Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
2205 Crt Problems
We have a 2205 with geometry problems on the crt. It has fairly
severe trapezoiding ,the spacing at the top is narrower than that at the bottom, appx .4div narrow at top, .2 div wide at bottom. Any idea what caused this? We tried degaussing the screen, absolutely no effect. I inspected the tube for visible damage inside, nothing sticks out as obvious. The horizontal deflection is fine, the trace is inline with the graticules across the screen within less than . 1div. Any ideas how to fix this? Thanks, Steve |
#2
Posted to sci.electronics.repair
|
|||
|
|||
2205 Crt Problems
On Jan 28, 8:59*am, sck0006 wrote:
We have a 2205 with geometry problems on the crt. *It has fairly severe trapezoiding ,the spacing at the top is narrower than that at the bottom, appx .4div narrow at top, .2 div wide at bottom. *Any idea what caused this? *We tried degaussing the screen, absolutely no effect. *I inspected the tube for visible damage inside, nothing sticks out as obvious. *The horizontal deflection is fine, the trace is inline with the graticules across the screen within less than . 1div. *Any ideas how to fix this? Thanks, Steve I forgot to add, adjusting geometry doesn't help. Thanks, Steve |
#3
Posted to sci.electronics.repair
|
|||
|
|||
2205 Crt Problems
|
#4
Posted to sci.electronics.repair
|
|||
|
|||
2205 Crt Problems
On Jan 28, 11:43*am, Jim Yanik wrote:
sck0006 wrote in news:5df1d999-e9fe-43cb-84ba- : On Jan 28, 8:59*am, sck0006 wrote: We have a 2205 with geometry problems on the crt. *It has fairly severe trapezoiding ,the spacing at the top is narrower than that at the bottom, appx .4div narrow at top, .2 div wide at bottom. *Any idea what caused this? * Probably got dropped;portables often suffer that. Field Techs would sit the scope on it's rear end,and then accidentally yank on the probe cable,and the scope would fall forward,WHACK,and sometimes the CRT would be damaged,sometimes break completely.(I've seen CRT necks snapped off) We tried degaussing the screen, absolutely no effect. *I inspected the tube for visible damage inside, nothing sticks out as obvious. *The horizontal deflection is fine, the trace is inline with the graticules across the screen within less than . 1div. *Any ideas how to fix this? Thanks, Steve I forgot to add, adjusting geometry doesn't help. Thanks, Steve it sounds like a misaligned deflection plate,as the horizonal gain varies significantly from top to bottom. Nothing you can do except get a new CRT. BTW,I have pulled CRTs,and I could tilt the tube and hear bits of glass from cracked electron gun rods tinkling as they slid around inside. Just looking at the gun,the breaks were not always visible.Sometimes,the particles would stick to the phosphor and create a dark or bright spot,or damage the mesh lens and create linear distortions in small areas. Also,TEK only spec'd the center part of the graticule,the outermost division both H and V were looser specs,considered to not be part of the measurement area. Was that 2205 a TEK ceramic bell CRT? Or some foreign tube? IIRC,the 2205 was from an Asian manufacturer. -- Jim Yanik jyanik at kua.net Looks like it's ceramic. Also, how does this tube work? There isn't an anode lead on it. Does it get the HV from the rear of the tube, or is it a different type? Fortunately, it is in tolerance at the center of the screen, and approximately equally out of tolerance at top and bottom, so really, it's just at ±2 div tolerance overall. Thanks, Steve |
#5
Posted to sci.electronics.repair
|
|||
|
|||
2205 Crt Problems
sck0006 wrote in
: On Jan 28, 11:43*am, Jim Yanik wrote: sck0006 wrote in news:5df1d999-e9fe-43cb-84ba- : On Jan 28, 8:59*am, sck0006 wrote: We have a 2205 with geometry problems on the crt. *It has fairly severe trapezoiding ,the spacing at the top is narrower than that at the bottom, appx .4div narrow at top, .2 div wide at bottom. *Any ide a what caused this? * Probably got dropped;portables often suffer that. Field Techs would sit the scope on it's rear end,and then accidentally yan k on the probe cable,and the scope would fall forward,WHACK,and sometimes th e CRT would be damaged,sometimes break completely.(I've seen CRT necks snapped off) We tried degaussing the screen, absolutely no effect. *I inspected the tube for visible damage inside, nothing sticks out as obvious. *The horizontal deflection is fine, the trace is inline with the graticules across the screen within less than . 1div. *Any ideas how to fix this? Thanks, Steve I forgot to add, adjusting geometry doesn't help. Thanks, Steve it sounds like a misaligned deflection plate,as the horizonal gain varies significantly from top to bottom. Nothing you can do except get a new CRT. BTW,I have pulled CRTs,and I could tilt the tube and hear bits of glass from cracked electron gun rods tinkling as they slid around inside. Just looking at the gun,the breaks were not always visible.Sometimes,the particles would stick to the phosphor and create a dark or bright spot,or damage the mesh lens and create linear distortions in small areas. Also,TEK only spec'd the center part of the graticule,the outermost division both H and V were looser specs,considered to not be part of the measurement area. Was that 2205 a TEK ceramic bell CRT? Or some foreign tube? IIRC,the 2205 was from an Asian manufacturer. -- Jim Yanik jyanik at kua.net Looks like it's ceramic. Also, how does this tube work? There isn't an anode lead on it. Does it get the HV from the rear of the tube, or is it a different type? some CRTs didn't have anode voltages,just large cathode voltages,and maybe +100 volts on the mesh lens or final gun element. A Sign of a low budget scope.... Fortunately, it is in tolerance at the center of the screen, and approximately equally out of tolerance at top and bottom, so really, it's just at ±2 div tolerance overall. How do time marks look on the display? or any fast-rise leading edge,displayed at 1 edge/major div. Set the vertical to display the signal on the entire graticule,top to bottom. Is everything straight? Thanks, Steve I hope you mean 2 MINOR div. ;-) It's a shame you can't buy a decent analog scope from TEK anymore. They really have trashed what used to be a great company. -- Jim Yanik jyanik at kua.net |
#6
Posted to sci.electronics.repair
|
|||
|
|||
2205 Crt Problems
On Jan 28, 1:22*pm, Jim Yanik wrote:
sck0006 wrote : On Jan 28, 11:43*am, Jim Yanik wrote: sck0006 wrote in news:5df1d999-e9fe-43cb-84ba- : On Jan 28, 8:59*am, sck0006 wrote: We have a 2205 with geometry problems on the crt. *It has fairly severe trapezoiding ,the spacing at the top is narrower than that at the bottom, appx .4div narrow at top, .2 div wide at bottom. *Any ide a what caused this? * Probably got dropped;portables often suffer that. Field Techs would sit the scope on it's rear end,and then accidentally yan k on the probe cable,and the scope would fall forward,WHACK,and sometimes th e CRT would be damaged,sometimes break completely.(I've seen CRT necks snapped off) We tried degaussing the screen, absolutely no effect. *I inspected the tube for visible damage inside, nothing sticks out as obvious. *The horizontal deflection is fine, the trace is inline with the graticules across the screen within less than . 1div. *Any ideas how to fix this? Thanks, Steve I forgot to add, adjusting geometry doesn't help. Thanks, Steve it sounds like a misaligned deflection plate,as the horizonal gain varies significantly from top to bottom. Nothing you can do except get a new CRT. BTW,I have pulled CRTs,and I could tilt the tube and hear bits of glass from cracked electron gun rods tinkling as they slid around inside. Just looking at the gun,the breaks were not always visible.Sometimes,the particles would stick to the phosphor and create a dark or bright spot,or damage the mesh lens and create linear distortions in small areas. Also,TEK only spec'd the center part of the graticule,the outermost division both H and V were looser specs,considered to not be part of the measurement area. Was that 2205 a TEK ceramic bell CRT? Or some foreign tube? IIRC,the 2205 was from an Asian manufacturer. -- Jim Yanik jyanik at kua.net Looks like it's ceramic. Also, how does this tube work? *There isn't an anode lead on it. *Does it get the HV from the rear of the tube, or is it a different type? some CRTs didn't have anode voltages,just large cathode voltages,and maybe +100 volts on the mesh lens or final gun element. A Sign of a low budget scope.... Fortunately, it is in tolerance at the center of the screen, and approximately equally out of tolerance at top and bottom, so really, it's just at ±2 div tolerance overall. How do time marks look on the display? or any fast-rise leading edge,displayed at 1 edge/major div. Set the vertical to display the signal on the entire graticule,top to bottom. Is everything straight? Thanks, Steve I hope you mean 2 MINOR div. *;-) It's a shame you can't buy a decent analog scope from TEK anymore. They really have trashed what used to be a great company. -- Jim Yanik jyanik at kua.net- Hide quoted text - - Show quoted text - Straight, but not vertical. In the middle of the screen, it's lined up, they tilt inward toward the top & outward toward the bottom in increasing severity as you get towards the edge of the screen. Sorry, I actually meant .2 Major divisions. I'm not sure what the specified tolerance is on this scope, I was just stating the actual measured tolerance. Thanks for your help, it's always great to get your input. Steve |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
I don't have MI5 problems, I have Mitsubishi problems | Electronics Repair | |||
Tektronix 2205 scope power problem | Electronics Repair | |||
find all solutions to skin care problems, hair care problems, nail care issues.. | Home Ownership | |||
Tektronix 2205-What is the "Option 40" feature? | Electronics Repair | |||
Extending a hallway, problems, problems... | UK diy |