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Sansui BA-3000

Pepa

Pepa

Well-Known Member
For the last few weeks (from time to time) working on ruin BA-3000 amplifier. According to this label (inv.number) on back plate, was owned by some institution for a long,long time (like cinema, theater,church...etc) and had a hard life for sure :tears:

Just take a look at that poor binding posts

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And another view:

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What could cause such a melting of resistor on one pair of speakers??

2-2.jpg


Since old binding posts are useless, it's time to make new one:

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You need to be careful with tools, and try to don’t over tighten these binding posts,otherwise....something just snapped,and I do not know what it was :D

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You did a great job but what a mess it was. Does everything work ok now ? What would you think about upgrading a power cord in a Sansui Amp like the AU-717. A detachable cord receptacle. Would that be an easy job and would it be recommended ? The stock cords are only 18 AWG.
 
Nice work bringing it back to life Pepa! Makes you wonder what they did to melt and destroy things like that..
 
Pepa said:
For the last few weeks (from time to time) working on ruin BA-3000 amplifier. According to this label (inv.number) on back plate, was owned by some institution for a long,long time (like cinema, theater,church...etc) and had a hard life for sure :tears:

Just take a look at that poor binding posts
Click to expand...

:tears:

Pepa said:
And another view:
Click to expand...

:tears::tears:

Pepa said:
What could cause such a melting of resistor on one pair of speakers??
Click to expand...

Being over-driven (clipping) or oscillation. :nono:

Pepa said:
Since old binding posts are useless, it's time to make new one:
Click to expand...

:yes: :banana:

Pepa said:
You need to be careful with tools, and try to don’t over tighten these binding posts,otherwise....something just snapped,and I do not know what it was :D
Click to expand...

:yes: :scratch2:

Seriously - Great Work Pepa - looks very nice now :thmbsp:
 
larry777 said:
You did a great job but what a mess it was. Does everything work ok now ?
Click to expand...

Tnx larry777....after all I've made ​​so far (all contacts and pots were cleaned,pcb were cleaned and resoldered,caps replaced,some diodes (vd1212) replaced with two in series 1N4148...) amp is working fine.

Only have one small problem...it takes 15 minutes for bias to reach his full value (20mA).At the moment I'm changing old thermal paste and insulators under the output transistors...we'll see after that (if the white smoke stay inside :D).

Perhaps the main reason for this behavior is missing plate above drivers pcb :scratch2:

larry777 said:
What would you think about upgrading a power cord in a Sansui Amp like the AU-717. A detachable cord receptacle. Would that be an easy job and would it be recommended ? The stock cords are only 18 AWG.
Click to expand...

You're asking about replacing (upgrading) a power cord....it is not a big deal and can be done in couple of minutes,or hour if you mean to install socket on back plate.But many of Sansui owners would keep original state as possible.
To tell you one thing,I have AU-X1111Mos vintage,one of the best of Sansui amp,and power cord is not detachable also. I think Sansui engineers knew their job, and if you want to change something,like that cord,or play with some upgrades is fine by me.
Just do it that way it can be returned to its original state, if you're unsatisfied with the sound.


tobyj17 said:
Nice work bringing it back to life Pepa! Makes you wonder what they did to melt and destroy things like that..
Click to expand...

tnx tobyj17....a little bit of plastic,a little bit of milling and that's it :D ...but I still can't understand the way some people treat their gear :no:

Hyperion said:
:tears:

:tears::tears:
:nono:
:yes: :banana:
:yes: :scratch2:

Seriously - Great Work Pepa - looks very nice now :thmbsp:
Click to expand...

That's the way I like it :D
tnx John :thmbsp:
 
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ManyMoonsAudio said:
Man, looks like someone took a torch to it!
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Yes Paul, it looks really awful

Transistors on one channel are original, while at the other...not

3-1.jpg


since I still have some NOS, I will replace them

3-2.jpg


thermal paste is not paste anymore,more like powder

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3-3-1.jpg



All insulators were changed, dc and bias are OK,but... but still needs 10-15 minutes to bias reaches its full value (rising slowly) :scratch2:

Anyone?
 
Both channels? How bout some more pics of the work there Pepa....
 
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ManyMoonsAudio said:
Both channels? How bout some more pics of the work there Pepa....
Click to expand...

Yes, both channels.

I have a feeling it happens if the amplifier is off for a long time (eg.over night)...on the other side,if I turn off the amp for half an hour,and then after turning on bias is normal.

At this point I am in the process of disassembling each pcb...again. I suspect at some cold solder joint or some connector...:scratch2:

I have a noticed couple degrees Celsius temperature difference between the sinks (at same bias; slightly but noticeable).

picture is comming..
 
Hmmmmm Don't sound that strange to me. Another BA-3K owner may chime in? Have you checked it out on a scope? Tested the amp for power and distortion?
 
I think your 2SA909/2SC1586 are also not original, but good replacements.
Original is Toshiba 2SB554/2SD424.
 
Not saying this is your problem, but......

The board in between each heatsink has a boat load of pass-throughs that are known to cause problems.

My fix for this is to de-solder all, and then poke a small piece of wire through them, then bend it over to make a mechanical connection on both sides. Then re-solder.

This needs to be done.

Also, there are VD-1212 diodes all over this amp. They all need to be replaced with series pairs of 1N4148's.
 
Nicowico said:
I think your 2SA909/2SC1586 are also not original, but good replacements.
Original is Toshiba 2SB554/2SD424.
Click to expand...

Originals are 2SA908/2SC1585.....(according to the service manual). The 2SA909 and 2SC1586 are higher voltage equivalents, and Sansui may have used them in this amp also. Hard to say what the hell they do sometimes.....
 
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Nicowico said:
I think your 2SA909/2SC1586 are also not original, but good replacements.
Original is Toshiba 2SB554/2SD424.
Click to expand...

Original power transistors at BA3000 are Sanken 2SC1585 2SA908 (Vcbo 150 V) but 2SA909 2sc1586 has Vcbo 200 V

EDIT: ManyMoonsAudio was fster :)
 
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ManyMoonsAudio said:
Hmmmmm Don't sound that strange to me. Another BA-3K owner may chime in? Have you checked it out on a scope? Tested the amp for power and distortion?
Click to expand...

Not yet...maybe latter this night

Nicowico said:
I think your 2SA909/2SC1586 are also not original, but good replacements.
Original is Toshiba 2SB554/2SD424.
Click to expand...

According to the SM and general condition (screws,thermal paste...),they are original....tnx anyway

Edit:....and I was the slowest :D
 
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ManyMoonsAudio said:
Not saying this is your problem, but......

The board in between each heatsink has a boat load of pass-throughs that are known to cause problems.

My fix for this is to de-solder all, and then poke a small piece of wire through them, then bend it over to make a mechanical connection on both sides. Then re-solder.This needs to be done.
Click to expand...

OK Paul,thanks for the tip...I'll check that :thmbsp:

ManyMoonsAudio said:
Also, there are VD-1212 diodes all over this amp. They all need to be replaced with series pairs of 1N4148's.
Click to expand...

I believe I have replaced all these diodes
 
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