Akai AX-60 problem with noise generator

[patrickvf1976]

My Akai AX-60 has a problem with the noise generator - the noise generator's output has become extremely low all of a sudden and I can't figure out what happened. It was working just fine yesterday and I was able to make some nice thunder and swoosh kind of sounds. Now it struggles to get to a reasonable volume. Everything else works just fine. Any ideas what could cause this problem?

[patrickvf1976]

So.. any suggestions, advice, anything? Anyone? Help??

[patrickvf1976]

Still could use some help here. Any hints what to look for or even some schematics would do.

[sneakthief]

http://manuals.fdiskc.com/flat/Akai%20AX-60%20Service%20Manual.pdf

first hit on google

Either 1) the noise generator isn't working or 2) the circuit that turns off both noise generators for Noise A and B. 1 seems more likely.

page 40 says that TR4, TR5 and IC21 are responsible for the noise

On page 37, you'll find the noise schematic. It uses these parts:
IC21: BA715STD
TR4: 2SC 3330
TR5: 2SC 3383

Check along the signal path to see if you're getting noise. The schematic lists voltages next to the ECB's of the transistors - that's a good and easy place to start to see if either are blown.

[patrickvf1976]

Finally found some time to open it up and look into it.. what's the best way to check the signal path? I don't have an oscilloscope, just a multimeter which I use to check common components with (caps, op-amps, etc...) I never went that technical as in using a service manual other than some schematics from the web for my really old gear.

[patrickvf1976]

Nevermind.. failed to read the part with the voltages.. freakin' ADD

So.. can the transistors be substituted for by regular Radioshack transistors or do they have to be exatly this type?