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Repairing LEVEL Control from a 7B50/7B90?
While troubleshooting the triggering problems in my 7B50, I discovered that the LEVEL pot is intermittent on one side. This is one of those stacked, plastic pots with a switch at the end and serves as both the LEVEL the SLOPE control. It is a TEK P/N 311-0912-00.
I'm thinking the stacked elements might be such that they can be pulled apart and repaired but not sure and before I try anything, I'd like to see if anyone has any experience with these. Thanks, Barry - N4BUQ |
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Re: TDS5/6/700 application software packages?
Sounds like an "eye" diagram.
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It's a diagram of multiple overlays of data and clocks that show when data is stable (with respect to the clock). You display data while syncing to clocks, but allow long persistence.? The multiple traces outline an area where data is stable.? The bigger the "eye" the more stable the data. Networking. Harvey On 2/11/2022 6:15 PM, Siggi via groups.io wrote:
I was idly looking at TekWiki the other day, and I noticed that on the |
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Re: 7904 problems
I have added 16 images to the album showing the cal signal via a properly adjusted probe at 1 ms per division (horiz) and 1 volt per division (horiz). Each image has the trace position half a division up, starting at the bottom of the screen, to show the distortion over the entire face of the CRT.
I also updated the title and description of the album to reflect Morris Odell¡¯s contribution. My apologies for the dimness of the trace, but it was in the middle of failing altogether. Morris, that certainly looks like very similar distortion. I¡¯m a little bit impressed that you put the 7904 on its side. Tom, I measured the regulated supply voltages and ripple. All the voltages (-8, +5, +15, +55, and +110) were within 0.02 V of expected value, but at four of the rails (all but the -8 V rail) had 0.5 V of 60 Hz ripple (the +15 V rail¡¯s ripple read as ¡°0 Hz¡± but I suspect that was not correct). I already know that 60 Hz was getting through to the Z-axis amp (ah, my old nemesis, we meet again), so finding 60 Hz ripple on the supply rails is only expected. I have not looked at a service manual yet, but I¡¯m guessing that this implicates the bulk filter caps. ¡ª Jeff Dutky |
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Re: 7B50 - Schematic Question
I think I found the prime problem. The LEVEL pot is defective. I don't know what made me decide to check that but, when I did, I found that the end that connects to P260-7 isn't making good contact inside the pot. I can push gently on it and get it to make contact but it doesn't stay that way when I release pressure.
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I don't know if these can be disassembled and repaired but I don't think I have much to lose by trying. If anyone has any experience tearing one of these down, I'd love to hear from you. TEK P/N 311-0912-00 Thanks, Barry - N4BUQ ----- Original Message -----
From: "Ozan" <ozan_g@...> On Fri, Feb 11, 2022 at 10:25 AM, n4buq wrote:...It looks like DC level is different in different mainframes. R7903 shows signals |
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Re: 212, 213, was Re: [TekScopes] New kid on the block...
Roy,
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I described a modification to use a lithium-ion 18650 cell plus a boost converter in an earlier message: /g/TekScopes/message/165764 --John Gord On Fri, Feb 11, 2022 at 11:13 AM, Roy J. Tellason, Sr. wrote:
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Re: TDS5/6/700 application software packages?
I was idly looking at TekWiki the other day, and I noticed that on the
TDS784 page () there's now a link to "Telecom Test and I-Pattern Software TTiP". I haven't seen this listed as an application before - does anyone here know what this is? On Fri, Sep 25, 2020 at 12:55 PM Siggi via groups.io <siggi= [email protected]> wrote: Hey y'all, |
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Re: 7904 problems
Hi all,
I have uploaded some pics of the 7904 problem to Jeff's photo folder of distortion on his 465B . They show two 7904 traces, one with the calibrator square wave and one without. They are OK on the lower half of the screen and distorted on the upper half. I tried putting the scope on it's side in case of something loose inside but it made no difference. Morris |
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Re: 7B50 - Schematic Question
On Fri, Feb 11, 2022 at 10:25 AM, n4buq wrote:
...It looks like DC level is different in different mainframes. R7903 shows signals centered around 0V. Diff pair following TP101/TP111 has good common mode rejection, 50-100mV DC shift at the input won't matter. You are seeing 200mVpp differential (I assume TP101 and TP111 are 180degrees out of phase) which is plenty of swing to steer the diff pair rail to rail regardless of 20mV delta in the inputs. This is not the source of the DC shift at TP124/TP129. I would think R135 should be able to bring them to the expected range. Ozan |
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Re: 7904 problems
If you have a Variac which can handle the current, you can do even better. Connect the coil to the output of the Variac. When degausing, turn the Variac up to the highst level you are using. Then, over a period of several seconds, gradually and smoothly reduce the voltage to zero. This will produce the gratest amount of randomness in the final domain orientation. Suddenly removing power would tend to leave the domains oriented in the direction they had at the instant the magnetic field collapsed.
Stephen |
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Re: 7904 problems
If the issue is mechanical damage, only CRT replacement can fix it. If the issue is magnetic interference, many remedies are possible. Long ago I built up a very large de-gaussing coil that could pass over an instrument or tube, it was powered from a beefy 24VAC transformer and could demagnetize most objects. This is a very handy tool (a left over from the color TV era), and can resolve many odd issues that seem to be "impossible".Oh yes! Been there, done that many times. And it usually works great. You can make a very effective degaussing coil by purchasing a 100 foot roll of #14 NM with ground electrical cable at your local building supply store. The cable will usually be in a coil about 12 to 14 inches in diameter and wrapped in plastic. Leave the plastic wrap on the coil. Carefully pull out both ends of the coil far enough to be able to strip all three wires at each end of the coil. Using the START and END of the coil, connect all three windings in series with each other like this: START BLACK wire connects to AC power Connect END BLACK wire to START BARE WIRE Connect END BARE wire to START WHITE wire END WHITE wire connects to AC power This will give you a 300 foot long coil of wire with one free black and one free white wire to connect to the mains power. When connected to the 120 VAC 60 Hz mains voltage, the combined DC resistance and AC impedance of the coil results in a current of about 12 amps through the coil, which #14 can handle satisfactorily. Because the wire is in a coil, it will eventually become too warm for continued operation, but that usually takes about 5 to 10 minutes depending on the ambient temperature, but certainly long enough to degauss an instrument or two. |
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Re: 212, 213, was Re: [TekScopes] New kid on the block...
The batteries are 5/4 AA size nicads. The holders are far more difficult to find then the batteries. I don't know if anyone has made a 3D printed version of them. It is very bad for the power supply to operate the? scope with the batteries bad or missing. They? are an integral part of the power supply regulator, and it will produce very excessive voltage without them.
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? Bruce Gentry, KA2IVY On 2/11/22 14:06, Roy J. Tellason, Sr. wrote:
On Thursday 10 February 2022 12:48:39 pm Michael A. Terrell wrote:Try this link to the military version of the 212 manual on my Google Drive.Got it, thanks. I don't know why I had such a hard time with that other instance of the google drive file... |
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Re: 212, 213, was Re: [TekScopes] New kid on the block...
On Thursday 10 February 2022 12:48:39 pm Michael A. Terrell wrote:
Try this link to the military version of the 212 manual on my Google Drive.Got it, thanks. I don't know why I had such a hard time with that other instance of the google drive file... Sometimes it works for me, and sometimes it doesn't. Either of you guys have any thoughts about where I might score some batteries for these scopes? -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin |
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Re: Super Clean 570 Curve Tracer on Craigslist
Thanks, Roy. And TekWiki¡¯s picture of a T52 (aka T0520) shows a spiral. So it has PDA even at the low acceleration of 4kV.
Dave Wise From: [email protected] <[email protected]> On Behalf Of Roy Thistle via groups.io Sent: Friday, February 11, 2022 11:06 AM To: [email protected] Subject: Re: [TekScopes] Super Clean 570 Curve Tracer on Craigslist On Fri, Feb 11, 2022 at 08:12 AM, Dave Wise wrote: The T51 CRT, used in the 535 (circa 1954) was the first Tek CRT with the post acceleration helix. 570 uses T52 CRT, which AFAIK has the post acceleration helix. -- Roy Thistle |
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Re: 212, 213, was Re: [TekScopes] New kid on the block...
On Thursday 10 February 2022 12:41:40 pm Jared Cabot via groups.io wrote:
That guy linked on tekwiki is me. :):-) I've uploaded the battery replacement document to tekwiki, so take a look.Got it, thanks. I have some spare bare PCB's as in my video if you want to build the rectifier upgrade in that document too. (I can probably scratch up all the parts needed too, if you want to buy it as a kit).I might be interested. How necessary is that mod? And what sort of cost are we talking about? Also, the 212 user manual on that Tekwiki page was one I recreated and re-typeset as close to the original as I could. It's much better than a scanned version, as I went to the trouble of redrawing the diagrams as vectors so it will print out as a booklet in high quality as per the original. (Print it duplex, 2-up (so 2 pdf pages per side of paper, I think that will work for a booklet)I snagged that already... Dunno if I'm going to want to print it out or not, we'll see. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin |
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Re: Super Clean 570 Curve Tracer on Craigslist
On Fri, Feb 11, 2022 at 08:12 AM, Dave Wise wrote:
The T51 CRT, used in the 535 (circa 1954) was the first Tek CRT with the post acceleration helix. 570 uses T52 CRT, which AFAIK has the post acceleration helix. -- Roy Thistle |
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Re: Super Clean 570 Curve Tracer on Craigslist
On Fri, Feb 11, 2022 at 07:19 AM, bobkrassa wrote:
It's one of the first ones (low serial number) that has the darker (brownish-blue?) Tek blue. -- Roy Thistle |
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