Re: OT: Electronics humor: Murphy's Electronics Laws
Not the first time I've seen this or similar, but it still brings a smile to my lips.
I too am currently battling with a piece of equipment with the builtin guarantee that the parts that are OK are all readily obtainable, and the parts that are suspect are all obsolete and a) Rare and very expensive, or b) are nowhere to be found and all substitutes are in category a), or c) total unobtanium custom parts, with not even a datasheet to be found :(
PS to all readers, I for one would much appreciate it if you could set your mail client to send "plain text" rather than RTF or HTML when sending to the list. Thank you.
Dave
________________________________
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Craig Sawyers
Sent: 21 September 2012 11:13
To: TekScopes@...
Subject: RE: [TekScopes] OT: Electronics humor: Murphy's Electronics Laws
Ha ha! I've forwarded that to a few colleagues. I'm the current victim of the fast acting fuse, the fail safe, coupled with obsolete components, BTW. All in the same unit. The fail safe even self destroyed.
Craig
|
Re: Calibration Fixture question
On 09/21/2012 06:20 AM, David C. Partridge wrote: Or just give up on originality and replace it with an SMB which is a) a better connector, b) much more readily available.
Regards,
David Partridge
-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Craig Sawyers
Sent: 21 September 2012 11:07
To: TekScopes@...
Subject: RE: [TekScopes] Calibration Fixture question
Quick question though - what kind of a connector is the Trig Out?
Looks
like a
mini BNC.
It is called a BSM (Bayonet Sub Miniature). Very rarely used, but present on a number of 7xxx series plugins like the 7T11.
You can sometimes pick up BSM-BNC adaptors on eBay.
Craig
Thanks all! Really appreciate the info. Mark
|
Re: Calibration Fixture question
Or just give up on originality and replace it with an SMB which is a) a better connector, b) much more readily available.
Regards,
David Partridge
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-----Original Message----- From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Craig Sawyers Sent: 21 September 2012 11:07 To: TekScopes@... Subject: RE: [TekScopes] Calibration Fixture question Quick question though - what kind of a connector is the Trig Out?
Looks like a mini BNC. It is called a BSM (Bayonet Sub Miniature). Very rarely used, but present on a number of 7xxx series plugins like the 7T11. You can sometimes pick up BSM-BNC adaptors on eBay. Craig ------------------------------------ Yahoo! Groups Links
|
Re: Calibration Fixture question
Like this one 350545458097
but hopefully a little cheaper.
Albert
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---
You can sometimes pick up BSM-BNC adaptors on eBay.
Craig
|
Re: OT: Electronics humor: Murphy's Electronics Laws
Ha ha!? I¡¯ve forwarded that to a few colleagues.? I¡¯m the current victim of the fast acting fuse, the fail safe, coupled with obsolete components, BTW.? All in the same unit.? The fail safe even self destroyed. ? Craig ?
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From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Mark Wendt
Sent: 21 September 2012 10:54
To: Tek O'scopes
Subject: [TekScopes] OT: Electronics humor: Murphy's Electronics Laws?
- The circuit designed to protect the unit from catastrophic failure won't.
- The circuit designed to be highly reliable isn't.
- Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable and three parts which are still under development.
- If x is the amount of time you wait to touch a hot vacuum tube, the time for the tube to be cool enough to touch is greater than x.
- ?
- An expert is one who knows more and more about less and less until he knows absolutely everything about nothing.
- A complex system that works has invariably found to have evolved from a simple system that works.
- Logic is a systematic method of coming to the wrong conclusion with confidence.
- Any component removed, tested, and found good has a extraordinarily high chance of breaking in the re-installation process.
- Build a system that even a fool can use and only a fool will want to use it.
- Always draw your curves, then plot your readings.
- Do not believe in miracles - rely on them.
- Firmness of delivery dates is inversely proportional to the tightness of schedule.
- Dimensions will always be expressed in the least usable term. For example, the velocity will be expressed in furlongs per fortnight.
- Any wire cut to length will be too short.
- Tolerances will be accumulated unidirectionally toward maximum difficulty to assemble.
- A fail-safe circuit will destroy others.
- A transistor protected by a fast-acting fuse will protect the fuse by blowing first.
- Only after completely disassembling the unit will you realize the reason it wasn't working was because it wasn't plugged in.
- Any error in calculation will be in the direction of most harm.
- In specifications, Murphy's Law supersedes Ohm's Law.
- If a safety factor is set through service experience at an ultimate value, an ingenious idiot will promptly calculate a method to exceed the safety factor.
- Given any problems containing 'n' equations, there will always be 'n+1' unknowns.
- Any sufficiently advanced technology is indistinguishable from magic.
- If the number of screws which must be removed when disassembling a given piece of electronic device is represented by x, the the number of screws used when reassembling it will be some number less than x.
|
Re: Calibration Fixture question
Quick question though - what kind of a connector is the Trig Out? Looks like a mini BNC. It is called a BSM (Bayonet Sub Miniature). Very rarely used, but present on a number of 7xxx series plugins like the 7T11. You can sometimes pick up BSM-BNC adaptors on eBay. Craig
|
OT: Electronics humor: Murphy's Electronics Laws
- The circuit designed to protect the unit from catastrophic
failure won't.
- The circuit designed to be highly reliable isn't.
- Any circuit design must contain at least one part which is
obsolete, two parts which are unobtainable and three parts which are
still under development.
- If x is the amount of time you wait to touch a hot vacuum
tube, the time for the tube to be cool enough to touch is greater than x.
- An expert is one who knows more and more about less and less
until he knows absolutely everything about nothing.
- A complex system that works has invariably found to have evolved
from a simple system that works.
- Logic is a systematic method of coming to the wrong conclusion
with confidence.
- Any component removed, tested, and found good has a
extraordinarily high chance of breaking in the re-installation process.
- Build a system that even a fool can use and only a fool will want
to use it.
- Always draw your curves, then plot your readings.
- Do not believe in miracles - rely on them.
- Firmness of delivery dates is inversely proportional to the
tightness of schedule.
- Dimensions will always be expressed in the least usable term. For
example, the velocity will be expressed in furlongs per fortnight.
- Any wire cut to length will be too short.
- Tolerances will be accumulated unidirectionally toward maximum
difficulty to assemble.
- A fail-safe circuit will destroy others.
- A transistor protected by a fast-acting fuse will protect the
fuse by blowing first.
- Only after completely disassembling the unit will you realize the
reason it wasn't working was because it wasn't plugged in.
- Any error in calculation will be in the direction of most harm.
- In specifications, Murphy's Law supersedes Ohm's Law.
- If a safety factor is set through service experience at an
ultimate value, an ingenious idiot will promptly calculate a method to
exceed the safety factor.
- Given any problems containing 'n' equations, there will always be
'n+1' unknowns.
- Any sufficiently advanced technology is indistinguishable from
magic.
- If the number of screws which must be removed when disassembling
a given piece of electronic device is represented by x, the the
number of screws used when reassembling it will be some number less
than x.
|
Calibration Fixture question
Picked up a 067-0587-01 Calibration Fixture recently. Been playing around with it and making sure everything works on it before I put it into real use.
Quick question though - what kind of a connector is the Trig Out? Looks like a mini BNC.
Thanks,
Mark
|
Re: 2247A Channel 1 issue
The 4051 CMOS multiplexor is one of those very common "jelly bean" ICs with many alternate sources and even improved versions. On Fri, 21 Sep 2012 01:51:39 -0000, "lldskjfoi" <k.templin@...> wrote: I think so too.
I have a "parts" 2246 that has the same chip.
I will swap out. It will be next week before I can get into the A10's.
I will let you know.
Thanks for help, KT
--- In TekScopes@..., "jtjewell83" <jtjewell83@...> wrote:
KT,
I money is on U506 has a bad input at pin 15. Lots of current's flowing into it, but it shouldn't be. Probably got zapped with a big dose of static electricity at the ring.
Jimmy
--- In TekScopes@..., "lldskjfoi" <k.templin@> wrote:
I have 2.5 at both ends of R106.
1.9 and 1 at R105.
--- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
What is the voltages on either side of R105 and R106?
It seems like C111 and U506 are the only possibilities if the voltage leaving R105 more or less agrees with what you see arriving at U506 pin 15.
tom jobe...
----- Original Message -----
From: lldskjfoi
To: TekScopes@...
Sent: Thursday, September 20, 2012 6:04 PM
Subject: [TekScopes] Re: 2247A Channel 1 issue
10k and 10k. What do you thin? the only thing left are the caps or the U506 itself.
KT
--- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
>
> What are the resistance readings across R105 and R106?
> That might help narrow the search down.
> tom jobe...
>
>
>
> ----- Original Message -----
> From: lldskjfoi
> To: TekScopes@...
> Sent: Thursday, September 20, 2012 5:19 PM
> Subject: [TekScopes] Re: 2247A Channel 1 issue
>
>
>
>
> I get 8.2 and 8.2 as well.
>
> KT
> --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> >
> > I just checked R101 and R102 on a bare 2246 mainboard and they both measured 8.2k ohms in circuit.
> > If the resistance is correct on your scope, then something is drawing enough current to drop 0.7 volts across R101.
> > Nothing in that simple circuit looks like a suspect to me, no nasty 10uF to 47uF tantalums, etc.
> > tom jobe...
> >
> >
> >
> > ----- Original Message -----
> > From: lldskjfoi
> > To: TekScopes@...
> > Sent: Thursday, September 20, 2012 1:20 PM
> > Subject: [TekScopes] Re: 2247A Channel 1 issue
> >
> >
> >
> >
> > Thanks again for the responce. I think we are getting there.
> >
> > Using cahannel 2 as the "working reference"
> >
> > pin 12 (channel 2) on u506 goes from the +2.5 to +1.4 when a 10x probe is connected.
> >
> > pin (15 channel 1) on U506 goes from +.9 to +.6 with the probe connected.
> >
> > Checking R102 for channel 2 it has +2.5
> >
> > R101, (channel 1), shows +2.5 in but only +1.8 out.
> >
> > What are your thoughts? Is it simply a bad resistor or would one of the cap, C111 cause the voltage drop?
> >
> > Thanks again, KT
> > --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> > >
> > > For the record, I slid the cover back on a very dead 2246 and checked pin 12 and pin 15 of U506, they both had +2.49 volts with no probes attached.
> > > This scope does not have any lights on the front, and none of the buttons work, so I could not see the reading I would get at ground, or with a 1X or a 10X probe.
> > > tom jobe...
> > >
> > >
> > >
> > >
> > >
> > > ----- Original Message -----
> > > From: lldskjfoi
> > > To: TekScopes@...
> > > Sent: Thursday, September 20, 2012 8:28 AM
> > > Subject: [TekScopes] Re: 2247A Channel 1 issue
> > >
> > >
> > >
> > > Thanks, thanks the info I was looking for. I started getting into the schematic last night I saw the path to U506. Will start checking it out.
> > >
> > > Also notice just letting the scope run with the probe attached the attenuation factor jumps back and forth- correct / incorrect. Does not change with no probe attached so it is getting an intermitant signal.
> > >
> > > KT
> > >
> > > --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> > > >
> > > > Maybe start by looking at the #1 "Vertical Inputs" schematic to see the simple circuit which starts at the junction of R101, C101 and R105 for channel 1.
> > > > That junction point is connected to the readout ring behind the BNC connector, so you could test for continuity and shorting to ground, etc.
> > > > If you compared both ends of R101 and R105 (Chan 1) with those of R102 and R106 (Chan 2) you might see if the readout voltage is getting that far.
> > > > If that looked okay, you could go to U506 and see if it arrives at pins 12 and 15 as you would expect.
> > > > With the scope on its back, you have excellent access to all of these resistors and U506 (16 pin DIP), with the blue outer cover slid back the width of your hand.
> > > > From reading the service manual, it appears that the readout signal gets changed to a digital signal at U506, but is a simple voltage up to U506.
> > > > tom jobe...
> > > >
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: lldskjfoi
> > > > To: TekScopes@...
> > > > Sent: Wednesday, September 19, 2012 9:08 PM
> > > > Subject: [TekScopes] Re: 2247A Channel 1 issue
> > > >
> > > >
> > > >
> > > > Some more checking shows channel 1 is not getting the code signal from the probe. Any idea on this circuit?
> > > >
> > > > KT
> > > >
> > > > --- In TekScopes@..., "lldskjfoi" <k.templin@> wrote:
> > > > >
> > > > > Hello everyone.
> > > > >
> > > > > Initial test show an issue with channel 1.
> > > > >
> > > > > Any direction on where to start?
> > > > >
> > > > > Channel 2 displays inputs correctly from the FG.
> > > > >
> > > > > Channel 1 displays 10 times the amplitude for the same signal.
> > > > >
> > > > > Example a 1 volt sine wave on channel 2 displays on the voltmeter function correctly at ~1v and 2 divisions at .5v / div.
> > > > >
> > > > > The same signal on channel one reads as ~10v. When set to 5v / div it fills two div.
> > > > >
> > > > > Thanks, KT
> > > > >
> > > >
> > >
> >
>
|
Can you display the left plugin using a 5D10?
My friend acquired a 5D10, a dual differential plugin and a 5116 mainframe a few years back. They hadn't been working very well so I'm cleaning them up for him and verifying that they work correctly.
I can't for the life of me get ANY left plugin to display on screen. The right (built in) ones work well with readout and full range of adjustment. I can trigger from the left plugin but it just won't show up on screen.
Is there something I'm missing? I'd thought the strength of the 5D10 was the ability to digitize and analyze data from the nice array of differential plugins available for the 5K series. It's starting to look like that's hearsay, not reality.
I guess the other possibility is that the leftmost slot of his mainframe is bad. I guess I'll have to plug the 5D10 into another mainframe!
I just looked at the 5116/5d10 datasheet I found on the internet and sure enough, it says it should not only display left and right channels but they should be color coded. That seals it, something is wrong with my friend's 5116. Bummer. It's a neat scope.
Anyone have experience with either?
Jamie
|
Re: Have you seen arcing around vertical output transistors?
I was thinking the same thing. I've seen much higher voltage circuits arc and once an arc starts it's tough to get rid of it. Of course this is only 100 volts, like you said. Very strange I'm thinking I'll de-solder them, clean the transistors and boards thoroughly and reinstall them, perhaps with some teflon sleeves on the leads. There are signs of arcing- brown on the board, etc. Maybe the carbon is letting the arc start.
I've seen some military amplifier boards that use high voltage caps in the output amp. Some of them have a brown plastic widget on the leads of the to5 and to39 case transistors. I had always thought it was just a spacer or something to protect them from impact but I wonder if it's also there to serve as an insulator.
The to-39 outputs are 2n3440 equiv- easy to come by and rather inexpensive. If I have to I'll just buy new ones and see if it helps.
I've never worked on an analog storage scope before. It should be fun to try to get it working again. I haven't even checked the voltages yet.
Jamie
toggle quoted message
Show quoted text
--- In TekScopes@..., David <davidwhess@...> wrote:
I have seen this happen sometimes around TV and monitor horizontal
output transistors and snubber networks. It seems to start off with
corona discharge until enough damage or metal migration occurs across
the surface of an insulator then it shorts out.
The vertical output transistors in the 5111A sustain less than 200
volts though which I would not expect to cause problems.
On Fri, 21 Sep 2012 03:44:54 -0000, "Jamie" <jamietyson@...>
wrote:
I was wrong, they're to-39 parts.
Still- I think it's interesting how they're arcing at the base of the pins. I also see an occasional arc in the storage circuitry as well. I wonder if this is why tek went to a to220 part on later scopes?
Jamie
--- In TekScopes@..., "Jamie" <jamietyson@> wrote:
I bought a 5111 on ebay for cheap and it mostly works but while working on it I noticed arcing around both vertical output transistors. I thought no big deal, probably just cold solder joints from heat cycling, right?
It would appear that the arcing is where the legs of the component enter the transistor. Has anyone seen this before?
It sure would explain the trace randomly jumping around on the screen a bit!
Jamie
|
Re: Have you seen arcing around vertical output transistors?
I have seen this happen sometimes around TV and monitor horizontal output transistors and snubber networks. It seems to start off with corona discharge until enough damage or metal migration occurs across the surface of an insulator then it shorts out. The vertical output transistors in the 5111A sustain less than 200 volts though which I would not expect to cause problems. On Fri, 21 Sep 2012 03:44:54 -0000, "Jamie" <jamietyson@...> wrote: I was wrong, they're to-39 parts.
Still- I think it's interesting how they're arcing at the base of the pins. I also see an occasional arc in the storage circuitry as well. I wonder if this is why tek went to a to220 part on later scopes?
Jamie
--- In TekScopes@..., "Jamie" <jamietyson@...> wrote:
I bought a 5111 on ebay for cheap and it mostly works but while working on it I noticed arcing around both vertical output transistors. I thought no big deal, probably just cold solder joints from heat cycling, right?
It would appear that the arcing is where the legs of the component enter the transistor. Has anyone seen this before?
It sure would explain the trace randomly jumping around on the screen a bit!
Jamie
|
Re: Have you seen arcing around vertical output transistors?
Are you sure it's not just dirty? There's not a real high voltage around
there, maybe a 100 volts or less.
Disclaimer: I did not look at the manual.
?
?
Regards,
t
?
?
?
toggle quoted message
Show quoted text
----- Original Message -----
Sent: Thursday, September 20, 2012 11:44
PM
Subject: [TekScopes] Re: Have you seen
arcing around vertical output transistors?
?
I was wrong, they're to-39 parts.
Still- I think it's interesting
how they're arcing at the base of the pins. I also see an occasional arc in
the storage circuitry as well. I wonder if this is why tek went to a to220
part on later scopes?
Jamie
--- In TekScopes@..., "Jamie"
wrote:
>
> I bought a 5111 on ebay for
cheap and it mostly works but while working on it I noticed arcing around both
vertical output transistors. I thought no big deal, probably just cold solder
joints from heat cycling, right?
>
> It would appear that the
arcing is where the legs of the component enter the transistor. Has anyone
seen this before?
>
> It sure would explain the trace randomly
jumping around on the screen a bit!
>
>
Jamie
>
|
Re: Another 2465B scope recovery operation
Victor, Thank you for the recommendation. I have it downloaded. I'm waiting for a time to finish the troubleshooting on this but I'll post back as soon as I have results.
toggle quoted message
Show quoted text
--- In TekScopes@..., "victor_j_silva" <daejon1@...> wrote:
Get the 2465B Service Manualfrom the Tektronix site. It has the revised documentation for the SM A5 Assembly.
--Victor
|
Re: Have you seen arcing around vertical output transistors?
I was wrong, they're to-39 parts.
Still- I think it's interesting how they're arcing at the base of the pins. I also see an occasional arc in the storage circuitry as well. I wonder if this is why tek went to a to220 part on later scopes?
Jamie
toggle quoted message
Show quoted text
--- In TekScopes@..., "Jamie" <jamietyson@...> wrote:
I bought a 5111 on ebay for cheap and it mostly works but while working on it I noticed arcing around both vertical output transistors. I thought no big deal, probably just cold solder joints from heat cycling, right?
It would appear that the arcing is where the legs of the component enter the transistor. Has anyone seen this before?
It sure would explain the trace randomly jumping around on the screen a bit!
Jamie
|
Re: Which Torx Size must I buy to refurberish someTM5000 Series Relais
Greetings,
I'm not exactly sure of the torx size you need.
However you might wish to consider this little set available from Amazon.
I have this set and it has a nice selection of small drivers including small torx.
For what its worth.
Regards,
Ken
On 20Sep, 2012, at 7:43 AM, Egge Siert wrote:
?
Hi to All,
Which Torx Size must I buy to put into the very very small Torx Screws, used for the fixation of the 148-0128-03 Relais in e.g. a FG5010? Thank you in advance.
Greetings,
Egge Siert
|
Re: Help I got a Tracking Generator for my Tek 2710 but how do I install it?
Hi Robert -
The TG mounts in the cavity on the left side of the analyzer. This also is the same cavity which houses the Variable Resolution BW board. You can only use one or the other, not both. It wasn't clear whether you have the VR BW board or not.
There are two semi-rigid cables that will need to be made. One routes the RF to the front panel and has an SMA on one end and a Type N on the other. The other routes the 2nd LO (2 GHz) to the TG. Did you receive these cables? The ribbon cable will plug into the main power supply board to provide the interface. in fact, I just remembered that one end of the ribbon cable is crimped to a IDC connector that is *soldered* to the power supply board. The other end uses at typical IDC connector that will plug into the TG. The 2712 (not 2710) service manual has a block diagram that will aide in making the necessary connections. This manual is down loadable from the Tek.com site and will be a better reference for what you are wanting to do. You will have some work to do to get your TG up and running. Take your time and it will go smoothly.
Good luck.
Jim
WB5KYE
toggle quoted message
Show quoted text
--- In TekScopes@..., "dreadlk" <dreadlk@...> wrote:
I posted about a month ago about searching for an internal tracking generator for my 2710 SA and I finally found one from an old Tektronix dealer.
Now I have this unit with Id No 119-3889-07 it's in a golden colored all metal case with 3 female SMA connectors and a 10 pin 2 row IDC connector.
Luckily I found several old Mobo serial connectors that are the right size but only use 9 of the 10 pins so I removed the wire and made a 10 wire straight pin to pin cable from the connector ends.
Now I open up my 2710 to locate grounds and power pins on this IDC connector and have a WTF moment. Where the Heck does this thing go!! I remember a side section that was free but the unit won't fit and all the card slots are used up! Plus its just too big, so I have no clue how this fits into a 2710.
I can find nothing on the net about this Option 04 tracking generator, it's not even listed in the 2710 service manual but I have seen several 2710 sold with Tracking Gens built in and the guy who sold it to me told me it works with the 2710 Arggggh....
Anybody have any idea what I should do next? I can't even locate the 10 pin connector that it supposed to plug into much less fit the unit into my 2710. Man I hope I did not waste all that money, I am having serious regrets now. Sorry if this comes of as a Crazy Rant but I should have done my homework before making this purchase, I am upset with myself.
Robert
KD8MJR
|
Re: 2247A Channel 1 issue
I think so too.
I have a "parts" 2246 that has the same chip.
I will swap out. It will be next week before I can get into the A10's.
I will let you know.
Thanks for help, KT
toggle quoted message
Show quoted text
--- In TekScopes@..., "jtjewell83" <jtjewell83@...> wrote:
KT,
I money is on U506 has a bad input at pin 15. Lots of current's flowing into it, but it shouldn't be. Probably got zapped with a big dose of static electricity at the ring.
Jimmy
--- In TekScopes@..., "lldskjfoi" <k.templin@> wrote:
I have 2.5 at both ends of R106.
1.9 and 1 at R105.
--- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
What is the voltages on either side of R105 and R106?
It seems like C111 and U506 are the only possibilities if the voltage leaving R105 more or less agrees with what you see arriving at U506 pin 15.
tom jobe...
----- Original Message -----
From: lldskjfoi
To: TekScopes@...
Sent: Thursday, September 20, 2012 6:04 PM
Subject: [TekScopes] Re: 2247A Channel 1 issue
10k and 10k. What do you thin? the only thing left are the caps or the U506 itself.
KT
--- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
>
> What are the resistance readings across R105 and R106?
> That might help narrow the search down.
> tom jobe...
>
>
>
> ----- Original Message -----
> From: lldskjfoi
> To: TekScopes@...
> Sent: Thursday, September 20, 2012 5:19 PM
> Subject: [TekScopes] Re: 2247A Channel 1 issue
>
>
>
>
> I get 8.2 and 8.2 as well.
>
> KT
> --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> >
> > I just checked R101 and R102 on a bare 2246 mainboard and they both measured 8.2k ohms in circuit.
> > If the resistance is correct on your scope, then something is drawing enough current to drop 0.7 volts across R101.
> > Nothing in that simple circuit looks like a suspect to me, no nasty 10uF to 47uF tantalums, etc.
> > tom jobe...
> >
> >
> >
> > ----- Original Message -----
> > From: lldskjfoi
> > To: TekScopes@...
> > Sent: Thursday, September 20, 2012 1:20 PM
> > Subject: [TekScopes] Re: 2247A Channel 1 issue
> >
> >
> >
> >
> > Thanks again for the responce. I think we are getting there.
> >
> > Using cahannel 2 as the "working reference"
> >
> > pin 12 (channel 2) on u506 goes from the +2.5 to +1.4 when a 10x probe is connected.
> >
> > pin (15 channel 1) on U506 goes from +.9 to +.6 with the probe connected.
> >
> > Checking R102 for channel 2 it has +2.5
> >
> > R101, (channel 1), shows +2.5 in but only +1.8 out.
> >
> > What are your thoughts? Is it simply a bad resistor or would one of the cap, C111 cause the voltage drop?
> >
> > Thanks again, KT
> > --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> > >
> > > For the record, I slid the cover back on a very dead 2246 and checked pin 12 and pin 15 of U506, they both had +2.49 volts with no probes attached.
> > > This scope does not have any lights on the front, and none of the buttons work, so I could not see the reading I would get at ground, or with a 1X or a 10X probe.
> > > tom jobe...
> > >
> > >
> > >
> > >
> > >
> > > ----- Original Message -----
> > > From: lldskjfoi
> > > To: TekScopes@...
> > > Sent: Thursday, September 20, 2012 8:28 AM
> > > Subject: [TekScopes] Re: 2247A Channel 1 issue
> > >
> > >
> > >
> > > Thanks, thanks the info I was looking for. I started getting into the schematic last night I saw the path to U506. Will start checking it out.
> > >
> > > Also notice just letting the scope run with the probe attached the attenuation factor jumps back and forth- correct / incorrect. Does not change with no probe attached so it is getting an intermitant signal.
> > >
> > > KT
> > >
> > > --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> > > >
> > > > Maybe start by looking at the #1 "Vertical Inputs" schematic to see the simple circuit which starts at the junction of R101, C101 and R105 for channel 1.
> > > > That junction point is connected to the readout ring behind the BNC connector, so you could test for continuity and shorting to ground, etc.
> > > > If you compared both ends of R101 and R105 (Chan 1) with those of R102 and R106 (Chan 2) you might see if the readout voltage is getting that far.
> > > > If that looked okay, you could go to U506 and see if it arrives at pins 12 and 15 as you would expect.
> > > > With the scope on its back, you have excellent access to all of these resistors and U506 (16 pin DIP), with the blue outer cover slid back the width of your hand.
> > > > From reading the service manual, it appears that the readout signal gets changed to a digital signal at U506, but is a simple voltage up to U506.
> > > > tom jobe...
> > > >
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: lldskjfoi
> > > > To: TekScopes@...
> > > > Sent: Wednesday, September 19, 2012 9:08 PM
> > > > Subject: [TekScopes] Re: 2247A Channel 1 issue
> > > >
> > > >
> > > >
> > > > Some more checking shows channel 1 is not getting the code signal from the probe. Any idea on this circuit?
> > > >
> > > > KT
> > > >
> > > > --- In TekScopes@..., "lldskjfoi" <k.templin@> wrote:
> > > > >
> > > > > Hello everyone.
> > > > >
> > > > > Initial test show an issue with channel 1.
> > > > >
> > > > > Any direction on where to start?
> > > > >
> > > > > Channel 2 displays inputs correctly from the FG.
> > > > >
> > > > > Channel 1 displays 10 times the amplitude for the same signal.
> > > > >
> > > > > Example a 1 volt sine wave on channel 2 displays on the voltmeter function correctly at ~1v and 2 divisions at .5v / div.
> > > > >
> > > > > The same signal on channel one reads as ~10v. When set to 5v / div it fills two div.
> > > > >
> > > > > Thanks, KT
> > > > >
> > > >
> > >
> >
>
|
Re: 2247A Channel 1 issue
KT,
I money is on U506 has a bad input at pin 15. Lots of current's flowing into it, but it shouldn't be. Probably got zapped with a big dose of static electricity at the ring.
Jimmy
toggle quoted message
Show quoted text
--- In TekScopes@..., "lldskjfoi" <k.templin@...> wrote:
I have 2.5 at both ends of R106.
1.9 and 1 at R105.
--- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
What is the voltages on either side of R105 and R106?
It seems like C111 and U506 are the only possibilities if the voltage leaving R105 more or less agrees with what you see arriving at U506 pin 15.
tom jobe...
----- Original Message -----
From: lldskjfoi
To: TekScopes@...
Sent: Thursday, September 20, 2012 6:04 PM
Subject: [TekScopes] Re: 2247A Channel 1 issue
10k and 10k. What do you thin? the only thing left are the caps or the U506 itself.
KT
--- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
>
> What are the resistance readings across R105 and R106?
> That might help narrow the search down.
> tom jobe...
>
>
>
> ----- Original Message -----
> From: lldskjfoi
> To: TekScopes@...
> Sent: Thursday, September 20, 2012 5:19 PM
> Subject: [TekScopes] Re: 2247A Channel 1 issue
>
>
>
>
> I get 8.2 and 8.2 as well.
>
> KT
> --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> >
> > I just checked R101 and R102 on a bare 2246 mainboard and they both measured 8.2k ohms in circuit.
> > If the resistance is correct on your scope, then something is drawing enough current to drop 0.7 volts across R101.
> > Nothing in that simple circuit looks like a suspect to me, no nasty 10uF to 47uF tantalums, etc.
> > tom jobe...
> >
> >
> >
> > ----- Original Message -----
> > From: lldskjfoi
> > To: TekScopes@...
> > Sent: Thursday, September 20, 2012 1:20 PM
> > Subject: [TekScopes] Re: 2247A Channel 1 issue
> >
> >
> >
> >
> > Thanks again for the responce. I think we are getting there.
> >
> > Using cahannel 2 as the "working reference"
> >
> > pin 12 (channel 2) on u506 goes from the +2.5 to +1.4 when a 10x probe is connected.
> >
> > pin (15 channel 1) on U506 goes from +.9 to +.6 with the probe connected.
> >
> > Checking R102 for channel 2 it has +2.5
> >
> > R101, (channel 1), shows +2.5 in but only +1.8 out.
> >
> > What are your thoughts? Is it simply a bad resistor or would one of the cap, C111 cause the voltage drop?
> >
> > Thanks again, KT
> > --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> > >
> > > For the record, I slid the cover back on a very dead 2246 and checked pin 12 and pin 15 of U506, they both had +2.49 volts with no probes attached.
> > > This scope does not have any lights on the front, and none of the buttons work, so I could not see the reading I would get at ground, or with a 1X or a 10X probe.
> > > tom jobe...
> > >
> > >
> > >
> > >
> > >
> > > ----- Original Message -----
> > > From: lldskjfoi
> > > To: TekScopes@...
> > > Sent: Thursday, September 20, 2012 8:28 AM
> > > Subject: [TekScopes] Re: 2247A Channel 1 issue
> > >
> > >
> > >
> > > Thanks, thanks the info I was looking for. I started getting into the schematic last night I saw the path to U506. Will start checking it out.
> > >
> > > Also notice just letting the scope run with the probe attached the attenuation factor jumps back and forth- correct / incorrect. Does not change with no probe attached so it is getting an intermitant signal.
> > >
> > > KT
> > >
> > > --- In TekScopes@..., "Tom Jobe" <tomjobe@> wrote:
> > > >
> > > > Maybe start by looking at the #1 "Vertical Inputs" schematic to see the simple circuit which starts at the junction of R101, C101 and R105 for channel 1.
> > > > That junction point is connected to the readout ring behind the BNC connector, so you could test for continuity and shorting to ground, etc.
> > > > If you compared both ends of R101 and R105 (Chan 1) with those of R102 and R106 (Chan 2) you might see if the readout voltage is getting that far.
> > > > If that looked okay, you could go to U506 and see if it arrives at pins 12 and 15 as you would expect.
> > > > With the scope on its back, you have excellent access to all of these resistors and U506 (16 pin DIP), with the blue outer cover slid back the width of your hand.
> > > > From reading the service manual, it appears that the readout signal gets changed to a digital signal at U506, but is a simple voltage up to U506.
> > > > tom jobe...
> > > >
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: lldskjfoi
> > > > To: TekScopes@...
> > > > Sent: Wednesday, September 19, 2012 9:08 PM
> > > > Subject: [TekScopes] Re: 2247A Channel 1 issue
> > > >
> > > >
> > > >
> > > > Some more checking shows channel 1 is not getting the code signal from the probe. Any idea on this circuit?
> > > >
> > > > KT
> > > >
> > > > --- In TekScopes@..., "lldskjfoi" <k.templin@> wrote:
> > > > >
> > > > > Hello everyone.
> > > > >
> > > > > Initial test show an issue with channel 1.
> > > > >
> > > > > Any direction on where to start?
> > > > >
> > > > > Channel 2 displays inputs correctly from the FG.
> > > > >
> > > > > Channel 1 displays 10 times the amplitude for the same signal.
> > > > >
> > > > > Example a 1 volt sine wave on channel 2 displays on the voltmeter function correctly at ~1v and 2 divisions at .5v / div.
> > > > >
> > > > > The same signal on channel one reads as ~10v. When set to 5v / div it fills two div.
> > > > >
> > > > > Thanks, KT
> > > > >
> > > >
> > >
> >
>
|
Re: 2247A Channel 1 issue
Well, unless I missed something you are down to C111 or U506
as being the culprit.
I would carefully lift one leg of C111.
It is near U506 pin 14, slightly further from the front of the
scope.
It might also be orange in color.
tom jobe...
?
toggle quoted message
Show quoted text
----- Original Message -----
Sent: Thursday, September 20, 2012 6:27
PM
Subject: [TekScopes] Re: 2247A Channel 1
issue
?
I have 2.5 at both ends of R106.
1.9 and 1 at R105.
---
In TekScopes@...,
"Tom Jobe" wrote:
>
> What is the voltages on
either side of R105 and R106?
> It seems like C111 and U506 are the only
possibilities if the voltage leaving R105 more or less agrees with what you
see arriving at U506 pin 15.
> tom jobe...
>
>
>
> ----- Original Message -----
> From: lldskjfoi
> To: TekScopes@...
> Sent: Thursday, September 20, 2012 6:04 PM
> Subject:
[TekScopes] Re: 2247A Channel 1 issue
>
>
>
>
> 10k and 10k. What do you thin? the only thing left are the caps or
the U506 itself.
>
> KT
> --- In TekScopes@..., "Tom
Jobe" wrote:
> >
> > What are the
resistance readings across R105 and R106?
> > That might help narrow
the search down.
> > tom jobe...
> >
> >
>
>
> > ----- Original Message -----
> > From: lldskjfoi
> > To: TekScopes@...
> > Sent: Thursday, September 20, 2012 5:19 PM
> > Subject:
[TekScopes] Re: 2247A Channel 1 issue
> >
> >
> >
> >
> > I get 8.2 and 8.2 as well.
> >
>
> KT
> > --- In TekScopes@..., "Tom
Jobe" wrote:
> > >
> > > I just
checked R101 and R102 on a bare 2246 mainboard and they both measured 8.2k
ohms in circuit.
> > > If the resistance is correct on your scope,
then something is drawing enough current to drop 0.7 volts across
R101.
> > > Nothing in that simple circuit looks like a suspect to
me, no nasty 10uF to 47uF tantalums, etc.
> > > tom
jobe...
> > >
> > >
> > >
> >
> ----- Original Message -----
> > > From: lldskjfoi
>
> > To: TekScopes@...
> > > Sent: Thursday, September 20, 2012 1:20 PM
> >
> Subject: [TekScopes] Re: 2247A Channel 1 issue
> > >
>
> >
> > >
> > >
> > > Thanks
again for the responce. I think we are getting there.
> > >
> > > Using cahannel 2 as the "working reference"
> >
>
> > > pin 12 (channel 2) on u506 goes from the +2.5 to +1.4
when a 10x probe is connected.
> > >
> > > pin (15
channel 1) on U506 goes from +.9 to +.6 with the probe connected.
> >
>
> > > Checking R102 for channel 2 it has +2.5
> >
>
> > > R101, (channel 1), shows +2.5 in but only +1.8
out.
> > >
> > > What are your thoughts? Is it simply
a bad resistor or would one of the cap, C111 cause the voltage drop?
>
> >
> > > Thanks again, KT
> > > --- In TekScopes@..., "Tom
Jobe" <tomjobe@> wrote:
> > > >
> > > >
For the record, I slid the cover back on a very dead 2246 and checked pin 12
and pin 15 of U506, they both had +2.49 volts with no probes attached.
>
> > > This scope does not have any lights on the front, and none of
the buttons work, so I could not see the reading I would get at ground, or
with a 1X or a 10X probe.
> > > > tom jobe...
> > >
>
> > > >
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: lldskjfoi
> > > > To: TekScopes@...
> > > > Sent: Thursday, September 20, 2012 8:28 AM
>
> > > Subject: [TekScopes] Re: 2247A Channel 1 issue
> >
> >
> > > >
> > > >
> > >
> Thanks, thanks the info I was looking for. I started getting into the
schematic last night I saw the path to U506. Will start checking it
out.
> > > >
> > > > Also notice just letting
the scope run with the probe attached the attenuation factor jumps back and
forth- correct / incorrect. Does not change with no probe attached so it is
getting an intermitant signal.
> > > >
> > > >
KT
> > > >
> > > > --- In TekScopes@..., "Tom
Jobe" wrote:
> > > > >
> > >
> > Maybe start by looking at the #1 "Vertical Inputs" schematic to see
the simple circuit which starts at the junction of R101, C101 and R105 for
channel 1.
> > > > > That junction point is connected to the
readout ring behind the BNC connector, so you could test for continuity and
shorting to ground, etc.
> > > > > If you compared both ends
of R101 and R105 (Chan 1) with those of R102 and R106 (Chan 2) you might see
if the readout voltage is getting that far.
> > > > > If
that looked okay, you could go to U506 and see if it arrives at pins 12 and 15
as you would expect.
> > > > > With the scope on its back,
you have excellent access to all of these resistors and U506 (16 pin DIP),
with the blue outer cover slid back the width of your hand.
> > >
> > From reading the service manual, it appears that the readout signal
gets changed to a digital signal at U506, but is a simple voltage up to
U506.
> > > > > tom jobe...
> > > > >
> > > > >
> > > > >
> > >
> >
> > > > > ----- Original Message -----
>
> > > > From: lldskjfoi
> > > > > To: TekScopes@...
> > > > > Sent: Wednesday, September 19, 2012 9:08
PM
> > > > > Subject: [TekScopes] Re: 2247A Channel 1
issue
> > > > >
> > > > >
> >
> > >
> > > > > Some more checking shows channel 1
is not getting the code signal from the probe. Any idea on this
circuit?
> > > > >
> > > > > KT
>
> > > >
> > > > > --- In TekScopes@...,
"lldskjfoi" <k.templin@> wrote:
> > > > > >
>
> > > > > Hello everyone.
> > > > > >
> > > > > > Initial test show an issue with channel
1.
> > > > > >
> > > > > > Any
direction on where to start?
> > > > > >
> >
> > > > Channel 2 displays inputs correctly from the FG.
>
> > > > >
> > > > > > Channel 1 displays
10 times the amplitude for the same signal.
> > > > > >
> > > > > > Example a 1 volt sine wave on channel 2
displays on the voltmeter function correctly at ~1v and 2 divisions at .5v /
div.
> > > > > >
> > > > > > The
same signal on channel one reads as ~10v. When set to 5v / div it fills two
div.
> > > > > >
> > > > > >
Thanks, KT
> > > > > >
> > > >
>
> > > >
> > >
>
>
>
|
David C. Partridge
David Hess