Hello,
I had a quick look on the 2232 schematics and my 2215A board layout:
The 2232 has a full wave rectifier (CR965 & CR967 coming from pin 20 and 22 of the transformer) and a capacitor C965 and a current limiting resistor R965 installed to power the additional fan.
Based on the empty room on my 2215A PCB it looks like they only planned a half wave rectifier?
There is room for 1 diode coming from pin 20 of the transformer, 1 capacitor and 1 resistor and a 2-pin connector for the fan.
Will try this,
Un saludo,
Leo
|
Hi, I for sure want to add a fan too! The album I made is open for the group, so you can simply add the pictures here: /g/TekScopes/album?id=64919Un saludo, Leo
|
Tom,
I recommend posting on groups.io
George
BTW, you owe me a lunch time visit...
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On Aug 4, 2018, at 5:08 PM, tom jobe <tomjobe@...> wrote:
Hello,
Do not forget that scopes such as the 2215A and the 2235 have the fan drive circuitry you need already printed on the mainboard, but it is un-documented in the service manual.
You just populate the half wave fan circuit with a few components, and put a 60mm 12 volt fan on the back panel, on the two fan mounting holes that are already there.
This Tektronix fan circuitry drives the fan at a much reduced voltage, so noise is not a problem.
About those large resistors under the CRT that often scorch the mainboard... on the later production 22xx scopes Tektronix raised those resistor up so air could get in underneath them.
You can easily raise your your existing resistors by removing them and attaching some simple extensions to the resistor's leads. Do check the value of your existing resistors to make sure they have not been cooked too much and had the value changed before you raise them. Also consider raising them at alternating heights so you don't make a "wall" of side by side resistors that is just up higher.
My guess is that the burnt mainboards are in scopes that were run 24/7 and had the scope installed in a level position, so there was no 'chimney' effect to make the heat rise through the scope.
I have some photos of the above modifications that I can send to anyone directly on request. If you want these photos to be posted elsewhere, you can do it.
tom jobe...
On 8/4/2018 6:58 AM, Vincent Trouilliez wrote:
No idea about FET temperature, as I have no way to measure temperatures yet ! A thermocouple for my DMM and a simple IR "gun" are on my list of things to buy, but the thing is sooooo long, no idea when I will get round to it ! ;-)
As for discoloration/overheating, I don't see any sign of it on my scope, anywhere. All power resistors look sparkling new and so does the PCB in their vicinity. I guess that only means my scope happens to be a low hour unit.
These beefy resistors overheating in the 2215 and 2215A ans 2235 scopes, as per your findings, is probably due to the fact that these 3 scopes are among the few 22XX scopes which did not have a cooling fan.... what a "coincidence" ! ...
Well I can only speak for my personal 2215, which definitely does not have a fan. However I just downloaded the service manual of both the 2215A and 2235 to have a quick look at their mechanical parts list, and they indeed do not seem to have a cooling fan. All these 3 scopes being so closely related technically (the 2215 being an updated 2215 AIUI, and the 2235 just being a 2215 with improved B/W), I guess it's consistent.
Probably why some people advise to add a cooling fan, especially since the back of the cabinet/chassis already provides the "grill" where a cooling fan would go. So it's not that big of a job as far as mechanical integration goes, at least.
All that being said, unless your scope is not working properly (other than SMPS issues I mean), then I don't see any emergency to replace those resistors. Unless of course your aim is to spend time and money to make the scope as good as it can get, and as reliable in the long term as can be.
If so then yes, I guess adding a cooling fan and replacing those resistors wouldn't hurt. While doing so, you could fit higher wattage resistor (a size up), since space is not at a premium in this area of the scope, from what I can see on my 2215. Also you could try and raise the resistor off the board by half an inch or so, to improve cooling a bit and keep them from burning the PCB any further.
I remember a discussion on here not so long ago, about dedicated tools used to form the leads of (these very ?) power resistors to raise them from the PCB.
Don't ask me to dig out that thread though...my searching skills are not that good... but it's there... somewhere...
I remember it because I found it cool to have a nice little tool to be able to form the leads "cleanly", in a professional looking manner. Will definitely get one of these tools some day...
As for my 2232, was involved indeed, especially since it was my first "meaty" repair experience (definitely more than just replacing a blow fuse I mean ! LOL) , and had zero working knowledge of the 22XX scopes not even SMPS in general...
Still, I need to get back to that scope, to recap the PSU, as well as try to get rid of the SMPS annoying whine issue, and another issue also, where the trace on the CRT look "dotted" at some sweep speeds. Never a dull moment with this old 2232 ! ^^ But that will be for later...
Regards,
Vincent Trouilliez
|
Vincent,
This is certainly a mod I want to do to my 2215. A modest amount of air improves the life of electronics a lot.
I¡¯d be grateful to get the pictures you have, with my thanks.
Roy Morgan
k1lky68@... <mailto:k1lky68@...>
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On Aug 4, 2018, at 8:08 PM, tom jobe <tomjobe@... <mailto:tomjobe@...>> wrote:
Hello,
Do not forget that scopes such as the 2215A and the 2235 have the fan drive circuitry you need already printed on the mainboard, but it is un-documented in the service manual¡.put a 60mm 12 volt fan on the back panel, on the two fan mounting holes that are already there. I have some photos of the above modifications
|
As an aside....i had to snub a massive desulfator pulse of about 600A that delivered significant back emf from cable and battery inductance.
I was unable to quantify it until I placed a pulse diode good to 2KA and feed a 2200uF cap and measure the Cap voltage rise over time.
Eventually had to place an automotive lamp of 25W to dissipate the energy.....worked well....lamp hits just north of 13V.
I improved the design recently with a redundant lamp.
|
Hi Fabio I sent the picts in an email to you PM but comcast has changed there email to a new system so I'm not sure if you got it or not.
Jim
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On August 3, 2018 at 12:23 PM Fabio Trevisan <fabio.tr3visan@...> wrote:
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
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
|
Hello,
Do not forget that scopes such as the 2215A and the 2235 have the fan drive circuitry you need already printed on the mainboard, but it is un-documented in the service manual.
You just populate the half wave fan circuit with a few components, and put a 60mm 12 volt fan on the back panel, on the two fan mounting holes that are already there.
This Tektronix fan circuitry drives the fan at a much reduced voltage, so noise is not a problem.
About those large resistors under the CRT that often scorch the mainboard... on the later production 22xx scopes Tektronix raised those resistor up so air could get in underneath them.
You can easily raise your your existing resistors by removing them and attaching some simple extensions to the resistor's leads. Do check the value of your existing resistors to make sure they have not been cooked too much and had the value changed before you raise them. Also consider raising them at alternating heights so you don't make a "wall" of side by side resistors that is just up higher.
My guess is that the burnt mainboards are in scopes that were run 24/7 and had the scope installed in a level position, so there was no 'chimney' effect to make the heat rise through the scope.
I have some photos of the above modifications that I can send to anyone directly on request. If you want these photos to be posted elsewhere, you can do it.
tom jobe...
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On 8/4/2018 6:58 AM, Vincent Trouilliez wrote: No idea about FET temperature, as I have no way to measure temperatures yet ! A thermocouple for my DMM and a simple IR "gun" are on my list of things to buy, but the thing is sooooo long, no idea when I will get round to it ! ;-)
As for discoloration/overheating, I don't see any sign of it on my scope, anywhere. All power resistors look sparkling new and so does the PCB in their vicinity. I guess that only means my scope happens to be a low hour unit.
These beefy resistors overheating in the 2215 and 2215A ans 2235 scopes, as per your findings, is probably due to the fact that these 3 scopes are among the few 22XX scopes which did not have a cooling fan.... what a "coincidence" ! ...
Well I can only speak for my personal 2215, which definitely does not have a fan. However I just downloaded the service manual of both the 2215A and 2235 to have a quick look at their mechanical parts list, and they indeed do not seem to have a cooling fan. All these 3 scopes being so closely related technically (the 2215 being an updated 2215 AIUI, and the 2235 just being a 2215 with improved B/W), I guess it's consistent.
Probably why some people advise to add a cooling fan, especially since the back of the cabinet/chassis already provides the "grill" where a cooling fan would go. So it's not that big of a job as far as mechanical integration goes, at least.
All that being said, unless your scope is not working properly (other than SMPS issues I mean), then I don't see any emergency to replace those resistors. Unless of course your aim is to spend time and money to make the scope as good as it can get, and as reliable in the long term as can be.
If so then yes, I guess adding a cooling fan and replacing those resistors wouldn't hurt. While doing so, you could fit higher wattage resistor (a size up), since space is not at a premium in this area of the scope, from what I can see on my 2215. Also you could try and raise the resistor off the board by half an inch or so, to improve cooling a bit and keep them from burning the PCB any further.
I remember a discussion on here not so long ago, about dedicated tools used to form the leads of (these very ?) power resistors to raise them from the PCB.
Don't ask me to dig out that thread though...my searching skills are not that good... but it's there... somewhere...
I remember it because I found it cool to have a nice little tool to be able to form the leads "cleanly", in a professional looking manner. Will definitely get one of these tools some day...
As for my 2232, was involved indeed, especially since it was my first "meaty" repair experience (definitely more than just replacing a blow fuse I mean ! LOL) , and had zero working knowledge of the 22XX scopes not even SMPS in general...
Still, I need to get back to that scope, to recap the PSU, as well as try to get rid of the SMPS annoying whine issue, and another issue also, where the trace on the CRT look "dotted" at some sweep speeds. Never a dull moment with this old 2232 ! ^^ But that will be for later...
Regards,
Vincent Trouilliez
|
One more possibility for the failures in the 2465x scopes.? The inrush thermistors are effective only when they are cold.? Turning off and immediately back on means there will be inrush current.? The thermistors will still be hot from recent operation, yet the storage capacitors will be discharged from the last power down cycle.? I would not think this could be a significant problem but it does happen.
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On ?Saturday?, ?August? ?4?, ?2018? ?04?:?44?:?03? ?PM? ?CDT, M Yachad <yachadm@...> wrote:
Gentlemen
Thank you all so much.
I have learnt so much stuff about a subject about which I knew almost nothing.
Important points:
SMPS does not have inductive kick, therefore a capacitor across the on-off switch poles is not useful.
Inductive kick is present on Linear power supplies, and therefore an X-Y cap is useful across the switch poles.
The user should make snappy contact, without delays, when activating a push-push switch, and/or install a firmer spring.
Relay contacts should be examined to see if the circuit can benefit from two diodes resulting in 2x Vf, or diode + resistor.
Menahem
|
Gentlemen
Thank you all so much.
I have learnt so much stuff about a subject about which I knew almost nothing.
Important points:
SMPS does not have inductive kick, therefore a capacitor across the on-off switch poles is not useful.
Inductive kick is present on Linear power supplies, and therefore an X-Y cap is useful across the switch poles.
The user should make snappy contact, without delays, when activating a push-push switch, and/or install a firmer spring.
Relay contacts should be examined to see if the circuit can benefit from two diodes resulting in 2x Vf, or diode + resistor.
Menahem
|
On 8/4/2018 4:30 AM, satbeginner wrote: 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 hi gh. (Higher ON-resistance?? )ty Remember, this same basic circuit used in the 2230/32 scopes where there is a much! higher load on the PS. The fet runs warm but not hot. The hot fet is most likely from slower turn on/off, been there, had that. This really! raises the operating temp. Sorry I can't remember the fet that I ended up using, but I did hand select it using a verity of test methods..
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
|
No idea about FET temperature, as I have no way to measure temperatures yet ! A thermocouple for my DMM and a simple IR "gun" are on my list of things to buy, but the thing is sooooo long, no idea when I will get round to it ! ;-)
As for discoloration/overheating, I don't see any sign of it on my scope, anywhere. All power resistors look sparkling new and so does the PCB in their vicinity. I guess that only means my scope happens to be a low hour unit.
These beefy resistors overheating in the 2215 and 2215A ans 2235 scopes, as per your findings, is probably due to the fact that these 3 scopes are among the few 22XX scopes which did not have a cooling fan.... what a "coincidence" ! ...
Well I can only speak for my personal 2215, which definitely does not have a fan. However I just downloaded the service manual of both the 2215A and 2235 to have a quick look at their mechanical parts list, and they indeed do not seem to have a cooling fan. All these 3 scopes being so closely related technically (the 2215 being an updated 2215 AIUI, and the 2235 just being a 2215 with improved B/W), I guess it's consistent.
Probably why some people advise to add a cooling fan, especially since the back of the cabinet/chassis already provides the "grill" where a cooling fan would go. So it's not that big of a job as far as mechanical integration goes, at least.
All that being said, unless your scope is not working properly (other than SMPS issues I mean), then I don't see any emergency to replace those resistors. Unless of course your aim is to spend time and money to make the scope as good as it can get, and as reliable in the long term as can be.
If so then yes, I guess adding a cooling fan and replacing those resistors wouldn't hurt. While doing so, you could fit higher wattage resistor (a size up), since space is not at a premium in this area of the scope, from what I can see on my 2215. Also you could try and raise the resistor off the board by half an inch or so, to improve cooling a bit and keep them from burning the PCB any further.
I remember a discussion on here not so long ago, about dedicated tools used to form the leads of (these very ?) power resistors to raise them from the PCB.
Don't ask me to dig out that thread though...my searching skills are not that good... but it's there... somewhere...
I remember it because I found it cool to have a nice little tool to be able to form the leads "cleanly", in a professional looking manner. Will definitely get one of these tools some day...
As for my 2232, was involved indeed, especially since it was my first "meaty" repair experience (definitely more than just replacing a blow fuse I mean ! LOL) , and had zero working knowledge of the 22XX scopes not even SMPS in general...
Still, I need to get back to that scope, to recap the PSU, as well as try to get rid of the SMPS annoying whine issue, and another issue also, where the trace on the CRT look "dotted" at some sweep speeds. Never a dull moment with this old 2232 ! ^^ But that will be for later...
Regards,
Vincent Trouilliez
|
Ed makes a good point on AC power push-push switches. When they become sluggish it is a problem. Replace them if possible. Cleaning with IPA may help but may just contaminate the PCB. One thing that has helped for me is to replace the front spring with a somewhat stronger spring to get the slide action response as originally present. The switch becomes stiffer but moves between positions fast. Spring replacement can usually be done without dismounting the switch.
Kevin
|
Hi Vincent,
I will wait for the proper parts, but after the test of the transformer I wanted some confirmation I was on the right track.
Question: do you have an idea of the temperature of the FET in your scope?
According to the datasheet, the FET installed now should be able to work up to 120 degrees Celsius, but like I said, I don't want stuff to be (so) hot.
Talking about hot: there is some discolouration of the PCB of the area around R256 - R259 and R266 - R271 (Vertical deflection circuit) and the second area around R888 - R 891 (Intensity, Focus & Blanking) .
I will check these too.
Looking for pictures of other 22xx scopes show that it's mostly the 2215A and the 2235 that seem to have the exact same thing going on, like this one here:
Several pictures of eg. a 2213 do not show the discolouration.
BTW, I read your 2232 repair story, that was quite a lot more work than I had to go through with my 2215A!!
Thanks for that information,
Un saludo,
Leo
|
Hi Leo,
Glad the scope is back to life, however as you noticed... trying to use salvaged parts that don't quite fit the bill, is a waste of your time as the scope only half works... overheating as you noticed. Just be a little patient and wait for the correct part/FET to arrive in your mail box ;-)
I looked at the datasheet for your overheating FET. The total gate charge of this puppy is on the high side of things... at 48nC typical, and up to 68nC !
The gate driver circuitry is probably on the limit here and is slowing down the FET, hence overheating.
Well, just my thoughts on it any way ! ;-)
You have clearly established the fact that a replacement FET will cure your scope... so just wait for a really appropriate part to arrive in your mail box, rather than wasting time and effort reusing salvaged FET's that don't really cut it. Well unless you have really nothing better to do with your time, of course ! ;-P
Regards,
Vincent Trouilliez
|
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
|
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
|
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
|
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.
|
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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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
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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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-------- 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
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