I have got a curve tracer from ebay. But, it neet some repairs. The collector supply seems working. The step generator seems working.
But, the beam is thick. I switched on the tacer there is a large green spot about 3mm in diameter in the screen. I turn the intensity knob to try to make it smaller but little change. I turn the focusing knob the shape of the spot changed from circular to rectanglar.
Grateful if anybody can tell me what is wrong? Is the Z amplifier has got problem??
Any helpful hints will be highly appreciated.
Eric
But, the beam is thick. I switched on the tacer there is a large green spot about 3mm in diameter in the screen. I turn the intensity knob to try to make it smaller but little change. I turn the focusing knob the shape of the spot changed from circular to rectanglar.
Grateful if anybody can tell me what is wrong? Is the Z amplifier has got problem??
Any helpful hints will be highly appreciated.
Eric
The first thing you should have is the service manual. If you did not get one, buy one on eBay or download one on line.
Verify all the low voltage supply points at the test points on the PS board. (+5, +12, -12, +30, -30) If most things are working these are probably OK.
Make sure the 577 is not in storage mode. The intensity control should dim the spot to nothing when fully counter clockwise and should begin to appear at 9 or 10 o'clock on it's rotation. If not, there is an intensity range adjustment through the top of the high voltage cover inside.
There is an astigmatism adjustment just outside of the HV cage to make the spot round. This adjustment is just below the horizontal gain adjust. Look for "astig" on the board.
Below that is the geometry adjustment, but that should not affect the intensity or spot. It only affects lines at the CRT edges.
Finally, if you just cannot get a clean reasonably focused spot with all adjustments, and voltages are correct, then you may have a poor CRT.
Do not adjust the HV adjustment at the rear of the HV cage unless you measure at the CRT socket like it says on cover (with intensity down). This adjustment should only be made if known off as it will affect the calibration of the vertical and horizontal amplifiers.
There is no accessible Z axis on this unit. But with beam intensity set low, the variable collector voltage knob will dim the spot when fully counter clockwise. This is normal operation.
(It's late over here, going to bed now)
Verify all the low voltage supply points at the test points on the PS board. (+5, +12, -12, +30, -30) If most things are working these are probably OK.
Make sure the 577 is not in storage mode. The intensity control should dim the spot to nothing when fully counter clockwise and should begin to appear at 9 or 10 o'clock on it's rotation. If not, there is an intensity range adjustment through the top of the high voltage cover inside.
There is an astigmatism adjustment just outside of the HV cage to make the spot round. This adjustment is just below the horizontal gain adjust. Look for "astig" on the board.
Below that is the geometry adjustment, but that should not affect the intensity or spot. It only affects lines at the CRT edges.
Finally, if you just cannot get a clean reasonably focused spot with all adjustments, and voltages are correct, then you may have a poor CRT.
Do not adjust the HV adjustment at the rear of the HV cage unless you measure at the CRT socket like it says on cover (with intensity down). This adjustment should only be made if known off as it will affect the calibration of the vertical and horizontal amplifiers.
There is no accessible Z axis on this unit. But with beam intensity set low, the variable collector voltage knob will dim the spot when fully counter clockwise. This is normal operation.
(It's late over here, going to bed now)
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Thank you very much for your information
If you do not mind would you give me your mobile number, I can consult you if required.
Thank you very much in advance
Eric
If you do not mind would you give me your mobile number, I can consult you if required.
Thank you very much in advance
Eric
Manual for the 577 is available on BAMA: http://bama.edebris.com/manuals/tek/
There is a very active Yahoo group for Tektronix: Yahoo! Groups
There is a very active Yahoo group for Tektronix: Yahoo! Groups
Dear All,
Thank you for all for you making contribution to my repair of 577 D1. I got it fixed. It is now working great.
I want to develop its application a bit more to cover the tracing of high power transistor for power amp and make it able to deliver 250 w power to test bi-polar transistor.
my range of interest of tracing would be 0-100V, 0-15A, I think we can use an external transformer and load resistor for the collector supply. Would any high hand people to propose which point in the tracer is best convenient for external collector supply like this?
Thank you very mcuh for your help in advance
Eric
Thank you for all for you making contribution to my repair of 577 D1. I got it fixed. It is now working great.
I want to develop its application a bit more to cover the tracing of high power transistor for power amp and make it able to deliver 250 w power to test bi-polar transistor.
my range of interest of tracing would be 0-100V, 0-15A, I think we can use an external transformer and load resistor for the collector supply. Would any high hand people to propose which point in the tracer is best convenient for external collector supply like this?
Thank you very mcuh for your help in advance
Eric
Dear Expert,
Grateful, if you guys expert can give me a hand to sort out why the curve of my 577 is not continuous. It was working well before.
IMG-3424 — ImgBB
Grateful, if you guys expert can give me a hand to sort out why the curve of my 577 is not continuous. It was working well before.
IMG-3424 — ImgBB
Never seen this one before but it appears like the beam is being intensity modulated for some reason. Do the spots change with a difference in step rate? (slow-medium-fast) Perhaps scope the CRT intensity circuits.
Hello,
"my range of interest of tracing would be 0-100V, 0-15A"
To do that, you will need to use pulsed Ib and Ic to stay on the SOA.
"my range of interest of tracing would be 0-100V, 0-15A"
To do that, you will need to use pulsed Ib and Ic to stay on the SOA.
There is modulation of the HV regulator for the CRT -- see page 3-11 of the manual and Schematic 8.
Hello,
The modulation of the HV regulator for the CRT has nothing to do with the modulation of Ic or Ib.
You are measuring transistors, not the HV CRT regulator.
Yoy will not be able to have at the same time 100V & 15A.
You will have either 100V & 1.25A in pulse mode , or 10/20A with 6.5V.
See characteristics at page 1.1.
The modulation of the HV regulator for the CRT has nothing to do with the modulation of Ic or Ib.
You are measuring transistors, not the HV CRT regulator.
Yoy will not be able to have at the same time 100V & 15A.
You will have either 100V & 1.25A in pulse mode , or 10/20A with 6.5V.
See characteristics at page 1.1.
look up the 176 test fixture to test high current and high voltage. I don't know if it will work in a 577, it does in a 576. You could possibly build a clone that will work on the 576.
176 - TekWiki
176 - TekWiki
My first guess judging from the shape and rate is something in the HV rectifier or cap on the HV is bad. Nothing else in the scope runs that fast. Also the deflection modulation would happen as the HV changes. The HV acts a little like a zoom lens. As the HV drops the image gets bigger.
If yours has a storage tube (the 577 seems to be only storage) its a little unusual since the cathode has the HV on it, along with the intensity floating at -3.5 KV. Normal CRT's are operated with the cathode near ground and the anode connection at HV. That means there are a number of places to check around the cathode. However since its all at HV you can't just take a scope probe to it. My first step would be to fire it up in darkness looking for arcing. Then check for dirt/dust causing leakage around the HV components finally check the components themselves. There are a number of components that could have failed. Check the frequency its operating at to see if its close to normal. It may be way low for some reason.
Storage tubes have a finite lifetime so don't expect the storage to work very well at its age, not that they ever were really good. I have been told b Tek that even unused they decay.
If yours has a storage tube (the 577 seems to be only storage) its a little unusual since the cathode has the HV on it, along with the intensity floating at -3.5 KV. Normal CRT's are operated with the cathode near ground and the anode connection at HV. That means there are a number of places to check around the cathode. However since its all at HV you can't just take a scope probe to it. My first step would be to fire it up in darkness looking for arcing. Then check for dirt/dust causing leakage around the HV components finally check the components themselves. There are a number of components that could have failed. Check the frequency its operating at to see if its close to normal. It may be way low for some reason.
Storage tubes have a finite lifetime so don't expect the storage to work very well at its age, not that they ever were really good. I have been told b Tek that even unused they decay.