Guys,
Thanks very much for all of your help and the link to Hakan¡¯s info - I¡¯ll certainly have a look! I managed to do a deal with a US seller for a complete, working board(s), but will repair mine in case others might need it in the future. While looking for a replacement, I noticed that the later versions have a different HT trans former, so will look into this and get back to you all. Once again, many thanks.
--
you can never have enough oscilloscopes, DMMs, valve testers or soldering irons . . .
|
Re: Kludging together a TDR or similar?
Guessing isn't good enough, you need to analyse the circuit and take into account the hysteresis of the 74AC14 Schmitt trigger.
Bruce
toggle quoted message
Show quoted text
On 08 July 2018 at 01:22 n4buq <n4buq@...> wrote:
Because I don't know what else is establishing the frequency (hence "...or is something else at work here?").
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Bruce Griffiths" <bruce.griffiths@...>
To: [email protected]
Sent: Saturday, July 7, 2018 8:15:53 AM
Subject: Re: [TekScopes] Kludging together a TDR or similar?
Why do you think that the frequency is equal to 1/RC?
Bruce
On 08 July 2018 at 01:03 n4buq <n4buq@...> wrote:
Looking at that schematic, it appears the frequency is determined by C3 and
R1. If I'm not mistaken, the exact values of those components would
result in a frequency of 3.129 kHz; however, the oscilloscope images
appear to show 4.81 kHz. Is that difference due to component tolerances
or is something else at work here?
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Michael A. Terrell" <mike.terrell@...>
To: [email protected]
Sent: Friday, July 6, 2018 7:32:15 PM
Subject: Re: [TekScopes] Kludging together a TDR or similar?
You can build a simple TDR with a 74AC14, some resistors and a couple
capacitors.
<>
If that doesn't work, it is from this page:
It is sold on Ebay by <> It was
$15.19
a couple months ago. It isn't available right now. I bought one, to test.
If
I like it I will make a surface mount version of it, and put it into a
small
extruded aluminum box. The box, and the three connectors will be about
80%
of the component costs in a SMD version.
Michael A. Terrell
-----Original Message-----
From: cheater cheater <cheater00@...>
Sent: Jun 29, 2018 3:20 AM
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?
hi guys, thanks for the replies.
I don't have the parts necessary to build a pulser. Can I use the
mainframe's pulse generator?
The cable goes from a local distribution box, part underground, part
overground, and then goes to a wall socket used only by my modem. There
is
no splitting and no neighbors using this. The run in my yard that is
overground is maybe 30m at most.
There was no thunder when this stopped working, just heavy rain.
|
Re: Kludging together a TDR or similar?
Because I don't know what else is establishing the frequency (hence "...or is something else at work here?").
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "Bruce Griffiths" <bruce.griffiths@...>
To: [email protected]
Sent: Saturday, July 7, 2018 8:15:53 AM
Subject: Re: [TekScopes] Kludging together a TDR or similar?
Why do you think that the frequency is equal to 1/RC?
Bruce
On 08 July 2018 at 01:03 n4buq <n4buq@...> wrote:
Looking at that schematic, it appears the frequency is determined by C3 and
R1. If I'm not mistaken, the exact values of those components would
result in a frequency of 3.129 kHz; however, the oscilloscope images
appear to show 4.81 kHz. Is that difference due to component tolerances
or is something else at work here?
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Michael A. Terrell" <mike.terrell@...>
To: [email protected]
Sent: Friday, July 6, 2018 7:32:15 PM
Subject: Re: [TekScopes] Kludging together a TDR or similar?
You can build a simple TDR with a 74AC14, some resistors and a couple
capacitors.
<>
If that doesn't work, it is from this page:
It is sold on Ebay by <> It was
$15.19
a couple months ago. It isn't available right now. I bought one, to test.
If
I like it I will make a surface mount version of it, and put it into a
small
extruded aluminum box. The box, and the three connectors will be about
80%
of the component costs in a SMD version.
Michael A. Terrell
-----Original Message-----
From: cheater cheater <cheater00@...>
Sent: Jun 29, 2018 3:20 AM
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?
hi guys, thanks for the replies.
I don't have the parts necessary to build a pulser. Can I use the
mainframe's pulse generator?
The cable goes from a local distribution box, part underground, part
overground, and then goes to a wall socket used only by my modem. There
is
no splitting and no neighbors using this. The run in my yard that is
overground is maybe 30m at most.
There was no thunder when this stopped working, just heavy rain.
|
Re: Kludging together a TDR or similar?
Why do you think that the frequency is equal to 1/RC?
Bruce
toggle quoted message
Show quoted text
On 08 July 2018 at 01:03 n4buq <n4buq@...> wrote:
Looking at that schematic, it appears the frequency is determined by C3 and R1. If I'm not mistaken, the exact values of those components would result in a frequency of 3.129 kHz; however, the oscilloscope images appear to show 4.81 kHz. Is that difference due to component tolerances or is something else at work here?
Thanks,
Barry - N4BUQ
----- Original Message -----
From: "Michael A. Terrell" <mike.terrell@...>
To: [email protected]
Sent: Friday, July 6, 2018 7:32:15 PM
Subject: Re: [TekScopes] Kludging together a TDR or similar?
You can build a simple TDR with a 74AC14, some resistors and a couple
capacitors.
<>
If that doesn't work, it is from this page:
It is sold on Ebay by <> It was $15.19
a couple months ago. It isn't available right now. I bought one, to test. If
I like it I will make a surface mount version of it, and put it into a small
extruded aluminum box. The box, and the three connectors will be about 80%
of the component costs in a SMD version.
Michael A. Terrell
-----Original Message-----
From: cheater cheater <cheater00@...>
Sent: Jun 29, 2018 3:20 AM
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?
hi guys, thanks for the replies.
I don't have the parts necessary to build a pulser. Can I use the
mainframe's pulse generator?
The cable goes from a local distribution box, part underground, part
overground, and then goes to a wall socket used only by my modem. There is
no splitting and no neighbors using this. The run in my yard that is
overground is maybe 30m at most.
There was no thunder when this stopped working, just heavy rain.
|
Re: Kludging together a TDR or similar?
Looking at that schematic, it appears the frequency is determined by C3 and R1. If I'm not mistaken, the exact values of those components would result in a frequency of 3.129 kHz; however, the oscilloscope images appear to show 4.81 kHz. Is that difference due to component tolerances or is something else at work here?
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "Michael A. Terrell" <mike.terrell@...>
To: [email protected]
Sent: Friday, July 6, 2018 7:32:15 PM
Subject: Re: [TekScopes] Kludging together a TDR or similar?
You can build a simple TDR with a 74AC14, some resistors and a couple
capacitors.
<>
If that doesn't work, it is from this page:
It is sold on Ebay by <> It was $15.19
a couple months ago. It isn't available right now. I bought one, to test. If
I like it I will make a surface mount version of it, and put it into a small
extruded aluminum box. The box, and the three connectors will be about 80%
of the component costs in a SMD version.
Michael A. Terrell
-----Original Message-----
From: cheater cheater <cheater00@...>
Sent: Jun 29, 2018 3:20 AM
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?
hi guys, thanks for the replies.
I don't have the parts necessary to build a pulser. Can I use the
mainframe's pulse generator?
The cable goes from a local distribution box, part underground, part
overground, and then goes to a wall socket used only by my modem. There is
no splitting and no neighbors using this. The run in my yard that is
overground is maybe 30m at most.
There was no thunder when this stopped working, just heavy rain.
|
Re: Questions about TM mainframes with Option 2
Ah kay. Thanks for explaining. So, looking at the pinout in the 5A22 schematics, sure enough, it's totally different from the TM5000's receptacle wiring.
I guess it would be kind of tedious, but it seems like a DIY frame/chassis to house and power these 5Axx plugins could be constructed with the correctly keyed edge connector.
Oh well, thanks for the info! You saved me a lot of trouble. :)
|
On Fri, Jul 6, 2018 at 18:37 Vintage Test via Groups.Io <mel.purcell= [email protected]> wrote: I've just laid my hands on one of these for a decent price, knowing it
didn't work. The owner said it worked one day and jus did tick, tick etc
the next - a familiar story! When I stripped it, I found a load of duff
diodes/transistors and two-way devices in the standby circuit, which I
replaced. I powered it up - still the same, except that the front-panel
LEDs all flashed too now. On a whim, I disconnected everything from the
processor board, and lo and behold -it powered up and worked properly into
a VGA monitor. Now, to the problem; the CRT driver assembly is clearly
faulty, but there's no schematic for it anywhere. I have the manual for
TDS540, which has a lot of similarities, but is monochrome and not colour,
so the CRT driver assembly is way different. Do any of you happen to have
any experience with these 'scopes? I did look for a schematic before I recapped the CRT driver in my TDS784D, but at the time there wasn¡¯t anything around that I could find. Since then, H?kan has made this < (Disp).pdf> available for download. Maybe it¡¯ll help? There may be other relevant docs on his site, he keeps adding stuff over time. People also convert those to LCD screens. There¡¯s the NewScope kit, but you can also just drive an LCD from the VGA output.
|
That link should redirect to:
Michael A. Terrell
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Show quoted text
-----Original Message----- From: ¸é±ð²Ô¨¦±ð <k6fsb.1@...>
service manual is 404 for me as well..broken.
The user reference is fine...link works
¸é±ð²Ô¨¦±ð
On 2018-07-06 11:04 PM, tmillermdems wrote:
The link works fine.
The .pdf manual is here.
|
Re: 2215 avoiding future CRT damage
On Fri, Jul 6, 2018 at 10:35 pm, John Kolb wrote: The hold-off circuit introduces a delay between one sweep cycle and the next.
Thus the longer the delay, the less often the sweeps occur, which affects the
brightness. If the trace is bright with minimum hold-off, you should be in
good shape. Thanks a lot John, in just a couple lines you managed to make it all limpid ! :-) So looks like the Hold-off feature can be used to "select"/pick a particular event in a complex waveform. I now understand why someone advised me to fiddle with hold-off when I was trying to get a clear picture of the switched currents in the inverter of the SMSP of my 2232 scope, which I was fixing. There was a "current sense" resistor which was common to both windings, so I conveniently used it. Of course that meant that I would see the switched current of both windings on the same trace, "interleaved". Without hold-off, the scope would trigger on both windings indistinctly, hence superimposing them on top of each other. Since the two currents did not have exactly the same amplitude, on the screen I would see a "double" waveform, as if the trace was unstable, which it was not then, just the two currents being "stacked" on one another. When I fiddled with hold-off I could get rid of the double waveform and "select" which of the two currents I wanted to see, and have only that one on the screen. Was great ! :-) Sorry for the rambling/thinking out loud, but I like it so much when someone with just a few words can clarify something that's been obscure for so long ! ^^ Thanks :-) Anyway, to get back on topic : looks like my CRT is not worn out, that's a big relief indeed... Vincent Trouilliez
|
service manual is 404 for me as well..broken.
The user reference is fine...link works
¸é±ð²Ô¨¦±ð
toggle quoted message
Show quoted text
On 2018-07-06 11:04 PM, tmillermdems wrote: The link works fine.
The .pdf manual is here.
----- Original Message ----- From: "Pete Lancashire" <xyzzypdx@...>
To: <[email protected]>
Sent: Saturday, July 07, 2018 1:08 AM
Subject: Re: [TekScopes] 114xx bezzel buttons
I must be doing something wrong.? The reference to a service manual comes
up 404 for me. Please let me know what I am doing wrong and what page(s) I
should be looking at.
=pete
On Fri, Jul 6, 2018 at 8:03 PM <jbau@...> wrote:
There's a link to the manuals on the TekWiki site:
|
Re: SC504 Gain Knob Removal
Thanks, Tom, for this reply, the only one I received.
I did loosen the knob set screw and remove the red VAR knob. My replacement skirted knob does have a long shaft that goes through some kind of (cam") switch near the front panel but it seems to have no means obvious to secure it inside the scope.
I did not even think of removing the small diameter plastic shaft to which the red VAR knob is attached. I just now loosened the set screw in the aluminum collar on the pot to which the plastic rod is attached and easily removed the red VAR knob and its shaft. I tugged as much as I thought wise and the skirted knob still did not come out.
The shaft on the replacement knob is long enough to enter the gray plastic collar that protrudes forward from the cam switch. Rotating the skirted knob, I see no screw to secure that knob shaft. I'm still puzzled.
I note the replacement knob has a shallow "V" groove that ends up somewhere inside the other (cam?) switch close to the front panel. Maybe there is some kind of detent spring inside that switch; I can't take that switch apart because I'd need to remove the bottom panel or side beam and I surely don't want to do that.
The red VAR knob and its shaft would hold the skirted knob in well enough but it might rub on the front panel without something to position it. The tolerances make the "V" groove seem unlikely to be what positions the knob. I don't see the thin washer you describe. Tell me again where that is located, please.
What do you mean by "...pried and pulled" to get the knob back out after first putting it back in? Pry? On what?
This seems like a high-risk task! But, that one knob has damaged nomenclature on the skirt and I was able to buy the exact replacement knob on eBay.
The interior of the end of the skirted knob shaft has some details that engage the shaft inside that switch thing near the front panel. That detail will keep the knob clocked but can't hold it in. It may be that shallow "V" groove that holds the knob in.
I surely don't want to damage something inside the cam switch or that other switch near the front panel. And, I really don't want to dribble anything down the skirted knob shaft in hopes of getting to that "V" groove.
I'm feeling kinda stymied...
By the way, I'm a mechanical engineer with a lifetime of small, precision instrumentation design. I'm not intimidated by this problem, just really cautious!
I'm in Anaheim, California, near Disneyland. Good Grief! It was 115.1¡ãF here this afternoon!
Larry
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On 7/6/2018 4:18 PM, tom jobe wrote: Hi Larry,
Your question got me wondering about this, so I took the side cover off of an SC504 to have a look.
The service manual mechanical parts diagram shows the knob has a longer part that goes back into the Channel switch so I looked to see if there was a screw or other fastening device back inside of the scope. I removed the plastic rod that goes through the knob assembly by disconnecting it at the aluminum collar on the VAR switch, and then the knob just fell out for some reason. I put the knob back in and then it would not come out again. So I nervously pried and pulled and got it back out again without damaging it.
A study of the knob shaft showed no locking mechanisms of any kind, so I rubbed a very thin smear of Johnson's paste wax on the knob shaft extension and put it back in. After that the knob slid in and out nicely and the only thing holding the knob in is the 1/8" fiberglass VAR shaft and small VAR knob in the center of the knob in question.
I guess the knob was just stuck from being in there for 30 or 40 years plastic on plastic?
Do be careful about a very thin aluminum washer that is on the knob's rear shaft extension, as it would be very easy to drop that washer into the scope. My guess is that this washer is part of the spacing arrangement that keeps the lettering on the back side of the knob skirt from hitting the front panel and getting damaged, and it also might keep the two plastic parts from rubbing on each other at the knob extension / attenuator surfaces?
tom jobe...
PS I wonder if one drop of water could be put in from the side where the knob shaft extension goes into the attenuator assembly to break it free as you wiggled the knob to spread it around? You would want to be very careful about anything you put in there, as the short and long term effects on the plastic parts could be devastating.
On 7/6/2018 11:30 AM, Larry McDavid wrote:
I have a SC504 scope module with a damaged Channel 1 knob skirt and I have a Tek replacement skirted knob. I can remove the small red central knob by loosening a set screw.
How is the skirted knob removed? I've tried gently pulling on it without success. The knob has a long plastic shaft with some internal ribs to fit over another shaft but I don't know how the knob is attached.
Anyone done this?
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
|
The link works fine.
The .pdf manual is here.
toggle quoted message
Show quoted text
----- Original Message ----- From: "Pete Lancashire" <xyzzypdx@...> To: < [email protected]> Sent: Saturday, July 07, 2018 1:08 AM Subject: Re: [TekScopes] 114xx bezzel buttons I must be doing something wrong. The reference to a service manual comes
up 404 for me. Please let me know what I am doing wrong and what page(s) I
should be looking at.
=pete
On Fri, Jul 6, 2018 at 8:03 PM <jbau@...> wrote:
There's a link to the manuals on the TekWiki site:
|
Re: Owon SDS7102 Deep Memory Digital Storage Oscilloscope
Michael A. Terrell
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Show quoted text
-----Original Message----- From: Harvey White <madyn@...>
Sent: Jul 7, 2018 1:18 AM
To: [email protected]
Subject: Re: [TekScopes] Owon SDS7102 Deep Memory Digital Storage Oscilloscope
On Sat, 7 Jul 2018 00:04:05 -0400 (GMT-04:00), you wrote:
Harlan Ellison always came across as too self important. I saw him interviewed a few times, and he always came across as an ass. He loved the line, "I don't owe my readers anything!" And he often delivered. And often, he didn't. I read a few of his works, and never picked up anything else. Different tastes for different people. :)
Have you ever read Venus Equilateral? It is about a system wide communications system, and it was written by George O. Smith. It was written in the early 1940s, and for its time the science wasn't too bad.
Got several copies, including "the complete venus equilateral" which
had a story or so not in the hardback.
That is what I posted a link for. You might also want to find a copy of "Lost in Space" by George O.
Smith as well, somewhat technological, but from a different viewpoint.
One of the few (classic) authors who was an electrical engineer, IIRC
and showed it, and allowed the story to be about technology as well.
Completely missed computers, as did Smith (until about the mid 50's). Computers were analog when he wrote the stories that became 'The Complete Venus Equilateral', so that is understandable. What use would most people ever have for an analog computer, outside of a lab, or a battlefield? Know about Skylark of Valeron, but that was a recreation of a brain,
not really a computer). Unlike Doc Smith, who was a chemist (hence
the Skylark series). Also his Lensmen series and other books. and I think we've blown the thread out of the water.... You're right, but those old stories lead a lot of us into electronics. I got into repairing test equipment as a kid, because TV shops had piles of junk. They were afraid to work on it, so they would give it away. A lot was from companies that no longer existed, so a tube data book and a VTVM taught me to repair things without a manual while I was still in high school. This was at a time when it was rare not to have a factory manual or a Photofact for the chassis on your bench. My first scope had a shorted power transformer, but a Stancor filament transformer with a good HV isolation allowed me to get it going. Others had bad resistors in the focus string, and other problems that made it much easier for me to repair the first Tektronix scopes that crossed my bench. That, plus an old TV tech that taught me to troubleshoot logically allowed me to repair a lot of equipment that others had given up on. Always verify the power supply. Then keep splitting a problem in half until you isolate the problem. That takes it from hours, to minutes in many cases. The important thing is that there were many influences to enter the field. Harvey
I had built a radio three years earlier, but I didn't start working in electronics for another two years.
Here is a link to the Venus Equilateral story in RTF:
<>
Michael A. Terrell
|
Re: 2215 avoiding future CRT damage
On 7/6/2018 12:25 PM, Vincent Trouilliez wrote: Plus, if I turn the var hold-off to the min, brightness comes back to normal, the trace becomes perfectly visible, no effort needed whatsoever.
I will admit I don't really master the var hold-off feature, I am not sure I get why it impacts the brightness level.. but obviously it does. Will need to do some reading and experimenting ! ^^ The hold-off circuit introduces a delay between one sweep cycle and the next. Thus the longer the delay, the less often the sweeps occur, which affects the brightness. If the trace is bright with minimum hold-off, you should be in good shape. If the trace goes dim with just a little hold-off, particularly at slow sweep rates, there may be a problem in the hold-off circuit. John
|
Re: Owon SDS7102 Deep Memory Digital Storage Oscilloscope
On Sat, 7 Jul 2018 00:04:05 -0400 (GMT-04:00), you wrote: Harlan Ellison always came across as too self important. I saw him interviewed a few times, and he always came across as an ass. He loved the line, "I don't owe my readers anything!" and he often delivered.
Have you ever read Venus Equilateral? It is about a system wide communications system, and it was written by George O. Smith. It was written in the early 1940s, and for its time the science wasn't too bad.
Got several copies, including "the complete venus equilateral" which had a story or so not in the hardback. You might also want to find a copy of "Lost in Space" by George O. Smith as well, somewhat technological, but from a different viewpoint. One of the few (classic) authors who was an electrical engineer, IIRC and showed it, and allowed the story to be about technology as well. Completely missed computers, as did Smith (until about the mid 50's). Know about Skylark of Valeron, but that was a recreation of a brain, not really a computer). Unlike Doc Smith, who was a chemist (hence the Skylark series). and I think we've blown the thread out of the water.... Harvey
I had built a radio three years earlier, but I didn't start working in electronics for another two years.
Here is a link to the Venus Equilateral story in RTF:
<>
Michael A. Terrell
|
I must be doing something wrong. The reference to a service manual comes
up 404 for me. Please let me know what I am doing wrong and what page(s) I
should be looking at.
=pete
toggle quoted message
Show quoted text
On Fri, Jul 6, 2018 at 8:03 PM <jbau@...> wrote: There's a link to the manuals on the TekWiki site:
|
Re: Owon SDS7102 Deep Memory Digital Storage Oscilloscope
Vince, If you like YouTube, try D Lab Electronics, Uncle Doug, Mr Carlson's Lab, El Paso Tube Amps and many other Tube amp related contributors. There is a wealth of good info on tube amp testing and repair plus allot of bad practice too, so stick with the guys with the best reviews. And this Tek scopes site is a tribute to what is good about the internet. I just joined and have been coached and helped way beyond what I expected by members who are light years beyond my understanding of scopes and their repair. You joined a good group. Good luck, Russ On Friday, July 6, 2018, Michael A. Terrell <mike.terrell@...> wrote: Harlan Ellison always came across as too self important. I saw him
interviewed a few times, and he always came across as an ass. He loved the
line, "I don't owe my readers anything!"
Have you ever read Venus Equilateral? It is about a system wide
communications system, and it was written by George O. Smith. It was
written in the early 1940s, and for its time the science wasn't too bad.
I had built a radio three years earlier, but I didn't start working in
electronics for another two years.
Here is a link to the Venus Equilateral story in RTF:
<
RivDsUhk3QOwDfDoEccZSVc_N?usp=sharing>
Michael A. Terrell
--
-----Original Message-----
From: Harvey White <madyn@...>
Sent: Jul 6, 2018 11:45 PM
To: [email protected]
Subject: Re: [TekScopes] Owon SDS7102 Deep Memory Digital Storage Oscilloscope
On Fri, 6 Jul 2018 20:38:09 -0400 (GMT-04:00), you wrote:
That was 'The Outer Limits' and it ran all day on the 4th of July on Me
TV. How many of you got into electronics after watching the 'Galaxy Being'
episode? I know several AM radio engineers who claim that's what got them
interested in Broadcast Engineering. :)
Already was in electronics by that time. Also consider "Demon with a
Glass Hand" which was one of the few things by Harlan Ellison that I
can like.
oh, and also "Behold, Eck!"
-- Good judgement comes from experience; experience comes from bad judgement. 99 times out of 10 a blown fuse is not due to a bad fuse.....
|
Re: Owon SDS7102 Deep Memory Digital Storage Oscilloscope
Harlan Ellison always came across as too self important. I saw him interviewed a few times, and he always came across as an ass. He loved the line, "I don't owe my readers anything!"
Have you ever read Venus Equilateral? It is about a system wide communications system, and it was written by George O. Smith. It was written in the early 1940s, and for its time the science wasn't too bad.
I had built a radio three years earlier, but I didn't start working in electronics for another two years.
Here is a link to the Venus Equilateral story in RTF:
<>
Michael A. Terrell
--
toggle quoted message
Show quoted text
-----Original Message----- From: Harvey White <madyn@...>
Sent: Jul 6, 2018 11:45 PM
To: [email protected]
Subject: Re: [TekScopes] Owon SDS7102 Deep Memory Digital Storage Oscilloscope
On Fri, 6 Jul 2018 20:38:09 -0400 (GMT-04:00), you wrote:
That was 'The Outer Limits' and it ran all day on the 4th of July on Me TV. How many of you got into electronics after watching the 'Galaxy Being' episode? I know several AM radio engineers who claim that's what got them interested in Broadcast Engineering. :) Already was in electronics by that time. Also consider "Demon with a
Glass Hand" which was one of the few things by Harlan Ellison that I
can like.
oh, and also "Behold, Eck!"
|
I've had a couple of TDS7x4 scopes with issues on that board. Below are some notes that I wrote up once for the group. Also I have a schematic that I got somewhere for a TDS544 HV board, and I was able to use that to troubleshoot the '754. As I remember, the ref designators were the same, but the board layout was slightly different. I put that schematic in a new folder called "TDS544_HV".
I also think I have a HV board from a TDS744 (that is bad) for parts: let me know if you want it. I think this board was DOA in a scope that was badly busted up and I didn't try to repair it - i was able to get a working board so I just replaced it.
Here are my old notes:
TDS754C arrived with dim screen and also the screen was too large in both dimensions. It was wrapping slightly around the edges of the tube.
I could adjust the brightness using the trimmers on the left side of the high voltage power board (these trimmers are available with the outside cover removed, just in front of the fan).
But even with the brightness back up, the screen still overlapped. The brightness adjustment didn't affect the screen overlap either.
There is a 75V and -75V rail on the high voltage board that is derived from the same flyback as the high voltage. +75V is available at J60, a wire leaving the PCB, just in back of the CRT socket.
On my board, the 75V rail measured 67.9V, or about 10% low.
Turning the HV adjustment (R58, on the right side of the board near the edge) had no effect at all.
I have another HV board from a TDS744, and ohming around U45 (the PWM generator that controls the HV) didn't help - it looked the same as the old board.
However, U45 was indeed bad. Replacing that IC (MC34060P) brought the 75V rail up to 76V (and I adjusted it down to 75V). The screen is much brighter (I turned the brightness back down), and the screen size is normal.
Here is a summary of the controls on the HV board, for future reference (note that your board may be different so no guarantees here):
HV adjust: R58
Horiz Size: R172
Horiz Position:
Vertical Size: R270
+21V adjust: R186
Vertical Position: R402 (available next to the fan)
Contrast: R404 (next to the fan)
Brightness: R403 (next to fan)
Contrast: R404 (next to fan)
Trace rotation: R401 (next to fan)
Hopefully that will help someone in the future.
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Re: Kludging together a TDR or similar?
I have to see if the old PCB design software I have still works. I'll probably make a sample run of ten, to see how they turn out. I am looking into a CNC controlled engraver to mark the extruded boxes. Engrave the information, then fill it with a white paint pencil.
The extrusions are 25mmx25mm in several lengths. I've found large flange BNC connectors that will replace the end caps, with a male on one end and a female on the other. The coaxial power connector will be on the side. This size should make it usable on the input of almost any scope, and I'm going to try it with one of the cheap DSP based single channel scope kits. It might fit into a case, with the TDR.
Here are the connectors and the one size of boxes:
Michael A. Terrell
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-----Original Message----- From: Dave Brown <2c39a@...>
Sent: Jul 6, 2018 11:32 PM
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?
I threw one of these together a year or so ago- photo of internals here-
It works very well- considering how simple it is.
But an SMD version would be nice......
DaveB, NZ
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Michael A. Terrell
Sent: Saturday, July 07, 2018 12:32
To: [email protected]
Subject: Re: [TekScopes] Kludging together a TDR or similar?
You can build a simple TDR with a 74AC14, some resistors and a couple capacitors.
<>
If that doesn't work, it is from this page:
It is sold on Ebay by <> It was $15.19 a couple months ago. It isn't available right now. I bought one, to test. If I like it I will make a surface mount version of it, and put it into a small extruded aluminum box. The box, and the three connectors will be about 80% of the component costs in a SMD version.
Michael A. Terrell
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Michael A. Terrell
Vince