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Re: 2465 no traces, no OSD
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The very first thing I would do is check all voltages and ripple on J119.? There is a table of specifications for this in the service manual section for power supply trouble shooting, just before the flow chart sections 10 and 11.? If all J119 voltages and ripple are right I would use the working 2465 you have to check signals going to the CRT.? Especially check the unblanking signals, VZOUT and VGOUT, the prescribed waveforms are given in the service manual (waveforms 65 and 66 in the 2465 Service manual).??If there is activity closely resembling the prescribed activity in shape and, especially, amplitude the scope is trying to drive the CRT.? The problem is very likey the high voltage board (A9) or the CRT
itself. If you have a high voltage probe you can just measure the voltage on the CRT anode pole.? But don't do this if you?lack experience with high voltage measurement techniques as the voltage here is 14,000 volts or more. It sounds to me that the scope is trying to operate?and there are some good indications.? When there?are faults known to the scopes computer (board A5) it presents an error message on the CRT ("Test xxx fail? Push A/B trigger") and the scope then tries to operate.? But since your screen is blank?you cannot see this message.? If there were high voltage and a VZ signal you should at least see a bright spot on the CRT.? Since you cannot, either there is no high voltage, no VZ, or the CRT may not be lighting up?(no filament or just a?bad CRT). You can go to the Qservice web site and see pictures of every
subassembly for reference of how they should look.? Tektronix produced these scopes for several years and used different generations of capacitors.? So boards will look different from generation to generation but the overall layout will remain the same and there whould be uniformity within a particular build. From: Sigur?ur ?sgeirsson
To: TekScopes@... Sent: Sunday, January 26, 2014 11:38 AM Subject: [TekScopes] 2465 no traces, no OSD
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Hi y'all,
I just bought a 2467 on eBay. It came with option 9 - which I understand is the counter/timer? Unfortunately it doesn't seem to light up the CRT at all, no traces, no OSD.
On power-up, it does seem to go into diagnosis, as I have to hit one specific front-panel control before it'll respond to any others. After this, I can mess with the front panel controls, and e.g. the channel/trigger lights all toggle with their corresponding buttons. However, any time I change any setting, all the front panel LEDs flicker. Also, when I set channels 1/2 to the 50 Ohm input setting, they stick for about a second or so, but then I hear a relay toggle again, and the GND input lights up again.
Do those symptoms ring a bell with anyone here? I took it apart and pulled the PSU?to see whether there's anything obviously broken. It looks to me like the PSU has been re-capped, as there's a mix of colors on there. I tested all the rails, and they look about right, though I couldn't load the 5V with more than a single 7.5 ohm resistance at a time. When I loaded J303, I saw an undershoot for a second or two, then it seemed to drop into regulation at ~4.9V. The 7.5 ohm on J232 didn't quite seem to be enough load, though the voltage dropped a fair bit when I did it. The 10V reference was spot on, as were e.g. the 87 and the +-15 rails. The others were all high, but then they were unloaded... I guess next I'll measure the rails with the PSU in-place, check ripple etc? Are there any pictures here of 2467/2465A PSUs in original condition that I might use for comparison?
Are there other quick things I can look at to assess the damage/hopes of repair? I understand the 2467 has a "screen saver" that'll shut down the CRT on a timer? Presumably this is under digital control - so I'm hopeful that the CRT or control circuitry isn't beyond rescue?
I have a functional 2465 I was hoping to replace with this one, so I can have peek around. Siggi |
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