On Sat, Jul 28, 2018 at 08:18 PM, Bert Haskins wrote:
Ringing test To check transformers.
The transformer must be removed first.
To do this you apply a small!!! pulse across one winding and observe the
amount of ringing.
This will show a lot of ringing on a good transformer.
If you don't have a good function generator, one of the 74xx14 pulse
generator/buffers can be made to work.
Example of waveform:
And then short one of the other windings.
This should make a great! difference in the appearance of the pulsed trace.
You can also try wrapping one or more turns of wire around the core and
shorting them.
If this checks out OK, I would very carefully check all of the other
parts around T906.
This method does take some practice but it is a great tool to have.
-Bert
Hi Bert, Vincent and others, The ringing test made sense to me, its is relying on the fact a coil has an inductance, so a steep current change will cause voltage to shoot up. (snubber tread all over :-) But as soon as one of the windings has a short, this will dampen the whole thing. I did the test, and it looks as if my transformer is still OK!! :-) So, while waiting for parts (the FET's & Diodes) I ordered, I started looking in my stack of -over the years- harvested PS boards to see if I could find some useable parts. I found for the diode a HER105 (400V, 1A, 75ns, 1,3V) and for the FET a P9NK70ZFP (700V, 7,5A, and faster rise- and fall times, 17ns - 13ns, 1 - 1,2 Ohm RDSon) Based on the 200ns rise- and fall times the switcher is using and I measured before they should be OK. The good news: it's working again! The bad news: the FET gets rather warm, temperature goes up to 68 degree Celsius, which should be OK, but I just don't like these temperatures that high. (Higher ON-resistance?? ) So I have decided to not leave these parts in, but replace them with the faster diode and lower On-resistance FET when they arrive. I also removed the brown, plastic TO-220 cover, and put in a small heatsink on both sides. The FET's I ordered are full plastic TO-220 housing, so I don't need extra insulation. I also ordered a 70mm 12V fan that I will put in, much like it's bigger brother, to create some airflow. I took some pictures of the working scope: /g/TekScopes/album?id=64919&p=pcreated,,,20,1,0,0 To be continued, Un saludo, Leo
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I have watched this thread from the beginning - lots of good points and info. Here are some observations that tie the paths of snubbing, switch arcing, and relay response, and may indicate the true cause of the problem described in the OP.
First, the OP was about switch contact burning on a particular switch in a particular unit (2465). It is true that a snubber of some sort should help to protect the contacts, especially with an inductive load as in a linear supply. It is also true that this application is for a SMPS, so it has little inductance to worry about, but lots of capacitance to charge on power-up. The typical NTC thermistor helps to limit inrush current in this case, also protecting the contacts somewhat.
Second, snubbers or clamps are typically used on relay coils to protect their drivers, but the nature of the clamping affects the relay turn-off response, and if it is significantly slowed down, can be bad for relay contact life, depending on the application.
Now, put these two concepts together, and consider the way a mechanical switch works. There are all kinds of them, for all kinds of uses, but aside from the classic manual knife switch, one thing they have in common is some degree of "snappiness" - to change states quickly (for a mechanical device), and not dwell long between making full contact, and reaching maximum separation, and vice versa.
I'd venture to say that the real problem is in the response of this particular type of switch contact mechanism during operation. I may be wrong, but as I recall, the power switch in the 2400 series scopes is a push-push type - the same basic style as many others used for controls in many types of equipment. The armature is a spring-loaded sliding piece that carries the contacts to meet the posts along the sides. The on/off state is maintained by the mechanical pawl flip-flop mechanism, but the actual change of the state is controlled by the operator's finger pushing the plunger in, or in, then letting back it out. There is a variable range to both the speed and position of the contacts.
Contrast this with a toggle switch. The toggle lever is pushed ever harder until it reaches the throwover point, then the armature and the lever quickly snap to the other state. There is (normally) no in-between influence from the user - it is digital. The apparent throwover point (click) in the push-push type is not where the contact changes state, but where the flip-flop holds or releases. Big difference.
So, I would say that the switch contact wear/burn is happening at both turn on and off, during the variable, finger-dependent operating zone, where the contact separation is small, and there's enough voltage and current to arc. Also, as the switch ages and wears or gets gritty, the mechanism may get sticky and slow, making it even worse. I've seen many push-push power switches on all kinds of equipment, that were so bad that they wouldn't even move on their own, and had to have the plunger pulled out manually to turn off. I prefer good old toggle switches for power, but sometimes the way things are built, you're stuck with whatever switch style they have.
In conclusion, for owners of 2400 series - or anything with P-P power switches - I'd recommend the following user interface technique:
1. Make it snappy. Push in firmly and quickly to turn on. Push in firmly but slowly during turn off, until the click indicates release, then let loose quickly.
2. Don't fast-cycle on-off-on, etc. Let things cool for maybe 15-30 seconds to allow any NTCs present to recover their cold resistance, before turning back on.
Ed
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On Fri, Aug 3, 2018 at 08:29 PM, Jim Olson wrote:
this 464 is sn#B145646 it has the latest dash number -16 A6 inter board and the 3324-01 board is correct
And the DM44 mod kit says B050102-up so it should be OK. Obviously the correct info is missing in the RPR. /H?kan
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Re: 3D Printing / Milling Tektronix parts
So far as I know, I don't need any. The post was mostly for Tam's benefit. I'm a severe technogeek who has been obsessed with all the things there are to be done and all ways there are to do them since childhood. And have a 5000 volume technical library to help me remember the things I forget.
A lot of people tend to assume that injection molding plastic takes huge expensive machines. While that is true of high volume production, at low volumes it becomes much simpler and building a machine and molds is a hobby shop level project.
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Hi Jim,
Feel free to send me the pictures (PM to fabio.tr3visan@...).
I will be glad to post it to the photos area of Tekscopes.io, and reply to you with a link to the folder.
Rgrds,
Fabio
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Show quoted text
On Fri, Aug 3, 2018 at 03:07 PM, Jim Olson wrote:
Fabio I have the pictures but I'm not using any kind of photo posting service
it's gotten to complicated and I don't post much to forums anyway so can I
send them to you and you can post them up?
Jim
On August 3, 2018 at 7:26 AM Fabio Trevisan <fabio.tr3visan@...> wrote:
Hello Jim,
I owed and restored a 464 with DM44 (now given to a friend) and I don't
think there are any other "optional" boards linked to the presence (or
absence) of the DM44.
The only optional boards that apply to the 464 / 466 are:
A. The optional DC inverter board (option 7)... That one can't co-exist with the DM44 (the inverter uses the same windings on the main transformer that are
used to power the DM44).
B. The composite video Sync Separator (Option 5), which bears some relation to the A5 sync board and could explain some changes.
I did hear once, from someone of this group, there was two versions of the
A5 Sync board... one that used the Tunnel Diodes, and another one which used a
Custom Tek IC to discriminate the trigger edge.
I`m not sure, but maybe this is what the -01 means...
I've never landed my eyes, however, on a schematic of the latter, or a later manual that included both.
But regardless of this board versioning, It seems rather odd to me that the
connections to the J6 are disconnected, and more so, that there is no
connection between the top and bottom side THROGUHOUT the board...
Moreover, there's nothing about the DM44 vs power to the A5 Trigger board... The DM44 takes its power from its own power supply and it's neither fed by the
A5 board, nor the A5 board feeds it.
Yet, the only reason I can think of for the through hole plating is missing throughout the board is, either a mass murderer technician stripped them off
by careless unsoldering, or yet, that it's a prototype board...
If it's the latter case, it could explain many things...
Maybe you can take a picture, post somewhere and link it here.
KRgrds,
Fabio
On Thu, Aug 2, 2018 at 11:40 PM, Jim Olson wrote:
I have a question about the A5 trigger generator sweep logic board
differences. I have two 466's with out the DM44 with the same trigger
board
670-3324-00 boards. I have a 464 with a DM44 with the 670-3324-01 board
and it
is vastly different from the 466 boards. All the DC voltage traces from
J-6
are disconnected all the through holes are unsoldered so there is no
interconnection from top to bottom through out the board. There appears to
be
no cable connection to the board from the DM44 to supply these?
The DM44 manual parts list's don't show that part number used for the
464/466
with the DM44 it shows the later 466 board and I can not find the optional
boards listed in the service manuals listed in the DM44 one.
The installation sheets for installing the DM44's don't list different or
optional boards used like the service manuals do?
So whats up with this bunch of missing info here!
Jim O
|
As did working with a 10 Henry choke back 25+ years ago for me.? Transistors kept dying when I switched off the power, and when I had my finger on the wrong spot, I instantly knew why!? Zap, a lesson I will never forget!
Jim
Sent from my Verizon, Samsung Galaxy smartphone
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Show quoted text
-------- Original message --------From: Chuck Harris <cfharris@...> Date: 8/3/18 6:09 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Snubber capacitors I did a little study on back emf diodes for relays back when I was a young engineer, and had noticed how a relay with a back emf diode was quick to acuate, but slow to release... thus subjecting the contact to burning on release. I found that simply adding a second silicon diode in series was usually sufficient to provided a nice snappy release. Whether one or two diodes works optimally depends on the voltage applied, and the inductance and resistance, of the relay coil.? A relay that is very sensitive, could take several seconds to release with a single silicon back emf diode. In some cases, better is to use a snubber where you can custom design the release time to fit the relay, and its application. That little self inflicted study made the equation that every EE memorizes in school: V(t) = L di/dt very real for me. -Chuck Harris G?ran Krusell wrote: I once read somewhere that one of the major relay vendors, don¡¯t remember which, suggests that a 10 V zener diode is inserted in series with the fly back diode. The purpose is to make certain that the relay for sure changes state.
G?ran
|
Hakan, this 464 is sn#B145646 it has the latest dash number -16 A6 inter board and the 3324-01 board is correct. I took some pictures of it but I am not using a photo posting svc. at this time so can i send them to you for your perusual and post it you feel so.
Jim
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Show quoted text
On August 3, 2018 at 11:10 AM zenith5106 <hahi@...> wrote:
On Fri, Aug 3, 2018 at 04:26 PM, Fabio Trevisan wrote:
I did hear once, from someone of this group, there was two versions of the A5 Sync board... one that used the Tunnel Diodes, and another one which used a
Custom Tek IC to discriminate the trigger edge. I`m not sure, but maybe this is what the -01 means...
I've never landed my eyes, however, on a schematic of the latter, or a later manual that included both.
The IC controlled Trigger board as well as other improvements was introduced at SN B200000. The Service manuals 464 / 070-4795-00 and 466 / 070-4796-00 are for B020000 and up.
Before that SN the Trigger board could be 670-3324-00 through -03. If I interprete the RPR (Replaceable Parts Record) correctly, and it could be wrong, only -02 or -03 would work
with DM44. Although no SN limits are given in the RPR there are in DM44 instruction sheet so it is probably right.
/H?kan
|
On Fri, Aug 3, 2018 at 04:26 PM, Fabio Trevisan wrote:
I did hear once, from someone of this group, there was two versions of the A5 Sync board... one that used the Tunnel Diodes, and another one which used a
Custom Tek IC to discriminate the trigger edge. I`m not sure, but maybe this is what the -01 means...
I've never landed my eyes, however, on a schematic of the latter, or a later manual that included both.
The IC controlled Trigger board as well as other improvements was introduced at SN B200000. The Service manuals 464 / 070-4795-00 and 466 / 070-4796-00 are for B020000 and up. Before that SN the Trigger board could be 670-3324-00 through -03. If I interprete the RPR (Replaceable Parts Record) correctly, and it could be wrong, only -02 or -03 would work with DM44. Although no SN limits are given in the RPR there are in DM44 instruction sheet so it is probably right. /H?kan
|
Fabio I have the pictures but I'm not using any kind of photo posting service it's gotten to complicated and I don't post much to forums anyway so can I send them to you and you can post them up?
Jim
toggle quoted message
Show quoted text
On August 3, 2018 at 7:26 AM Fabio Trevisan <fabio.tr3visan@...> wrote:
Hello Jim,
I owed and restored a 464 with DM44 (now given to a friend) and I don't think there are any other "optional" boards linked to the presence (or absence) of the DM44.
The only optional boards that apply to the 464 / 466 are:
A. The optional DC inverter board (option 7)... That one can't co-exist with the DM44 (the inverter uses the same windings on the main transformer that are used to power the DM44).
B. The composite video Sync Separator (Option 5), which bears some relation to the A5 sync board and could explain some changes.
I did hear once, from someone of this group, there was two versions of the A5 Sync board... one that used the Tunnel Diodes, and another one which used a Custom Tek IC to discriminate the trigger edge.
I`m not sure, but maybe this is what the -01 means...
I've never landed my eyes, however, on a schematic of the latter, or a later manual that included both.
But regardless of this board versioning, It seems rather odd to me that the connections to the J6 are disconnected, and more so, that there is no connection between the top and bottom side THROGUHOUT the board...
Moreover, there's nothing about the DM44 vs power to the A5 Trigger board... The DM44 takes its power from its own power supply and it's neither fed by the A5 board, nor the A5 board feeds it.
Yet, the only reason I can think of for the through hole plating is missing throughout the board is, either a mass murderer technician stripped them off by careless unsoldering, or yet, that it's a prototype board...
If it's the latter case, it could explain many things...
Maybe you can take a picture, post somewhere and link it here.
KRgrds,
Fabio
On Thu, Aug 2, 2018 at 11:40 PM, Jim Olson wrote:
I have a question about the A5 trigger generator sweep logic board
differences. I have two 466's with out the DM44 with the same trigger board
670-3324-00 boards. I have a 464 with a DM44 with the 670-3324-01 board and it
is vastly different from the 466 boards. All the DC voltage traces from J-6
are disconnected all the through holes are unsoldered so there is no
interconnection from top to bottom through out the board. There appears to be
no cable connection to the board from the DM44 to supply these?
The DM44 manual parts list's don't show that part number used for the 464/466
with the DM44 it shows the later 466 board and I can not find the optional
boards listed in the service manuals listed in the DM44 one.
The installation sheets for installing the DM44's don't list different or
optional boards used like the service manuals do?
So whats up with this bunch of missing info here!
Jim O
|
Re: 3D Printing / Milling Tektronix parts
Reginald, I can make some knobs in castable resin with my SLA printer if someone wants to make some molds. Mike kd5rjz On Thu, Aug 2, 2018 at 6:50 PM, Reginald Beardsley via Groups.Io < pulaskite@...> wrote: I think it worth pointing out that injection molding knobs would not be
that difficult or expensive to set up for small production. It requires a
heating chamber, a mold and a lever actuated pump. That arrangement would
be slow unless you had multiple molds and could interchange them while they
cooled. But if you're making 2 of this and 3 of that at a time it should
be OK. Going faster gets complicated because of the need to heat and cool
the molds.
The molds can be made by using silicone mold mastic to make a copy of the
desired part, making a plaster copy, drying it and then casting zinc alloy
pieces for the mold. This is a common technique in prototype fabrication
and for jewelry production, although that often involves investment casting.
If you want more information contact me directly.
|
Actual URL please????
Kevin
|
If the previous link didn't work - try this one.
<>
Rolynn
|
Hello Jim,
I owed and restored a 464 with DM44 (now given to a friend) and I don't think there are any other "optional" boards linked to the presence (or absence) of the DM44.
The only optional boards that apply to the 464 / 466 are:
A. The optional DC inverter board (option 7)... That one can't co-exist with the DM44 (the inverter uses the same windings on the main transformer that are used to power the DM44).
B. The composite video Sync Separator (Option 5), which bears some relation to the A5 sync board and could explain some changes.
I did hear once, from someone of this group, there was two versions of the A5 Sync board... one that used the Tunnel Diodes, and another one which used a Custom Tek IC to discriminate the trigger edge.
I`m not sure, but maybe this is what the -01 means...
I've never landed my eyes, however, on a schematic of the latter, or a later manual that included both.
But regardless of this board versioning, It seems rather odd to me that the connections to the J6 are disconnected, and more so, that there is no connection between the top and bottom side THROGUHOUT the board...
Moreover, there's nothing about the DM44 vs power to the A5 Trigger board... The DM44 takes its power from its own power supply and it's neither fed by the A5 board, nor the A5 board feeds it.
Yet, the only reason I can think of for the through hole plating is missing throughout the board is, either a mass murderer technician stripped them off by careless unsoldering, or yet, that it's a prototype board...
If it's the latter case, it could explain many things...
Maybe you can take a picture, post somewhere and link it here.
KRgrds,
Fabio
toggle quoted message
Show quoted text
On Thu, Aug 2, 2018 at 11:40 PM, Jim Olson wrote:
I have a question about the A5 trigger generator sweep logic board
differences. I have two 466's with out the DM44 with the same trigger board
670-3324-00 boards. I have a 464 with a DM44 with the 670-3324-01 board and it
is vastly different from the 466 boards. All the DC voltage traces from J-6
are disconnected all the through holes are unsoldered so there is no
interconnection from top to bottom through out the board. There appears to be
no cable connection to the board from the DM44 to supply these?
The DM44 manual parts list's don't show that part number used for the 464/466
with the DM44 it shows the later 466 board and I can not find the optional
boards listed in the service manuals listed in the DM44 one.
The installation sheets for installing the DM44's don't list different or
optional boards used like the service manuals do?
So whats up with this bunch of missing info here!
Jim O
|
I can't get through either.? anyone able to check with stan for details? ===================================================================== Use this... <> Rolynn
|
I can't get through either.? anyone able to check with stan for details?
it would be a shame to lose that content.
-walter
--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:-
We're all in one boat, no matter how it looks to you. (WS2)
All you need is love. (John Lennon)
But, that doesn't mean other things don't come in handy. (WS2)
|
Having a resistor R in series with the back emf diode means:
? - the peak reverse voltage is higher: not ~0.6 but ~0.6+IR
??? where I is the relay's on current
? - the current falls faster, since the energy is dissipated in R
??? as well as the diode
Having two diodes will have a similar effect, since the 0.6 will
become 1.2.
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Show quoted text
On 03/08/18 14:09, Chuck Harris wrote: I did a little study on back emf diodes for relays back when I
was a young engineer, and had noticed how a relay with a back
emf diode was quick to acuate, but slow to release... thus
subjecting the contact to burning on release.
I found that simply adding a second silicon diode in series
was usually sufficient to provided a nice snappy release.
Whether one or two diodes works optimally depends on the
voltage applied, and the inductance and resistance, of the relay
coil. A relay that is very sensitive, could take several seconds
to release with a single silicon back emf diode.
In some cases, better is to use a snubber where you can custom
design the release time to fit the relay, and its application.
That little self inflicted study made the equation that every
EE memorizes in school:
V(t) = L di/dt
very real for me.
-Chuck Harris
G?ran Krusell wrote:
I once read somewhere that one of the major relay vendors, don¡¯t remember which, suggests that a 10 V zener diode is inserted in series with the fly back diode. The purpose is to make certain that the relay for sure changes state.
G?ran
|
I did a little study on back emf diodes for relays back when I
was a young engineer, and had noticed how a relay with a back
emf diode was quick to acuate, but slow to release... thus
subjecting the contact to burning on release.
I found that simply adding a second silicon diode in series
was usually sufficient to provided a nice snappy release.
Whether one or two diodes works optimally depends on the
voltage applied, and the inductance and resistance, of the relay
coil. A relay that is very sensitive, could take several seconds
to release with a single silicon back emf diode.
In some cases, better is to use a snubber where you can custom
design the release time to fit the relay, and its application.
That little self inflicted study made the equation that every
EE memorizes in school:
V(t) = L di/dt
very real for me.
-Chuck Harris
G?ran Krusell wrote:
toggle quoted message
Show quoted text
I once read somewhere that one of the major relay vendors, don¡¯t remember which, suggests that a 10 V zener diode is inserted in series with the fly back diode. The purpose is to make certain that the relay for sure changes state.
G?ran
|
I once read somewhere that one of the major relay vendors, don¡¯t remember which, suggests that a 10 V zener diode is inserted in series with the fly back diode. The purpose is to make certain that the relay for sure changes state.
G?ran
|
His IP address was 50.246.236.85 which is pointed to by the domain "reprise.com". It is a standard Comcast address. "ping", "ftp" or a website (http) are not currently active at that address. Lyle On Thu, 02 Aug 2018 21:33:29 -0700 "penguin2004au" <clansman2011@...> wrote: I have been unable to access this site for some time. Does anybody
know what has happened? John Foster
-- 73 NM6Y Bickley Consulting West Inc. "Black holes are where God is dividing by zero"
|
I have been unable to access this site for some time. Does anybody know what has happened?
John Foster
|
satbeginner
zenith5106
Fabio Trevisan
Mike D
ROLYNN PRECHTL K7DFW
G?ran Krusell
Lyle Bickley