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
|
|||
|
|||
Tektronix 7905 Oscilloscope
I bought a used non-working 7905. Have almost everything fixed except:
When increasing the trace brightness to an acceptable level there is a halo present. It is not a uniform halo, but is displaced slightly up and to the right of the trace, probably 20% brightness at normal brightness of main trace. The focus and astigmatism controls work properly. Your help will be appreciated, Thanks, Emil |
#2
|
|||
|
|||
"egb" wrote in
oups.com: I bought a used non-working 7905. Have almost everything fixed except: When increasing the trace brightness to an acceptable level there is a halo present. It is not a uniform halo, but is displaced slightly up and to the right of the trace, probably 20% brightness at normal brightness of main trace. Could be a bad CRT. Can you display a signal of amplitude enough to cover the entire graticule and check to see if it's distorted in any way? I used to use the 50Khz ref signal from a SG503 leveled sine wave generator. The focus and astigmatism controls work properly. Your help will be appreciated, Thanks, Emil Well,you could have a 7904(4 holer) or a 7903(3 hole rack mount),but there is no 7905 TEK scope. -- Jim Yanik jyanik at kua.net |
#3
|
|||
|
|||
Yes, you're absolutely correct, excuse me. It is the 7904. Thanks for
the correction. Emil |
#4
|
|||
|
|||
Jim, thanks for the reply. The display is just fine in every other
respect. Single trace,or 4 trace everything works, regardless of amplitude. |
#5
|
|||
|
|||
"egb" wrote in message oups.com... I bought a used non-working 7905. Have almost everything fixed except: When increasing the trace brightness to an acceptable level there is a halo present. It is not a uniform halo, but is displaced slightly up and to the right of the trace, probably 20% brightness at normal brightness of main trace. Are you sure all of the CRT voltages are within specifications? |
#6
|
|||
|
|||
"egb" wrote in
oups.com: Jim, thanks for the reply. The display is just fine in every other respect. Single trace,or 4 trace everything works, regardless of amplitude. Some CRTs had more halo than others,and depended on trace brightness and sweep speeds.Also Z-axis unblanking could be a problem. -- Jim Yanik jyanik at kua.net |
#7
|
|||
|
|||
"Charles Schuler" wrote in
: "egb" wrote in message oups.com... I bought a used non-working 7905. Have almost everything fixed except: When increasing the trace brightness to an acceptable level there is a halo present. It is not a uniform halo, but is displaced slightly up and to the right of the trace, probably 20% brightness at normal brightness of main trace. Are you sure all of the CRT voltages are within specifications? Yes,like the cathode V,-2960V IIRC.(which also determines the anode V) The thick-film network can go out of spec.(no new replacements available) It could also be a electron gun element knocked out of alignment,and part of the beam striking it and diffracting. Thus the test I mentioned for geometry in another post. -- Jim Yanik jyanik at kua.net |
#8
|
|||
|
|||
Jim and Charles,
Thanks for all the help. I'll go over everything you gentlement suggested this weekend. Emil |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Tektronix TDS220 oscilloscope startup problem | Electronics Repair | |||
FA Ebay UK Oscilloscope Tektronix 465B 100mhz | Electronics Repair | |||
Tektronix 2230 Oscilloscope failure | Electronics Repair | |||
Tektronix TDS 540 and options | Electronics Repair | |||
Is 10 GigaSamples/Sec really POSSIBLE, with a Tektronix TDS420 ?! | Electronics Repair |