Sansui AU-555A

[Trnsfmr]

Hi Trnsfmr,

Could you explain more about these terms, please ?
- hi zuit audio caps
- two output caps...which ones are they ?
- coupled amp capacitors...which ones are they
How huge is the improvement ?
Thanks

Hi,
Hi zuit audio caps. (Slang) These are caps made specifically for audio, Nichicon UKW comes to mind. They are approximately 3X the cost of normal caps.

The two output caps are on the main board, the biggest ones there. They are either 1500 or 2200uf, 63v. They couple the amp output to the speakers. All the audio for this type of amp goes through these capacitors. Thus, they are very important for sound quality.

Coupled amp capacitors. same as previous.

How huge the improvement. Well... If you are comparing to the original stock Sansui caps that are 45-50 years old now, the improvement should be huge. Night and day. Way more low end. Much more definition and musicality.

 

[Sprungtol]

Thank you for your explanation, Trnsfmr
I kept hearing such a good recap review like this.
You mean these big coupled output caps ?
This is from Sansui AU 5500, i have one too. Heavy like a german tank.

This is going to be my guinea pig.
Nothing to complain about except for whenever i played K-Pop dance Mp3 the bass sounded ....burrp burrp.... at some points.
You know those K-Pop hip hop songs are so rich with deep bass beats.
My speakers are JM Lab Focal. 6 inch speaker, 8 ohm. Max output is 70 watts.

Hi,
Hi zuit audio caps. (Slang) These are caps made specifically for audio, Nichicon UKW comes to mind. They are approximately 3X the cost of normal caps.

The two output caps are on the main board, the biggest ones there. They are either 1500 or 2200uf, 63v. They couple the amp output to the speakers. All the audio for this type of amp goes through these capacitors. Thus, they are very important for sound quality.

Coupled amp capacitors. same as previous.

How huge the improvement. Well... If you are comparing to the original stock Sansui caps that are 45-50 years old now, the improvement should be huge. Night and day. Way more low end. Much more definition and musicality.

 

[Trnsfmr]

Hi Sprungtol,
No, not the ones in the picture. The AU5500 uses a different kind of amp, where output coupling capacitors are not used. I was talking about the AU555A, AU505, 2000-5000rcvr, QRX 6500, and many others.

The AU5500 is a later generation of amps using a different design.

 

[Sticky]

We've rebuilt at least 20 of the 555A and 505. In my opinion, stay away from the hi zuit audio caps for the two output caps. These coupling caps flow hi current, and Audio grade caps are not necessarily designed for high current.

I recommend caps made for switching power supply use (snap in), which is high current and high frequency use (abuse, really). Sansui used pretty much the highest value caps they could reasonably fit in such a small amp. We go to 10,000uf at 50 or 63v for the outputs. The voltage doesn't matter as much as you might think, as the only time the full voltage at the input would appear across the cap is if you hooked the output to ground.

Here's a mouser link
http://www.mouser.com/Passive-Compo...apacitors-Snap-In/_/N-75hr0?P=1yztzazZ1yx4avv

Check out the ESR and Ripple current rating of the few caps they usually have in stock, just what you want for a capacitor coupled amp. They don't have normal leads, but you can make them work.

Every single 555A or 505 we have seen, the output caps are destroyed, not even measurable for value, with tons of leakage, and high ESR. They should be immediately changed before use. The improvement in sound quality is huge.

Thanks for the uber detailed reply Trnsfmr! Greatly appreciated

 

[Sticky]

So ive almost completed the recapping (Just waiting on a single cap to turn up that was on back order) I ended up using a combination of Nichicon FG's and Elna Silmic II's. I also bought some replacement BD139/BD140 transistors, but due to the condition of the current transistors, im struggling to work out which one is which (to replace NPN/PNP) . Would anyone know which ones are which? The ones in my amp aren't the "flying saucer" style ones. The most i can get off one of them is SANYO C375E..something, the other ones i cannot make out.

 

[gslikker]

for transistors, just put 2S in front, so C375 will be 2SC375
Also nice to know is that all transistors starting 2SA....and 2SB....are PNP, and 2SC/2SD are NPN

 

[Sprungtol]

My sansui AU 5500 has also has no UFO shaped trannys.
2SC1313R (G)s
But i can't see what under the metal plate behind the unit.
It will take disassemble this and that...so i skip that.

 

[Sticky]

So, after what appears to be almost 2 years, i have gotten around to replacing the transistors on the main board, EQ board and the tone board (Bought a house, forgot about amp packed away, found amp, had a kid, forgot about amp again). I used MJE340 in place of the 2SC875E x4 and 2SC627 x1, MJE350 in place of the 2SA532E x2, ZTX795A in place or the XA-495 x2 and BC549 in place of the 2SC1222 x4. Plugged it in today to test it out......nothing but some static. Before i replaced the transistors, and after recapping, it still had issues with pops, crackles and one of the channels would come in and out (and i think stopped working entirely).

Does anyone have some tips as to where to start? could i have them in backwards? Maybe the tone board as this didn't have the Base, Collector or Emitter markings, i went by the data sheet for the C1222's, and fitted the BC549 accordingly.

Any help appreciated.

 

[stereofun]

It is very likely you have one or more transistors wrong - so easy to do. Best way is to grab a laptop then go to hifiengine.com, and get a screen shot up of the board in question as the service manual will display the pin out. Next identify the pin outs of the replacements - newer ones will have a shape to them, eg flat toward you = ECB left to right. Now visually check each installed transistor vs the screen shot of the board in question. It's fairly quick to do. With the screen shut up you might also check that your solder work doesn't touch a neighbor trace when it shouldn't or vice versa.