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Re: Update: Re: Help with 7D15 Tek logic gates
Say, Dave, the Vee to Gnd shorted thing may be unrelated, but I will bring up the Vtt appearing to be shorted to Gnd issue anyway.? Saw it first back in the late 1980s when I first worked with ECL.? Vtt is the voltage that the 50 ohm terminations connect to, usually -2 V.? All the 50 ohm terminations on the board, each in series with the output impedance of its driving gate, about a few tens of ohms, are effectively in parallel.? Could read as low as a few ohms or less and look like a short.? Just a thought.? ?HTH.? ? Jim FordSent from my T-Mobile 4G LTE Device
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-------- Original message --------From: "Dave Peterson via groups.io" <davidpinsf@...> Date: 12/28/21 12:00 AM (GMT-08:00) To: [email protected] Subject: [TekScopes] Update: Re: Help with 7D15 Tek logic gates Incredulous would be the word that comes to mind when I think how I felt about my diagnosis of U287C being dead in this 7D15. But I could not reason why else I was getting no signal out on pin 14. Stuck HI (0.7v) IIRC.I really didn't believe that the issue was U287C specifically. With U287C suspect I couldn't say anything about U287D, but U287A and B appeared to be working if I recall my testing results. Would a single instance of a quad just fail? There was nothing physically questionable about this part, and well isolated from inputs to have been overloaded.After waiting to procure a proper desoldering station to remove the MECL 1662 NOR quad pack from the A6 Interface Board, I finally got the little bugger out this morning.I had also purchased a couple of NOS 1662s online. I did a little study, then set up a breadboard test bench, and after working through a few snafus I was able to prove that indeed, U287C alone is non-functional in this package. All three other NORs are working, and all four of one of the replacements are as well.Thanks for the inputs. The feedback has gone a long way to bringing me up to speed on ECL logic in Tek parts.I have some board clean up to do from the removal process, and I think I may have measured a short from Vee to Gnd. Shorted Tant? Maybe. Don't hold me to that yet. Careful testing and reassembly shall ensue. I won't call it fixed until I can have it in a scope and running some counts.I'll post an update if/when fixed.Dave
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Update: Re: Help with 7D15 Tek logic gates
Incredulous would be the word that comes to mind when I think how I felt about my diagnosis of U287C being dead in this 7D15. But I could not reason why else I was getting no signal out on pin 14. Stuck HI (0.7v) IIRC.
I really didn't believe that the issue was U287C specifically. With U287C suspect I couldn't say anything about U287D, but U287A and B appeared to be working if I recall my testing results. Would a single instance of a quad just fail? There was nothing physically questionable about this part, and well isolated from inputs to have been overloaded. After waiting to procure a proper desoldering station to remove the MECL 1662 NOR quad pack from the A6 Interface Board, I finally got the little bugger out this morning. I had also purchased a couple of NOS 1662s online. I did a little study, then set up a breadboard test bench, and after working through a few snafus I was able to prove that indeed, U287C alone is non-functional in this package. All three other NORs are working, and all four of one of the replacements are as well. Thanks for the inputs. The feedback has gone a long way to bringing me up to speed on ECL logic in Tek parts. I have some board clean up to do from the removal process, and I think I may have measured a short from Vee to Gnd. Shorted Tant? Maybe. Don't hold me to that yet. Careful testing and reassembly shall ensue. I won't call it fixed until I can have it in a scope and running some counts. I'll post an update if/when fixed. Dave |
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Tektronix 2445 Rebuild and Fan Issue
So, I recently became the owner of a Tek 2445 and low and behold when I got it, it worked. Been doing some reading and took a peek inside and how its running I don't know but it's time for a re-cap. I have all the caps on order and when I get that done I have to figure out what to do about the fan. The fan does not seem to run and after doing quite a bit of reading looks like converting to a computer fan is pretty much the only option now adays.
1. The collet fell apart after I got it out and it does not look like anyone is selling these - I'm a year or two too late. 2. I've seen the post on the fan rebuild and I know my limits - not going that route unless I can send it to someone to do for me. I've got a back from a 2445A (or B not sure) that is setup for the small computer fan 80x80x20 so the only thing I need is to wire it up and I am looking for ideas for fan circuits. I guess there are two schools of thought. 1 - run it full out (Since my work bench is in my garage I'm not against this) 2 - make it variable. (A little bit of quiet in the cooler months would'nt be bad though) 3- make it variable with a switch that would force it to run full out (this would be ideal as in the summer I could just flip the switch on the back and know its getting all the air it needs and have it run quiet(er) in the cooler months.) I am not an EE by any means but love to dabble and learn new things and have just started going down this path - thanks ham radio. Does anyone have a simple circuit schematic if I want to go 1, 2, or 3 - with my preference to option 3? I looked at the 2465A schematic and unfortunately cannot identify what they have listed as A1111 (51) between RT1110 and R1112. So unless someone knows what that refers to that design is out. I figured someone had to have come up with something simpler by now though. |
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Re: 495P SpecAn problem
Any chance those could be nearby strong broadcast signals? Especially the 1 MHz & 1.4 MHz, which are in the AM broadcast band (in North America, at least). My location is up against a national park on the side where I'm above ground, and I'm below ground on the other side. You'd think it ought to be pretty RF-quiet, but there's this 1.1 MHz that gets all over everything. Once I was working with a raw strain gauge bridge type pressure sensor, and my scope showed what looked like amplitude modulated 1.1 MHz all over it. I connected a small earphone directly to the raw pressure sensor, and was listening to "WTAM 1100 AM". Turns out their 100KW transmitting tower is directly across the valley from me, about 3mi line of sight. I can actually see the lights on the tower out my basement windows at night! So you may wish to look for a similar interfering signal in your area.
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Steve Hendrix On 2021-12-27 08:46 PM, n49ex via groups.io wrote:
I'm looking for some help with my 495P spectrum analyzer. Hadn't used in a while or never noticed, but from zero to about 4MHz there are bunch of spikes at about 1MHz, 1.4MHz, 2.something MHz, etc. Shorted input, not background noise, but somehow internally picked up or generated. Also? not completely symmetric on the negative frequency side. Above 3MHz all is fine, and works well otherwise with input signals over the entire range of the instrument. Just has these spurious spikes down low, |
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495P SpecAn problem
I'm looking for some help with my 495P spectrum analyzer. Hadn't used in a while or never noticed, but from zero to about 4MHz there are bunch of spikes at about 1MHz, 1.4MHz, 2.something MHz, etc. Shorted input, not background noise, but somehow internally picked up or generated. Also? not completely symmetric on the negative frequency side. Above 3MHz all is fine, and works well otherwise with input signals over the entire range of the instrument. Just has these spurious spikes down low,
Anybody know what causes this or how to fix? Thanks!Reinhard Metz |
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Re: 492BP external mixer ident issue
Sort of working - but badly. As a test I tried injecting a sq wave from a cheapo chinese VNA, into the mixer port of the external diplexer, now I see groups of energy peaks pretty much as expected on the upper normal trace but on the lower ident trace I can only see a tiny right shifted version. At least the sw and hw is shifting the signal but why so much lower? ...and there is still nothing but noise on the lower ident trace with a real cw signal.
I would have thought the level would not change in ident mode. Zoomed out to max span it all looks even enough. Ideas anyone? (...chirping of crickets...) |
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Re: 7904 Display Board CRT Brightness
It's easy to miss -- the manuals are pretty thick, and if you've been deep in debug mode, it's natural to overlook the operator instructions!
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-- Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 12/27/2021 16:19, Dave / NR1DX wrote:
Duhhhhhh ... I dont know how I missed that ... |
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Re: 7904 Display Board CRT Brightness
Duhhhhhh ... I dont know how I missed that ...
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Thanks all who replied Dave manuals@... On 12/27/2021 5:22 PM, Harvey White wrote:
I have an old 7904.? The third knob down (A, B, knob) has a switch (inner) for control illumination, and an outer knob for readout intensity.-- Dave Manuals@... www.ArtekManuals.com --
This email has been checked for viruses by Avast antivirus software. |
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Re: 7904 Display Board CRT Brightness
I'll check mine when I get back home next week.? Just for the hell of it.? Can't hurt to know more about one's gear.? Thanks for the inspiration, Dave and Harvey.? ? ? ? ? ?Jim Ford?Sent from my T-Mobile 4G LTE Device
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-------- Original message --------From: Harvey White <madyn@...> Date: 12/27/21 2:26 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 7904 Display Board CRT Brightness I have an old 7904.? The third knob down (A, B, knob) has a switch (inner) for control illumination, and an outer knob for readout intensity.HarveyOn 12/27/2021 5:08 PM, Dave / NR1DX wrote:> I never paid it much mind in the past, but In playing with this old > 7904 I notice that the numerical display on the CRT for the plug-ins > is a bit bright. Is there a way to turn that brightness down a bit.? > There appears to be no adjustment externally or internally and I saw > nothing in the adjustment section of the manual for the display board>> Dave>> manuals@...>
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Re: 7904 Display Board CRT Brightness
I have an old 7904.? The third knob down (A, B, knob) has a switch (inner) for control illumination, and an outer knob for readout intensity.
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Harvey On 12/27/2021 5:08 PM, Dave / NR1DX wrote:
I never paid it much mind in the past, but In playing with this old 7904 I notice that the numerical display on the CRT for the plug-ins is a bit bright. Is there a way to turn that brightness down a bit.? There appears to be no adjustment externally or internally and I saw nothing in the adjustment section of the manual for the display board |
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Re: WTB: Tek Model 3 scope cart and 500 series
Still have the model 3 scope cart.? Model 203 is gone.? Still have 547 and plug-ins except 1a2.? Also have 2? ?M? ?4 channel? plug-ins.? 547 doesn't turn on.?
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Carl Hallberg (W9CJH) On Tuesday, December 21, 2021, 10:15:44 PM CST, Carl Hallberg via groups.io <n9ess@...> wrote:
Chris, I checked both carts and one is model 3 for 7000 series 4 bay and the other is model 203 for 7000 series 3 bay.? They both work but I need to clean them up a bit.? The 203 has a bit or rust.? Wheels turn fine.? Also want to get rid of all my 500 scopes except the 575 curve tracer at this time.? Have 1s1, 1s2, 1l5, 1l10, 1l20, 547s, 1a1s, 1a2s, and more.? Will not ship.? Need to get them a new home. Carl Hallberg On Wednesday, December 8, 2021, 11:33:17 AM CST, Chris Wilkson via groups.io <cwilkson@...> wrote: Hi All, I'm in need of another scope cart (or 2). I'm looking specifically for Tektronix Model 3 Scope Mobile carts. I'm willing to drive a fair distance from Detroit to pickup. Will pay cash or trade equipment. Please contact me off list if you have one for sale. Cheers, Chris |
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7904 Display Board CRT Brightness
I never paid it much mind in the past, but In playing with this old 7904 I notice that the numerical display on the CRT for the plug-ins is a bit bright. Is there a way to turn that brightness down a bit.? There appears to be no adjustment externally or internally and I saw nothing in the adjustment section of the manual for the display board
Dave manuals@... -- Dave Manuals@... www.ArtekManuals.com -- This email has been checked for viruses by Avast antivirus software. |
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Follow UP: 7904 with no -15V
It turns out that lack of -15V and yet some other problems are all caused by interconnect cables not seating properly / totally
After I got my bearings straight on the power supply regulator board and the lack of -15V. the problem was traced to one of the interconnect cables. While flipping the scope over and upside down the thing suddenly came to life. I buttoned up and it was dead again. I started plugging and unplugging cables and finally found the culprit. At that point I should have continued "exercising" the rest of the interconnects ( There are a lot !!) . Anyway with -15V reliably in hand, i I started checking my "collection" of plug-ins and stumbled on the fact that the right most time base would not trigger in internal mode from either the left or right vertical plug-ins, but triggered just fine with a external trigger source. Discovered that i could get the internal trigger to work by pressing on the interconnect board behind the push button switches, confusingly the right most time base was affected by a cable on the far left hand side of the board ! The MORAL to the story:? got an old 7904 that is acting flaky open it up and exercise the *ALL* the interconnect cables . This scope is over 35 years old and hadn't been used in almost 10 years... You get the idea. Note the connectors did not appear to be unseated nor were they corroded that I could see they just want to be "exercised I guess. I can hardly wait when in another 10 years some of those transistors that are plugged an and not soldered start to go intermittent. Dave ARTEKMANUALS -- Dave Manuals@... www.ArtekManuals.com ( ) ( ) This email has been checked for viruses by Avast antivirus software. www.avast.com ( ) ( #DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2 ) |
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Re: Testing Tunnel Diodes
On Mon, Dec 27, 2021 at 01:12 PM, Mike Dinolfo wrote:
He has a ton of some of the best electronic content on You Tube. I have spent HOURS watching Alan explain various circuits and instruments. He is a wonderful teacher. -- Michael Lynch Dardanelle, AR |
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Re: vintageTEK Demo Board Available
A tech reporter did something similar with the first Macbook Air he was to review. He put it in a manila envelope, admired that it fit, then set it aside. Out it went with the trash the next day.
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Oops. -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 12/27/2021 12:33, Dave Voorhis wrote:
On 27 Dec 2021, at 19:48, Jean-Paul <jonpaul@...> wrote:seems to be sold out already!I¡¯m kicking myself because I ordered one in the previous run, got it, tested it, put it back in its envelope to await ordering and arrival of an appropriate case and power supply¡ |
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Re: vintageTEK Demo Board Available
On 27 Dec 2021, at 19:48, Jean-Paul <jonpaul@...> wrote:
seems to be sold out already!I¡¯m kicking myself because I ordered one in the previous run, got it, tested it, put it back in its envelope to await ordering and arrival of an appropriate case and power supply¡ ¡and then inadvertently put it in my stack of empty envelopes and discarded it. :-( |
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Re: vintageTEK Demo Board Available - Sold Out
Tayda has the chips. I'm fairly certain it's the ones used in it.
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Vince. On 12/27/2021 03:14 PM, Bob Haas wrote:
Sorry, the latest batch has sold out. We will have more when we get more chips, but that's hard to predict. --
Michigan VHF Corporation -- nobucks dot net K8ZW - |
Dave Peterson
Michael W. Lynch
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