Bought a 485 on ebay in supposedly excellent condition. Turns out the channel 1 y-pos knob is literally broken (I can pull out about 12 cm of plastic rod), but channel 2 looks nasty, too. I is impossible to focus the beam to better than about 1.2 mm, and there are always these shadows. Turning down the intensity will not get rid of shadows nor narrow the focus. There is no focus dial per se, just those tiny "gain" screws at the bottom corners of the screen. Haven't tried those. Should I?
On top of this, a lot of trigger switches are shaky, you look at them and the trigger is gone. Also, I cannot test B-trigger at all because I only have one channel to work with.
My main concern is really the tube. The Hamegs and Tek 465 I have used so far have a far better focus without ghosts. I suppose this can't be fixed with moderate effort?
Better return for refund, even if it was only 100 € after the discount the seller is offering?
On top of this, a lot of trigger switches are shaky, you look at them and the trigger is gone. Also, I cannot test B-trigger at all because I only have one channel to work with.
My main concern is really the tube. The Hamegs and Tek 465 I have used so far have a far better focus without ghosts. I suppose this can't be fixed with moderate effort?
Better return for refund, even if it was only 100 € after the discount the seller is offering?
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Fuzzy focus and ghosting are not normal. It is possible that you just need to adjust the scope to fix those problems.
I don't think there is anything wrong with the tube. I would turn down the brightness a bit - it may be simply too bright with the ghosts showing up from that. (I see you said that changing the brightness doesn't make the ghosts go away - OK) "Brightness" in this case being the "Intensity" knobs at the upper left corner of the display. Turn down both intensity knobs, and see if that helps.
You can find manuals for the scope here.
There are several links to manuals on that page. The first in the list is broken. The rest are OK.
Have a look at the maintenance and calibration sections. You may be able to adjust away the fuzziness and ghosting. If adjusting it doesn't help, then tracking down a problem in one scope without a second scope is difficult.
The rest, though, sounds like a reason to ask for a refund. Broken and wobbly knobs are not what I'd call "excellent condition."
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If my old scope were to start showing focus and ghosting problems, I'd try to fix it. I've had it for a very long time, though, and don't like the idea of parting with it.
The scope you've bought isn't personally special to you. It's probably simpler to send it back and use the money to buy a scope in better shape.
I don't think there is anything wrong with the tube. I would turn down the brightness a bit - it may be simply too bright with the ghosts showing up from that. (I see you said that changing the brightness doesn't make the ghosts go away - OK) "Brightness" in this case being the "Intensity" knobs at the upper left corner of the display. Turn down both intensity knobs, and see if that helps.
You can find manuals for the scope here.
There are several links to manuals on that page. The first in the list is broken. The rest are OK.
Have a look at the maintenance and calibration sections. You may be able to adjust away the fuzziness and ghosting. If adjusting it doesn't help, then tracking down a problem in one scope without a second scope is difficult.
The rest, though, sounds like a reason to ask for a refund. Broken and wobbly knobs are not what I'd call "excellent condition."
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If my old scope were to start showing focus and ghosting problems, I'd try to fix it. I've had it for a very long time, though, and don't like the idea of parting with it.
The scope you've bought isn't personally special to you. It's probably simpler to send it back and use the money to buy a scope in better shape.
The focus and astigmatism adjustments are on the back of the scope.
This picture shows where:
485 Oscilloscope
That page is in German - should be right up your alley.
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Schöne Grüße aus Rheinland-Pfalz.
Joseph
This picture shows where:
485 Oscilloscope
That page is in German - should be right up your alley.
---
Schöne Grüße aus Rheinland-Pfalz.
Joseph
JRE, thanks for your quick answer. I have all the manuals and service manuals. The top intensity knob will turn down the trace and the ghosts to the same degree. The second knob is without any discernable effect, but then I can't use B trigger because I only have channel 2 to work with.
I have several other analog and digital scopes, I just don't want to spend a whole weekend fixing this little princess up because I know I'll never get to it, and if I did, I'm not sure I can fix everything that is wrong with it. The channel 1 knob seems doable (see new pic), the tube is an unknown, and the irreproducible results from various trigger knobs and levers are screaming don't do it at me even if a good dose of "Kontaktspray" might do the job.
I am right in letting this chance at a high bandwith old-time scope go? I am finding I am using a recently acquired TDS3032 (300 MHz) DSO more than I thought possible, so I am questioning the effort of fixing up a 485 on top.
PS: just saw your post on the focus and ast knobs - maybe I'll try that first even if the darn thing is already packed up.
I have several other analog and digital scopes, I just don't want to spend a whole weekend fixing this little princess up because I know I'll never get to it, and if I did, I'm not sure I can fix everything that is wrong with it. The channel 1 knob seems doable (see new pic), the tube is an unknown, and the irreproducible results from various trigger knobs and levers are screaming don't do it at me even if a good dose of "Kontaktspray" might do the job.
I am right in letting this chance at a high bandwith old-time scope go? I am finding I am using a recently acquired TDS3032 (300 MHz) DSO more than I thought possible, so I am questioning the effort of fixing up a 485 on top.
PS: just saw your post on the focus and ast knobs - maybe I'll try that first even if the darn thing is already packed up.
Attachments
Thumbing through the manuals, I see that the 485 has a single trace CRT and uses a bunch of extra circuitry to handle Timebase B and the second channel. I expect the problems lie in the switching and blanking for all of that.
Its typical of microchannel CRT's to have some ghosting at high intensity. That was Tek's fastest portable scope (many many moons ago) and one of the first with the new generation CRT's. They traded spot focus for speed. This can be great instruments but the small screen and weight are a real drawback.