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au-999

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chw12868

New Member
Hi, the subject is speaker popping noises when this amp is used....my unit has been on the shelf for 15-20 years and was recently placed in service again (i am the original owner); there are 2-ground wire termnals in the back of the unit and are presently hooked up via shielded wire from the unit to a metal pipe in the crawl space...speaker popping is going on with all 3-zones of speakers.
If memory serves me right, when i used this unit originally (in the early 70's... sparingly for a few years) the same problem occurred...the ground wires from the unit at that time were attached to a metal pin that was placed in the earth outside the house.

The fuses are operational.

My goal is to resolve the popping noise in the speakers; wiring at both the speaker and amp end are attached cleanly...no wire strands hanging around causing issue. If this problem cant be solved, I am looking for suggestions on a replacement unit...i have 3-separate speaker zones (2-outdoors) and 1-indoors...multiple source input is needed (satellite radio, cd-player, etc....no home theater issues).

Your thoughts are welcome.

Thanks,

Chuck
 
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I had an AU-555A that had a popping problem. Not at power up but while I was listening to it. Occasionally it would make a popping noise. I replaced the transistors that looked the pic below. It worked great after that.
You may have the same transistors in your amp.
That's my two cents.

100_0909.jpg


Rob
 
chw12868 said:
Hi, the subject is speaker popping noises when this amp is used....my unit has been on the shelf for 15-20 years and was recently placed in service again (i am the original owner); there are 2-ground wire termnals in the back of the unit and are presently hooked up via shielded wire from the unit to a metal pipe in the crawl space...speaker popping is going on with all 3-zones of speakers.
If memory serves me right, when i used this unit originally (in the early 70's... sparingly for a few years) the same problem occurred...the ground wires from the unit at that time were attached to a metal pin that was placed in the earth outside the house.

The fuses are operational.

My goal is to resolve the popping noise in the speakers; wiring at both the speaker and amp end are attached cleanly...no wire strands hanging around causing issue. If this problem cant be solved, I am looking for suggestions on a replacement unit...i have 3-separate speaker zones (2-outdoors) and 1-indoors...multiple source input is needed (satellite radio, cd-player, etc....no home theater issues).

Your thoughts are welcome.

Thanks,

Chuck
Click to expand...

Chuck, welcome to AK and the [Exclusively Sansui] forum. :thmbsp:

Your unit needs service. You may be able to do it yourself, but unless you have some background in electronics you may want to seek help.

Do a search here in the ES forum for "pops", "snaps", and "intermittent" and you should dig up a lot of info on how these problems are handled.

Paul
 
Only the earliest AU-999's were shipped with the 'flying-saucer' transistors. Apparently, even Sansui figured out that they sucked, because later model 999's shipped with regular Japanese-numbered 2SA and 2SC devices. The NPN 'flying-saucer' transistors (8002-1) were replaced in later production runs with a 2SC875. The PNP flying-saucer devices (XA495) were replaced with 2SA640's. Although these transistors are also long out of production, let's look at specs:

2SC875 - Vceo = 75V, Ic = 200mA, Pc = 500mW, B = 100, Ft = 170MHz
2SA640 - Vceo = 50V, Ic = 50mA, Pc = 250mW, B = 450, Ft = 100MHz

This gives us a basis to decide what to use. With this info you can choose a good replacement, but on the two 999's that I had to toss the old transistors out of, I used Zetex ZTX795A to replace the XA495 (PNP) transistors, and ZTX694B to replace the 8002-1 (NPN) transistors.

FWIW, D801 and D803, the offset adjust diodes on the driver boards, should be replaced with plain-Jane 1N4148 diodes.
 
IMO its worth fixing up your AU-999. I had one and enjoyed it.

I would not think all those grounds to be needed either.

Evan
 
EchoWars said:
Only the earliest AU-999's were shipped with the 'flying-saucer' transistors. Apparently, even Sansui figured out that they sucked, because later model 999's shipped with regular Japanese-numbered 2SA and 2SC devices. The NPN 'flying-saucer' transistors (8002-1) were replaced in later production runs with a 2SC875. The PNP flying-saucer devices (XA495) were replaced with 2SA640's. Although these transistors are also long out of production, let's look at specs:

2SC875 - Vceo = 75V, Ic = 200mA, Pc = 500mW, B = 100, Ft = 170MHz
2SA640 - Vceo = 50V, Ic = 50mA, Pc = 250mW, B = 450, Ft = 100MHz

This gives us a basis to decide what to use. With this info you can choose a good replacement, but on the two 999's that I had to toss the old transistors out of, I used Zetex ZTX795A to replace the XA495 (PNP) transistors, and ZTX694B to replace the 8002-1 (NPN) transistors.

FWIW, D801 and D803, the offset adjust diodes on the driver boards, should be replaced with plain-Jane 1N4148 diodes.
Click to expand...

Awesome info, Echo. I went to digikey to look at the 1N4148 and was overwhelmed with choices - do you recommend a particular part number as you do transistors? I dont want to get the wrong kind - also, is the rectifier upgrade only for the old models with flying saucer transistors, or all AU-999 models?

One last thing - any other suggestions or advice to upgrade failure prone or outdated parts (except for the electrolytics, of course)

THANKS!
 
If you want to get ambitious, replace all the old 'FS' transistors.

1N4148FS-ND. That's all you need.
 
Thanks Echo - I am ambitious! I am also going to try orange drops for the first time...

EDIT: HAH! $0.04 each... I think this is the cheapest part I've had to source yet! Im suprised digikey will even go through the trouble of putting it in a plastic baggie for four cents.
 
0.04 cents breaks down to 0.02 cents for the bag and label and 0.02 cents for the diode.

- Pete
 
xoaphexox said:
I am also going to try orange drops for the first time...
Click to expand...
Orange drops? Where? These are generally used as coupling caps for tube gear, where input impedances are an order of magnitude greater than what they are in transistor gear. I can't think of too many places where they can be used to any real advantage in a solid-state integrated amplifier.
 
You are the expert echo - I got the idea from this thread
http://www.audiokarma.org/forums/showthread.php?t=129691

If the orange drops are a waste of time just lemme know - save me some cashish.

I will mention though, that this site:
http://amp8.com/english/eindex.htm
Also replaces a lot of mylar caps in Sansui units..

I would imagine there is some purpose for doing it... these caps dont "go bad" with time nearly as quick as electrolytics from what I've read, so the reason for changing them out must be some sort of upgrade?

Thanks in advance for your advice. It has helped me out many times.
 
The input cap to the driver board is indeed a 1uf film job...I had forgotten that. Still, IMHO, orange drops sound better with a good amount of polarizing DC voltage across them. For low-voltage solid-state work, I'd prefer a metalized polypropylene, such as the Panasonic ECWF(B) series.
 
My AU-999 just arrived today. It is in great costmetic shape - blue tape around the whole bezel. I dont think this unit has ever come out of the wooden case. The schematic was still taped to the bottom in a sealed envelope!

Anyhow, I opened it up and noticed it does have the "FS" transistors all over.
I am waiting to get a service manual so I can make a list of what to get from DigiKey.

So far I have the two diodes you mentioned for the driver boards and the two power supply capacitors.
 
For anyone that is interested here was my total transistor count to replace from the AU-999

8002's -> 6
9002's -> 2
495's -> 18
 
Which would be better filter cap replacements: Panasonic TSHA, or Nichicon VZ?

They seem to be the only types Digikey offers at the 6800uf/50v rating Quadbob suggests
 
You need to determine the physical size (particularly the diameter) of the stock caps, and search within that subgroup. I think the stock caps are 40mm in diameter, but go check...
 
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