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Brand new to the group, and enjoy the older scopes ........

Problem 1
Just acquired a 465 that will display the highlighted trace when switched to "A INTEN" but pulling and dailing the second(delayed) timebase knob clockwise doesn't cause the highlighted portion of the trace to get narrower in conjuction with shortening the second timebase. So it tries to do delayed sweep but doesn't git'er done..


Problem 2 - worse problem
There is also a bit of hash/noise on the traces. It is worse on Ch 1 than Ch 2, but present on both channels. It is about 2 millivolts on Ch 1 and less that 1 mV on Ch 2. Pulling the 20 MHz BW knob controls it for the most part, filtering it out I guess just prior to the delay line. But even with the BW filter on, the noise prevents a good sharp trace. The noise is also present to the same extent when grounding the probes and setting the input coupling switches to GND, so its not RF or some such coming in through the probes. I think this is telling me that there is some munge getting into or created within the vertical preamps. It appears to be high frequency crud. I was thinking at first that maybe it was some kind of triggering signal getting back into the vert preamp. I unplugged the Trigger View plug from the vertical preamp board, but that didn't help.



I am also fortunate enough to have an apparently well-functioning 465 as a comparison and measurement instument, but I have only had both of them for a few days. So, I'm not schooled up yet on troubleshooting them (yet). I also have the service manual already and am getting familiar with it.

Could a 465-savvy person please spare some thoughts on where to start on these issues? Maybe I should post them separately, not sure of the prevailing practice on this board.

Thanks in advance, and I'm looking forward to getting aquainted!! Regards! DENM

Hi, some months ago I had a very similar problem with a 465. I posted a thread on the forum under '465 interference on trace' . I eventually discovered the solution to the problem was a failed FET, the post read as follows

Ive seen quite a few threads where the trace on a 465 series was thicker/wider than it should be causing blurring. In this case it was caused by an oscillation into the RF region which I could trigger on.

I had narrowed the fault down to the A/B sweep generator circuitry and checking the voltages around that circuit revealed +29v on the collector of Q1096, when it should be about 13v, I substituted Q1096 with an alternative with no improvement. The voltages around Q1090 were also incorrect and it appeared this N-channel jfet was faulty.I didnt have a direct replacement, but one from a scrap board from British scope cured the fault and restored correct operation. I dont know why this transistor had failed but it had, causing major problems on both timebases.

Hope this helps you.
Regards
Bill


--- In TekScopes@..., "denm651" <denm651@> wrote:

Brand new to the group, and enjoy the older scopes ........

Problem 1
Just acquired a 465 that will display the highlighted trace when switched to "A INTEN" but pulling and dailing the second(delayed) timebase knob clockwise doesn't cause the highlighted portion of the trace to get narrower in conjuction with shortening the second timebase. So it tries to do delayed sweep but doesn't git'er done..


Problem 2 - worse problem
There is also a bit of hash/noise on the traces. It is worse on Ch 1 than Ch 2, but present on both channels. It is about 2 millivolts on Ch 1 and less that 1 mV on Ch 2. Pulling the 20 MHz BW knob controls it for the most part, filtering it out I guess just prior to the delay line. But even with the BW filter on, the noise prevents a good sharp trace. The noise is also present to the same extent when grounding the probes and setting the input coupling switches to GND, so its not RF or some such coming in through the probes. I think this is telling me that there is some munge getting into or created within the vertical preamps. It appears to be high frequency crud. I was thinking at first that maybe it was some kind of triggering signal getting back into the vert preamp. I unplugged the Trigger View plug from the vertical preamp board, but that didn't help.



I am also fortunate enough to have an apparently well-functioning 465 as a comparison and measurement instument, but I have only had both of them for a few days. So, I'm not schooled up yet on troubleshooting them (yet). I also have the service manual already and am getting familiar with it.

Could a 465-savvy person please spare some thoughts on where to start on these issues? Maybe I should post them separately, not sure of the prevailing practice on this board.

Thanks in advance, and I'm looking forward to getting aquainted!! Regards! DENM

Problem 1
Just acquired a 465 that will display the highlighted trace when switched to "A INTEN" but pulling and dailing the second(delayed) timebase knob clockwise doesn't cause the highlighted portion of the trace to get narrower in conjuction with shortening the second timebase. So it tries to do delayed sweep but doesn't git'er done..


Problem 2 - worse problem
---
Regards! DENM

I have a 465 but I'm not very familiar with the innards. My first action would be to search for a mechanical cause. If you turn the knob (pulled out), is there really a switch drum rotating as well? There could be a loose setscrew, a broken coupling element between shafts or a broken drum (that happened in my 576). In similar knobs at time base plugins like 7B53A it's easy to assemble the several knob components the wrong way, I would also consider such a possible fault.

Albert

Problem 1
Just acquired a 465 that will display the highlighted trace when switched to "A INTEN" but pulling and dailing the second(delayed) timebase knob clockwise doesn't cause the highlighted portion of the trace to get narrower in conjuction with shortening the second timebase. So it tries to do delayed sweep but doesn't git'er done..


Problem 2 - worse problem
---
Regards! DENM