Akula0083 30 Watt Self Running Generator.

[JohnnBlade]

Hi JohnBlade,

This post may also be of use to you: -->havuhung - track layout - Reply #971 on: April 27, 2014, 05:15:19 PM<--

All the Best

  Chris

Thnx Chris!

[TinselKoala]

From the looks of the screen shots this is a frequency roll off due to a bad input stage. I would check the input stage coupling capacitor as this might be causing the attenuation issue. How does it do on DC? If the issue is AC only I would check the front end for channel 2 for damaged components.

If you look at the screen shots the rise time is what is being affected, this makes me think of a bad capacitor since it cannot keep up with the incoming signal (charging the cap). Open her up and replace the input capacitor, if you have a tester I would pull it and test it. Probably a inexpensive fix.

I agree, that's why I asked if there was any difference when coupling was changed from AC to DC and back. No answer...
We can see that the A1 channel is set to DC-coupled.  But we need the information for channel A2!

It's always something....

[TinselKoala]

i think its better to add a 12 step switch on the spot ( pin 5) where the cap is so you can easily change the cap values and have different ranges that you can test. i did that with my 555 timer circuit that i have been using for a while now. cause it would be a waste to desolder the cap everytime when you wanna try a different range.

Greets JB

You probably have more inter-lead capacitance in there than the actual cap on the 34063, which is only 2.2 nanoFarads!

Just kidding.... sort of.


I'll bet you have a great collection of colored clipleads..... am I right?

(The reason the cap values in Akula's circuits keep changing, is so that you will keep chasing them. Red Herrings abound and are easy to chase, but you won't catch the big fish doing it. You will more likely get eaten, yourself.)

[TinselKoala]

@starcruiser

I opened her up and at the CH2 entry the components are so small I am really not inclined to even try to poke around. I thought that maybe by fluke chance I could have seen a workable cap showing some evidence of blow up or overheating but these components are way to small. So I will use the CH A on this scope and then use my other scope, a Hitachi V650F. Not as advanced but this workhorse had served me well for many years with simple no frills waveform. Damn it, just when I wanted to do a video of my AK30, those frill would have come in handy.

@JohnnBlade

It's good to know that there are others here that have this stubborn streak when you decide to do something, you go all the way. Can't wait to learn what the cap values are for Pin 5. That damn pin 5 has had different values in every build schematic Akula put out. AK30 is at 3n, anther at 10n, I think another at 2.2n shown on the schematic. But this is supposed to provide the frequency range so why not just put what I have always thought should be there, a 1n cap.

wattsup

The AC-coupling capacitor is probably the physically largest one in the front-end. It will be a good poly-film type of 300 V or more. Do you have the Service Manual for the scope, or a link to a digital version?

Now, I'll try again: I am asking questions for a reason. If you actually answer the questions I and other people actually ask, we might get somewhere.
1. Again: was the channel2, the one with the problem, set to AC coupled, or DC coupled?
2. What happens when you hook the Channel A2 probe to the sig gen, through a 0.1 uF coupling capacitor? Probe tip to cap, cap to FG.

[havuhung]

Hi All,

Has anyone tested the resistance measurement on the ferrite core? . .
I have no ferrite pot core, so I can not measure to see if the resistance value on the core surface is how much (Kohm/cm)? . .


Regards