How to check for low/high frequecy oscillations with a Tektronix 2213A - diyAudio
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Old 23rd May 2008, 02:02 AM   #1
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The repaired channel of my CLC High Power JLH blew up again! This time I have speaker protection velleman kit K4701 connected and it saved the Jordan Jx53. I guess I did not really fixed it last time by just replaced the output transistors and prolong the life of the amp until last night.

I would like to rebuild this CLC High Power version replace all Mj21194 with 2SC5200. Do I need to replace the rest of the parts in the amp currently with adjusted values or different parts? Can these 2SC5200 be just a drop in replacements or I need to change other components as well?

Also I would like to learn how to check low/high frequecy oscillations with a Tektronix 2213A Oscilloscope. I also bought a copy of the copied instruction manual, and in hand I have a copy of the XYZs of Oscilloscopes from www.tektronix.com. I still have no clue what to do with the scope after reading thru both many times.

I think I should buy new probs first. The only probe came with the scope seems very filmsy and it is a short coax cable.

I am seeking help as to how and where to put the probes when checking for amp oscillation. How to set up the scope to do just that. What else is required to set this test rig up? Do I need a CD player as input ? Do I need speakers ?
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Old 23rd May 2008, 02:04 AM   #2
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Default This is the circuit from Geoff's site I used

This is the circuit from Geoff's site I used
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Old 23rd May 2008, 02:08 AM   #3
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Default Scope

Here is the scope that I bought.
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Old 23rd May 2008, 02:13 AM   #4
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Tried to compensate the coax probe by following the manual but the manual instructions stated to connect 10X probes which I do not have. So the result is this
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Old 23rd May 2008, 07:32 AM   #5
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Quote:
I would like to rebuild this CLC High Power version replace all Mj21194 with 2SC5200. Do I need to replace the rest of the parts in the amp currently with adjusted values or different parts? Can these 2SC5200 be just a drop in replacements or I need to change other components as well?
I went from 2 2n3055 per channel to 4 2SC3281 per channel. Obviously I added emitter resistors. Otherwise nothing was changed and it worked flawlessly. Even the CD offset needed only a minor correction.

(I already had a small cap parallel to the feedback resistor (47 pF If I remember correctly) to avoid oscillation.

I actually never bothered to check for oscillation on a scope as I have none. It sounds fine though, but If I ever have access to such a thing I'll do some measurements (provided I can find out how to do such thing).

Succes, MArco
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Old 23rd May 2008, 11:42 AM   #6
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Marco,

Thank you for the encouragement. When you have learn how to use the scope for checking amps please share it with me. Glad to hear your JLH works fine now
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Old 23rd May 2008, 11:49 AM   #7
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What frequency is the calibrate signal on your scope.
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Old 23rd May 2008, 11:51 AM   #8
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Is the overshoot on that squarewave the same on different volt/div settings, and what about on channel 2 ? The input attenuator inside the 'scope will have it's own set up procedure but unless this has been twiddled it should not that far out.
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Old 24th May 2008, 02:22 AM   #9
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Quote:
Originally posted by Mooly
What frequency is the calibrate signal on your scope.

Sorry about the late reply Mooly,

I was following the step by step from the manual.

1. Preset instrument controls and obtain a baseline trace.

2. Connect the two 10X probes to the CH1 and CH2 input(which I do not have. I have only 1 COAX probe 1X I guess connected to the CH1 input)

3. Set both VOLTS/DIV switches to 10mV and set both input Coupling switches to DC.

4. Select CH1 VERTICAL MODE and insert the tip of the Channel 1 probe into the PROBE ADJUST output jack.

5. Using the approximately 1 kHz PROBE ADJUST square-wave signal as the input, obtain a 5-division display of the signal. (guessed work here for me)

6. Set the SEC/DIV switch to display several cycles of the PROBE ADJUST signal. Use the Channel 1 POSITION control to vertically cneter the display. (guessed work here for me)

7. Check the waveform presentation for overshoot and rolloff. If necessary, adjust the probe compensation for flat tops on the waveform. (took picture here)
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Old 24th May 2008, 02:26 AM   #10
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Quote:
Originally posted by Mooly
Is the overshoot on that squarewave the same on different volt/div settings, and what about on channel 2 ? The input attenuator inside the 'scope will have it's own set up procedure but unless this has been twiddled it should not that far out.

I am going to buy 2 new probes tonight the 100MFz Probe Kit DL-8100 from ebay. The original probe P6109B type is very expensive! It is almost 2/3 the price of the scope that cost me itself.
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