Wavetek Model 130 Function Generator - Power supply problem

[budm]

Re: Wavetek Model 130 Function Generator - Power supply problem

You are getting negative Voltage through R108, 106.
As I indicated, R8 is the Bias resistor, so when IC6 is removed then you should have over 20V on the Emitter of Q17.
So what DCV do you have at each end of R8?
Is one end of R8 actually making electrical connection to the Base of Q18?
What DCV do you have at the Base of Q17?
What DCV do you have at the Base of Q18?
Right now Q17/18 is not getting the bias current through R8.

[Dgtech]

Re: Wavetek Model 130 Function Generator - Power supply problem

I actually got an Idea. I'm just wondering if this would work. What if I simply bypass all this crap by eliminating this section of the power supply by implementing two 15 volt regulator IC's?

Here is my plan:
Pull Q17,18,and 19.
pull CR19

Input of 15V regulator at +29V, ground TP1, output to "J"point past TP2 leaving jumper open. I just have to heatsink it to something.

Do you guys think this could work or am I going too far? I just think this circuit is over complicated for DC power supply of 15V.

[Dgtech]

Re: Wavetek Model 130 Function Generator - Power supply problem

zero volts on base of Q18.
-6.6 volts on anode of CR19

That R88 measures good out of circuit and point to point ohms out to its connections. 29 volts on one side. zero on the other. its not smoked either. I dont think its dropping the voltage.

[Dgtech]

Re: Wavetek Model 130 Function Generator - Power supply problem

So unless R88 is open circuit or the two new transistors are bad or not properly installed or bad trace in that section, you do have +22V feeding the Transistor so it has to have output Voltage.

After I pulled this out of the board to diode check it. I saw the leg was tucked over the other one. Once installed CORRECTLY. 15VDC on TP2.

Put everything back together and hooked up the output to the scope - ALL IS WELL. All ranges of frequencies look good on my scope as well as the Fluke meter.

So to recap: The replacement of Q17 and 18 would have done the trick if some goofball (ME) would have installed it right the first time. And I used to work as a board inspector/tester. I used to get on the assemblers for making mistakes like that. The shoe is on the other foot today.

Bud, Longbow, Redwire - thanks for all the assistance.

[budm]

Re: Wavetek Model 130 Function Generator - Power supply problem

Thanks for the follow-up. When something defy the logic, it is when you have to recheck the works.

[budm]

Re: Wavetek Model 130 Function Generator - Power supply problem

BTW, it would have saved lots of times if follow my suggestion on post #2.

[Longbow]

Re: Wavetek Model 130 Function Generator - Power supply problem

This fix is a good example of the importance of visual inspection. I say that to someone who is a trained inspector, I guess. Good fix.