Re: R7103 backplane repair
I got chronic and acute backwards. It is late here. On Sun, 20 Jan 2013 00:12:10 -0600, David <davidwhess@...> wrote: I have seen two common types of aluminum electrolytic capacitor wear
out syndromes which could be considered chronic versus acute.
The chronic case involves a high ripple current application where the
increase in equivalent series resistance causes the capacitor
dissipation and temperature to rise which causes it to fail even
faster in a positive feedback loop. Circuit failure will often be
because of just one capacitor. Series connected DC balancing
capacitors in half bridge designs are particularly susceptible to
this. The resonating capacitor in the Tektronix designs would be if
it were electrolytic. I try to derate the replacement as much as
possible for longer life.
The acute case involves a whole bunch of significantly derated
capacitors of the same age which just slowly dry out. Circuit
operation becomes more erratic over time. In this case, I find all of
the similar capacitors and change them all. Testing usually shows
that they all have a fraction of their rate capacitance and several
times their rated dissipation factor instead of being completely open.
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Re: R7103 backplane repair
I have seen two common types of aluminum electrolytic capacitor wear out syndromes which could be considered chronic versus acute. The chronic case involves a high ripple current application where the increase in equivalent series resistance causes the capacitor dissipation and temperature to rise which causes it to fail even faster in a positive feedback loop. Circuit failure will often be because of just one capacitor. Series connected DC balancing capacitors in half bridge designs are particularly susceptible to this. The resonating capacitor in the Tektronix designs would be if it were electrolytic. I try to derate the replacement as much as possible for longer life. The acute case involves a whole bunch of significantly derated capacitors of the same age which just slowly dry out. Circuit operation becomes more erratic over time. In this case, I find all of the similar capacitors and change them all. Testing usually shows that they all have a fraction of their rate capacitance and several times their rated dissipation factor instead of being completely open. Sometimes there is a third case in between chronic and acute where the designers just screw up the derating factors. This occurs with input and output capacitors in high ripple current switching regulators. I replace them all and try to increase the derating. On Sun, 20 Jan 2013 00:26:45 -0500, Peter Gottlieb <hpnpilot@...> wrote: You could be right about that. I had gotten it in a lot of scopes I got from a
Govliquidation auction and it was the one I figured was going to be parted out.
It had a lot missing like knobs, both handles broken, really dirty front panel.
It sat in the back of my lab for about a year and when I got to it and opened it
up it was so pristine inside I just didn't have the heart to scrap it. There
were a couple minor electrical issues I fixed and then it worked so well I
cleaned it up and gradually found the parts I needed to complete it. Now I use
it as my main bench scope.
But I never re-capped the power supply and it would seem likely there is at
least one low capacitance high ESR cap in there. Worth a shot...
Peter
On 1/19/2013 10:54 PM, David wrote:
The first 7834 I bought which has the bad CRT geometry, maybe it was
dropped during shipping, does that occasionally and my 7904 does it as
well although less often so far. I suspect the power supplies just
need to have their electrolytic capacitors replaced.
On Sat, 19 Jan 2013 22:46:28 -0500, Peter Gottlieb
hpnpilot@... <mailto:hpnpilot%40verizon.net>> wrote:
Perfect then. The less I have to deal with Yahoo the better. I consider Yahoo to
be a company which could have become something great but never strove for
excellence or really truly caring, and thus remain second rate.
I think for these groups the best thing is to put any photos up on a photo
sharing site (or your own site) and post links as appropriate.
Next I open up my R7844 used on my bench. It just started having a power supply
(very) intermittent fault, enough to flicker the screen and panel lights every
so often.
Peter
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Re: R7103 backplane repair
You could be right about that. I had gotten it in a lot of scopes I got from a Govliquidation auction and it was the one I figured was going to be parted out. It had a lot missing like knobs, both handles broken, really dirty front panel. It sat in the back of my lab for about a year and when I got to it and opened it up it was so pristine inside I just didn't have the heart to scrap it. There were a couple minor electrical issues I fixed and then it worked so well I cleaned it up and gradually found the parts I needed to complete it. Now I use it as my main bench scope.
But I never re-capped the power supply and it would seem likely there is at least one low capacitance high ESR cap in there. Worth a shot...
Peter
toggle quoted message
Show quoted text
On 1/19/2013 10:54 PM, David wrote:
The first 7834 I bought which has the bad CRT geometry, maybe it was
dropped during shipping, does that occasionally and my 7904 does it as
well although less often so far. I suspect the power supplies just
need to have their electrolytic capacitors replaced.
On Sat, 19 Jan 2013 22:46:28 -0500, Peter Gottlieb
hpnpilot@... <mailto:hpnpilot%40verizon.net>> wrote:
Perfect then. The less I have to deal with Yahoo the better. I consider Yahoo to
be a company which could have become something great but never strove for
excellence or really truly caring, and thus remain second rate.
I think for these groups the best thing is to put any photos up on a photo
sharing site (or your own site) and post links as appropriate.
Next I open up my R7844 used on my bench. It just started having a power supply
(very) intermittent fault, enough to flicker the screen and panel lights every
so often.
Peter
On 1/19/2013 2:37 PM, Fabio Eboli wrote:
Il 2013-01-19 19:49 Peter Gottlieb ha scritto:
Sorry, Yahoo seems to be blocking the image, won't accept my login
without
multiple layers of entering captcha codes, and generally being such a
pain to
use that its not worth it.
Don't worry, there was no attachment,
comes from something wrong
with my mail.
Fabio.
--------------------------------------------------------------------------------
No virus found in this message.
Checked by AVG - www.avg.com <>
Version: 10.0.1430 / Virus Database: 2639/5544 - Release Date: 01/19/13
|
Re: 2445 CPU Address line failed
I think it has been discussed here before but I do not have a link to where. Maybe there two different versions of U800? On Sun, 20 Jan 2013 03:56:28 -0000, "ykochcal" <Kochcal@...> wrote: But now back to the question left
3. Given the U800 history, does any one know what a "Horiz mod Kit" was on a very early 2445?
John
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Re: 2445 CPU Address line failed
--- In TekScopes@..., "victor_j_silva" wrote: Interesting story, I find this statement a little humerous:
"In late 2012 a dog next door bit my wife and I needed a scope" I see I need to explain that a bit more, I did not want to add too much non-scope stuff in my first entry in the forum. So to expand, Neighbor relations prohibit lethal ideas I got my kids a Ryobi drill, sawsall and flash light so they could work on there tree house for xmas (I got the circular saw). I saw that extra flash lights are only $13 but they connect to a 18 volt battery with some good power. My idea was to take one of the flash lights, connect an high power tweeter with and ultrasonic oscillator and see if that would help. The scope (Oscilloscope that is) was to work on matching the circuit with the tweeter and get maximum power out. I thought I might need a custom transformer and the cheep tweeters don't seem to have any specs. So Scopes are surly found in many ways, and I found 6 more, so I now have 7 scopes, all need some work except one. The funny part is, the one fully working scope was the cheapest, I got it for just a bite. ($.25 less then two bits) But now back to the question left 3. Given the U800 history, does any one know what a "Horiz mod Kit" was on a very early 2445? John
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Re: R7103 backplane repair
The first 7834 I bought which has the bad CRT geometry, maybe it was dropped during shipping, does that occasionally and my 7904 does it as well although less often so far. I suspect the power supplies just need to have their electrolytic capacitors replaced. On Sat, 19 Jan 2013 22:46:28 -0500, Peter Gottlieb <hpnpilot@...> wrote: Perfect then. The less I have to deal with Yahoo the better. I consider Yahoo to
be a company which could have become something great but never strove for
excellence or really truly caring, and thus remain second rate.
I think for these groups the best thing is to put any photos up on a photo
sharing site (or your own site) and post links as appropriate.
Next I open up my R7844 used on my bench. It just started having a power supply
(very) intermittent fault, enough to flicker the screen and panel lights every
so often.
Peter
On 1/19/2013 2:37 PM, Fabio Eboli wrote:
Il 2013-01-19 19:49 Peter Gottlieb ha scritto:
Sorry, Yahoo seems to be blocking the image, won't accept my login
without
multiple layers of entering captcha codes, and generally being such a
pain to
use that its not worth it.
Don't worry, there was no attachment,
comes from something wrong
with my mail.
Fabio.
|
Re: R7103 backplane repair
Perfect then. The less I have to deal with Yahoo the better. I consider Yahoo to be a company which could have become something great but never strove for excellence or really truly caring, and thus remain second rate.
I think for these groups the best thing is to put any photos up on a photo sharing site (or your own site) and post links as appropriate.
Next I open up my R7844 used on my bench. It just started having a power supply (very) intermittent fault, enough to flicker the screen and panel lights every so often.
Peter
toggle quoted message
Show quoted text
On 1/19/2013 2:37 PM, Fabio Eboli wrote:
Il 2013-01-19 19:49 Peter Gottlieb ha scritto:
Sorry, Yahoo seems to be blocking the image, won't accept my login
without
multiple layers of entering captcha codes, and generally being such a
pain to
use that its not worth it.
Don't worry, there was no attachment,
comes from something wrong
with my mail.
Fabio.
--------------------------------------------------------------------------------
No virus found in this message.
Checked by AVG - www.avg.com <>
Version: 10.0.1430 / Virus Database: 2639/5544 - Release Date: 01/19/13
|
Re: Tektronix DMM-4020 Opinions?
Hi David: ? That is good information to know.? I have been looking for good overall bench DMM for some time, and stumbled upon this one.? When compared to my Fluke 867B this seems like a real bargain! ? Are you aware of any issues with this particular DMM? ? Rich
toggle quoted message
Show quoted text
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of David DiGiacomo
Sent: Saturday, January 19, 2013 8:59 PM
To: TekScopes@...
Subject: Re: [TekScopes] Tektronix DMM-4020 Opinions?? ? On Sat, Jan 19, 2013 at 5:56 PM, Rich Miller av8torrich@...> wrote:
> I have the opportunity to buy one of these far below the list price. I wonder if anyone has used this DMM, and what were your impressions of it> While I know it is not a Keithly, it seems like a lot of Bench Top DMM the $200.00 I am going to pay for it.
It's not a Keithley, it's a Fluke 8808A. At that price you might as
well try it, you would have no trouble reselling it.
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Re: Tektronix DMM-4020 Opinions?
On Sat, Jan 19, 2013 at 5:56 PM, Rich Miller <av8torrich@...> wrote: I have the opportunity to buy one of these far below the list price. I wonder if anyone has used this DMM, and what were your impressions of it> While I know it is not a Keithly, it seems like a lot of Bench Top DMM the $200.00 I am going to pay for it. It's not a Keithley, it's a Fluke 8808A. At that price you might as well try it, you would have no trouble reselling it.
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Re: 2445 CPU Address line failed
Actually, my neighbor has an aggressive pit bull -- it gets close enough to us that no 'scope is needed, but a laser sight might be useful for when it hops over the fence.
My take on this -- most of us have more than one oscilloscope, and choose the 'scope best suited for the task at hand. ?For that pit bull? ?My .357 has the nicest iron sights, the 9mm can throw the most lead downrange the fastest (if
"point-blank" constitutes "downrange"), and the short-barrel 12 ga pump shotgun gives the likeliest chance of a hit.
So all in all, the task of trouble-shooting (so to speak) the pit bull is well in hand, although it is most definitely NOT a project I want to undertake any time soon, if ever.
73 Jim N6OTQ
From: Rob
To: TekScopes@...
Sent: Saturday, January 19, 2013 7:12 PM
Subject: RE: [TekScopes] Re: 2445 CPU Address line failed
I know I was going to ask if it was a rifle scope…. but refrained….. now I cannot resist.Sorry as always for when my funny bone kicks in and thanks as always for the bandwidth. Rob From: TekScopes@... [mailto:TekScopes@...] On Behalf Of victor_j_silva
Sent: Saturday, January 19, 2013 7:02 PM
To: TekScopes@...
Subject: [TekScopes] Re: 2445 CPU Address line failed Interesting story, I find this statement a little humerous:
"In late 2012 a dog next door bit my wife and I needed a scope"
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Re: 2445 CPU Address line failed
I agree. ? I had so many comebacks for this but the rest of the story explained it. ? Joe ?
toggle quoted message
Show quoted text
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of victor_j_silva
Sent: Saturday, January 19, 2013 7:02 PM
To: TekScopes@...
Subject: [TekScopes] Re: 2445 CPU Address line failed? ? Interesting story, I find this statement a little humerous:
"In late 2012 a dog next door bit my wife and I needed a scope"
|
Re: 2445 CPU Address line failed
When you break your funny bone, it's real bad.
Don Black.
On 20-Jan-13 12:12 PM, Rob wrote:
toggle quoted message
Show quoted text
?
I know I was
going to ask if it was a rifle scope…. but
refrained….. now I cannot resist.
?
Sorry as always
for when my funny bone kicks in and thanks as always
for the bandwidth.
?
Rob
?
?
Interesting story, I find this statement a little
humerous:
"In late 2012 a dog next door bit my wife and I
needed a scope"
|
Re: 2445 CPU Address line failed
I know I was going to ask if it was a rifle scope…. but refrained….. now I cannot resist. ? Sorry as always for when my funny bone kicks in and thanks as always for the bandwidth. ? Rob
toggle quoted message
Show quoted text
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of victor_j_silva
Sent: Saturday, January 19, 2013 7:02 PM
To: TekScopes@...
Subject: [TekScopes] Re: 2445 CPU Address line failed? ? Interesting story, I find this statement a little humerous:
"In late 2012 a dog next door bit my wife and I needed a scope"
|
Re: 2445 CPU Address line failed
A rifle scope?
Don Black.
On 20-Jan-13 12:02 PM, victor_j_silva wrote:
toggle quoted message
Show quoted text
?
Interesting story, I find this statement a little
humerous:
"In late 2012 a dog next door bit my wife and I needed a
scope"
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|
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Re: scanned: 1958 Tek Personnel
Maybe not.? On page 58 of the 1958 photo album, we find the same photo of Ms. Lusk, with the same calendar.? Perhaps the photo was taken in 1953? ? Also, I got one of the possible years wrong; it would be 1942, not 1943.? But, as Don Black commented, Tek did not yet exist in 1943. ? Regards, ? Tony ?
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Show quoted text
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of sipespresso
Sent: Saturday, January 19, 2013 4:07 PM
To: TekScopes@...
Subject: [TekScopes] Re: scanned: 1958 Tek Personnel? ? Thanks. Seems right. -Kurt
--- In TekScopes@..., "Tony Jacobson" wrote:
>
> I see calendars on (PDF) pages 32, 56, 82, 88, and 112. I can't make out a
> year in any of the photos, but the one on page 56 appears to be from
> December, with Christmas on a Friday. This would suggest that photo was
> taken in December of 1943, 1953, 1959, 1964, or 1970. (I don't think it
> would be older or newer than these years.)
>
>
>
> I would put my money on 1959.
>
>
>
> Regards,
>
>
>
> Tony
>
>
>
> From: TekScopes@... [mailto:TekScopes@...] On Behalf
> Of sipespresso
> Sent: Saturday, January 19, 2013 12:12 PM
> To: TekScopes@...
> Subject: [TekScopes] Re: scanned: 1958 Tek Personnel
>
>
>
>
>
> Here is another photo album similar to the one I posted before.
>
>
>
> Can anybody figure out the date of this one? thanks, -Kurt
>
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Re: 2445 CPU Address line failed
Interesting story, I find this statement a little humerous:
"In late 2012 a dog next door bit my wife and I needed a scope"
|
Tektronix DMM-4020 Opinions?
Hello: ? I have the opportunity to buy one of these far below the list price. I wonder if anyone has used this DMM, and what were your impressions of it> While I know it is not a Keithly, it seems like a lot of Bench Top DMM the $200.00 I am going to pay for it. ? ? Thanks
Rich
|
Re: scanned: 1958 Tek Personnel
Nicely spotted. Pretty good if it's 1943, thats before the company
existed.
Don Black.
On 20-Jan-13 7:18 AM, Tony Jacobson wrote:
toggle quoted message
Show quoted text
?
I see calendars on (PDF) pages 32,
56, 82, 88, and 112.? I can’t make out a year in any
of the photos, but the one on page 56 appears to be
from December, with Christmas on a Friday.? This would
suggest that photo was taken in December of 1943,
1953, 1959, 1964, or 1970. ?(I don’t think it would be
older or newer than these years.)
?
I would put my money on 1959.
?
Regards,
?
Tony
?
?
?
Here is another photo album similar to the one I
posted before.
Can anybody figure out the date of this one?
thanks, -Kurt
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Re: Bench Built Isolation Transformer
Ah, Dave,
But the electrical system in the US is grounded. What you are
referring to is the ability for the GFCI to work without the
presence of a ground conductor attached to the GFCI. The electrical
system? in the building is a grounded system, defined as neutral
connected to gound at one point for reference, even though a green
or bare ground wire is not present at the receptacle.
Remember, for current to flow there needs to be a complete circuit.
Once an isolation transformer is in a circuit, there is no longer a
current path between sides.
You think this is hard to get a mental picture, Some rural places
used to use a distribution system of 15 to 30 killoVolts three
phase, one phase GROUNDED! This was for lightning protection.
On the opposite side we have Navy ships with neither conductor
connected to ground. No ground reference, just monitors for if a
wire becomes grounded. Gives time to fix the wire without a circuit
going down when it is needed....? And no electrocution hazard until
the first wire becomes grounded, hence the monitors. The GFCI won't
work on this circuit either, just like after a GFCI/RCD.
Frank DuVal
On 1/15/2013 1:52 AM, Dave C wrote:
toggle quoted message
Show quoted text
?
Stefan,
The GFI works on differential measurement, regardless
the presence of ground.
Here in USA these GFI's are legal to use in an
ungrounded electrical system in residential buildings, as
long as a label is attached to the face plate stating
"ungrounded".?
Dave
-=-=-=-
On 14 January 2013, at 10:41 PM, Stefan Trethan
wrote:
And
obviously it won't work after an isolation
transformer, the GFI
needs a grounded grid.
_
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David Hess