Project: Sansui AU-717 (Restore / Rebuild)

[Super Noob]

In the quest of vintage stereo, my adventure continues. Last weekend I found the Thanksgiving project.

A non-working unit popped up, and I snagged it. The unit was a non-working sister to an AU-717 operational unit sitting at member @MtnBeachBum. Chris definitely was a AU-717 fan. Thanks to Chris for selling this unit to me. (bit of hike for me 2.5 hours each way)

Sansui AU-717
Weight: 37 pounds (I like to buy equipment by the pound, and this didn't disappoint)
Power output: 85 watts per channel into 8Ω (stereo)
Year: 1977-1979

This unit looks modern in regards to the black aluminum faceplate... I guess more of a forward looking unit at the time with the BPC era advancing quickly.

First Impressions:
WOW - this thing is built. Maybe not a brushed aluminum face or large meters - but don't be fooled, this thing looks to be built for performance.
Dual Power Supply.
Am under the hood of many units, and this unit is impressive in regards to build quality and serviceability.

Plenty of covers / neat / and all business inside. The pictures say enough. This unit is build like a "****-brick-house".

As a hobbyist, I found that our guru member @Leestereo did a rebuild of this unit. With over 53,000 views of that thread = it is clear that we all respect Leestereo's work and his aspects to rebuilds. He is miles ahead of my small brain, so like a good sheep - I follow almost all his modifications and upgrades. Leestereo, I have read so many of your threads, and I want to thank you for sharing your ideas and builds. Thanks Ben!

Here is the AU-717 (bible build) Leestereo:
https://audiokarma.org/forums/index...estoration-upgrade-of-a-sansui-au-717.641945/

Here goes my attempt at this non working unit. Am attaching my list in PDF and WORD. Keep in mind that I didn't do everything exactly as Ben - as I have taken some liberties (relating to a few parts). When in doubt = Go with Ben's suggestion.

PDF:
https://drive.google.com/file/d/14RYyGiK6cUEpcYZFQYp7c3fH9jqiiUh_/view?usp=sharing
Word Doc:
https://drive.google.com/file/d/14RYyGiK6cUEpcYZFQYp7c3fH9jqiiUh_/view?usp=sharing

My attempt and detail is to show with good tools, mindset, and research that even a hack can score a good rebuild. As always stated in my threads - my goal and hope is this rebuild will inspire someone to consider rebuilding the AU-717 in the future. It is worthwhile.

 

[Super Noob]

Okay = Non Working. The power supply was working, and the problem seemed to be related the amp boards. I started here and found plenty of components taken out by that notorious Sansui glue.

F-2721 (Amp Driver Circuit Board) Right / Left Total (2)
D02 – 1S2473 / Now 1N4148
C02 & C04 – Original 33uF 25v / Now 100uF 35v (Nichicon UPW1V101MPD)
C11 & C14 – Original 470uF 63v / Now 1000uF 63v (Nichicon UPW1J102MHD)
ZD01-ZD02 – EQB01-22, 22v 1-Watt Zener Diode / Now 22v 1.3-Watt (BZX85B22-TR)
R16 –Original 27K Ohm 1/4 -Watt Carbon Resistor / Now 27K Ohm 1/4-Watt Metal Film (KOA Speer MF1/4DC2702F)
R23 & R25 – Original 150 Ohm Fusistor / Now 150 Ohm 1/4-Watt Metal Film (1% KOA Speer MF1/4DCT52A1500F)
TR01-TR02 – Original 2SC1400 ECB / Now KSC1845F (HFE Matched)
TR03-TR04 – Original 2SA750 (PNP) ECB / Now KSA992FB
ZD01-ZD02 – EQB01-22, 22v 1-Watt Zener Diode / Now 22v 1.3-Watt (BZX85B22-TR)
VR1 – Original 100 Ohm Trim Resistor / Now 100 Ohm Single Turn Sealed 3/8” (Bourns 3386H-1-101LF)
VR2 – Original 2.2K Ohm Trim Resistor / Now 2.2K Ohm Single Turn Sealed 3/8” (Bourns 3386H-1-222LF)
VR3 – Original 1K Ohm Trim Resistor / Now 1K Ohm Single Turn Sealed 3/8” (Bourns 3386X-1-102LF)

Here is that glue:

Before:

After:

Multi-turn offset trimmers are not needed as the there is rough adjustment on VR1 and fine turn on VR2. I went in and changed the small transistors TR01-TR04 = they were all in great shape (no black creep); however, I have yet to replace small transistors and be unhappy. Fusistors were all open and other resistors were taken out by that glue. Ben's replacement on the coupling caps were each same size with 4x the capacitance. Ben's mechanical fit of replacement is awesome. Went ahead and replaced glue impacted components and zeners.

 

[Super Noob]

Power supply was up next... tip for servicing - desolder 6 power supply leads from the bottom of board, remove the mount brackets, and the board can be pulled forward for rebuilding.

F-2263 – Power Supply
C05-C08 – Original 220uF 63v / Now 820uF 63v (Nichicon UPW1J821MHD)
C09, C10, C11, C12 – Original 100uf 63v / Now 330uf 63v (Nichicon UPW1J331MHD)
C17-C18 – Original 470uF 16v / Now 470uf 25v (Nichicon UPW1E471MPD)
C19-C22 – Original .47uf 50v (LL) / Now .47uf 100v (WIMA MKS2D034701E00JSSD)
C23-C26 – Original 100uF/35v / Now 220uF 50v (Nichicon UPW1H221MPD)
C701- C704 – Original 15000uf 63v / Now 15000uF 63v KEMIT ALT22A153DE063 (85C 26k Hour)
C707- C710 – Bypass Caps Polyester Film 2.2uf 100v / New 2.2 uF 450v Polypropylene Film (Panasonic ECW-FE2W225J)

ZD01 and ZD02, RD13E 33E, (½-Watt) / Now 13V, ½-Watt, Zener, 1N5243B

R7, R8, R9, R10, R11, R12, R13, R14 - Original 10k Ohm ¼-Watt / Now 10k ½-Watt SFR25H001002FR500 (1% Metal Film)
R33-R34 – Original 22k ¼-Watt / Now 22K ½ Watt MFR4-22KFI (1% Metal Film)

D01-D02, 10D2 1-Amp Diode / Now MUR220RLG, 2A / 200V Ultrafast Diode
D05-D012, 10D2 1-Amp Diode / Now MUR220RLG, 2A / 200V Ultrafast Diode
D604 - VD1212 Varistor / Now Double (Series) 1N4148 Diodes

Before:

Glue coated components were still operation but I replaced all. On the R25-R26... I cut off the glue affect areas on the leads, then I pull them down into the through hole and resolder (can see this by how they are bent over in the after pictures).

If you know my rebuilds, I always replace the relay. When I desolder the relay - the contacts looked brand new (mean absolutely no wear). So I popped it back in. The Omron is direct replacement.

Fuser holders were not perfect - I have stock, so I replaced these too.

After:

 

[Super Noob]

F-2263 – (Continued) Protection Circuit
C601 – Originally 47uF 50v / Now 100uf 63uF (Nichicon UPW1J101MPD)
C604, 470µF 10V / Now 470uF 25v (Nichicon UPW1E471MPD)
C605 – Originally 33uF 50v / Now 47uF 50v (Nichicon UPW1H470MED)
C606-C607 4.7µF 50V / Now 4.7uF 50v (NichiconUPW1H4R7MDD)
C29-C30, rated 220µF 6.3V (bipolar) / Now 220uf 25v (Nichicon UES1E221MHM) less than ideal go with 16v

D608 – Original, 10D1 (1S2226) 1Amp 100v Diode / Now 1N4004 1-Amp 400V
ZD601 – Original EQA01-06R 5.6v Zener / Now 5.6v 1-Watt Zener (Nexperia BZV85-C5V6,113)
ZD602 – Original RD-6.2E 6.2v ½-Watt Zener / Now 6.2v ½-Watt Zener (On Semi 1N5234C)

Relay = Omron MY2-02-DC24

 

[Super Noob]

F-2720 –Tone Control
C05-C06 - Original 0.33uF Polyester Film / Now .33uF 450v Polypropylene Film Panasonic ECW-FE2W334J (5%)
C07-C08 – Listed 10pF Found 22pF Ceramic / Now 22pF 100v (C0G) RDE5C2A220J0M1H3A (5%)
C15-C16 – Original 10uF 16v / Now 10uF 35v (Nichicon UKL1V100KDDANA)
C21-C22 – Original 10uF 16v (signal) / Now 10uF 35v (Nichicon UKL1V100KDDANA) LeeStereo- Ben Prefers UES Here
C23-C24 – Original Listed 10pF Found 22pF / Now 22pf 100v (C0G) 5% RDE5C2A220J0M1H3A
C25-C26 – Original 0.47uF Polyester Film / Now to 0.47uF 250v Polypropylene Film WIMA MKP4F034704D00JB (5%)
C27+C29 & C28+C30 – Original 100uF 6.3v Polar In Series for Bi-Polar Configuration / Now Single 47uf 16v Nichicon UES1C470MPM (Bi-Polar)
C31 & C32 – Original .1 uF Film (bypass) / Removed
C33+C35 & C34/36 – Originally 4.7uF 50v (LL) in Series for Bi-Polar / Now Single 2.2 uF 450v Polypropylene Film Panasonic ECW-FE2W225J (5%)
C39-C42 – Original 47uF 50v / Now 220uF 50v (Nichicon UPW1H221MPD)
C45-C46 – Original 10uF 25v (LL) / Now 10uF /35v (Nichicon UKL1V100KDDANA)

D01-D02 – Original VD1212 Varistor / Now Double (Series) 1N4148 Diodes

R37-R40 – Original 82ohm ¼ Watt Fusitor / Now 82ohm ¼ Watt Metal Film KOA = MF1/4DCT52R82R0F (1%)

TR01-TR06 – Original 2SA726 (PNP) ECB / Now KSA992FB (HFE Match) TR1/TR5 & TR2/TR6
TR09-TR12 – Original 2SC1400 ECB / Now KSC1845F
TR07-TR8, TR13-TR14 – Original 2SA750 (PNP) ECB / Now KSA992FB

Before:

C05-C06 Polypropylene Replacement

C27-C30 Replacement... polar in series (bi-polar simulation) replaced with Bi-Polar:

C33/C35 & C34/36 - Replaced with Polypropylene Film

Other set is more straight forward (just showing space on back of board - populated on front)

C25-C26 – Polypropylene Film WIMA

These are smallest MKP that I could find.... it is tight in there but they fit. One required some leg work.

 

[Super Noob]

F-2720 –Tone Control
Continued.....

Leestereo caps = exact same size (NICE!)

After Shoot:

 

[Super Noob]

F-2670 – Pre-Amp Switch Board
C01 - C04 – Originally 10uf 25v (polar caps in series for bipolar) / New 2.2 uF 450v Polypropylene Film (Panasonic ECW-FE2W225J)

Look at the build document for more detail in 1st post. These polypropylene replacements fit good (barely). They are smallest ones that could be found at Mouser - they are new.

Push the the pins of the retainers from inside unit to release the plastic binders.... they are glued.

Before:

After:

 

[Super Noob]

F-2723 – Tone Control Board
C01-C02 – Original 1uF Polyester Film / Now 1uF 450v Polypropylene Film TDK B32672Z4105J00 (5%)
C03-C04 – Original 100pF Ceramic / Now 100 pF 100v Polypropylene Film WIMA FKP2D001001D00JO00 (5%)
C05-C06 – Original 220uF 6.3v / Now 470uf 25v Nichicon UKA1E471MPD1TD (Leestero prefers Bi-Polar Here)
C19-C20 – Original 10uF 16v / Now 10uF 35v (Nichicon UKT1V100MDD)
C27+C29 & C28+C30 – Original 10uF/25V (LL) in Series / Now 4.7uf 63v Stack Polyester Film WIMA MKS2C044701M00JO00 (5%)
C31-C34 – Original 10uf 50v / Now 47uf 63v (Nichicon UPW1J470MPD)

D01-D04 – Original VD1212 Varistor / Now Double (Series) 1N4148 Diodes

R47-R50 – Original 82ohm ¼ Watt Fusitor / Now 82ohm ¼ Watt Metal Film KOA = MF1/4DCT52R82R0F (1%)

TR01-TR02, TR05-TR06 – Original 2SA906 (PNP) BCE / Now KSA992FB (HFE Match) TR1/TR5 & TR2/TR6
TR03-TR04 – Original 2SA726 (PNP) ECB / Now KSA992FB
TR09-TR10, TR15, TR16 – Original 2SA750 (PNP) ECB / Now KSA992FB
TR07-TR8, TR11-TR14 – Original 2SC1400 ECB / Now KSC1845F

Okay as noted by Ben... pull the retainer clips of the control rods (on face-plate) and slide them off the board.

Before:

C27-C30 polar in series for bi-polar configuration (replaced with single film)

All of these fuse-resistors were open....

 

[Super Noob]

Missed earlier.... rework the heatsinks with Wakefied 120

 

[Super Noob]

The main filters... existing filters measured 15-20% off stated valve.

C701- C704 – Original 15000uf 63v / Now 15000uF 63v KEMIT ALT22A153DE063 (85C 26k Hour)
C707- C710 – Bypass Caps Polyester Film 2.2uf 100v / New 2.2 uF 450v Polypropylene Film (Panasonic ECW-FE2W225J)

I usually go with best size for replacement and Kemits were the best. Improvement.

Open up the holes...

Trim down the interior posts for re-routing the bridge with ease.

After:

Pretty clean replacement.

 

[Super Noob]

Finishing Up:

Need to repaint the top shell / cover, and she is done. Bias dialed up to 20mv and offset is stable under 1mV.

I Know, I Know: How Does She Sound?

Well have you ever heard angels sing = I HAVE!

 

[AUD101]

Beautifully executed - period! - Really superb pix - period! - Excellent attention to detail - will be over for a listen later - Lol
I really do like the sonic signature of the AU-717 - It's a true power house from the late 70's - will easily drive a pair of 4 / 8ohm speakers with ease to high power levels

Edit:
Those Kemets are a great choice as the main filter cap's

 

[Robisme]

That's a lot of work. Nice job.

Rob

 

[Leestereo]

Excellent work and pictures!

 

[Super Noob]

Excellent work and pictures!

It is really just your rebuild = Thanks Ben!
You are the man!

 

[MtnBeachBum]

Awesome job!

 

[-Alexey-]

Great job. But what if you followed the service manual?

 

[Skywatcher]

Great job. But what if you followed the service manual?

You can if you like. Actually you can follow what is in the unit instead of the service manual and it will be fine. There may be some changes made during production that will not be in the service manual after it was printed. However the "changes" made in this thread do improve the sound.

 

[-Alexey-]

No change, worse?

 

[Hyperion]

No change, worse?

No change = better, but not best.