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Re: Tek 7854 intermittent issues
Albert -
Yep, those are the steps I'm following. Oddly though, my 0.5ms/div works as reported at 512 P/W, and fails gracefully as described at 0.2ms/div, but at 1024 P/W, it works at 2ms/div & fails at 1ms/div. I never get the immediate error. I've got a 'newer' model w/ combined RAM/ROM board, you? Nick - Happy to poke around & take readings for ya - let me know if I can be of help. |
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
I believe it, Harvey.? A former coworker had experimented with tubes, and he said that while you can run the filaments from A.C., try D.C. for audio; you'll like it.Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Harvey White <madyn@...> Date: 9/2/20 7:01 PM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 1S1 sampling unit; (also 7B53AN & 7A18 plugins) I once had a Heathkit OM3, which had a horrible hum problem (eventually).? I solved it by running the filaments off DC.? If you ever have that problem, I can suggest it.? The IO-14 was billed as a lab scope, I think.HarveyOn 9/2/2020 9:19 PM, David Collier wrote:> Hi Garth,> I'm in Canberra (Oz).> Some US sellers won't ship to Oz, a few charge ridiculous shipping of US$400 to 500, which is where they hope to profit!> A Heathkit IO-14 from USA is costing me US$50 carriage via the Global Shipping Program, which seems very inexpensive.> David C.>> >>
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
I once had a Heathkit OM3, which had a horrible hum problem (eventually).? I solved it by running the filaments off DC.? If you ever have that problem, I can suggest it.? The IO-14 was billed as a lab scope, I think.
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Harvey On 9/2/2020 9:19 PM, David Collier wrote:
Hi Garth, |
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
David Collier
Hi Garth,
I'm in Canberra (Oz). Some US sellers won't ship to Oz, a few charge ridiculous shipping of US$400 to 500, which is where they hope to profit! A Heathkit IO-14 from USA is costing me US$50 carriage via the Global Shipping Program, which seems very inexpensive. David C. |
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Re: HAPPY 20th BIRTHDAY TEKSCOPES!!!
Thanks for the mention Dennis and your efforts as a moderator. I've really enjoyed being a member of this group and look forward to the daily digest I receive. The knowledge and helpfulness of the other members here is a great resource. I also enjoy helping other when I can too.
I hope this group continues for a long tiome to come! Morris Odell VK3DOC locked down in Melbourne, Australia |
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Re: TWD 120's FREE
Charlie,
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Well, I have SCSI adapters galore, and an operating PC running Windows 98, necessary for operation of a legacy DSP analyzer (PC bus hardware). So, I have a system that could PROBABLY work with it. There is already a Tek analog scope on that bench, but the storage capability could be handy. If no one more needy puts up their hand, I would take one of those. Zip code 97520. 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 9/2/20 1:24 PM, Charlie Conger wrote:
I just found one, maybe two, complete TWD120's while unpacking after a move. These had been missing for years. These are 100 Mhz 2channel Digital Storage Digitizers originally made for GE medical. They require a PC to act as a display to be fully functional. As I last recall these were fully functional the last time I used them. |
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Re: TWD 120's FREE
Looks like an interesting bit of hardware.
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Does it use all three interfaces to communicate with the PC (as listed in the wiki)? or just the SCSI: " Adaptec ASPI SCSI driver is required for the software to communicate with the digitizer. SCSI configuration can be tricky." and the serial and parallel were for other things? That it was designed to work with windows 3.1 and becomes a tough thing to keep operational as OSes progressed is why these PC based scopes are such a mixed bag. Makes me glad I have older hardware based scopes. :-) On Wed, Sep 2, 2020 at 1:24 PM Charlie Conger <ctconger@...> wrote:
I just found one, maybe two, complete TWD120's while unpacking after a |
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Re: Strange Tek2440 issue
On 09/02/2020 02:50 PM, Siggi wrote:
On Wed, Sep 2, 2020 at 2:07 PM Vince Vielhaber <vev@...> wrote:Double checked, followed the foil, Channel 2 is definitely on pin 1.I had actually done that last nite, but didn't have the parts layout I got the power supply board out right now so it's definitely going to see some new caps. I'll also take a real close look at Q870 and Q879. I measured R478 with a 4 wire ohmmeter and it's 10.01. Haven't checked any of the other ... yet. I did look at the +8 and _15v rails as well as the 5V unreg and the +10 ref. All were ok with both the voltmeter and the scope. While the board's out I'm also going to track down U870's inputs to see if something's backward in the schematic. More later! Thanks! Vince. Even so, it still doesn't make sense, as the voltage-control op-amp starts-- K8ZW |
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TWD 120's FREE
I just found one, maybe two, complete TWD120's while unpacking after a move. These had been missing for years. These are 100 Mhz 2channel Digital Storage Digitizers originally made for GE medical. They require a PC to act as a display to be fully functional. As I last recall these were fully functional the last time I used them.
see here for more details If anyone is interested PM me and I will be happy to send for cost of shipping. |
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Re: HAPPY 20th BIRTHDAY TEKSCOPES!!!
Hmmm. Mine shows I joined 09/30/03 (Account -> Identity - Account Profile). I must've been a lurker for a while.
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Thanks, Barry - N4BUQ ----- Original Message -----
From: "Dave Daniel" <kc0wjn@...> |
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Re: HAPPY 20th BIRTHDAY TEKSCOPES!!!
Oh. Duh. The date is on the ¡°personal¡± under ¡°Account Settings¡±.
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On Sep 2, 2020, at 15:45, n4buq <n4buq@...> wrote: |
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Re: HAPPY 20th BIRTHDAY TEKSCOPES!!!
I searched for my member ID. Apparently I joined on or about April 7, 2004.
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I smile when I see that I asked my first Tek question and the second reply was from none other than Stan Griffiths. Then I see my reply to his saying "Yes, you are correct". How embarrassing. I didn't know who he was at the time. Thanks, Barry - N4BUQ ----- Original Message -----
From: "Dave Daniel" <kc0wjn@...> |
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Re: HAPPY 20th BIRTHDAY TEKSCOPES!!!
Is there a way to figure out when one joined the original (Yahoo groups) list?
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DaveD On Sep 2, 2020, at 14:06, Dennis Tillman W7pF <dennis@...> wrote: |
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Re: HAPPY 20th BIRTHDAY TEKSCOPES!!!
Thank you, Dennis, for moderating!? A very informative and enjoyable group, for sure.Jim Ford, member since late 2016 or early 2017 (can't remember exactly)Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Dennis Tillman W7pF <dennis@...> Date: 9/2/20 11:06 AM (GMT-08:00) To: [email protected] Subject: [TekScopes] HAPPY 20th BIRTHDAY TEKSCOPES!!! Michael Dunn started TekScopes 20 years ago on August 31, 2000. There wasjust one post that day from Walter Shawlee who joined that same day and hehas been an active member ever since.To Walter: Thank you for 20 years of contributions to TekScopes and for allthe parts and instruments you have on your web site!* Three days later Stan Griffiths W7NI (RIP) joined.* Three more members, including Tom Gootee, joined in October, 2000.* By the end of 2000 there were 13 members.* A year later it was clearly important: there were 68 members and >150posts each month. John Miles and Morris Odell joined TekScopes in that firstyear. To John and Morris: Thank you for your regular contributions over the 19years you have been members!* I was a late comer. When I joined in mid-November 2002 there were already250 members. I was looking for something like this for a long time and Ijumped right in with my first post that same day. Apparently I have beenbusy ever since I joined - I just noticed this will be my 5,000th post sinceI joined.Today we have over 8,000 members worldwide and there are 500 to 1500 postsper month.Thank you, Michael Dunn, for realizing the need for a Tektronix supportgroup, for all you did to keep it going the first 17 years, and for beingthere for me when I need occasional help and/or guidance as I continue tomoderate it. Dennis Tillman W7pF
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Re: Tek 7854 intermittent issues
Hi Paul,
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I think the "official" method is: set the 7B87 for single sweep [and wait until the Ready light is off], then press AQS at the 7854, then activate the 7B87 again by pressing the single sweep Reset button. When I do so at 1024 P/W, then 0.5 ms/div works fine but 0.2 ms/div immediately gives a beep and error, even before I press the Reset button. No busy light and of course no need to stop acquisition. The previously acquired waveform is still displayed. When follow the procedure at 0.5 ms/div, but just before pressing Reset change to 0.2 ms/div, then a waveform is acquired at 0.2 ms/div without error. But the waveform is far from perfect, with dots scattered around it and even with obvious outliers (as in one of Nick's photos). According to my observations these results can also be obtained with the 7B87 in Norm mode, AQS at scope, and playing with trigger level to generate a single sweep. But this is a far less comfortable way since the trigger event is not well defined and switching from 0.5 ms/div to 0.2 ms/div [and faster] often produces a "false" trigger event. Perhaps you can help Nick with his perhaps too hot transistor in the vertical amplifier. My 7854 has an EMI shielding option; the panels are difficult to remove and to install properly, so I had rather not do that. Albert On Wed, Sep 2, 2020 at 04:12 PM, Paul wrote:
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Re: Strange Tek2440 issue
On Wed, Sep 2, 2020 at 2:50 PM Siggi via groups.io <siggi@...>
wrote: On Wed, Sep 2, 2020 at 2:07 PM Vince Vielhaber <vev@...> wrote:As an aside, love the pics of the warm green glow of the CRT :).I had actually done that last nite, but didn't have the parts layout |
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Re: Strange Tek2440 issue
On Wed, Sep 2, 2020 at 2:07 PM Vince Vielhaber <vev@...> wrote:
I had actually done that last nite, but didn't have the parts layout Uh, this makes no sense to me. The base of Q870 should be pulled toward +15V unreg through R864(? hard to read on the schematic), and the two op amps shunt it towards ground when they detect too high voltage or too high current, respectively. Whichever of pins 1/7 is lower is the op-amp in control of the output. ... time passes ... Yeah, still doesn't make sense to me. I'm going to guess that either the op-amps are (pins 1/7 are) reversed on the schematic, or that your channel designations are. Even so, it still doesn't make sense, as the voltage-control op-amp starts dialing more voltage (Channel 2 normal at 5.54V rises to 16.94V), while the current limit op-amp goes on the limit (Channel 1 normal at 16.76V dips to 6.16V). What doesn't make sense here is that the current control op-amp is dialing a voltage that exceeds the voltage control's usual/normal voltage. I haven't done the maths, but as there's a bias on the current limit op-amp's feedback input, it might be that it's simply kicking in because the output voltage has sagged. I think you need to look further afield, how's the +8V rail doing, the +-15V rails, raw and regulated? How is the -5V rail doing? Any other rails you can find... If you can't find a bad rail, start looking at the biasing for Q870 & Q879, have the resistors drifted? If R864(?) or R478 have drifted significantly upward, that'd explain why the transistors can't meet the current demand. If the biasing is OK, you need to look at the transistors themselves. If their gain is down, that'd also explain things. You can measure the base current to Q879 indirectly by the voltage drop over its base resistor. Even looking at what's happening on Q870's emitter under collapse - is that transistor going to saturation, indicating that Q879 is dozing off on the job? Good luck! |
Charlie Conger
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