Function Generator help

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looking at TP2 with a scope using various ranges
Click to expand...
John said the oscillator doesn't work - I hope that's true.
Then there could be no oscillation at Pin TP2.
At Pin2 of IC3 was measured 11V - It's directly connected to TP2.
At the same Time at Pin3 of IC4 ( =TP3 ) was measured -11V.
So i think that is OK.
But You're right. When move VR1 there must be seen a Change of that Voltage.
Let's see what results bring the measurement around IC7.
 
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Hi KeepItSimpleStupid, WKRUG, JimB.
I have just put the scope on R112 reads 800mV approx with a sine/square and triangle waves also frequency switches seem to be working ok.
Tried turning amplitude pot up not working signal stayed the same.
Tr5 = S1 = 15.33Vdc, D1 = 450mV triangle wave, G1 = 450mV triangle wave 225mV 50% positive 225mV 50% negative don't understand this.
S2 = -500mV Vdc, D2 = -14.86Vdc, G2 = -15.34Vdc.
Tr6 = emitter 1.14Vdc with Dmm but 3VDC with scope.
WKRUG I have edited the pin number to 13 from 11 sorry about that Pin 9 still reads 1.83Vdc.
Hope this helps, John.
 
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wkrug, Ne527 pin9 voltage is definitely 1.8volts linked to pin 13 dn74ls37 100ohm resistor. See attached photo post 1.
Regards, John.
Read post 24 pin 9 voltage.
 
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"AC/DC 1,83V at Pin 9" means a rectangular wave between 0V and 3,66V or what??
That value is OK

The Voltage at Pin 13 of IC 9 must swing from <0.7V to >2.4V to get a proper function of the 74LS37.

When yes the TTL Output must work!
Does it?

The Duty Cycle Pot only works when the S8 Switch is turned on.
Only the rising and the falling edges of the triangle signal at the Gate of TR5 will be longer or shorter when twisting of this Pot.

You always write " a Voltage of x.y V " - AC / DC and the Potential of AC to GND will be very useful informations too.

Is it possible to load up Oscilloscope Screen Shots here. With the Parameters ( V/div and Time Base ) and the Zero Line?
Then give us a Oscillogramm of Pin 13 IC9 and TP2 please.

I've Skype - You too? Then we can try to solve that problem via a Skype session.
 
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Where is switch 8?
What turns it on?
All measurements have been referenced to gnd.
Will try to photo oscilloscope tomorrow.
I dont have skype but will try to install tomorrow.
I use Messenger. I have 5vdc on ttl I will double check tomorrow.
 
It looks like you guys are getting somewhere. The TTL output would be worth getting out of the way. From what I gathered, you appear to have the basic wave shapes, but lack it at the output?

e.g. You should have signal at the test point mixsig with no amplitude control or attenuation controls.
The TTL output is not open collector, so pullups aren't needed. They are totem pole outputs, and 5V is a bad number to have there. It should at least be 5 V minus a diode drop. You can also check in 11 of IC9. The gates in IC9 in parallel just increase the fan-out or the ability to drive an external circuit.
 
I'll go so far as to say that nearly ALL function generators have a triangle waveform as their basic waveform. It's the positive and negative constant current sources that are switched on and off to generate this linear ramp. There are no true oscillators involved. If the power supplies check out OK, get the triangle function working first. The triangle is sent on to a sine shaper circuit to provide the sine wave; it's sent to a comparator to obtain a square wave. The TTL output is derived from that. Get the triangle working first. If you get it fixed, it may well be that you'll have fixed everything.
 
John and I had talked via SKYPE.

So we figured out, that the whole Oscillator section is working fine.
The failure is in the output amplifier.
The Output has +15V and not 0V how expected.

TR12, 13, 16, and 17 has a collector to base short ( when soldered out ).

John would replace them and then look for further problems.
But he had to wait for spare parts.

Why all transistors in the input stage of the amp can go away - I don't know.
The drivers TR18, TR19 and the output Transistors seems to be OK, when tested with diode tester.

I guess there once was connected an higher external Voltage at the Output connectors.

Let's see what going on...
 
Hi Willi and Dean, Willi I changed out the transistors 3904 and 3906 I have a -3.3 volts between R76/R77.
I connected the BNC to 50ohms to scope shows a 1.2 - wave tried all waves all ok but -1.2volts.
Tried moving VR18 this was maximum amplitude on generator with amplitude pot turned up full.
John.
Thanks for replying Dean.
 
Remember the 0db position and the 600 ohm output position will generally give you the highest voltage out. This assumes that your scope's input Z is 1 Meg usually shunted by 20 pf or so.
 
Hi everyone, I now have a functionong generator.
The problem was in the amplifier section when I changed out the 3904 and 3906 2219 and 2905 I had mistakenly due to my inexperience removed 2 shorted tracks from TR16 to TR12 and TR13 to TR17. I would like to thank all who participated and especially Willi Krug (wkrug) as Willi solved the puzzle ha ha.
Thx again, John.
 
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