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Re: Odd 2247A problem, looking for insight
walter shawlee
some more data on this odd fault:
1. the resistor is 1/4w, fairly big to burn up. 2. when set to DC coupling, both inputs measure almost exactly 1Mohm with my 34401A. 3. vertical cal is good on the channel that had teh burned resistor. on a related topic, this 2247A unit has the same terrible frequency cal issue (on screen counter) I have seen in other units. the adjustment is incredibly sensitive, and no matter how you set it, once closed up and run for a while, it drifts low by about 50 Hz. I am going to put a hole in the case to set it, it's just too frustrating the way it is. all the best, walter -- Walter Shawlee 2 Sphere Research Corp. 3394 Sunnyside Rd. West Kelowna, BC, V1Z 2V4 CANADA Phone: +1 (250-769-1834 -:- +We're all in one boat, no matter how it looks to you. (WS2) +All you need is love. (John Lennon) +But, that doesn't mean other things don't come in handy. (WS2) +Nature is trying very hard to make us succeed, but nature does not depend on us. We are not the only experiment. (R. Buckminster Fuller) |
Re: Slightly OT: How can I dissolve Potting Compound?
On Sun, Jan 3, 2021 at 02:53 PM, Greg Muir wrote:
As one of my profs used to say... erring on the side of caution, isn't about erring at all... it's about accessing risk, when there is a lack of scientific data. There are a lot of studies on the affects of MEK and Acetone... both are heavily used industrial chemicals... and both are sold and used by consumers.... either as the pure product, or as a significant component of a product. |
Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
Hi Tom - I found the TR502 manual online, info on the crystal in the tek common
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parts manual (mechanical!), and a catalog page on Bliley crystal website. Whether Bliley wants to grind another? I dunno.. The only resonance mode I have seen in the tiny TO-5 package is a SC, Maybe nothing else will fit? JimMc -----Original Message-----
From: "Tom Lee" <tomlee@...> Sent: Sunday, January 3, 2021 5:34pm To: [email protected] Subject: Re: [TekScopes] Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603 Hi Jim, Very interesting -- could you post a link to where you found that information? Thanks! -- Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 1/3/2021 10:24, J Mcvein wrote: Greetings Attilio - I did some research on the 502, and the xtal that tek used. |
Re: Slightly OT: How can I dissolve Potting Compound?
I've been working with MEK for years with no apparent health issues. MEK is the solvent of choice for virtually al adhesives except CA and epoxies used in speaker building and repair. I do have positive ventilation running when I'm working with the stuff, but have never worn a mask or gloves.
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I might add that MEK is nowhere near as volatile as acetone or methylene chloride and for most things is a better solvent. I'm 69 years old and as long as I get my afternoon nap, I'm OK to go. Maybe if I had spent my life avoiding all potential toxicity, I might be in better shape, but I doubt it. It would also have likely been a much less enjoyable and productive experience, living like that. For cleaner/defluxer/degreaser, I have found that solvent blends are often more effective than a single solvent full strength. Water (as a solvent with tri sodium phosphate surfactant) plus orange oil plus alcohol plus MEK in various combinations can be pretty amazing. To make an excellent defluxer, you usually don't need more than about 30% MEK to get it done and can have as much as 50% water. The MEK, alcohol and, to a lesser extent, orange oil, are the most aggressive parts of the mix but without the water and TSP, the MEK and alcohol quickly dissipate and the gunk redeposits. The water with TSP float it up to where its relatively easy to mop up with absorbent towel or even just wash off in running water, if that's practical. Thomas Garson Aural Technology, Ashland, OR By my calculation, the dynamic range of the universe is roughly 679dB, which is approximately 225 bits, collected at a rate 1.714287514x10^23 sps. On 1/3/21 1:49 PM, Roy Thistle wrote:
On Sun, Jan 3, 2021 at 10:08 AM, Greg Muir wrote:MEK is not MEKP... and MEK is not known to be toxic to the liver. Acetone is not as "bad" (whatever that means) as MEK... and acetone is present in the human body, and disposed by it, during normal metabolic processes. |
Re: Slightly OT: How can I dissolve Potting Compound?
Bob Albert
I recall my late sister telling me 'everything in moderation'.? She was referring to food, but the same applies to solvents.? If you are involved with the stuff, do so very sparingly and you probably won't be harmed.
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I am reminded of the Burgess Battery Company which I believe was shuttered due to hazardous chamicals harming its employees.? The batteries were good but the employees paid the price. On Sunday, January 3, 2021, 02:53:18 PM PST, Greg Muir via groups.io <big_sky_explorer@...> wrote:
I figured that I would probably elicit an over reactive response from you, Roy. To those not familiar with handling chemicals dangerous to one¡¯s health it is better to be more safe than sorry.? If you peruse the medical research reports you will most likely come across some of the deleterious effects from these solvents. If you can stand up and definitely say that using such chemicals do not have physiological effects on the internal organs I welcome the proof.? Otherwise it is bet to err on the cautious side. Hopefully the end of another spitting match. Regards, Greg |
Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I have similar ideas, phase detection, AC and DC voltage measurement, and PNP/NPN transistor lead ID, beta, and leakage to frame.? Going to be more complicated than the existing projects because I threw a bit of technology at it.
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Chasing hardware redesign bugs for the moment, then on to the software. Harvey On 1/3/2021 4:57 PM, Andy Warner wrote:
I have also thought about a TM500 tester that included: |
Re: Slightly OT: How can I dissolve Potting Compound?
I figured that I would probably elicit an over reactive response from you, Roy.
To those not familiar with handling chemicals dangerous to one¡¯s health it is better to be more safe than sorry. If you peruse the medical research reports you will most likely come across some of the deleterious effects from these solvents. If you can stand up and definitely say that using such chemicals do not have physiological effects on the internal organs I welcome the proof. Otherwise it is bet to err on the cautious side. Hopefully the end of another spitting match. Regards, Greg |
Re: Slightly OT: How can I dissolve Potting Compound?
Dennis,
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Can't help much on the spectral tube side of things, but I used to work in thick film hybrids many moons ago where we had to occasionally 'de-pot' circuits. One of the few things which will attack epoxy is dichloromethane, also known by its older name methylene chloride. Its availability has become a little more restricted under the CFC regulations but it is available as a reagent. It doesn't /dissolve/ epoxy, but it does cause it to jellify, swell, and lose strength allowing it to be unpicked. It will attack almost all synthetics including the polyethylenes and polypropylenes: a handful of materials are more tolerant of it such as PTFE, PEEK and PVDF. Dichloromethane is a very aggressive chemical which boils at a low temperature; we used to use it with a water blanket which prevented loss to atmosphere - water is considerably less dense than dichloromethane and immiscible, so it forms a barrier layer above the solvent. Jon. On 03/01/2021 02:18, Dennis Tillman W7pF wrote:
I need to dissolve the black HV potting compound of a 12VDC powered |
Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
Hi Jim,
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Very interesting -- could you post a link to where you found that information? Thanks! -- Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 1/3/2021 10:24, J Mcvein wrote:
Greetings Attilio - I did some research on the 502, and the xtal that tek used. |
Re: 2230 storage deja vu
On 1/3/2021 8:24 AM, Kevin via groups.io wrote:
Hi allKevin Are all of these combinations OK in analog mode? I would check the cables and the switches that play into the mode changes. I have a bunch of the 2230. 2221A, and 2232 scopes and I have had to replace a few of the ribbon cables because of some really strange problems. My 2230 is off the air right now, the line input filter blew up and I still haven't gotten everything back together. I think that the only scope that is harder to work on than the 2230 is the Sony Tek 335 which is damn near impossible to service! If you like your 2230 you will love the 2232, it seems like Tek improved almost everything between the two models. Feel free.... ? Bert |
Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I have also thought about a TM500 tester that included:
- Presence/absence (but not correctness or ripple) of each of the supply voltages - Brought out all supplies to banana jacks for metering and load testing - Indicated correct/incorrect phasing of the AC supplies - Pass/fail indication for the pass transistors The Tek fixture demonstrates how to indicate the correct phasing. After looking into those cheap component testers, they all seem to be AVR based, the code and principles of operation are openly available, and I was thinking that it should be possible to bludgeon the code into submission to expect an NPN transistor on one set of pins, and a PNP on another, measure the hFE and provide red/amber/green indication for each transistor (amber being low hFE (< 20.) At first, I was thinking of making a board that fitted into a module, but bringing all the supplies out to jacks/binding posts, and the indications just seemed like a headache given the front panel real-estate - plus the PCB would be large, but mostly empty, therefore not very cost effective. I am coming round to the idea of an external box plus a butchered Jamma cable, thoughts ? On Sun, Jan 3, 2021 at 9:35 AM Colin Herbert via groups.io <colingherbert= [email protected]> wrote: Some time ago I had similar thoughts on accessing the connections to the-- Andy |
Re: Slightly OT: How can I dissolve Potting Compound?
On Sun, Jan 3, 2021 at 10:08 AM, Greg Muir wrote:
MEK is not MEKP... and MEK is not known to be toxic to the liver. Acetone is not as "bad" (whatever that means) as MEK... and acetone is present in the human body, and disposed by it, during normal metabolic processes. Respect chemicals; but running in a panic for the hazmat suit, at the mention of the word "chemical" isn't necessary. On the other hand... worrying about being bored to death, by studying too much chemistry... doesn't seem to be much of a problem. |
Re: Odd 2247A problem, looking for insight
Let's see, 62 ohm resistor (that feels like a 1/10 watt just to start), input capacitance of some sort (20 pf, but you'd think that wouldn't be much), feed the scope RF.? 27 Mhz, 20pf gives about 294 ohms, 144 mhz gives about 55 ohms.? I'll suggest someone was trying to look at the output of a transmitter directly.? I'm surprised more didn't go....
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Harvey On 1/3/2021 2:35 PM, walter shawlee wrote:
I have a nice looking Tek 2247A scope here that has been sitting on the shelf for a while, due to a bad Channel i input. the signal is a horribly attenuated and differentiated replica of the actual input. Everything else is perfect. In a moment of covid-induced boredom, I felt I had to get to the bottom of this. I had a hunch that this was the input resistor being broken or damaged (there is always a flying resistor from the input BNC to the vertical input on 2200 series scopes). It was the only thing I could think of that could give this result. |
Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I see no significant advantage to a group purchase of the wafer switch for this tester. DigiKey has 100+ available and the discount for a quantity purchase is not that much. Further, it is likely that most folks will need to buy some other parts so just combine the switch with that order.
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Packaging a chunky wafer switch with planar circuit boards will complicate the packaging for me and I really have enough to do already. But, it does make good sense to do a single buy of a quantity of the board sets. I expect significant cost savings from that and ordering boards by Gerber files is not in everyone's experience. Larry On 1/3/2021 9:36 AM, Craig Cramb wrote:
... Larry is there a chance that there might be a purchase of the Rotary switch as a group purchase from DigiKey or all parts sourced up to the individuals.-- Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) |
Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Colin, I don't know a cost yet for the board set and I am not sure I can get an accurate estimate of shipping to the UK. My experience shipping to Europe is that it cost a *lot* more than our domestic USA shopping. You may know more about those shipping costs than do I.
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But, you can't sit on the fence. I will know more about the cost for USA deliveries in total but I will need commitments from international buyers so that I know how many board sets to order. Remember, too, that you will most likely need to buy some of the parts, surely that $25 switch from DigiKey. Karry On 1/3/2021 7:07 AM, Colin Herbert via groups.io wrote:
Hi Larry, --
Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) |
Re: Odd 2247A problem, looking for insight
Walter,
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I suppose it is possible that U112 has beefy input protection (diode clamps to the supplies?) that might survive enough current to burn a small 62 ohm resistor. At maximum sensitivity the attenuators would be switched out of the circuit. --John Gord On Sun, Jan 3, 2021 at 11:35 AM, walter shawlee wrote:
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Odd 2247A problem, looking for insight
walter shawlee
I have a nice looking Tek 2247A scope here that has been sitting on the shelf for a while, due to a bad Channel i input. the signal is a horribly attenuated and differentiated replica of the actual input. Everything else is perfect. In a moment of covid-induced boredom, I felt I had to get to the bottom of this. I had a hunch that this was the input resistor being broken or damaged (there is always a flying resistor from the input BNC to the vertical input on 2200 series scopes). It was the only thing I could think of that could give this result.
It takes some effort to de-can the scope, and remove the complex shield over the vertical inputs, but sure enough, when opened, the barely visible input resistor (62 ohm carbon film) was BURNED. I replaced it, and ta-da, everything is working. What the heck? Here's what I just can't figure out, this scope has no 50 ohm input function, so no low impedance path exists to help burn this resistor due to over-driving, SO HOW DID it get burned and leave the scope undamaged? I am totally mystified by this, and keen to hear any opinions. I just can't see how this fault happened without vaporizing the vertical input channel. all the best for the new year, walter (walter2 -at- sphere.bc.ca) sphere research corp. |
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