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D707F Extra Help

S

SennMan

New Member
Hi all, I posted a short help notice in the general section yesterday, but maybe someone in this particular forum may have some extra information regarding the actual circuit diagram or manual info for the D707F Extra I have here, repairing/restoring for a friend. I do have the D9 manual, but the output and protection circuitry has differences and a circuit exclusively for the D707F Extra would be appreciated for clarity.
The D9 uses 2SA899/C2238 pairs, whereas the D707F I have here uses 2SA999/C2320 pairs (x2 per channel), except that one of the C2320 and A999 devices per pairing has a 820 ohm resistor soldered to the base. To add to the mix, the LC has a 2SA1091 in only one of the pairs, an replacement addition it seems, as it is vastly over-rated at 300v compared to the 50v A999/C2320 pairs, which look original, other than that A1091. The A899/C2320 pairs are 150V devices.
Bit of a mess for me without knowing what is actually supposed to be there.
Is there any definitive help among this group, please? Many thanks for good and welcome advice. I presume someone here has now or previously owned the (110V, in my case) D707F Extra.
 
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Now that is genuinely useful! Many thanks. I have no idea why there is an 820 ohm resistor tagged onto the base leg of one of the C2320 and A999 per side, your photo shows nothing like that anywhere.
I suspect someone has been 'at' this one in it's past. Here are a couple of pics of the one I have here. That list BTW is excellent, thanks again. The one with the 2SA1091 is the LC. P9110697.JPGP9110701.JPG
 
Peter lye said:
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mine, production date April, 1982 ,yours could be an earlier production 1981?, just guessing.
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Thank you, the one I have here is also 100V, my mistake. I have a quality 240v-100V step down transformer to go with it. I reckon I'm going to go with returning the transistors in question back to original status, removing the 820 ohm resistors as well.
 
SennMan said:
Thank you, the one I have here is also 100V, my mistake. I have a quality 240v-100V step down transformer to go with it. I reckon I'm going to go with returning the transistors in question back to original status, removing the 820 ohm resistors as well.
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if it is working well, i would leave them alone. you can find alot of this resistor attach to leg of transistors on the AU-9900/11000 very common.
 
most likely , if you encounter any problem with this unit , Black flag and sansui glue problem is the usual culprit in the F-3252 board.
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Peter lye said:
most likely , if you encounter any problem with this unit , Black flag and sansui glue problem is the usual culprit in the F-3252 board.
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Good to know, this is my second Sansui, the other is an AU-2900. I have re-capped the 707F at the owner's request, but a tech shorted out the bias pins and took out one of the output transistors, an A999, C1904 and the dual FET input opamp. Not cheap. That tech has gone a bit AWOL, so it's up to me to repair the damage. I have encountered the dreaded glue problem on many an other amp, Pioneers included, it's amazing how that stuff just corrodes the legs of nearby parts. I very much appreciate the advice you have provided, Peter.
 
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