Sansui G-6000 Help please.

hopjohn

Silver Face
Troubleshooting a G-6000 and struggling a bit. The unit seems 100% operational. Comes out of protect on startup in about 6 seconds. I've tested every input, AM/FM, even the microphone. They all work. Headphone out works. Speaker outputs work. Lights work. Meters, all of them work. DC offset and bias all seem reasonable. Even checked some voltages here and there on the supply but nothing seemed amiss.

The problem is its doing all of this while one fuse is blown (F602 1A, since pulled). I started to think maybe it was meant to be this way and went ahead with a recap of most the boards and replaced the fuse resistors on the tone amp and mic amp. Later I found a post by LBPete that briefly mentioned that both 1A fuses (F602, F603) should be in use. With that I kept hunting for something wrong. I found that a rectifier D604, a 10D2 is failed closed. Yep closed, basically acting as a jumper. Ok progress, so what else might I look for that would've caused that to happen? ... and what else may have been damaged as result? Help.
 
The shorted rectifier would have been enough to blow the fuse on its own - but any electrolytic capacitor on the cathode side of the rectifier will be damaged as a result of the shorted state of the rectifier. for identification - cathode ----I<I---- anode

The exact replacement is a 1N5393 but in almost all cases you can replace with 1N4002 - (or any of that range from 1N4002 - 1N4007).
 
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Without that fuse, you are loosing half the transformer output. It may work, but it will start clipping way early. Like John said, check the diodes.

- Pete
 
Understood Pete, and I assumed as much after reading that post.

Upon inspection the D604 diode that went faulty, as well as all the others installed on the supply, are actually 10D1 diodes and not 10D2 as the parts list and schematic has them. The 1N5393 show as 1.5A over the 1N4004 et. al. at 1A. The datasheet I find for the 10D1 and 10D2 have them at 1.5A. Hyperion, I'm assuming you thought the 10D2 was 1.5A?, unsure. Anyway what would you recommend knowing all this?

Just as an FYI, the two capacitors nearest to the cathode side of D604 were 1000uf 50v and read around 700uf each (out of tolerance), their ESR looks normal. They'll be replaced same as all the other electrolytics.

P.S. I haven't yet checked the other diodes out of circuit.
 
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If they are 10D1 - then the exact replacement becomes 1N5392, but the first suggested will be fine also. These diodes are seldom used in positions which might get even close to the 1.5A spec - hence the suggestion that 1N400x series, 1.0A would very likely be suitable.
 
Followed your 15393 suggestion and just replaced the entire bridge with them. I looked diligently for any other faulty components on PS and beyond but found only a few caps that were borderline and nothing more.

I finished the recap, added new lamps, set the idle and DC bias, and have been putting it to the test over the last several hours driving my little Boston HD5s.

Color me impressed it has a very nice sound signature. Also gotta say the FM tuner is impressive. Sansui used some very nice variable caps in these.

I appreciate you gentlemen taking the time to respond @LBPete @Hyperion Thanks!
 
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