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tds-420a recapping (smell on startup)
hi,
When I turn on the 420a, it give out -for just 30secs- a strong smell of rubber/car tire that disappear fast (no errors reported though); I think the caps are in need of a swap. Does anybody out there have a list to all the caps needed for all the tds420a boards (power supply, acquisition, etc)? I'd rather take the 420 apart once I have the needed caps instead of having to dismantle it and leave the pieces around until the components gets ordered and arrive. many thanks in advance Massimo |
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Re: Tek 603 - question on transistor heatsinking material
Chuck Harris
Beryllium ceramic is fascinating stuff. We all would use it a lot
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more but for the liability issues. It feels a lot like aluminum in that it draws the heat away from your skin very quickly, making it feel perpetually cool when all but the part that is touching you, is at room temperature. Most other ceramics are pretty good insulators, so they feel warm and cozy as their surface warms quickly to your skin temperature. Another fun ceramic is the foamed stuff used for the space shuttle's heat shield. This stuff heats up instantly bright yellow when you play a propane torch on its surface, but take the flame off of the tile, and you can touch it immediately, and it doesn't even feel more than warm. -Chuck Harris Bruce Griffiths wrote: I have some pink tinted alumina TO3 insulators as well as some blue tinted beryllia ones from the 1970's. |
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Re: Tek 603 - question on transistor heatsinking material
There exists (existed?) a product called beryllia microspheres which can be used safely to increase the thermal conductivity of epoxy, silicone encapsulants, etc. They are also suitable for mixing into silicone grease; and (I think) they are the critical ingredient in high quality white thermal greases. They are very small but not as small as dust, which is the dangerous form. Also, they have smooth surfaces without dangerous microscopic roughness. I think they were developed in the 1960s or 1970s (a quick google search of patents turns up some filings in that time period). They were not cheap (I bought a pound around 1970 and the price, as I recollect, was not in the budget class - at least for a graduate student). They have come in very handy over the years.
Stephen |
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Re: Tek 603 - question on transistor heatsinking material
I have some pink tinted alumina TO3 insulators as well as some blue tinted beryllia ones from the 1970's.
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The beryllia ones are much colder to the touch than the alumina ones. Bruce On 03 July 2020 at 02:19 stevenhorii <sonodocsch@...> wrote: |
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Re: Tek 603 - question on transistor heatsinking material
On 2020-07-02 2:46 a.m., John Gord via groups.io wrote:
Toby,That is correct. If I went with the mica, I can always use 2 pieces; I ordered some anyway, it's quite cheap at Digikey. I guess a bonus is that it's unlikely to break when clamped. --Toby --John |
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Re: Tek 603 - question on transistor heatsinking material
On 2020-07-02 9:24 a.m., Chuck Harris wrote:
It probably shattered when it was tightened. It will do that inThanks as always, Chuck! These pads are under the low voltage (< 45V) TO-202 Darlingtons. Most likely I can reuse them. --Toby -Chuck Harris |
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Re: Tek 603 - question on transistor heatsinking material
Beryllium and compounds have an unusual toxicity profile. Beryllium is not
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directly toxic as, say, arsenic is. However, how it harms you is to cause an intense allergic reaction. In the lungs, this results in fibrosis from the inflammation and severely affects lung function. Chuck is correct in that most companies tinted BeO parts pink but I have certainly seen non-tinted parts. I once found some long white pipes in a surplus yard. Though they were not pink, they had a warning label on them. I alerted the owner to this and he said he¡¯d be careful, but he was somewhat pleased because beryllia scraps out at a higher price than alumina. Chuck is also correct in that beryllium and its compounds are safe if you don¡¯t create dust or fumes from them (no grinding or welding). Slivers of beryllium can cause an allergic reaction in your skin around the sliver. You should be safe using the heatsink pad as intended but it does need heatsink compound to be effective. Steve H. On Thu, Jul 2, 2020 at 09:19 Chuck Harris <cfharris@...> wrote:
It has been reported that Tektronix used BeO ceramic all |
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Re: Looking for 7D02 Personality Modules
Chuck Harris
Hi Dennis,
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Have you ever used a software logic analyzer of this sort? I did at one of my customer's locations. They spent a gob of money on a set of software personality modules for their 1240 logic analyzer... which is a way more capable logic analyzer than the 7D02..., and it was essentially useless. I can imagine that anything for the very primitive 7D02 will be even less useful. The only thing the personality module does is decode the state the cpu is in, so it knows when it is fetching instructions, and then looks up the instruction in a table, to translate it into a mnemonic, and spills out the hex codes for the rest of the bytes it fetches before the next instruction. The problem is, you get no labels other than raw hex addresses. So, you get a listing on the screen that says: $1000 NOP $1001 LDA $BE $1003 JE $10:01 $1001 LDA $BE $1003 JE $10:01 $1006 JMP $10:00 ... Gobs and gobs of jibberish that shows what it executed, but nothing of the actual structure of the program in memory. So, without a listing of the actual program, in loader code, you will feel like you are totally blind. You will learn the address ranges the CPU hops around in, but you will learn nothing of what is in the registers, what is in memory, and nothing of what the code looks like in memory. If you want to hack the ROMS in some device, you will have a far more fruitful time of it, using a disassembler, and a software debugger/emulator. All you will learn with a "software" logic analyzer is that a NOP goes to the next instruction in memory, as does an ADD, SUB, INC, DEC, ... And that conditional jumps sometimes do, and sometimes don't. But you won't know why. -Chuck Harris Dennis Tillman W7pF wrote: I am looking for the following Personality Modules for the 7D02 Software |
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Re: Tek 603 - question on transistor heatsinking material
Chuck Harris
It probably shattered when it was tightened. It will do that in
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a blink if the aluminum under it is not perfectly flat. I would goop it up, and put the pieces back into service. I you can't, or are unwilling to do that, replace them all with a thick silicone heatsink pad. The down side is anything but the ceramic will have different a different dielectric constant, and will change the capacitance to ground. That may, or may not be important. -Chuck Harris toby@... wrote: On 2020-07-02 1:00 a.m., John Gord via groups.io wrote:Toby,That sounds probable. It sure is brittle, while this board was hard to |
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Re: Tek 603 - question on transistor heatsinking material
Chuck Harris
It has been reported that Tektronix used BeO ceramic all
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over the place. Some common examples are the heat sink insulators for the 5000 series H and V output transistors. They also used it as the heat sink bar that fits under the EHT for the 657 scopes. This particular heat sink insulator looks probable to me. Some more responsible companies tinted their BeO ceramics pink or purple as a warning, but not tektronix, as far as I have seen. You needn't be terribly fearful, though. If you aren't machining it into a fine dust, you should be ok. Regardless of what it is, you will need heatsink compound. The pieces you have are probably still serviceable, as I doubt there is enough voltage there to jump the thickness of the pad even if it were free air. Goop them up with compound, and screw the device back down. About the only stuff that doesn't need heatsink compound are silicone heatsink pads... which are made out of heatsink compound. -Chuck Harris John Gord via groups.io wrote: Toby, |
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Re: Tektronix 2230
Hello Saroj,
sorry to hear about the breakdown of your replaced parts... :-( Since you already confirmed that the scope worked when fed from a secondary power supply, and I assume it still does? If that's the case, there still must be something wrong with the first switcher... I would check all surrounding parts, and when necessary, remove them before checking, because in-circuit checking can give distracting results. At the moment I do not have other suggestions than to check if the scope is still running on the external 43V power supply, and check again very thoroughly all other parts and their polarity in the first switching part of the power supply... Good luck, Leo Again, sorry for |
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Re: Tek 603 - question on transistor heatsinking material
Toby,
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It looks like there are several devices held in place with a common clamp bar. If that is the case, you need to match thickness fairly well, or perhaps use a thinner insulator like mica while adding a resilient spacer under the clamp bar to compensate for the difference. --John On Wed, Jul 1, 2020 at 11:09 PM, <toby@...> wrote:
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Re: Tek 603 - question on transistor heatsinking material
On 2020-07-02 1:29 a.m., John Gord via groups.io wrote:
Toby,Unless Walter at Sphere has the alumina, I might have to go with mica -- Digikey has some reasonably compatible rectangular pieces. Thanks a lot, John. It was lazy of me not to consult the parts list before posting... --Toby --John Gord |
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Looking for 7D02 Personality Modules
I am looking for the following Personality Modules for the 7D02 Software
Logic Analyzer Plugin. Please contact me off list at dennis at ridesoft dot com if you can help. It is very important that I find these three: PM-111 6809 PERSONALITY MODULE PM101 Option 02 6502 PERSONALITY MODULE PM102 6800 PERSONALITY MODULE It would be nice to find these two: PM101 Option 01 8080 PERSONALITY MODULE PM-111 6809 PERSONALITY MODULE I don't have much hope of ever finding these three: PM-110 Z8001 PERSONALITY MODULE PM-108 Z8002 PERSONALITY MODULE PM-112 MULTIBUS PERSONALITY MODULE The 7D02 is a software logic analyzer plugin for the 7000 series as opposed to the 7D01 which is a hardware logic analyzer plugin. The difference is night and day. * The 7D01 hardware logic analyzer can help you analyze a computer bus or any system with a lot of interconnected signals by simultaneously capturing the timing relationship of up to 16 signals. * The 7D02 software logic analyzer disassembles the addresses and software instructions being executed by a CPU as it steps through its instructions and reads or writes data. In order to do this the 7D02 requires a Personality Module for the particular CPU it will be analyzing. The Personality Module intercepts each software instruction and converts it to human readable instructions and provides this along with the address of the instruction, the data being fetched or written, etc. The useful product lifetime of a logic analyzer is extremely short in part because they are extremely difficult to develop and just about the time they are ready for market the CPU manufacturers come out with newer architectures that make the logic analyzers obsolete. In addition, logic analyzers are very expensive the entire development cost will have to be spread across relatively few customers. A side effect of that is to make customers even more reluctant to invest in something that costs so much if the costs can't be amortized over at least 5 years. Bottom line: Not many 7D02 logic analyzers were ever sold. In order to use the 7D02 you had to also buy the right Personality Module to go with it. Tektronix made 12 different personality modules for the 7D02. These are rather small and easy to be misplaced. After a customer completed development of their product the 7D02 would be put in a cabinet and probably never get used again. The personality module would eventually get separated from the logic analyzer and, since it didn't look like much, eventually it would get tossed. By now the personality modules are almost impossible to find. I have a particularly romantic attachment to the 16-bit CPUs that were prominent in the mid to late 1970s when I built my first personal computer. I learned how to write assembly language for several of those CPUs and disassembling the firmware that is running on these simple CPUs, and debugging the code is some of the most challenging fun I can have. Any help locating the personality modules I am looking for would be greatly appreciated. Dennis Tillman W7pF |
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Re: Tek 603 - question on transistor heatsinking material
On 2020-07-02 1:00 a.m., John Gord via groups.io wrote:
Toby,That sounds probable. It sure is brittle, while this board was hard to remove, there would have been no major shocks, so I was surprised to see it shattered. Hope I can replace it, or is there a better alternative now? --Toby
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Re: Tek 603 - question on transistor heatsinking material
Toby,
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It looks like the part number is 342-0082-00, described as an insulator plate, 0.52" x 0.52" x 0.015", material: alumina (aluminum oxide). It is likely used with thermal compound added, --John Gord On Wed, Jul 1, 2020 at 08:52 PM, <toby@...> wrote:
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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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