Sansui AU 517 power supply "upgrade" questions

zoeffiex

Active Member
Hi Guys,

(hope my englisch is ok, normally i speak dutch.)

I am looking to restore and "upgrade"a AU517.
Inspired by a recap and upgrade of a AU717 done by @Leestereo i would like to do some upgrades to the regulated power supply.

I agree with him that the most benefits can be made here .
Except for the power supply and the tone control boards of the AU517, the pre/main switch board, the equalizer board and the driver circuit boards are allmost identical to the AU717.
(in a few places other resistor values are used.)
So i can do the upgrades leesetereo did on the "shared" (allmost identical ) boards. (BONUS!:))


Next the schematic of the 517 psu


PSU.png

Main power supply uses 30D2 diodes.
The 4 power supply main capacitors (C701-C704) are rated at 12,000µF/63VuF. I would like to upgrade them to the same value as the 717, 15000uF/63v, If the 30d2 diodes are up to that. Or should i replace them? MUR1520G are recommended by some. Same reverse en forward voltage etc.

Now on the regulated supply:

As we can see raw DC is filtered by C5-C6-C7-C8 and are rated at 220uF/63V
Next capacitors are C9-C10-C11-C12 rated at 100uF/35V. (These shunt the zeners?)
Then come TR01 + TR 03 and TR 02 + TR04. These are 2SD438 + 2B560 pairs.
C25-C26-C27-C28 are 220p ceramics
The zeners ZD01 + ZD03 and ZD02 + ZD04 are RD33E(B)
R13 - R16 says 22 on the schematic. I guess it is 22R
After that C13-C14-C15-C16 rated at 100uF/35V
And final are C19-C20-C21-C22 rated at 47uF/50V


Now, this is it! And it is way different then the AU717 .
If i am correct, the 717 uses local decoupling on the tone control board.
The 517 does not. Hence the extra 47uf capactors?

Ok, now to my question (s)

Can i upgrade C5-C6-C7-C8 to 820uF or more?
If i read the schematic correctly, C9-C10-C11-C12 shunt the zeners? If so i would like to upgrade them to 120uF.

Can i upgrade C13-C14-C15-C16 to 330uF or more?
Can i upgrade C19-C20-C21-C22 to 150uF or more?

Can i do these upgrades without any harm to the other components or do i need to upgrade these also.

On the zeners, i was thinking of replacing them with BZX55C33 (2%) or 1N5257B since the original RD33E(B) zeners are Min 29.68v/Max 33.11V according to the datasheet.

Also, need to look for the fusistors...And replace them.

Well, that is the story. Hope some of you can advise me on this,

Best Regards,
René (Zoef)
 
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Oh my, i´ve been `sneaking´ around here since Aug 1, 2015....this is my first post :eek:

Shame on me.......
 
Just did leestereo on a 717.
I put in everything he did and the main caps! I could not believe they were way out of spec. Anyway, during the job getting close to the end I was not happy with the noise floor. It was quite but could use some improvement. I replaced the known bad/noisy transistors 2sa726 and 2sa750 and it made a big difference. Hunt around this forum and you will see the problems with those.
Cheers
Gord
 
For the last AU-517 that was on the bench, the following replacements were installed on the F-2675 board: 820uF/63V for C05-C08; 220uF/50V for C09-C22. On the F-2673 Tone Control board, the local decoupling capacitors are the 0.047uF ceramic capacitors (C27-C30); these were replaced with 0.47uF polyester film types.
 
I'm working on one I will have to try this.
capacitors are the 0.047uF ceramic capacitors (C27-C30); these were replaced with 0.47uF polyester film types.
.

Ben, do you mind to explain us why to up the capacitance 0.047 to .47uf?

Cheers!
@zoeffiex, sorry to hi jack your thread but I'm sure you would likr to know too.:rolleyes:
 
The decoupling capacitors C27-C30 on the F-2673 board in the AU-517 counteract the inductance of the wiring from the power supply board. The 47uF decoupling capacitors on the F-2720 board in the AU-717 perform the same function and, due to their capacity, also provide additional filtering/reserve. Due to the limited physical board available for the C27-C30, the replacement capacitors could only be increased to 0.47uF.
preamp after.jpg
 
The decoupling capacitors C27-C30 on the F-2673 board in the AU-517 counteract the inductance of the wiring from the power supply board. The 47uF decoupling capacitors on the F-2720 board in the AU-717 perform the same function and, due to their capacity, also provide additional filtering/reserve. Due to the limited physical board available for the C27-C30, the replacement capacitors could only be increased to 0.47uF.
View attachment 1121484


would agree with the comments made by Leestereo.

as for all the cap value changes, I would think its more important as to which type of cap you select vs. the value change. Go for high temp low ESR types like the Nichicon UPW types. They should last a very long time in a Sansui.

I have rebuilt four or five 717s over the last few years and have always had good luck with the nichicon UPWs.

Am sure you are already aware of it, but if not be sure to clean all the old glue away from the through holes. that stuff is corrosive and conductive with time.

two years ago, I rebuilt a dead Au217. AC voltage was good so started looking past the rectifiers. Found both main PS filters had a lead missing. the cap leads had been completely eaten through by the corrosive nature of the stick on glue used by the factory back when the amp was first assembled, there was no electrical contact between the trace and one lead on each cap.....
 
Well then, I picked up a pretty lady today.
I will post some pictures and hopefully some nudes if she is willing tomorrow.
I feel like a little boy again. Owning my first sansui. (au 515) She is in very good cosmetic condition. Had a partial recap. (all small caps) She was a bargain. Although I had to drive 4 hours to pick her up.

Maybe someone can tell me a bit about her? Serial number is 227081140
 
For the last AU-517 that was on the bench, the following replacements were installed on the F-2675 board: 820uF/63V for C05-C08; 220uF/50V for C09-C22. On the F-2673 Tone Control board, the local decoupling capacitors are the 0.047uF ceramic capacitors (C27-C30); these were replaced with 0.47uF polyester film types.

Thanks again.

Hope i can bother you with some additional questions. @Leestereo I'm in the progress of ordering the new parts,
On the F2675 the protector parts:
I looked closely at the schematics of the 517 and the 717 and at the upgrades you did on 717.
Like you did on the 717 , can i replace C601 for a 100uF/63V (listed at 47uF/50V).
C604 for a 470uF/24v. (listed at 330uF/16V)
C605 for 47uF/50V (listed at 33uF/50v)
C23 and C24 where as listed . 100uF/6.3v. Replace with Nichicos ES 25v types?
New relay MY2-02-DC24?

Due to the glue i needed to remove R11, R15 and R7 from F2721.
Replace all with 0,25W? How about tolerance?
There was so much glue on the board even the yellow 20awg wire was "gone".
Can i replace this with a 18awg? Or does it have to be the same size.

The trimmers...what is the power rating of those?


last one,

F2674, Bass and treble volume control. (on the schematic "part" of F2673)
Replace c13 + C14 (10p ceremics) with C0G?


Hope i did my homework ......
 
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In the last two days i cleaned the amplifier and took out most of the boards. All parts i want to replace are carefully removed. Those new caps also!!!!
Glue removed. The glue was a hell of a job. I made some scratches on the board during the removal... (aargh!!!)

first the PSU / protector

 
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On the F2675 the protector parts:
I looked closely at the schematics of the 517 and the 717 and at the upgrades you did on 717.
Like you did on the 717 , can i replace C601 for a 100uF/63V (listed at 47uF/50V).
C604 for a 470uF/24v. (listed at 330uF/16V)
C605 for 47uF/50V (listed at 33uF/50v)
C23 and C24 where as listed . 100uF/6.3v. Replace with Nichicos ES 25v types?
New relay MY2-02-DC24?.

For C604, install a 330µF/25V; agree with the other replacements.

Due to the glue i needed to remove R11, R15 and R7 from F2721.
Replace all with 0,25W? How about tolerance?
There was so much glue on the board even the yellow 20awg wire was "gone".
Can i replace this with a 18awg? Or does it have to be the same size.
The trimmers...what is the power rating of those?

All carbon film 0.25W resistors that had be replaced were replaced with 1% metal film 0.25W types.
If >20AWG wire is used, you might have to enlarge the solder pad to accept the wire.
Replacement trimmers are rated at 0.5W.

F2674, Bass and treble volume control. (on the schematic "part" of F2673)
Replace c13 + C14 (10p ceremics) with C0G?

No need to replace the C13/C14 Miller capacitors.
 
For C604, install a 330µF/25V; agree with the other replacements.



All carbon film 0.25W resistors that had be replaced were replaced with 1% metal film 0.25W types.
If >20AWG wire is used, you might have to enlarge the solder pad to accept the wire.
Replacement trimmers are rated at 0.5W.



No need to replace the C13/C14 Miller capacitors.
Thanks!
Will order the parts today.
 
thanks for the pictures:). What brand of capacitors were used in the first repair? He was not careful in cleaning the glue:confused:

Ha! No he was not. Or.... he did not at allo_O

I removed nichicon vz and yageo caps.
All are going to be replaced by Nichicon PW
For the few audio caps used, Nichicon ES/BP an Elma SilmicII

(the elma's because i have a bunch of them. why buy others.....?)

The high value coupling caps 4.7uf 10uf etc.. i want to try film caps. mks2 (yes i did say that)
If it sucks...i can always replace them again. Or did someone try this?

My thought. Why not use al the same type and brand in the whole signal path. ( just want to try)
 
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