps get a Poly cap 6 to 10uf and a 100pf as well.

 

3: 1uf film caps on the signal path of the tone board.

 

4: Just remember they are about face.

 

5: There are also some other mods to lower the noise floor.

 

 

 

1: Do you have a particular recommendation of brand / product range?

 

2: Same question I guess also voltage at 50-63v?

 

3: Make all 1uf caps WIMA MKS or in addition to?

 

4: I didn't understand what you meant by this could you explain?

 

5: I'd like to know about those if I can implement them, any improvement!

 

That 505 looks nice... I'll keep my eye out for one.

 

It's a bit jumbled but have a quick look if you get time at my spreadsheet.

https://drive.google.com/file/d/1I4uYAiG5i8ju3wGpT1blOu7XNyAqNLpy/view?usp=sharing

Edited August 4, 2021 by SansuiSushi

[sloper]

Goodaye

 

1: Have used Jantzen and Suntan caps, l cant hear  a difference in the brand, so its what l have on hand.

2: The poly caps are usally in the 200v range so its overkill.

3: On the tone board use the wima 1uf film caps in place of the electrolytic.

4: The 2SC871 is BCE the KSC1845 is ECB. so you have to put the transister in the other way, but check that it hasent been changed during a repair.

5: l will get back too you.

 

l'll PM you the cap list l use.

 

regards Bruce

[SansuiSushi]

Small update:

Parts ordered! (from various places, ebay, mouser etc)

 

I may have forgotten the odd thing, and I ordered various transistors as in my reading I found various opinions about each type so only takes a few mins to solder different ones in so I'll give it a go!

 

Let you all know more when it happens

[SansuiSushi]

Small update as a few components arrived.

 

Replaced R835, R836, R837, R838. 

3W 0.47 5% (Original: 2W .5 Ohm, 10%)

 

R839, R840

1W 470 Ohm 5% (Original: 1/2W, 10%)

 

 

I did something wrong after that...  TIP41C as replacements for 2SC1060, or in my case TIP31A / C1986, anyway.. soldered them to TR809, 810, 811, 812, and 4 fuses later I returned the originals, not sure what I did wrong. I got the idea from this post 

 

 

Perhaps I got the pin outs wrong?  

 

EDIT:  Further research came up with this post  

 

Quote

 

There's the answer, with power off test for continuity between each transistor tab, as it appears if I am not mistaken, that you have all the collectors common, with each other, via the heatsink, which if its touching other components spreads the connection of the collectors all common being also with what the heatsink touches. You need to use a isolating washer that surrounds the screw-  usually found in a TO3 or TO220 mounting kit

 

The tab of the transistor, that you have the screw attached to is ALSO its collector. The transistors are unlikely to have survived, unless you had some current limiting, or were using a variac to lower voltage.  you can test them, with semiconductor resistance, once you have each tab screw isolated from the heatsink.

 

 

 

So I go and find some isolating washers for those screws, by some new TIP41C and try again, lucky they were cheap, but I learned something so that's of value too!

 

 

Also I came up with a way to see where the PCB goes because fitting the board transistors was giving me a headache with their pin out and orientation.

 

 

By shining a torch I can see without flipping the amp back and forth what connects to what and comparing it to the schematic to get the correct pin out. Not a new idea to many of you I'm sure but I thought it was ingenious!

 

 

Look forward to hearing your comments.

 

BONUS mess..

 

Edited August 8, 2021 by SansuiSushi

[SansuiSushi]

And so it begins again.... 

 

 

[SansuiSushi]

And so it begins again.... 

 

 

Scared to turn it on

[SansuiSushi]

 

 

It powers on, makes a sound.... will check the test points before turning it up too loud.

[SansuiSushi]

While I'm waiting I did a quick photoshop mock up of some cnc in the side panels. What do you all think of the idea?

 

[SansuiSushi]

New cord. Same plug. 

[SansuiSushi]

 

New speaker terminals

[SansuiSushi]

I'm please to announce I have finished installing the capacitors and now the transistors, after a whole day with the schematic, a soldering iron, and the breeze blowing through the window. I have done it, and it sounds absolutely lovely! 

 

Biased at 20mv per channel. The meters ain't no Fluke, but, did the job.

 

 

 

Another view of the meters attached

 

 

Prior to biasing 

 

Soldering iron is a Pinecil, highly recommend it. 

 

Bonus pictures from today...

 

 

 

Comparing sizes of old and new.

 

 

 

47uF cap.... Reading 84.4uf slightly out of the 20% range!  

C-709

C-710

 

Purple Silmic II (Different to others I ordered from Mouser) got these from eBay as I needed them quick and mousers delivery is £12. That being said they add a nice bit of colour. 

C-709

C-710

[BLAH BLAH]

[SansuiSushi]

Perhaps a few resistors to swap out... I'm going to enjoy it for a week or so now Sansui indeeeeeed. 

[SansuiSushi]

 

Just a little shot with his temporary friend (Sony STR-DH700), I can see another Sansui there perhaps a 505, 555...

Edited August 15, 2021 by SansuiSushi