You might find something online at Triode Electronics, otherwise, your only real option is to see if there is any tech support for Sansui at all. You may find a few parts at www.radiojunkyard.com.
You did not state what went wrong with yours, but on a guess, the output transistors blew out a few resistors when they failed? If so, it may take some good amount of transistor theory to bring it back to life unless someone has one stuffed away somewhere..
:I know it's not an antique, and it's a long shot to post this here, but I really need the schematic of the Sansui R-30 receiver(power amplifier part). If anyone even has the device, please mail me.
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You' re half way there.. One of the impulsion transistors in left channel failed due to overheat, and it was just to be replaced, but at first I couldn' t find the right one, so I tried with equavilent.
I really don't know what went wrong, but that resulted in instant aninhilation of the power transistores on the heat-sink, and it blew out a couple of resistors.
OK..I replaced resistors and the transistor with the original one; I pulled out the power transistors for the purpose of measuring(both them and on-board values without them).
The problem is, I didn't remember their array and I can't put the new ones in;(. I know..It was stupid enough and I' m not sure I want to gues and destroy them once again.
They could be 2sa768 and 2sc1827 in place of tr19(also tr20) or tr21(also tr22)
However, Basic transistor theory might be enough.
If the output to speaker is driven directly, The collectors of both transistors should tie together to go to the speaker (+). The power supply should provide 2 seperate supplies of 20-25 volts: One measures positive to ground, the other would be measured as a negative to ground (minus supply). The PNP transistor will have the Emitter (the case of a TO-3 transistor is the collector) tie to the B+, and the NPN Emitter ties to the B-.
That is the simple description from a transistor manual for complementary pairs, with an unbalanced input, and unbalanced output (one side ties to ground reference). If you have deviation from this basic design, the unit is not listed in Sams from what I can tell. In that event, you are looking for the resistor that is used to establish a bias voltage between the Emitter and Base, and work from there with the above mentioned voltage refence points- Except referenced to the collector- which will be opposite from relationship with the Emitters.
As your eyes have glazed over at this point- If you only planned to replace one pair of outputs, test it with the old pair that seem reasonable still- They might fail soon too of their own accord, and for purposes of balanced performance between channels, it is usually best to replace both pairs of finals. So you do essentially have a pair available for testing. If they are backwards, you will know instantly, as well as if they are in correctly too. As a final determining factor of whether to reuse the old transistors, compare the reverse bias resistance (this is the higher of the two resistance readings between any two terminals, but especially between Emitter and Collector) between the old pair of good transistors, and the reverse bias resistance of the new transistors- If they are not the same, or deviate more than 5% lower than the new ones- they will be noiser, and you WILL hear it.
::You did not state what went wrong with yours, but on a guess, the output transistors blew out a few resistors when they failed? If so, it may take some good amount of transistor theory to bring it back to life unless someone has one stuffed away somewhere..
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:You' re half way there.. One of the impulsion transistors in left channel failed due to overheat, and it was just to be replaced, but at first I couldn' t find the right one, so I tried with equavilent.
:I really don't know what went wrong, but that resulted in instant aninhilation of the power transistores on the heat-sink, and it blew out a couple of resistors.
:OK..I replaced resistors and the transistor with the original one; I pulled out the power transistors for the purpose of measuring(both them and on-board values without them).
:The problem is, I didn't remember their array and I can't put the new ones in;(. I know..It was stupid enough and I' m not sure I want to gues and destroy them once again.
:They could be 2sa768 and 2sc1827 in place of tr19(also tr20) or tr21(also tr22)
:
It is most probable that the one above is in stake, but let me present it graphically:
/C-
>--- B OUTER TR on the heat-sink
\E
IMPULSION PART *-- SPEAKER --->
/E
>--- B INNER TR
\C+
As for the particular resistor you mentioned, I dunnot have enough knowledge to recognize it..
Now.. Is it right to conclude that the outer transistor is PNP and the inner is NPN?
/C-
>--- B OUTER TR on the heat-sink
\E
IMPULSION PART *-- SPEAKER --->
/E
>--- B INNER TR
\C+
Where you have the positive voltage at the bottom- That would be the Collector of the NPN transistor.
Therefore, the one transistor on top in the representation would be the PNP transistor.
Now, is the item marked "IMPULSION PART" a capacitor? It would likely be 500uf (or another value likely close to that if it is marked), and it will have a voltage- probably 35 to 70 volts DC (or VDC, or WVDC). If it is marked as such, you will probably want to replace those caps outright as they may be shorted. In such an event, you blow out voice coils, or the flex lead on the speaker.
Also too, make sure you use adequate dielectric grease between the transistor and mica insulator, as well as between mica insulator and heat sink- This assures heat transfer so you do not burn out the transistor. The mica insulator may, or may not be used, or it may be a small sheet of Beryllium, or a silicone rubber. It is critical that these pieces are re-used/replaced if they were present initially. If they were in place, you may have had nylon screws, or liners to insulate the screws too, and they need to be used again.
:The schematic didn't come out right.. Anyway, the collector of the outer transistor is on the negative output of the grez, and the inner is on positive, and the emiters are connected together and lead to the speaker...
I installed them, rechecked and everything seemed fine, and it actually was fine. IT WORKS;))! I owe you on this one..
:Now, is the item marked "IMPULSION PART" a capacitor? It would likely be 500uf (or another value likely close to that if it is marked), and it will have a voltage- probably 35 to 70 volts DC (or VDC, or WVDC). If it is marked as such, you will probably want to replace those caps outright as they may be shorted. In such an event, you blow out voice coils, or the flex lead on the speaker.
Nooo.. The part I marked as 'impulsion' is not bound to have that name in english since I just literaly translated(also inducement, mainspring etc..) and represents the unit between pre-amlifier and power-amplifier. I really don't know the english label; but it works fine, since it was on my drawing(which, as I said, didn't come out right) only for orientation..
:Also too, make sure you use adequate dielectric grease between the transistor and mica insulator, as well as between mica insulator and heat sink- This assures heat transfer so you do not burn out the transistor. The mica insulator may, or may not be used, or it may be a small sheet of Beryllium, or a silicone rubber. It is critical that these pieces are re-used/replaced if they were present initially. If they were in place, you may have had nylon screws, or liners to insulate the screws too, and they need to be used again.
You don't need to worry! Apart from the things you mentioned, I also added a fan, so that it doesn't happen again.
But another thing became a problem now that everything is fine.. The transistor(2SD313 SI-N 60V 3A 30W 8MHz) in the 'power-supply part'(also dunnot know the label) used to overheat, but never burned out, so I assumed that one of the blown transistors heaved the current(which would be logical); but the problem persisted after this little repairment of ours. That led me to a conclusion that it wasn't anything unusual, but it still bothered me. Shall I try with a stronger one, possibly:
2SD476 SI-N 70V 4A 40W 7MHz
2SD712 SI-N 100V 4A 30W 8MHz
?