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Re: Tek 603 - question on transistor heatsinking material
Toby,
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If it is a hard, brittle ceramic-like slab, it is probably alumina (aluminum oxide). It is a good electrical insulator and a reasonably good thermal conductor. Beryllium oxide looks similar, but is unlikely here because of its hazards. --John Gord On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:
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Tek 603 - question on transistor heatsinking material
Hi,
In preparation for testing/replacing components on the HV & regulator board, I removed it, and seem to have accidentally broken one of the heatsink pads under a bottom transistor (see pic). What is this material? /g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0 Should it be used with thermal paste or not? Thanks --Toby |
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Re: S-52 only works with lowered +15 V power supply
Hi Albert,
sorry for the late reply but during the week I work hardly and in the evening I am too tired to take care of my Teks and I want to avoid mistakes. Anyway I took just now some photos of the pulser while operating, varying the positive supply between 13.5 V and 15.5 V, in 0.5 V intervals. I've created a new photo album, you can see it at the following link: /g/TekScopes/album?id=249667 NOTE: The TD is the original one, carefully reassembled . The optimal voltage seems to be around 14.5V. The pulse are stable and clean.NOTE: The TD is the original one, carefully reassembled . You can see, at 15V the impulse disappears and only the impulse of pre-bias with the ramp remains. The pot R90 (trig level) is almost fully counterclockwise (it's in the original position when I bought the thing). At 15V ,turning it completely ccw I do not get appreciable effects anyway I think the resistors, one or more, changed their values, In the weekend I will check carefully their values. I can confirm that the couple of 2.7 ohm resistors in parallel give me a reading of 2.8 ohm and not 1.4 as it should be ... Max |
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Re: Wikipedia is not an appropriate topic for TekScopes. WAS repair tools: Autotransformers/variacs
Ray, W4BYG
Reg,
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I would be interested. could you provide more detail? Ray, W4BYG at ATT dot net On 7/1/2020 00:17, Reginald Beardsley via groups.io wrote:
I have two of these:-- They say a smart person learns from their mistakes. A wise person learns from the mistakes of others. --
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Re: What's the Tektronix part number for a dead spider
At least two of them.
On Mon, Jun 29, 2020 at 1:41 AM snapdiode via groups.io <snapdiode= [email protected]> wrote: Can you see it? |
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Re: D34 ghosting blur
Ahhh I see, so it's a feature not a fault, Denises explanation is really thorough and easy to understand.
Since I replaced the Telequipment special blanking JFET with generic J113 I wasn't sure if what I'm seeing isn't insufficiently closed jfet and therefore what I'm seeing is not some aftereffect of returning blanked beam. It's good to learn there's nothing wrong with the machine |
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Re: 2215 CRT problem, PSU filtering?
That's great Max. Good job. They are nice little scopes.
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Regards, Tom On 7/1/2020 2:16 AM, Maxsimmonds1337@... wrote:
Good news! I replaced the PSU filter caps, and I noticed the 33uF/160V on the 100V PSU output, and it's all good! --
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Re: 2215 CRT problem, PSU filtering?
On Wed, Jul 1, 2020 at 09:10 AM, <tekscopegroup@...> wrote:
This is Very Good advice. I would not go into a scope and just replace one of the caps. They all can easily be in a similar condition in the near future. -- Michael Lynch Dardanelle, Arkansas |
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Re: 2215 CRT problem, PSU filtering?
While in there you might want to replace all the caps that where listed above, so as to future proof the PS section some more. Use nearest value and voltage equal or higher. Modern caps will be smaller in size, so a somewhat higher value will still be an easy fit. Order good quality caps (and any other parts in general) from Mouser.com or similar reputable outfits, avoid ebay china crap.
C937 1800 uF/ 75 V --> Use 2200uF 100V C961 33 uF/ 160 V --> Use 33uF 160V C965 270 uF/ 40 V --> Use 330uF 50V C971, 972, 975, 976, 985 840 uF/ 12 V --> Use 1000uF 16V |
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Re: 2215 CRT problem, PSU filtering?
Good news! I replaced the PSU filter caps, and I noticed the 33uF/160V on the 100V PSU output, and it's all good!
Looking at the base of this capacitor, it was quite obvious that it was the failed one, the black epoxy has come off near one of the legs and when I attempt to measure it's capacitance on my (cheap) multi-meter it reads almost 0nF. In fact, I think the black epoxy had come off under such pressure that it pushed the cap up, and crack the solder joint! Look at the difference nice new caps have ! Thanks very much for your help, Tom, very much appreciated! Max |
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Tek 603 - recapped LV board, now moving on to other problems. Advice on -30V reg?
Hi,
I've been working on a 603 XY and began by recapping and testing on Variac, which cleared up display bloom and a squiggle. What I have now is: * a somewhat defocused (2-3mm), very bright spot * unresponsive intensity control * focus control has effect but cannot focus spot All the above seems to indicate a HV issue. I am waiting on a HV probe so I don't have a measurement yet. But, possibly related: Was not able to bring the -30V into spec, rails currently measure +215: about 250 +15: about 17.7 -30: about -36 The -30V adjustment is R878 trimmer but it has no effect on the voltage. I'm looking at the regulator section schematic, I've checked the VR870 zener and it's nominal ~ 6.2V. I'm pretty new to repair so I was hoping for a pointer or two to where I could look at re this initial inability to regulate or trim -30V. I believe this is the most relevant part of the schematic: /g/TekScopes/photo/249616/0?p=Created,,,20,2,0,0 --Toby |
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Re: Wikipedia is not an appropriate topic for TekScopes. WAS repair tools: Autotransformers/variacs
I have two of these:
Now obsolete for my purposes as I have a couple of Leo Bodnar's marvelous <40 ps units. If anyone is interested in them PM me and I'll take photos. I am only keeping them until they find a proper home. I'm in central Arkansas. Have Fun! Reg |
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Re: S-52 only works with lowered +15 V power supply
Hi Max,
Any progress? Today I used an S-52 on an extender, case removed, and then thought of your problem. I read your first post once more: The only missing waveform was the TD output.The 1N3130 is a 50mA/25pF TD, while the original one is 50mA/1.5pF. Hence I think the small cap C65 will not pass enough current from the snap-off diode to fire the TD in a stable way. The bias current would have to be unrealistic close to the firing current. To my surprise, around + 13V I notice that an output waveform appears, although not synchronized.I doubt so. The proper output pulse probably doesn't start nearly immediately after the sweep start (period 8) but earlier, in period 7, so up to 1 us earlier. Simply because the arming bias current in period 7 is already high enough to fire the TD. In my previous post I wrote: An increasing supply voltage also has effect on trigger level as if the wiper of R90 is turned towards theHere I overlooked the current delivered via R97+R98. That current will increase when you increase the "+15V" level. Are the values of these resistors still in spec (not replaced by smaller values)? When you say that the pulse disappears, does that mean that the output stays low, or that the output is high over a so long period that you don't consider this as the proper pulse? Albert |
Mlynch001
Michael W. Lynch
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