Hello

This website is very great and very informational. Anyway I'd like to get some input and help. Just been given a Sansui 9090DB (beautiful) but it is unable to produce any sound - two vu meters at front doesn't move either. Everything else seems to look fine and okay. Protection goes to red and will turn green. However not producing any sound. I was told to check the fuse and found 2 x 10A are dead, so I replace and installed but soon after turning it on, it blew the newly installed fuses? Appreciate your your thoughts and recommendations on what may be wrong with the receiver. Thank you in advance

Output transistors are blown. They usually take an assorted list of parts on the driver board with them when they go so they won't be lonely in silicon heaven.

The 9090db is a fairly easy unit to repair. Get it to a trusted tech.

You have shorted output transistors. Where are you located, there are many AKers here that can assist. Replacements are available.

Hi Thanks,

Im in Northern California. Bay area.

Yes, output transistors.

Note that on the driver board, there are a number of fuseable, flameproof resistors that just love to change their values (they increase substantially.)

The way to know if a prospective tech should be allowed to work on your machine is to ask about those resistors. If you get a "huh?" type response, move on. Also, ask what kind of output transistors they use. If they say "original Japanese part numbers" or Motorola (ON) numbers, that's good. If they say "NTE," run.

Fred Longworth

The 9090 uses MJ10015 and MJ10016 Onsemi replacements. I have found that when replacing originals with newer subs it pays to replace them all, i.e., don't just do the blown ones if the mate is good. They seem to run hot when you do that.

Rob

Just a point of clarification. The 9090DB can use the MJ10015/16 combination. The 9090 would just use the NPN version, MJ10015. OnSemi has shifted production to meet the new lead free standards so the part numbers now have a G on the end. I believe the original part numbers have been discontinued but may still be available from some suppliers.

That said, Echo Wars generally recomends and upgraded model, the MJ21193G/MJ21194G for these applications.

- Pete

Thank You for the advise and recommendations. I'll keep you posted on the outcome. take care

I am having a similar situation right now with an AU-9500. I would like to know if you find any parts on your driver boards to be bad. Every time I turn on the unit it powers up but doesnt click out of protection. The right channel's output transistors fail the diode test (left channel fine) and a fuse blows every time it gets turned on.

If the outputs are blown, it's a good bet that the driver transistor(s) is also blown. They are generally mounted on a small heat sink on the driver board. There may be other damage as well. I generally remove and test any of the other semiconductors in the area.

- Pete

I agree with LBPete, if you are blowing fuses then the outputs are blown. The Driver board probably has, as EW so eloquently stated, donated some silicon so the outputs are not lonely in Silicon Heaven.