AU 317 Recap Project

[p4spooky]

F-2754

• p4spooky
• May 3, 2018

Sansui Experts: Found a bargain on AU 317 few weeks ago - got it free along with TU217 tuner

Ordered parts from Mouser following some great threads here. I will be posting pictures of the work done along with some changes I made. The good news is the AMP is working great!

I noticed F-2754 board does run warm (about 54 deg C - Lower right corner below the Phono board) after couple of hours of use around the area where C03, C04, C09, C10 is located next to the 18v Zeners. I currently have used 33uF 50V Silmic II caps (85 Deg C) as replacement. Appears to be an incorrect choice now that I am looking at the schematic closely and the temps in this location.

Also can someone explain what this cap does parallel to the 18v Zener? Can I replace this cap with 100uF 63v UHE or equivalent? Please see attached schematic.

 

[Hyperion]

Also can someone explain what this cap does parallel to the 18v Zener? Can I replace this cap with 100uF 63v UHE or equivalent? Please see attached schematic.

The capacitors are there to clean and smooth the supply getting to the differential pair IC01. You're on the right track with the 'UHE' in my opinion (low ESR, higher temperature, not audio grade) - but perhaps a slightly lower voltage rating (say... 25V or 35V) as it will only ever 'see' 18V due to the zener diodes.

The temperature you mention seems high so you may have other issues, have you checked the bias yet?

 

[p4spooky]

@Hyperion: Thanks. Yes both bias and DC offset are OK.
Couple of resistors in this area are running at 44 Deg C. I will change out the caps as you have suggested and check again.

 

[Hyperion]

OK, maybe I am being a bit alarmist about the temperature - it's a long time since I've had an AU-317 on the bench.

Keep us posted with progress.

Oh and I forgot (to look at your post count), Welcome to AK and especially to the 'Exclusively Sansui' forum.

 

[p4spooky]

With some excellent information on AU 317 I started my recap journey last week. Special thanks to @Hyperion , @Karl vd Berg, @Leestereo , @skippy124 , @AUD101 for their invaluable suggestions and tips

Tools:

0: Built myself a DBT and verified that it works!
1: Basic soldering tools I had + De-soldering tool (Wick is too slow! but still required!)
2. Deoxit D5


Parts Selection and approach:

0: Took pictures with cover open before touching anything!
1. Did not disassemble main amp board - used back access panel and two diodes (D09/D10) were accessible once heat sink was removed. I did not feel comfortable removing all the wires which is required for a full disassembly
2. Used UCC KZN caps throughout - deviation from Nichicon UHE recommendation. No particular reason, KZN has slightly better ripple specs and life hours
3. VD1212 diode pack was replaced with two IN4148 in series
4. WIMA/ELNA Silmic II caps used throughout audio path
5. Headphone board had two mylar caps (0.047) replaced with WIMA. Headphone output is excellent and highs are slightly better!
6. 470uf filter caps upgraded to 820uf 63V KZN (@Leestereo style!) - could not fit 1000uf 63V caps - the leads were too thick to fit the board
7. Fusistors on main amp replaced (150R) with 150R 1/3W (see @Karl vd Berg thread)
8. All diodes/Zeners/Rectifiers replaced
9. Replaced all ceramic caps with COG type (may be overkill!) - see pics
10. Pads are extremely fragile - had to do one patch work on Tone control board.
11. Did NOT replace any transistors at this point
12. Main filter caps upgraded to 15000uf 63V CDE (383LX153M063A062) 5 pin type

1. Cover open - this is what I saw



2. Mark polarity of all caps (-ve) before removal, basic cleaning complete



3. Oh! the Glue



4. Glue cleaned (excellent glue removal thread tips!) - Used Goof Off cleaner while staying away from Mylar caps in the area



5. TO-3 transistors removed - carefully marked position on the board from left to right



6. Heatsink removed - flaky paste after 42 years! - Note some parts did not have proper contact. Remove the two clip on heatsink for transistor T09 and T10 attached to the main heatsink. clean and reapply thermal grease for T09 and T10



7. New components installed (Caps, Diodes, COG caps, Multi turn BIAS and DC OFFSET variable resistors and main filter caps) - Note UCC KZN used throughout



8. Tone Control, Mic and Phone preamp board recapped



To be continued.....

 

[p4spooky]

9. F-2754 Closer view - Note the COG caps installed



10. Final Assembly





11. Summary parts replaced:





to be continued....

 

[p4spooky]

12. Front Panel cleaning (before and after)



13. Final BIAS and DC offset adjustments (done after 30 min post power on) - Note all the wires tied down!



14. Did a full 10 hour test - No issues - SOUNDS INCREDIBLE!

 

[p4spooky]

I did not replace any transistors at this point. Open to recommendations if anything needs to be changed as a precaution to protect the outputs. Will create project on mouser site and share it - hope it will help someone attempting this.

 

[Karl vd Berg]

Very good work, P4spooky! Thanks for sharing.

You made best choice by replacing the small ceramic caps with C0G ones for better stability. The stock transistors in the AU-317 are still the best possible ones, if they are still good. I have newer, "more modern" spare transistor parts, but I kept the stock ones in it until they last. The C0G caps however were a good decision.

Curious to see the whole list of parts.

 

[Jigo]

if you ever replace any other transistors, make sure you tell us which ones you bought as you won't find the same original ones/specs anymore

 

[ghamilton]

 

[Hipocrates]

Nice write up and work!

 

[ghamilton]

The way those outputs are in there it kind of reminds me of the old NAD 3020. I wonder how it would compare.

 

[dedero]

Hi!, Thanks a lot for sharing!, you've made an awesome work in here

I finished last year a restoration of a AU-217 and yesterday I bought an AU-317 so I'm extremely excited to start the restoration, would you please share the part list or the Mouser project mentioned above?, that would be awesome!

Cheers,
Bruno.

 

[p4spooky]

Upgrade and full restoration is worth it as these amps come to life after one. Not to mention the satisfaction of working on one yourself. I got distracted with other projects and forgot to post the link.

AU 317 Restoration Project - MOUSER

Notes:

1. Qty is in multiples of 10 due to dramatic part cost decrease and I was working on multiple projects
2. Some parts (main filter cap) is significantly cheaper from Digikey
3. COG replacements are NOT mandatory. There are lots of them on the power amp board.
4. For all small parts (resistors, ceramic caps, diodes) - Remove part, replace observing polarity (diode), double check your soldering work and move to the next part. This avoids errors and countless hours troubleshooting
5. For bigger Electrolytic Caps, mark -ve polarity with a pen, take lots of pics, remove, clean glue and replace observing polarity. Double check solder joints
6. Let me know if you see any errors or missing parts and I will update the project accordingly

 

[SoundOfSound]

 

[dedero]

Hi @p4spooky , thanks a lot for sharing your Mouser project! it helps a lot with my restoration.

I would like to ask you 2 concerns I'm having now before ordering every components:

- The original main caps are 10000uf 50v and I would like to replace it for some ones with the same 4 pin fit and I saw you've replaced them for a 15000uf 63v with 4 pins, seems to be "plug and play" ones but I didn't take the measures, using such capacity upgrade did you have to changed/upgrade anything else in the circuit like the power supply diodes?
- I your project list you've purchased multi turn Bourns trimpots "W" series which have the 3 pins in-line but the original ones should be the "Y" series with a triangle pin shape (https://www.mouser.de/datasheet/2/54/296-776415.pdf). As the Y series is quite difficult to get stock (at least in Mouser) did you have any trouble to fit the "W" in-line pins series?

Cheers,
Bruno.

 

[Hyperion]

As the Y series is quite difficult to get stock (at least in Mouser)

Sometimes search selections don't find the trimmers you are looking for - I am thinking you missed them for this reason.

https://www.mouser.co.uk/ProductDetail/Bourns/3296Y-1-101LF?qs=sGAEpiMZZMvygUB3GLcD7n4W/LGLppVQ9l60jp8zEVA=

https://www.mouser.co.uk/ProductDetail/Bourns/3296Y-1-202LF?qs=sGAEpiMZZMvygUB3GLcD7sSg8po3Zpo3ZM5R4rf2Xc4=

The above are links to the trimmers listed in the SM - 100Ω and 2.2KΩ (link for 2KΩ given above) - 'top adjust' 'triangle spaced leads' Bourns series 3296Y

 

[p4spooky]

Hi Bruno:

1. D602-D605 is being upgraded to 511-STTH4L06 (4A current handling capability) which is higher spec than 30D2 diodes to handle the capacitance upgrade. If you want to go higher you can get 511-STTH5L06RL (overkill).
2. The "W" series does fit. Which is what I used. You are correct, "Y" will be an easier fit if you can get it in Germany.

Hope this helps.

 

[dedero]

Hi All, Thanks a lot for the very useful information!!

Cheers,
Bruno