20K Day-1

1st , Snow,,, Thank you... this is a beauty...armor plated packing too!

Not alot of time today.... But the score so far...
Power supply's are are online..
Audio final bricks and pre drivers pulled..
Unit will not come out of protect ... I assume since there are so many missing bits..now.
Preamp section works almost.. ( had to pick off a bit upstream ) .
Meters work ( in input mode ) 1/2 the meter backlights are out.
After realizing the balance pot was not on the shaft correctly (30 degree offset) 1) Final brick 100%
3) Shorted transistors in the other
1) Smoked 2507 board...no detail on damage on that....

AND SOUNDS AMAZING!!!!

Great to hear it arrived safely and you have had some success with it :yes: I will follow this thread until you are done with it.


REGARDS SNOW

vigman said:

1st , Snow,,, Thank you... this is a beauty...armor plated packing too!

Not alot of time today.... But the score so far...
Power supply's are are online..
Audio final bricks and pre drivers pulled..
Unit will not come out of protect ... I assume since there are so many missing bits..now.
Preamp section works almost.. ( had to pick off a bit upstream ) .
Meters work ( in input mode ) 1/2 the meter backlights are out.
After realizing the balance pot was not on the shaft correctly (30 degree offset) 1) Final brick 100%
3) Shorted transistors in the other
1) Smoked 2507 board...no detail on damage on that....

AND SOUNDS AMAZING!!!!

Click to expand...

How's the output trannies doing?

One thing is for sure - you are the master of jumping wires. :yes:

1 brick is 100% the other lost 1/2 of the transistors (3 ) ....
AND
I THINK I figured out why protection isn't letting go ( on paper anyway ) ...
F-2511 Points R-S and P-Q goes to pr-10 on the output block.. which I assume is a thremistor.

I believe if this is open ( which it currently is, due to bricks on the ground ) protection will not release.... which keeps the reed relay from letting the pre out... out to the back jacks... the red & blue easy hooks bypass that relay...So tomorrow I'll measure the thermistor values and " fool " the protection board... and check that out.

I have the 3.9 ohm resistors jumped so I can power up.... so whaaaaaaaaaa it's only 4 clip leads....

I still do not have a working theory on why the smoke escaped @ Snow's place... but the pre driver that smoked goes with the brick that 3 devices are dead shorted...

Tomorrow I " think " I should have a digikey order together ( at least for KNOWN issues ) .

Not sure if the unit is ( was ) 100% original.. I see some " not same age" solder re works.... but all the tube nylon wire ties are ( were ) original.

Well, one good channel sounds good.

That pre-driver looks badly blown. It's just a matter of time that smoke has to come out once you have 3 shorted outputs and keep replacing the blown fuse and try to figure out why it wouldn't turn on.

But think of this way. It's better that smoke comes out before you place an order with the digikey so you got all of them replaced. All these driver trannies are seriously stressed even if they don't let the smoke out.

Time to put the Theory aside and pull the protection board and check for leaky caps and flaky diodes? It could be notoriously famous diodes and dry lytics.

Why u jumped the 7W 3.9r resistors in the first place? Are they opened?

I have a gut feeling the thermistor is fine. Unless the themistor wire was accidentally cut by very rare chance that the thermistor is really open, the protection shouldn't trip at start up. Every time I think a termistor is a culprit, I found it wrong and it's due to people messing with it or wire was cut to check it and didn't re-solder it properly and got a lose connection on the board.

As the driver board still has the notorious VD1212 its more than likely its completely unrestored and with original components. Maybe its time for complete restoration job after you get it running first?

Mega both 3.9's are open.. I might of misdirected you on the protection… the finals are OUT of the amp, ergo no connection to F-2511 Points R-S and P-Q.. so the thermistor is ~240 ohm cold I popped in a 200 ohm resistors across those each of those points, Protection now works.
Power on ( red led ) ~5 sec CLICK ( no led ) and I can remove 2 clip leads since the reed relay now energizes and passes audio to the rear panel.. LOVELY.

I started cleaning El smoke-O and the first " sign " was the screw holding TR-10 was LOOSE.. WAY WAY loose plus VR-02… well wasn't " in circuit ".. it has corroded wiper itis but a scrub or two and a wee spritz and it's back in the game ..
R-23 & 24 went boom in a major way but 27 & 31 went total thermo nuclear.. and that's as far as I ve gotten on the 1am… Hmmm I wonder..

Plus it still has the original glue on caps

Tomorrow ( well later today ) I'll print out the 2507 portion of the schematic and start pulling the funky parts out… running the Hakko solder sucker @ 2:30am doesn't make the GF happy! LOL

Some good reference threads:
Kales restore
http://www.audiokarma.org/forums/showthread.php?t=456841
Thru hole issues
http://www.audiokarma.org/forums/showthread.php?t=172151
Similar scorching
http://www.audiokarma.org/forums/attachment.php?attachmentid=104466&d=1219015988
Cap List:
http://www.audiokarma.org/forums/showthread.php?t=446308
Toni's 22000uf swap
http://www.audiokarma.org/forums/showthread.php?t=581085
Toni's transistor X ref
http://www.audiokarma.org/forums/showthread.php?t=583009

Yes and we start another EXCITING morning of unsoldering , testing , marking up a copy of the schematic ( with lovely red & green highlighters ) making a shopping list, burning finger tips oh it almost compares to the sheer thrill of doing TAXES...

AU-20K day 2

Well the board is clean ( er ) and prepped.. time to start spending $$…
Other things noticed… did Sansui use " different" heat sink compound for smaller devices?
Both these boards have some silicone clear viscous compound
, not the white stuff like on big TO-3 devices.. and ALL of it was cooked off TR-10.

And what is everybody using for their fav transistor sub cross reference… my " books " are VERY OLD…

Mike

Since 3.9R resistors are opened, much current has passed in the relays? Guess it doesn't hurt the pocket to replace these two relays!

Not sure about the heatsink compound used on the smaller trannies but the usual white stuff works fine on all big and small trannies.

I don't have a transistors cross reference book but you need to post the transistor numbers for cross referencing and other experts I guess who replaces transistors frequently will chime in. Or make a new thread and request for the sub number which is what I usually do in AK.

You've been working hard!

Brain hurts… need a wee bit O help with these crosses if possible….
Going ADD reading all the 20K posts…

Mega the resistors are for " surge startup " the second you give it the juice relay 02 pull's in and shunts the resistors and the BULK of 120V current goes thru the relay contractors ….. Voltages are all within 3-5% So I'll call that good ( for now ) … Since I have no finals in now… and I soft start via the variac… the resistors are not THAT nessa at this point… But I did find a source for them & they are on order...

I stopped wrenching on the unit a couple of hours ago… But still listening to it… thru the aux in on my fisher 400 and JBL's AHHHHHHHH

Parts list ( spares included ) Semi's only I know what diodes to get…
Please review & throw input in …..
Output city
6) 2SA424 NPN X to MJ15003 (NPN)
6) 2SB554 PNP X to MJ15004 (PNP)

Pre drive
X) 2SC1669 NPN X to MJE15034 or Equivalent NTE375 T-NPN
X) 2SA839 PNP X to MJE15035 or NTE398 TRANSISTOR PNP

Note the pinout is different, but the board is drilled & silk screened to accommodate this… ( updated 3/26/14 )
Fixes bias overshoot...
X) 2SC1628/2SC1811 NPN X to KSC 3503
X) 2SA818 PNP X to KSA 1381

Note have to do a Base - Emitter flip new devices are pined out different for the KSC/KSA
X) 2SC945 NPN X to KSC945 or NTE123AP NPN audio transistor
X) 2SA733 PNP X to KSA733 or NTE290 TRANSISTOR PNP

And no I don't want to use NTE but I have it there to confirm X

I would ask myself the reasons why the Inrush / Surge Protector resistors died? 7W Wirewound can withstand at least 3x 5x or even 10x inrush current of the rated limits for a period of time before they let the smoke out and finally become totally opened!

If the relay contacts closed, there should be almost '0'R so all the buck current flowed through the relays. If the relays contacts are dirty and overcurrent drawn from the primary of the transformer, the dirty relay contacts may increase resistance and thus creates higher current flown through these 3.9R resistors.

Even if the relay contacts are CLEAN (let's say it's a new relay) and BIG enough overcurrent flowed through both the relay '0'R and the resistors to open the 3.9R wirewound, you know how much of these relays contacts are abused. These relays are normally rated for 20A?

I would check the condition of the relay contacts and clean them well but If it's not hard to buy one, I would buy and replace these relays. They are as old as the amp.

Contacts are good.... I think the " burnout " was from the shorted amp module.. and attempts to restart with a shorted secondaries... not enough current to pull in RL-02.
This is also evident from the torched power switch...

phase 1 Digikey order in....

vigman said:

Other things noticed… did Sansui use " different" heat sink compound for smaller devices? Both these boards have some silicone clear viscous compound , not the white stuff like on big TO-3 devices.. and ALL of it was cooked off TR-10.

And what is everybody using for their fav transistor sub cross reference… my " books " are VERY OLD…

Click to expand...

Yes, mine was like that too - clear stuff on the driver board transistors. And it had mostly dried out.

My books are old and have very few substitutes to offer too so I am now mostly using this: http://alltransistors.com/

EDIT: comment to Hyperions suggestion. Yes, most likely all equivalents have already been discussed on the forum. Widen your search to outside Sansui-section to get most results. I have noticed that even most usable google search results point to old AK discussions (and sometimes to one diy-forum).

Or just use AK search - it's good enough to find where people have previously asked about, and got answers to, transistor equivalent questions.

Just type the type number in the search box...

John did that got mixed results…but will retry….
So did a little recapping of the reg board… just the ones that were crying HELP..
BTW the reg screws on that one were loose too!!! So that MIGHT BE a potential failure point.. so new motto… check torque on any device screwed to a heat sink.
The PS's are a WEEE bit closer… was ~ 1.5 to 2 volt diff now every things ! .5 to .7 spread on the bi polars….