First you need to familiarise yourself with the controls.
Connect the probe (use the left hand one in your pic with a X1/10 switch on it) to terminal marked "A" on the scope. It's a dual or two channel scope by the way. We will use channel A although both are identical.
Make sure the probe is in X1 position. The other position on the probe marked X10 divides the signal by 10. We will use X1 for now.
Switch the scope on. Does a trace appear ? Don't have it too bright.
Set the two V/cm controls to 1/Vcm as in picture.
Set the S/cm knob to 5S/cm as in picture.
Set the three small slide switches to AC which is the middle position.
Without using it I'm not sure how the trigger controls work but you want "Int" trigger so press the top trigger button in.
The two small knobs below S/cm want to be pushed in.
You should have a line across the screen. What does AUS mean ? language problem as there should be a way of turning off channel B
Connect the probe (use the left hand one in your pic with a X1/10 switch on it) to terminal marked "A" on the scope. It's a dual or two channel scope by the way. We will use channel A although both are identical.
Make sure the probe is in X1 position. The other position on the probe marked X10 divides the signal by 10. We will use X1 for now.
Switch the scope on. Does a trace appear ? Don't have it too bright.
Set the two V/cm controls to 1/Vcm as in picture.
Set the S/cm knob to 5S/cm as in picture.
Set the three small slide switches to AC which is the middle position.
Without using it I'm not sure how the trigger controls work but you want "Int" trigger so press the top trigger button in.
The two small knobs below S/cm want to be pushed in.
You should have a line across the screen. What does AUS mean ? language problem as there should be a way of turning off channel B
They are Wharfedale TSR-110, same age as Rotel. The topic now has many pages so you probably missed that the scratchiness is there only while using volume pot without knob, touching its metal shaft with bare hands.
As for your off-topic question, of course I will do it, it is the least I can do for you. I believe the original hoster of that show is now dead, but I will check the facts and get back to you via e-mail
If you now connect the probe tip to the front socket marked "CAL" (calibration signal) the trace should trace out a squarewave on the screen.
The CAL output is 1 volt peak to peak so the trace should be deflecting or showing 1 "squares worth" of signal. It doesn't show the frequency so we can work that out later. It will probably be either 1Khz or maybe even just 50/60 hz... it could be anything.
If you adjust the S/cm control that will alter the speed the spot (trace) moves across the screen. The trigger control (Niveau ???) should allow the trace to be "locked" so that the display is stable.
The CAL output is 1 volt peak to peak so the trace should be deflecting or showing 1 "squares worth" of signal. It doesn't show the frequency so we can work that out later. It will probably be either 1Khz or maybe even just 50/60 hz... it could be anything.
If you adjust the S/cm control that will alter the speed the spot (trace) moves across the screen. The trigger control (Niveau ???) should allow the trace to be "locked" so that the display is stable.
Hi Mooly,
and thank you very much for your effort. Unfortunately I am alone with my small son now, and it is probably not a good idea to go poking around with the scope if I want to keep the amplifier healthy
I probably wont be available until 22PM, when he goes to sleep. I will do per your instructions and get back then. Will took a picture or two of the scope screen.
I believe AUS in german means off.
Thank you again
Marko
No problem... will probably be tomorrow when I see it then
You can't damage anything on the scope as such... but don't connect it to the amplifier yet as you have to do it correctly.
Try and get the "CAL" waveform displayed properly. And play with the controls to see what they do and to get a feel for it. Remember its "just" a voltmeter on the vertical axis and time on the horizontal.
If AUS is off then you can turn the B channel off as we are only using one channel for this.
Try measuring DC voltages too (batteries) and you will see the trace deflect one way or the other depending on which way round you connect the two probe leads.
If you can get the CAL waveform stable try and calculate the frequency. It's 1/T where T is the time per division on the horizontal axis. So 50Hz has a "T" of 20milliseconds for ONE cycle of the waveform. 1000Hz is 0.001 seconds or 1 millisecond.
You can't damage anything on the scope as such... but don't connect it to the amplifier yet as you have to do it correctly.
Try and get the "CAL" waveform displayed properly. And play with the controls to see what they do and to get a feel for it. Remember its "just" a voltmeter on the vertical axis and time on the horizontal.
If AUS is off then you can turn the B channel off as we are only using one channel for this.
Try measuring DC voltages too (batteries) and you will see the trace deflect one way or the other depending on which way round you connect the two probe leads.
If you can get the CAL waveform stable try and calculate the frequency. It's 1/T where T is the time per division on the horizontal axis. So 50Hz has a "T" of 20milliseconds for ONE cycle of the waveform. 1000Hz is 0.001 seconds or 1 millisecond.
this speaker:
Wharfedale TSR 110 | Flickr - Photo Sharing!
by a closer look to the circuit arround the volume control and baxandall equalizer I note, that there are two caps with 47 uF (C517/518) and two with 33uF (C515/516, AC-NFB); all the other capacity values are smaller.
I guess, for C517/518 also 10uF is to use without audible loss in bass transmission and also for C515/516. about
bei reichelt elektronik
you can order wima caps for the signal pad with all values you need.
Hi Mooly,
sorry once again for not being available sooner. As a "scope virgin" I really don't know what to say about my first time. Instead of square-wave I got two "overtaking allowed" lines, one square or cube or cm apart, at least that is OK. But look at the pictures, first is just a scope without probe touching anything, second is with probe in cal hole, third I am probing myself.
Attachments
That looks OK, certainly usable.
Picture 1. OK
Picture 2. I think OK. Is it an effect of the camera photographing a moving spot that part of the trace is "missing" ? The amplitude is 1 volt peak to peak as it should be. You are seeing the scope show the voltage alternately jump from zero to 1 volt and then back to zero again repeateadly.
Picture 3. Same as above. Is it an effect of the camera that part of trace is missing. It is showing that "you" are picking up the household 50/60hz mains supply that is all around.
Now we'll work the frequency out.
Look at picture 3. Pick any point on the waveform and count how many squares along the horizontal axis until that same point on the waveform is reached again. I make it about 3.4 squares.
So 3.4 times 5 milliseconds per division (the S/cm setting) is 3.4*5e-3 which is 0.017 seconds.
The frequency is 1/T (just the reciprocal) so 1/0.017 is 58.8 Hz. So I'm guessing your on 60 Hz mains over there. Within the accuracy of looking at a screen and the accuracy of an uncalibrated scope thats very acceptable result.
Picture 2 looks the same frequency so we can deduce the CAL signal will be derived off the mains transformer and just squared up. A squarewave should jump between the two voltages instantly and so that is what you see.
Here are some shots of "squarewaves" where you can see the rise and fall clearly,
http://www.diyaudio.com/forums/analog-line-level/196461-different-opamp-compensation-technique.html
The trigger controls on your scope... I am not sure how these controls will behave.
TV-Z and TV-B will be filters for TV line rate and frame rate to make looking at TV signals easier. For looking at high frequency signals it may be difficult to get the trace to lock and be steady if these are set incorrectly. You want "internal triggering" but without filters... well come to that as and when
Is it probing the amp next then ?
Picture 1. OK
Picture 2. I think OK. Is it an effect of the camera photographing a moving spot that part of the trace is "missing" ? The amplitude is 1 volt peak to peak as it should be. You are seeing the scope show the voltage alternately jump from zero to 1 volt and then back to zero again repeateadly.
Picture 3. Same as above. Is it an effect of the camera that part of trace is missing. It is showing that "you" are picking up the household 50/60hz mains supply that is all around.
Now we'll work the frequency out.
Look at picture 3. Pick any point on the waveform and count how many squares along the horizontal axis until that same point on the waveform is reached again. I make it about 3.4 squares.
So 3.4 times 5 milliseconds per division (the S/cm setting) is 3.4*5e-3 which is 0.017 seconds.
The frequency is 1/T (just the reciprocal) so 1/0.017 is 58.8 Hz. So I'm guessing your on 60 Hz mains over there. Within the accuracy of looking at a screen and the accuracy of an uncalibrated scope thats very acceptable result.
Picture 2 looks the same frequency so we can deduce the CAL signal will be derived off the mains transformer and just squared up. A squarewave should jump between the two voltages instantly and so that is what you see.
Here are some shots of "squarewaves" where you can see the rise and fall clearly,
http://www.diyaudio.com/forums/analog-line-level/196461-different-opamp-compensation-technique.html
The trigger controls on your scope... I am not sure how these controls will behave.
TV-Z and TV-B will be filters for TV line rate and frame rate to make looking at TV signals easier. For looking at high frequency signals it may be difficult to get the trace to lock and be steady if these are set incorrectly. You want "internal triggering" but without filters... well come to that as and when
Is it probing the amp next then ?
Not in my own hifi system, but for modification (for creating an outdoor crossover network). One of my first tasks with the simulation software "bassyst" (approximately 12-15 years ago). The result was satisfy; unfortunately I haven't store schematic documentation of the new topology.
That looks OK, certainly usable.
Picture 1. OK
Picture 2. I think OK. Is it an effect of the camera photographing a moving spot that part of the trace is "missing" ? The amplitude is 1 volt peak to peak as it should be. You are seeing the scope show the voltage alternately jump from zero to 1 volt and then back to zero again repeateadly.
Picture 3. Same as above. Is it an effect of the camera that part of trace is missing. It is showing that "you" are picking up the household 50/60hz mains supply that is all around.
Now we'll work the frequency out.
Look at picture 3. Pick any point on the waveform and count how many squares along the horizontal axis until that same point on the waveform is reached again. I make it about 3.4 squares.
So 3.4 times 5 milliseconds per division (the S/cm setting) is 3.4*5e-3 which is 0.017 seconds.
The frequency is 1/T (just the reciprocal) so 1/0.017 is 58.8 Hz. So I'm guessing your on 60 Hz mains over there. Within the accuracy of looking at a screen and the accuracy of an uncalibrated scope thats very acceptable result.
Picture 2 looks the same frequency so we can deduce the CAL signal will be derived off the mains transformer and just squared up. A squarewave should jump between the two voltages instantly and so that is what you see.
Here are some shots of "squarewaves" where you can see the rise and fall clearly,
http://www.diyaudio.com/forums/analog-line-level/196461-different-opamp-compensation-technique.html
The trigger controls on your scope... I am not sure how these controls will behave.
TV-Z and TV-B will be filters for TV line rate and frame rate to make looking at TV signals easier. For looking at high frequency signals it may be difficult to get the trace to lock and be steady if these are set incorrectly. You want "internal triggering" but without filters... well come to that as and when
Is it probing the amp next then ?
Hi Mooly,
and before answering your questions and add couple of mine I just want to recapitulate what we are doing here: You are guiding me with just your posts across the English Channel, miles away, to use a scope which is older and probably in need of service more then the amp we are trying to repair, and I am eager but electronically totally uneducated, never used scope before, so you have to troubleshot not just the amp itself but my testing procedures also.Me not frying anything is your success already and for that you deserve to be called King of the scopes, ayatollah of solid state amps and guru of troubleshooting.
That being said I see no reasons not to continue
1. Thank God
2. It is indeed an effect of the camera, I was worried because vertical lines were missing
3. Another effect of the camera, we have 50 Hz mains here
As for the frequency I will count precisely those squares and get back.
I tried all trigger controls while looking at the screen and they all looked very similar to me.
If it's 50Hz mains then one cycle should be 20 milliseconds (F=1/T), so that would (should) be four squares at 5ms/div. If the scopes a little inaccurate it doesn't matter.
The setting for trigger controls matters far more for higher frequency signals. What the trigger circuit does is start the spot sweeping across the screen at the same point on the waveform and so the waveform appears locked and stationery on screen.
There should be a calibration adjustment to get close to the correct 4 squares for the full 50Hz cycle.
You can then check the accuracy of the two or three horizontal steps either side of that. The step accuracy of the switches is usually pretty good.
Wouldn't like to say without first hand look. DC offset (for minimal drift) maybe.
Markings on front panel... on/off rotary/brightness
Are we ready for the amp testing ?
Might be later today when I look in
Don't blow anything up.
If it's 50Hz mains then one cycle should be 20 milliseconds (F=1/T), so that would (should) be four squares at 5ms/div. If the scopes a little inaccurate it doesn't matter.
The setting for trigger controls matters far more for higher frequency signals. What the trigger circuit does is start the spot sweeping across the screen at the same point on the waveform and so the waveform appears locked and stationery on screen.
Mooly and Andrew,
It is definitely 50Hz mains, looking at pictures I also counted just 3 squares between cycles, and it is easier for me to count squares on the pictures because the waveform is far from stationery even in slowest mode which is adjusted by the niveau button.
If I understood you correctly Andrew you want me to try putting that line either higher or lower on the screen and perhaps get a more precise reading which should be 4 squares?
I absolutely wont connect the amplifier until I get green light from you, these are just questions I should ask first so not to forget later.
That probe I am using under the tip itself there is a metal ring, can that ring be isolated with tape?
For the ground can we use any part of the chassis, or should it be center-tap?
Alligator clip that goes to ground, can it be prolonged by another piece of wire so I have more maneuver space?
Wouldn't like to say without first hand look. DC offset (for minimal drift) maybe.
Markings on front panel... on/off rotary/brightness
Are we ready for the amp testing ?
Might be later today when I look in
My hands are shaking from excitement but I am ready.
I will be home by 4PM, and will listen carefully
.The horizontal axis is time.
Timebase uses values like 5ms/cm or 2us/cm (div = cm square)
The vertical axis is voltage
Voltage uses values like 2mV/cm or 5V/cm
The two Trim Pots next to the vertical adjustment knobs look like vertical (voltage) trimmers.
We need to try and find a horizontal trimmer, so that a 50Hz signal fits the correct number of div (cm squares).
Let's investigate what the vertical adjustments do.
Set your 1Vpp test signal height by using the switch setting of 1V/cm it should jump up and down 1 square. Set the switch to 2V/cm. It should now jump up and down by half a square.
set to 0.5V/cm, gives 2quares
set to 0.2V/cm, gives 5squares. You may have to adjust the position pots to keep the test signal on the screen.
If you set to 0.1V/cm, the square wave test signal should go at least partly off screen. You should have 8div (cm squares) in the vertical direction, which on the 0.1V/div gives a total range on the display of 800mVpp. Just a bit less than the 1V test signal.
The vertical position adjusters should be able to bring one of the horizontal voltage back on to screen.
Check out this part of the operation and come back and confirm you understand this and the scope does as expected.
Timebase uses values like 5ms/cm or 2us/cm (div = cm square)
The vertical axis is voltage
Voltage uses values like 2mV/cm or 5V/cm
The two Trim Pots next to the vertical adjustment knobs look like vertical (voltage) trimmers.
We need to try and find a horizontal trimmer, so that a 50Hz signal fits the correct number of div (cm squares).
Let's investigate what the vertical adjustments do.
Set your 1Vpp test signal height by using the switch setting of 1V/cm it should jump up and down 1 square. Set the switch to 2V/cm. It should now jump up and down by half a square.
set to 0.5V/cm, gives 2quares
set to 0.2V/cm, gives 5squares. You may have to adjust the position pots to keep the test signal on the screen.
If you set to 0.1V/cm, the square wave test signal should go at least partly off screen. You should have 8div (cm squares) in the vertical direction, which on the 0.1V/div gives a total range on the display of 800mVpp. Just a bit less than the 1V test signal.
The vertical position adjusters should be able to bring one of the horizontal voltage back on to screen.
Check out this part of the operation and come back and confirm you understand this and the scope does as expected.
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