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Re: Help needed with no trace no beamfinder on 465 (not b)
Is this the PDA? /g/TekScopes/photo/49286/2?p=Name,,,20,1,0,0
I was thinking it was the end of the HV mulitplier... |
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Re: PG502 Failure points?
Now it's coming back to me. The 10H was a geometry shrink with reduced
internal capacitances and higher fT so they could improve speed and lower power. Pinout issues aside, the MC10H109 might well work in place of the MC1660, the only way to know would be to try it. That would be my second choice, sourcing an MC1660 would be my first. Steve |
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Re: Help needed with no trace no beamfinder on 465 (not b)
Chuck Harris
Post Deflection Accelerator. It is the Anode cap at
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the edge of the CRT's funnel usually to the left of the screen. -Chuck Harris Keith Ostertag wrote: Thanks! That's jumper P1445, I believe. |
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Re: Help needed with no trace no beamfinder on 465 (not b)
Yes the 1330 manual is the correct manual for your unit. while the 1861 manual can be useful at times, as it pertains to your unit? you need to be very careful . Some circuits in the later manual are very different and some are essentially unchanged from the earlier version.
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good luck -dc manuals@... On 5/27/2018 9:24 PM, Keith Ostertag wrote:
My 465 SN is B175976. --
Dave Manuals@... www.ArtekManuals.com |
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Re: Help needed with no trace no beamfinder on 465 (not b)
Hi Keith,
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as others have already shown, that's not the one. Apparently I was mistaken. The ground lead doesn't come out from between the two boards. Here's a picture of what it looks like when the vertical board is removed: The ground lead pokes through the board. My mistake, apologies. Others have already shown what to remove to isolate the HV multiplier. All of them have way more experience than I have. Good luck, Ian. On Mon, May 28, 2018 at 12:44 AM, Keith Ostertag <stuff@...> wrote:
So... if I remove that ground strap, and I still don't see anything on the --
One man's "magic" is another man's engineering. "Supernatural" is a null word. -- Excerpt from the notebooks of Lazarus Long, from Robert Heinlein's "Time Enough for Love" |
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Re: Tek S4 sampling head
Craig Sawyers
Correcting myself here already - Frye says the diodes switch off in 5 - 10ps. Say 7.5ps - so an
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effective bandwidth of 50GHz. Dunno where I got 2ps from So at least in theory, for someone who can handle chip level devices measuring 0.3mm square, and access to a wire bonder, could fix an S4 using current generation microwave schottkys. Maybe. Craig -----Original Message-----GaAs devices from MACOM which have adiodes have a junction capacitance of 0.01pF (ie 10 femto-farads). And scaling from MACOM's drawings, the(and capacitance) of an 80GHz device. Scaling that gives a bandwidth of the S4/S6 diodes of 222GHz -close enough to the 175GHz worked out from Frye's data.150pF and an unspecified but almost always significant voltage up to 10kV, and connect that to ajunction with 10fF capacitance. The result ought to surprise no one.I urge others to do so too. |
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Re: Tek P6046 Differential Probe
Craig Sawyers
Is the P6046 hard to find? Costly?eBay is your friend. There are a range of prices from $50 for a probe only and no accessories, to low hundreds. Worth lurking until you see something you like (I did that maybe ten years ago, and snagged a new-old-stock one) Tek manufactured this probe for 28 years (1968 until 1996), with many different iterations and tweaks as semiconductors were obsoleted (particularly the input JFET's). It stood the test of time, and lots and lots were made. And lots and lots are for sale at any one time. Whether it is useful or not depends on what you want to measure with it. It can do measurements that are difficult to do in any other way. Craig |
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Re: Tek S4 sampling head
Craig Sawyers
Frye reckons that the diodes (which will be schottky barrier) switch in 2ps. Which implies a 3dB
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bandwidth per diode of 175GHz. The nearest you can get to that performance are microwave schottkys, for example this range of GaAs devices from MACOM which have a bandwidth of 80GHz. They have a junction capacitance of 0.02pF, which implies that the S4/S6 diodes have a junction capacitance of 0.01pF (ie 10 femto-farads). And scaling from MACOM's drawings, the actual junction is about 50um square. The S4/S6 diodes are 30um square - so 0.36 times the area (and capacitance) of an 80GHz device. Scaling that gives a bandwidth of the S4/S6 diodes of 222GHz - close enough to the 175GHz worked out from Frye's data. Which is why the darned things are static damageable. Take a human with a body capacitance of 150pF and an unspecified but almost always significant voltage up to 10kV, and connect that to a junction with 10fF capacitance. The result ought to surprise no one. Note from the MACOM datasheet two things. First is a junction breakdown voltage in the range 4.5 - 7V, entirely consistent with the S4/S6 spec that says do not exceed 5V on the input. And secondly, handling where MACOM say "Static sensitivity: Schottky barrier diodes are ESD sensitive and can be damaged by static electricity. Proper ESD techniques should be used when handling these Class 0 devices" Some interesting numbers here though regarding body voltage when properly grounded nsitive-operations.php . In particular "international ESD losses that now exceed an estimated $90 billion" All of which is why I take very great care of my unfixable samplers and fast pulse generators. And I urge others to do so too. Craig Per square nanometer. 1 square nanometer is 30um square - which is the size of the S4/S6 diode |
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Re: Deceptive fault in a 535A
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----- Original Message -----
From: "Morris Odell" <vilgotch@...> To: <[email protected]> Sent: Monday, May 28, 2018 12:12 AM Subject: [TekScopes] Deceptive fault in a 535A Hi all, Crappy old capacitors - the gift that keeps on giving! Morris Wow, is that ever an understatement. Haha. |
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Re: Help needed with no trace no beamfinder on 465 (not b)
P1445 is the 4 pin connector right next to the jumper that disconnects the HV multiplier ground. The PDA cable is the high voltage that goes to the front of the CRT tube. You just need to pull it our about an inch to unload the multiplier output.
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Once you do this and the -2450 VDC cathode comes back, you have found the bad multiplier. Regards, Tom ----- Original Message -----
From: "Keith Ostertag" <stuff@...> To: <[email protected]> Sent: Monday, May 28, 2018 12:26 AM Subject: Re: [TekScopes] Help needed with no trace no beamfinder on 465 (not b) Thanks! That's jumper P1445, I believe. What's the "PDA lead "? I don't recognize what PDA stands for... |
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Re: Help needed with no trace no beamfinder on 465 (not b)
PDA = Post Deflection Acceleration.
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Bruce On 28 May 2018 at 16:26 Keith Ostertag <stuff@...> wrote: |
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Deceptive fault in a 535A
Hi all,
Much has been written here about the epoxy potted HV transformer thermal runaway problem in later 500 series scopes including the 545B, 547, 549, 556 etc. I recently encountered a similar problem in a 535A, a scope with a beeswax potted transformer that is not known for thermal runaway.The symptoms were almost identical. The scope would start normally and then after a minute or two the display would dim and bloom. A voltmeter on the screen of the 6AU5 oscillator tube showed a steady increase from 75 to 150 as the feedback loop tried to keep the output constant and then oscillation would cease. The speed of the increase suggested thermal effects in a small component. Everything looked normal and the tubes tested OK by substitution. The fault was no different with the CRT unplugged. It turned out the culprit was the 0.001 mfd resonating capacitor across the HV transformer primary. This was a black moulded Sprague cap with red printing, not an oil filled or bumble bee type. After it was removed there was a bulge visible on the underneath that was not easy to see when it was in situ. Replacing it with a modern 630V polyester cap cured the problem. I wasn't game to put a finger on it while it was going to see how hot it got! Crappy old capacitors - the gift that keeps on giving! Morris |
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Tek P6046 Differential Probe
Roy Morgan
Hi everyone,
I have a Tek 1A5 preamplifier meant for use with the P6046 Differential Probe, but no probe. Is the P6046 hard to find? Costly? Is the probe and plugin often useful? I am wondering what it might take to get this plug-in into operation. Thanks, Roy Roy Morgan k1lky68@... <mailto:k1lky68@...> |
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Re: Help needed with no trace no beamfinder on 465 (not b)
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----- Original Message -----
From: "Keith Ostertag" <stuff@...> To: <[email protected]> Sent: Sunday, May 27, 2018 9:24 PM Subject: Re: [TekScopes] Help needed with no trace no beamfinder on 465 (not b) My 465 SN is B175976. I am looking at a manual marked "tek-070-1330-00" (236 pages, with yellow addendum pages added in the back), as well as a manual for later version 465's (070-1861-00, B250000 & up, says Rev B, June 1975, 291 pages). I think the first is the correct one, but it is more limiting (for instance, no trouble shooting flowchart). |
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Re: Help needed with no trace no beamfinder on 465 (not b)
My 465 SN is B175976.
I am looking at a manual marked "tek-070-1330-00" (236 pages, with yellow addendum pages added in the back), as well as a manual for later version 465's (070-1861-00, B250000 & up, says Rev B, June 1975, 291 pages). I think the first is the correct one, but it is more limiting (for instance, no trouble shooting flowchart). |
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Re: Help needed with no trace no beamfinder on 465 (not b)
You need to match the manual to your scope for starters.
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There are two different manuals ....;. what is the serial number on your scope? -DC manuals@... On 5/27/2018 7:30 PM, Keith Ostertag wrote:
Also, one manual says in order to isolate the HV multiplier one needs to unsolder "dummy resistor"... huh? illustration points to near R1449,R1447, R1448... but maybe that's also not relevant to my scope? --
Dave Manuals@... www.ArtekManuals.com |
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Re: Help needed with no trace no beamfinder on 465 (not b)
The ground strap you show is not the one. The 0 ohm resistor next to P1445 and the nylon nut is the ground for the HV multiplier.
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----- Original Message -----
From: "Keith Ostertag" <stuff@...> To: <[email protected]> Sent: Sunday, May 27, 2018 6:44 PM Subject: Re: [TekScopes] Help needed with no trace no beamfinder on 465 (not b) So... if I remove that ground strap, and I still don't see anything on the screen (not even using the beamfinder)... that suggests the HV multiplier is NOT the fault that's causing my problem? Is this the ground strap you mean? /g/TekScopes/photo/49286/0?p=Name,,,20,1,0,0 Doesn't seem likely to me, as it isn't under the HV cover, but near the front end... but it is the only ground strap visible on that side of the main board on my scope. Here is a photo of the area under the HV cover, and I don't seen anything resembling a ground strap coming up between the "main board and the vertical amplifier board" as you describe: /g/TekScopes/photo/49286/1?p=Name,,,20,1,0,0 |
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