Sansui G-2000 Keeps Blowing Fuses

[BackInThe70s]

It appears that Walmart has several $8-10 meters with a diode test function AND other useful ranges. The 830 models they show online are based upon the Mastech 830, which should be fairly capable.

That's the one I have.

For performing Bob's test, remove both of those 4A fuses and the adjacent 1A fuse and set them aside. Power the unit on, set your meter to measure AC voltage, connect the black probe to a good chassis ground (probably any metal area) and CAREFULLY touch the red probe to each of the purple wires (one at a time) and then to each of the blue wires. You should be able to back-probe the circuit board connector without removing it. Make a note of the voltage at every test point.

When I probed the two purple wires I got back a reading of 21.x. When I probed the blue wires, the right side wire (looking straight down) read 18.1, but the left wire read .4

 

[Watthour]

When you test the diodes, verify the circuit/device has no power, set the meter on the diode test range ( -►|- ) and touch each of the probes to opposite ends of the diode being tested. Note the reading, then reverse the probes on the device and test again. This applies a forward and reverse voltage from the meter to the diode. One direction (forward) should result in a reading of approximately 0.5 to 0.7V drop, and the opposite polarity should result in something much higher, and possibly out of the meter's test range, indicated by "OL" or something similar. Test each diode in this manner and note the results.

 

[BackInThe70s]

Don't power this unit on... you can test cold as described.. get a dmm.. you can get a cheap one for sometimes less than 20$. home depo etc.. Also... Look on the sides of the large mains capacitors (middle pic) and report what you read.

CEW85 (degrees) ELNA

 

[Watthour]

When I probed the two purple wires I got back a reading of 21.x. When I probed the blue wires, the right side wire (looking straight down) read 18.1, but the left wire read .4

That is exactly what the schematic indicates the AC voltages from the transformer should be, ±5% or so for line voltage variation. It is probably safe to say the transformer is intact and undamaged, as was suspected.

Now you can power the unit off and proceed with testing.

 

[Watthour]

CEW85 (degrees) ELNA

I'm betting the other side reads "4700µF - 35WVDC" or something similar.

 

[BackInThe70s]

When you test the diodes, verify the circuit/device has no power, set the meter on the diode test range ( -►|- ) and touch each of the probes to opposite ends of the diode being tested. Note the reading, then reverse the probes on the device and test again. This applies a forward and reverse voltage from the meter to the diode. One direction (forward) should result in a reading of approximately 0.5 to 0.7V drop, and the opposite polarity should result in something much higher, and possibly out of the meter's test range, indicated by "OL" or something similar. Test each diode in this manner and note the results.

One is 648 and 1500, and the other is 635 and 1800 (approximate as they both fluctuate). These are the two diodes to the right of the fuse bank.

 

[Watthour]

Those numbers look correct. Check ALL the diodes indicated in the photo above, and test the two larger filter capacitors using a resistance range around 2KΩ.

 

[Binkman]

@BackInThe70s (What's your first name? Rather post to that than OP ... easier..
Okay you're doing testing.. Have you gotten into testing the output transistors? transistor testing? instructions on line or the stickies above?
You say you have soldering skills? Have you a decent solder sucker? Do you understand electrolytic capacitor polarity? very important.

Just pointing out looking ahead caps will be in order.. you have some aged caps. Generally speaking blowing a 4amp fuse indicates pre output driver transistors and possibly an output transistor(s).

this type of solder sucker works well. what type of soldering iron do you have?


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[BackInThe70s]

@BackInThe70s (What's your first name? Rather post to that than OP ... easier..
Okay you're doing testing.. Have you gotten into testing the output transistors? transistor testing? instructions on line or the stickies above?
You say you have soldering skills? Have you a decent solder sucker? Do you understand electrolytic capacitor polarity? very important.

Just pointing out looking ahead caps will be in order.. you have some aged caps. Generally speaking blowing a 4amp fuse indicates pre output driver transistors and possibly an output transistor(s).

this type of solder sucker works well. what type of soldering iron do you have?
View attachment 1431597

Bink

Thanks for all the suggestions. I normally don't have time to troubleshoot something like this during the week, so anything further will have to wait until next weekend, at least. And I have no soldering skills. More than likely I will have to find someone in my area that can do the needed repairs. Even if I were able to identify the problem to a specific component on the board, I wouldn't be able to remove and replace, not without very likely damaging something else in the process. But thanks for all the helpful suggestions. If I just had more time I could try my hand at this, but as it is I don't.

 

[Binkman]

Well you're not alone in experience.. most are hobbyists members. This project is a little to complex to learn on but it is educational. For soldering find a junker i.e. vcr to practice soldering de-soldering. There are kits out there that provide all the parts for headphone amps to stereos. Many just focus on speakers as their past-times, others turn tables. Don't be afraid to post questions.. Myself I don't see a lot of equipment brands posted but I do read many service manuals of posted equipment and you begin to see a lot similarities of designs and you can pick up a lot following posting responses, too. Photo's speak a 1000 words.
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