Sansui AU-217 restoration

[p4spooky]

Excellent work - I use my restored AU217 as desktop amp and it rocks. Can you please specify the changes you implemented on F2758 (@Leestereo insired). I read the thread twice and did not see exactly what component values were changed. Will be very helpful if you can specify.

 

[mcgjohn]

Starting on my Sansui AU-217 restoration. This particular unit is in great condition. It is all original. And really no cosmetic flaws. When I received the unit it did not power up. I found a cut in the power cord and one of the conductors was fully sheared. I temporarily repaired the cord with butt splices. The unit powered up but had no sound out of the left channel. I cleaned all of the controls with F-5. Fully functional now.

Does anyone have a good lead on where to get replacement factory style power cords?

Having just finished my AU-117 rebuild the first thing I noticed under the hood of the AU-217 is a retainer bracket for the input selector shaft. The AU-117 does not have a retainer bracket for the input selector shaft and that resulted in the shaft walking out on my AU-117 and losing mechanical connection to the electrical end. It looks like Sansui resolved this on the AU-217 with the retainer bracket. Was this a running change on all models or only on the AU-217?

Now that everything is working and functional I plan to update/improve the electronics. Big thanks to @Leestereo for the technical support on the spec. If you have any questions about the BOM you can message him directly.

More fun.

Hi-Fi Engine AU-217
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about 12 years ago, restored a 217. Nice little amp. It has now seen 24/7 service to drive my PC speakers. Never has been any issue. Will say that once you get into it, make sure you carefully remove all the glue the factory used to hold components in place before going to soldering. I used IPA with a Q-tip to soften the glue, wait a few min then used a wood stick to gently pry the glue off the circuit board.
Don't use a screwdriver or you will scratch off the silk screening on the board as well as add small scratches to the board itself.

 

[Leestereo]

...Can you please specify the changes you implemented on F2758 (@Leestereo insired). I read the thread twice and did not see exactly what component values were changed...

The AU-217 RIAA feedback topology was modified to match that used in the higher x17 models, i.e., a set of parallel RC pairs, by installing the replacement resistors for R19/R20 in parallel with C07/C08. The resistors R19/R20 and R21/R22 were replaced with 267kohm and 22.6kohm metal film types, respectively. The capacitors C07/C08 and C09/C10 were replaced with 12nF and 3.3nF polypropylene types, respectively. The modified AU-217 RIAA equalization is accurate ±0.15dB from 20Hz-20kHz.

 

[Leestereo]

Additional tweaks for the AU-217: upgrade the 2W emitter resistors to 5W types and replace the the resistor parallel to the output inductor with a 2.2ohm 2W metal film type. The former change can alleviate dynamic compression under heavy current demands (e.g., playing loud with low sensitivity speakers) and the latter change matches the topology in the larger x17 amplifiers.

 

[graphixman]

Boy this brings back memories. I still have my paired 217 and TU-317 I bought brand new in 1978 in Yuma Arizona.
Still works great as is, but this thread give me ideas for when things go south.