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Re: First avalanche pulser and 7A26

 

Mike <zuckerme@...> ha scritto:

Try clipping the capacitor out entirely, or using a smaller one. I've sometimes found 1-3 pF is needed to compensate for stray lead inductance.
Ok I removed the cap and the pulse was the same, with the spike
still there.

However I must say your assembly technique looks great, very low stray reactance. I think you will need to buy lots more equipment soon, because your risetimes should surpass a 7103/7A29 ;^)
Thanks, but now I'm thinking that can be also a problem, I explain
better later my suspect. As for other equipment I checked ebay for
terminators and attenuatos but the prices asked are higher than plugins :)
From now on the equipment I will buy will be bargain price only,
otherwise I'll soon have to sell all to survive :)

I am not familiar with that DSO, but they are typically not designed for clean pulse response faster than the rated risetime. I think the 7A26 is also affected by the overshoot; you can see some of it.
So, correct me if I'm understanding wrong, there is a sign of a spike
with uncontrolled amplitude at the start of the pulse?
I modified the circuit, here is the schematic:


R3 R4 R5 before were all 0805 resp. 22 22 47, now I used 1/8W leaded,
with the leads trimmed short,and values of 39 4.7 47, now the pulse is
a little better but the spike is still there.
I will try to return to 0805, but it seems that doesn makes
visible difference.


See Tom and David's comments (and BTW, you have just independently measured your cable insulator's dielectric constant)
Oh, good... I think.

See above, I believe the layout looks plenty good enough for <300 ps
This is what I suspected:
is it possible that the parasitic capacitance of the unleaded
0805 resistor divider prevails and passes that high spike without attenuation?
This is why i used again leaded components.

(if you selected too low Z components, you could see the first "step" go down into the cellar; but this quenches the avalanche, so you only get one step).
These are the pulses with the modified circuit, the reflection is better,
the total amplitude is a safer 3V, the spike remains but I discovered
that the DSO shows the spike at 2V per division, but cuts it below
that level, at 2V/div I can ear an internal relay that switches so
probably the internal signal path changes and so change the input
characteristics of the instrument.

DSO 500mV/div

2V/div, higher BW?

7A26 amplitude and overall pulse:

7A26 risetime.



BTW from this picture and your schematic, you can deduce the effective impedance of your transistor junction while avalanching, which is a cute party trick.
This is definitely over my knowledge by a fair margin :)

Fabio.

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Re: Input from or challange for the experts amongts us (or Brain Candy) whichever ti

Tom Jobe
 

If you are interested in the current Bob Parker ESR meter designs, have a look at the EVB meter. It comes from Portugal as either a kit or as a finished ESR meter for a very fair price. I also have the "Blue" ESR meter which functions identically, but I find the ESR chart on the front of the EVB meter to be more useful than the ESR chart on the Blue meter.
I have no connection with the EVB company other than being one of their happy customers.

tom jobe...

----- Original Message -----
From: "Mark Wendt" <mark.wendt@...>
To: <TekScopes@...>
Sent: Tuesday, May 22, 2012 3:00 AM
Subject: Re: [TekScopes] Re: Input from or challange for the experts amongts us (or Brain Candy) whichever ti


On 05/22/2012 12:21 AM, Don Black wrote:
Dick Smith Electronics was bought out by Woolworths a number of years
ago and has just become another electronics goods shop (new TV, Ipod,
etc.). They no longer sell the ESR kits but Altronics have taken over
the kit and still sell it
<>. I have one
and it works extremely well, the test pulse amplitude is low enough not
to turn on semiconductor junctions and it can normally be used in
circuit. It tests well down to less than 1 ???F.

Don Black.
Just for curiosity's sake, has anyone done a side by side comparison
between the the K2574 and the "Blue" meter? The "Blue" meter kit is
about $10 cheaper. Not that I'm a tightwad, but that's $10 that could
go towards another plugin... ;-)

Mark


------------------------------------

Yahoo! Groups Links
Re: Is it better to ventilate a TCXO or keep it away from room temp variations

G?ran Krusell
 

开云体育

Hi Dennis,
?
There are five parameters which affect frequency accuracy of high quality oscillators like OCXO and TCXO (in falling importance): aging, initial offset, temperature variation, capactive load variation, supply voltage variation.
You will have the best stability over time if you let the oscillator operate under constant conditions within its operating temperature range.
What a fan does is to add a cooling effect and this may affect the frequency or phase drift. This can easily be seen if you have an oscillator locked in a loop with a low bandwidth, like 1 mHz, and then you breath or blow on it. The phase will take a walk...
?
G?ran
?

Re: Input from or challange for the experts amongts us (or Brain Candy) whichever ti

Mark Wendt
 

On 05/22/2012 12:21 AM, Don Black wrote:
Dick Smith Electronics was bought out by Woolworths a number of years
ago and has just become another electronics goods shop (new TV, Ipod,
etc.). They no longer sell the ESR kits but Altronics have taken over
the kit and still sell it
<>. I have one
and it works extremely well, the test pulse amplitude is low enough not
to turn on semiconductor junctions and it can normally be used in
circuit. It tests well down to less than 1 ???F.

Don Black.
Just for curiosity's sake, has anyone done a side by side comparison between the the K2574 and the "Blue" meter? The "Blue" meter kit is about $10 cheaper. Not that I'm a tightwad, but that's $10 that could go towards another plugin... ;-)

Mark
Re: 7704A power supply

Albert
 

The SMPS will be in tick mode then. There is an old message about which load at the big connector would work.
Raymond, you probably confuse a hissing sound with those "ticks", about 2 per second. My first thought with "hissing" would be HV noise, but that is out of the question here since you disconnected the 25 kHz cables to the HV. There is no reason for a hissing sound now when it wasn't there previously, unless your ears can come closer now.
But why remove (or suspect) the PS in the first place? You can check the voltages at many other places, for instance at the Hor Amp board power connector, where you also find about +130 V (IIRC) which is generated by the HV box in the display unit. If those voltages are correct then leave the SMPS alone. Check the Z-axis and CRT circuits for delivering the required Grid Bias and required output at maximum intensity (see calibration). If you have a suitable probe, measure the HV test point.
BTW you did not overlook the separate A and B intensity knobs?

Albert

I have tried it with just the bottom half but it never works. I have never damaged one by trying.
Jerry Massengale

Thanks for responding, Jerry. Of course, it's a 7704A, my bad.
Do you know if operating without Display Unit causes damage, did you ever do/try?

Raymond
Re: Speaking of curve tracers

Mark Wendt
 

On 05/21/2012 04:46 PM, Steve Vineyard wrote:
I think I found the book you are interested in. Go to the following link:



Steve,
KJ5RV
Steve,

Thanks!!!! What a great group!

Mark
Re: Is it better to ventilate a TCXO or keep it away from room temp variations

 

Some manufacturers enclose the crystal or oscillator in styrofoam to maintain temperature stability and to prevent drafts.
Rick
==================================================================

--- In TekScopes@..., "Dennis Tillman" <dennis@...> wrote:

Specifically, if you have a Temperature Controlled Crystal Oscillator (TCXO)
like you find in a few Tek TM5000 instruments with the high stability time
base option:

. Is it better to enclose the plugin with a solid aluminum top
extrusion, bottom extrusion, and side covers?

OR

. Is it better to allow it to breathe with a vented top, bottom and
side panels (the ones with all the holes)?



By BETTER mean which choice will result in a more stable TCXO frequency
output?

And by STABLE I mean the least drift over time,

And by TIME I mean anything from a day to a week.



ASSUMPTIONS:

Assume for arguments sake we are talking about a temperature controlled
environment like a home or office where the room temperature doesn't vary by
more than 10 deg F.

Assume there are no power line fluctuations.

Assume the local temperature rise due to the oven is not great enough to be
detrimental to the lifetime of the rest of the components around it.

Ignore crystal aging which is another matter.



It seems to me, if you enclose the plugin that the TCXO resides in, the
temperature will reach a stable equilibrium and fluctuate less than if you
ventilate the plug-in. But I think there are also good reasons to keep
things cool with a fan blowing heat away.



Is there a definitive answer or does it depend on something I might have
missed?



Dennis
Re: First avalanche pulser and 7A26

 

you can also turn off email messages without unsubscribing. Just change the options in your group profile. That's what I do, although I read almost all of the messages from within the group website. That way you still have access, but your in-box doesn't get overwhelmed.
Bob

--- In TekScopes@..., Seibert <katgod@...> wrote:

I would like to get out of this group, I have asked to unsubscribe about 20 times over the last week but I have had no luck.
Can someone else enlighten me as to what I am doing wrong or is this some sort of hotel california? I am using the unsubscribe
at the bottom right of the email and have also asked specifically to unsubscribe in the email although I don't think that should
be necessary.
Mark

On May 21, 2012, at 4:32 AM, Mike wrote:

Fabio-

No, not really. The LT application note is misleading on this point.

Risetime is useful to characterize response to a step function, having well-defined initial and final DC levels and a monotonic slope between. It's _not_ appropriate for describing the response to an impulse.

If you wish, you can convert your project into a step generator quite easily, by substituting a scrap of coaxial cable (with the far end open-circuit) in place of the capacitor.

There's much more discussion in recent archives of this group. Search on "avalanche."

Have fun,

Mike

--- In TekScopes@..., Fabio Eboli <fabioeb@> wrote:

Can I conclude that the Philips has a 4nS risetime?
Mark
Re: Input from or challange for the experts amongts us (or Brain Candy) whichever ti

 

I might try duplicating an impedance bridge with a pair of 10 turn
potentiometers and a couple of range switches. The ESI 250DA and a
couple of others from that era used eye tubes as null indicators which
an oscilloscope display could easily handle. I suspect taking
advantage of a 2 dimensions would make it possible to visualize
dielectric absorption or other imperfections.

Getting from the reactance and D/Q settings to the oscilloscope
readout would be tricky though. There I would go the full
microcontroller route to generate the necessary readout control
signals which would also allow easy conversion between D, Q, and ESR.

On Mon, 21 May 2012 08:11:09 -0000, "fred" <fredschneider@...>
wrote:

The best way is to look at phase that is what they do in a IV impedance meter, a high end LCR meter or a VNA. And because this is the only good way you do not see agilent or Fluke ESR meters. If you build it right it would be foolish not to make an LCR meter out of it because it would be allmost as complicated. If you have capaitance and D ( old LCR bridged let you measure that) and calculate Xc from that on the working frequency ( ESR changes with frequency but not so much a bad cap looks good on low frequency, for instance 5 mOhm at 100KHz can be 100 mOhm at 100 MHz. That is 20x higher but also very high in frequency. It only becomes higher so if the cap is bad it will be also at 100KHz or lower.
Re: print/plot option for 2230

 

开云体育

Try the open source KE5FX plotter emulator software from John Miles

?

You will need a USB-Serial converter, If your PC/laptop does not have a serial port. For the fewest hassles, try to get one with the FTDI chipset.

?

?

?

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of photo692002
Sent: Friday, May 18, 2012 12:42 PM
To: TekScopes@...
Subject: [TekScopes] print/plot option for 2230

?

?

Hello All

I have a 2230 scope which is equipped withe the standard 9 pin analog plotter port and the option 12 RS-232 port which can print to a HPGL, Thinkjet or certain Epson printers.

I used this many years ago with a small TEK plotter to print saved waveforms.

Now I would like to print/plot to my XP PC rather than a hard printer. Does anyone know of a PC app, preferably freeware or inexpensive shareware which allows that? USB on PC would be nice but I can install a RS-232 port if necessary.

Thanks for any info provided.

Larry
Re: Input from or challange for the experts amongts us (or Brain Candy) whichever ti

Don Black
 

Dick Smith Electronics was bought out by Woolworths a number of years ago and has just become another electronics goods shop (new TV, Ipod, etc.). They no longer sell the ESR kits but Altronics have taken over the kit and still sell it <>. I have one and it works extremely well, the test pulse amplitude is low enough not to turn on semiconductor junctions and it can normally be used in circuit. It tests well down to less than 1 ???F.

Don Black.

On 21-May-12 8:39 PM, John Miles wrote:
Which looks to be no longer available. Is the "Blue" meter equivalent
with "modern" cosmetics?
I'm not sure; it looks pretty similar to what I have, though. One page is
quoting their price as $149 for an assembled and tested model, which seems
excessive. I definitely didn't pay that much for mine.

The Peak Electronics ESR meter that Fred mentioned is cheaper and does more
stuff. They originally had a bit of a design flaw, though, in that you had
to press the Test button each time you wanted to check a capacitor. The
usual service "workflow" for these instruments involves quickly checking
lots of capacitors across one or more PC boards, so this was a real
forehead-slapper.

(That's also why I don't think much of turning the job into a vector network
analysis problem, interpreting X/Y displays or phase difference readings or
anything else. With any good ESR meter, the difference between a bad
capacitor and a good one is usually unmistakably and immediately apparent.
When it's not, you're going to have to take the capacitor out of circuit
anyway.)

I see on Peak's web page ()
that they appear to have corrected this in their current ESR60 and ESR70
models. I've never used their ESR meters but I have their Atlas DCA
semiconductor analyzer, and it's come in handy many times. If I needed a
new ESR meter at this moment, I'd probably buy theirs.

Don't neglect the value of the ESR meter as a generic "low ohms meter," too.
The Bob Parker meter is good at helping locate shorts by allowing you to
observe how the resistance between copper traces changes as you move the
probes around. Hopefully that's true of the revised Peak Atlas models as
well. You can indeed make two-wire resistance readings very close to 0 ohms
with these gadgets.

-- john, KE5FX




------------------------------------

Yahoo! Groups Links
Re: 7704 power supply

 

Raymond,
I have repared my 7704A two times. Be sure to have the right manual. Most manuals are about the 7704 and that has no switching power supply.
The powersupply will not start without a load but it keeps trying.
I removed the psu and then connected it outside the mainframe. If there is. Problem on the rails most chances are bad caps. I had to replace to electrolitics and two tantaliums. Both rather small filtercaps. Problem is tht it is hard to get acces fr measuring while powered on.
My problem was trace compression just after starting it up.

The second problem was an easy fix, again trace compresion but this time permanent. The problem was a dirty pot on the X amp on top of the CRT, that distrorted the sawtooth. They are very nice scopes but also complex.

A hiss and penetrant smell are typical for a cooking electrolyte. I becomes hot and builds up pressure in side. Modern caps have a top that pops open, so they are easy to spot, old caps blow there guts to the underside.

Connect your psu outside the mainframe but in such a way it is connected. I can not remember if i used a sort of extension lead, sorry bit my memory is very bad.
Then measure ripple and voltages. The psu is comlicated but explained in the manual. Much rils depends on each other, so if one rail is wrong, search in that rail, if more are wrong the problem is probably one common level under that. Your scope worked so the psu can not be terrible bad. If it is not used fr many years and fired up after that the caps have. Hard time. If you are lucky they reform. If not they start leaking DC and cook dry.

If the rails are OK, check the HV testpoint. If there is a problem there you have most times problems with intensity and focus.

Good luck, hope you can fix it, it is a great scope.

Fred pa4tim

--- In TekScopes@..., jerry massengale <j_massengale@...> wrote:

You must be talking about the 7704A which is different from the 7704. The power supply needs the display unit to have minimum load. I usually measure what I can at the horizontal input connector.


Jerry Massengale





-----Original Message-----
From: raymonddompfrank <r.domp.frank@...>
To: TekScopes <TekScopes@...>
Sent: Mon, May 21, 2012 8:20 pm
Subject: [TekScopes] 7704 power supply





I am a newbie Tek collector, having used my own 465 until some 20 years ago. I am reasonably knowledgeable in electronics.

The other day, I purchased a 7704 after only giving it a very quick test. I agree that wasn't very clever. Unfortunately I noticed some brightness and timebase issues and I decided to have a look inside the instrument. That wasn't very clever either...
I checked the +54.2 +- 0.25V without removing the power supply. It turned out OK (54.4). I decided to check some other voltages on the top regulator board and decided to remove the display unit (D7704) to reach in. I realized that many switching power supplies don't like very light loads but decided it was easier and the location of the description of how to remove the D7704 in the maintenance manual was such that I concluded it was safe. Also, I haven't found any warning re. this procedure.
Anyway, since I removed the D7704 and switched the PS on, there's a hissing sound from it and from what I measured, all preregulated voltages are much lower than normal: +54V now is 30V, -54V is -30V, 7V is 2V etc. Also, the front lights remain off (not surprising).
I'm anxious leaving the PS on for more than a few seconds.

My Question: Did I indeed blow up the PS and if so, is there a component that usually blows up and is the repair doable or even easy? There's no nasty burning smell or anything.
Or is this just a coincidence, and have I just witnessed another electrolytic capacitor dying?

Thanks for any ideas!

Raymond
Re: 7704 power supply

 

Hi,

I have tried it with just the bottom half but it never works. I have never damaged one by trying.

Jerry Massengale



-----Original Message-----
From: raymonddompfrank
To: TekScopes <TekScopes@...>
Sent: Mon, May 21, 2012 9:40 pm
Subject: [TekScopes] Re: 7704 power supply

?

Thanks for responding, Jerry. Of course, it's a 7704A, my bad.
Do you know if operating without Display Unit causes damage, did you ever do/try?

Raymond

--- In TekScopes@..., jerry massengale wrote:
>
> You must be talking about the 7704A which is different from the 7704. The power supply needs the display unit to have minimum load. I usually measure what I can at the horizontal input connector.
>
>
> Jerry Massengale
>
>
>
>
>
> -----Original Message-----
> From: raymonddompfrank
> To: TekScopes <TekScopes@...>
> Sent: Mon, May 21, 2012 8:20 pm
> Subject: [TekScopes] 7704 power supply
>
>
>
>
>
> I am a newbie Tek collector, having used my own 465 until some 20 years ago. I am reasonably knowledgeable in electronics.
>
> The other day, I purchased a 7704 after only giving it a very quick test. I agree that wasn't very clever. Unfortunately I noticed some brightness and timebase issues and I decided to have a look inside the instrument. That wasn't very clever either...
> I checked the +54.2 +- 0.25V without removing the power supply. It turned out OK (54.4). I decided to check some other voltages on the top regulator board and decided to remove the display unit (D7704) to reach in. I realized that many switching power supplies don't like very light loads but decided it was easier and the location of the description of how to remove the D7704 in the maintenance manual was such that I concluded it was safe. Also, I haven't found any warning re. this procedure.
> Anyway, since I removed the D7704 and switched the PS on, there's a hissing sound from it and from what I measured, all preregulated voltages are much lower than normal: +54V now is 30V, -54V is -30V, 7V is 2V etc. Also, the front lights remain off (not surprising).
> I'm anxious leaving the PS on for more than a few seconds.
>
> My Question: Did I indeed blow up the PS and if so, is there a component that usually blows up and is the repair doable or even easy? There's no nasty burning smell or anything.
> Or is this just a coincidence, and have I just witnessed another electrolytic capacitor dying?
>
> Thanks for any ideas!
>
> Raymond
>
Re: 7704 power supply

raymonddompfrank
 

Thanks for responding, Jerry. Of course, it's a 7704A, my bad.
Do you know if operating without Display Unit causes damage, did you ever do/try?

Raymond

--- In TekScopes@..., jerry massengale <j_massengale@...> wrote:

You must be talking about the 7704A which is different from the 7704. The power supply needs the display unit to have minimum load. I usually measure what I can at the horizontal input connector.


Jerry Massengale





-----Original Message-----
From: raymonddompfrank <r.domp.frank@...>
To: TekScopes <TekScopes@...>
Sent: Mon, May 21, 2012 8:20 pm
Subject: [TekScopes] 7704 power supply





I am a newbie Tek collector, having used my own 465 until some 20 years ago. I am reasonably knowledgeable in electronics.

The other day, I purchased a 7704 after only giving it a very quick test. I agree that wasn't very clever. Unfortunately I noticed some brightness and timebase issues and I decided to have a look inside the instrument. That wasn't very clever either...
I checked the +54.2 +- 0.25V without removing the power supply. It turned out OK (54.4). I decided to check some other voltages on the top regulator board and decided to remove the display unit (D7704) to reach in. I realized that many switching power supplies don't like very light loads but decided it was easier and the location of the description of how to remove the D7704 in the maintenance manual was such that I concluded it was safe. Also, I haven't found any warning re. this procedure.
Anyway, since I removed the D7704 and switched the PS on, there's a hissing sound from it and from what I measured, all preregulated voltages are much lower than normal: +54V now is 30V, -54V is -30V, 7V is 2V etc. Also, the front lights remain off (not surprising).
I'm anxious leaving the PS on for more than a few seconds.

My Question: Did I indeed blow up the PS and if so, is there a component that usually blows up and is the repair doable or even easy? There's no nasty burning smell or anything.
Or is this just a coincidence, and have I just witnessed another electrolytic capacitor dying?

Thanks for any ideas!

Raymond
Re: DPO question

 

--- In TekScopes@..., "Steve" <ditter2@...> wrote:


During the scope development, DPO was called "Color Graded InstaVu". The marketing name (Which I considered incredible over hyped and I was on the scope team when it was developed) was assigned later.

Both InstaVu and DPO are not extremely useful for VIEWING the waveform. The real power is to initially look at a waveform and find rare events which can be used to refine the complex trigger capabilities. Once you see the width or amplitude of a narrow intermittant runt, you can set the advanced trigger to the correct conditions so the scope triggers on the fault condition. Once you do this, you have a very sharp waveform view of the fault.

When I was involved with customer training while at Tek, this is how I promoted both InstaVu and the color garded variety of it.

As for upgrading, if you are not seeing the fault you are looking for with IV, you may not see it with DPO either. The latter uses a new generation of display processor, which does capture even more of all real time however, so it *may* catch some things that IV does not. But given enough time, IV would catch it as well.

- Steve
So, it sounds like you're saying that DPO is an enhanced version of Instavu (at least the first generation DPO on the TDS7XXD). The marketing I've seen for the TDS7XXD series makes a big deal out of the ability to view a composite video waveform with similar detail to an analog scope. This is the type of thing I'm really looking for. Instavu on the 744A is good for certain applications, but it's cumbersome to use.

The TDS744A is great when I know what I'm looking for, but it's almost useless for general use because it misses anything that's too fast for the chosen sweep rate. For example, you can have several volts of high frequency ripple on a power supply rail, but it will look like clean DC if the 744A is at a slow sweep rate. An analog scope will see that type of problem easily at any sweep rate, and that's why I still have a 475 next to my work bench. If I could find a digital scope that did more of what my 475 does for not that much more money, it would be worth it. They certainly make it look like a TDS7XXD goes in that direction.

Thanks,

Andy
Is it better to ventilate a TCXO or keep it away from room temp variations

 

开云体育

Specifically, if you have a Temperature Controlled Crystal Oscillator (TCXO) like you find in a few Tek TM5000 instruments with the high stability time base option:

·???????? Is it better to enclose the plugin with a solid aluminum top extrusion, bottom extrusion, and side covers?

OR

·???????? Is it better to allow it to breathe with a vented top, bottom and side panels (the ones with all the holes)?

?

By BETTER mean which choice will result in a more stable TCXO frequency output?

And by STABLE I mean the least drift over time,

And by TIME I mean anything from a day to a week.

?

ASSUMPTIONS:

Assume for arguments sake we are talking about a temperature controlled environment like a home or office where the room temperature doesn’t vary by more than 10 deg F.

Assume there are no power line fluctuations.

Assume the local temperature rise due to the oven is not great enough to be detrimental to the lifetime of the rest of the components around it.

Ignore crystal aging which is another matter.

?

It seems to me, if you enclose the plugin that the TCXO resides in, the temperature will reach a stable equilibrium and fluctuate less than if you ventilate the plug-in. But I think there are also good reasons to keep things cool with a fan blowing heat away.

?

Is there a definitive answer or does it depend on something I might have missed?

?

Dennis
Re: 7704 power supply

 

You must be talking about the 7704A which is different from the 7704. The power supply needs the display unit to have minimum load. I usually measure what I can at the horizontal input connector.

Jerry Massengale



-----Original Message-----
From: raymonddompfrank
To: TekScopes
Sent: Mon, May 21, 2012 8:20 pm
Subject: [TekScopes] 7704 power supply

?
I am a newbie Tek collector, having used my own 465 until some 20 years ago. I am reasonably knowledgeable in electronics.

The other day, I purchased a 7704 after only giving it a very quick test. I agree that wasn't very clever. Unfortunately I noticed some brightness and timebase issues and I decided to have a look inside the instrument. That wasn't very clever either...
I checked the +54.2 +- 0.25V without removing the power supply. It turned out OK (54.4). I decided to check some other voltages on the top regulator board and decided to remove the display unit (D7704) to reach in. I realized that many switching power supplies don't like very light loads but decided it was easier and the location of the description of how to remove the D7704 in the maintenance manual was such that I concluded it was safe. Also, I haven't found any warning re. this procedure.
Anyway, since I removed the D7704 and switched the PS on, there's a hissing sound from it and from what I measured, all preregulated voltages are much lower than normal: +54V now is 30V, -54V is -30V, 7V is 2V etc. Also, the front lights remain off (not surprising).
I'm anxious leaving the PS on for more than a few seconds.

My Question: Did I indeed blow up the PS and if so, is there a component that usually blows up and is the repair doable or even easy? There's no nasty burning smell or anything.
Or is this just a coincidence, and have I just witnessed another electrolytic capacitor dying?

Thanks for any ideas!

Raymond
7704 power supply

raymonddompfrank
 

I am a newbie Tek collector, having used my own 465 until some 20 years ago. I am reasonably knowledgeable in electronics.

The other day, I purchased a 7704 after only giving it a very quick test. I agree that wasn't very clever. Unfortunately I noticed some brightness and timebase issues and I decided to have a look inside the instrument. That wasn't very clever either...
I checked the +54.2 +- 0.25V without removing the power supply. It turned out OK (54.4). I decided to check some other voltages on the top regulator board and decided to remove the display unit (D7704) to reach in. I realized that many switching power supplies don't like very light loads but decided it was easier and the location of the description of how to remove the D7704 in the maintenance manual was such that I concluded it was safe. Also, I haven't found any warning re. this procedure.
Anyway, since I removed the D7704 and switched the PS on, there's a hissing sound from it and from what I measured, all preregulated voltages are much lower than normal: +54V now is 30V, -54V is -30V, 7V is 2V etc. Also, the front lights remain off (not surprising).
I'm anxious leaving the PS on for more than a few seconds.

My Question: Did I indeed blow up the PS and if so, is there a component that usually blows up and is the repair doable or even easy? There's no nasty burning smell or anything.
Or is this just a coincidence, and have I just witnessed another electrolytic capacitor dying?

Thanks for any ideas!

Raymond
Re: Input from or challange for the experts amongst us (or Brain Candy) whichever ti

Rob
 

"Based on the nature of the questions doswoodman asked I believe he is
interested in building something that is affordable and educational at the
same time".

This was indeed the basis of my initial query. I am however truly grateful
for all replies as I am learning a lot. In hind sight I should have
realized my line of questioning for technically minded EE was akin to when I
am asked "What does it take to make bio-diesel" or better yet "Can gasoline
be made from common household garbage" as a Chem E.... Several layers to
either of those onions if you will...

In any event, the discourse has been truly enlightening. I do actually think
I may continue research into the subject with the goal in mind of perhaps
being able to come up with a "trouble shooting aid" via injecting suitable
signal for a go-nogo determination on caps, etc. via a 7000 series plug-in
and or scope measurements in general.

The overall goal being something I can utilize/putz with vs. market, and/or
be 'technically' useful for measurement, etc.


Thanks again all. As always I hope this finds you well
Rob aka Doswoodman....
P.S. Hopefully at the interlude instead of conclusion.

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of Dennis Tillman
Sent: Monday, May 21, 2012 8:54 AM
To: TekScopes@...
Subject: RE: [TekScopes] Re: Input from or challange for the experts amongts
us (or Brain Candy) whichever ti

Based on the nature of the questions doswoodman asked I believe he is
interested in building something that is affordable and educational at the
same time.

Fred makes some good points but I can't afford a VNA and I doubt many of us
can. A few lucky members may have access to one at their workplace. From the
nature of the questions doswoodman was asking a simple ESR meter, curve
tracer or inexpensive solution is what he was after.

An ESR meter is affordable, and as Fred points out you can make your own
simple one. The versatility of the instruments you own depends in part on
the user. I discovered there are lots of other uses for an ESR meter - it
measures the ESR of batteries for instance, and it can be used to find
shorts. Reading the theory of operation was enlightening as well because it
explained a great deal about ESR and the difficulty of measuring it.

As Fred mentions curve tracers can measure capacitance. I have frequently
used a curve tracer with excellent results to measure capacitors in circuit.
Most people never measure anything other than semiconductors on a curve
tracer. Curve tracers are general purpose instruments that can measure much
more than semiconductors. Any electrical device can be measured on a curve
tracer. Many plans have been published on the web for a simple curve tracer
that is easy to build and not expensive at all.

Fred's post did remind me of a RCL meter that is based on some very
sophisticated software I came across that anyone can build that owns a PC
with a sound card. The required external hardware is just 2 resistors and 2
capacitors. So the cost is almost nothing. Here is the URL


It measures
- capacitances (5pF to 5uF)
- inductances (5uH to 50mH)
- resistances (5 Ohm to 50 MOhm)

Version 1.10 includes an improved phase shift measurement, making the
software less critical toward the quality of the soundcard.

Dennis

-----Original Message-----
From: fred, Sent: Monday, May 21, 2012 1:11 AM

<snip>
i do not agree, measuring ESR in circuit is only an indication, most ESR
meters re only indicators who have problems measuring accurate under 10 uF
because they do not measure the phase difference but only the voltage drop
caused by the ESR, and that is a " floating" drop so most measure a to high
value. You can not meaure that drop with a detectot but your eye and brain
can.

A ESR meter that does work is just your scope and a simple squarewave
generator. But a low ESR gives a very small drop on a rather large signal so
you need a sensitive scope. You can build one with a 555. Must be a lot
cheaper as 100 dollar

The best way is to look at phase that is what they do in a IV impedance
meter, a high end LCR meter or a VNA.

Fred

--- In TekScopes@..., "Dennis Tillman" <dennis@...> wrote:
* ESR meters such as the Dick Smith ESR meter and others like it use
pulses to measure the ESR. It is all well explained in the theory of
operation for the Dick Smith ESR Manual which you should be able to
fine on the web. One advantage of this method is it cam measure the
ESR of a cap in circuit. You can buy a good ESR meter on eBay for
~$100 which would be far less than the cost (in time) of making one.

Dennis


------------------------------------

Yahoo! Groups Links
Re: Looking for Tek 2445x 2465x Fan assembly parts etc.

Tom Jobe
 

开云体育

Hi John,
I have a little bag of burned up fan parts here, and the only part in common between the 4xx and the early 24x5 fan assemblies is the bare fan motor body. The circuit board, the fan, and how?the fan?attaches to the shaft are all different, as is the fan assembly mounting.
The two fans run on different voltages too, one uses an unregulated 15 volt line that is about 21 volts as I remember, and the other runs on maybe 15 volt regulated supply. Don't hold me to this, as it has been awhile since I messed with those fan assemblies.
You need the complete early style 24x5 fan assembly, or maybe you need to look at using a modern flat computer fan like the later 24x5's had.
Maybe you will get lucky and Victor the 24x5?master, will weigh in on your fan problem.
tom jobe...
?
?
?
?
?

----- Original Message -----
From: John B
Sent: Monday, May 21, 2012 2:44 PM
Subject: [TekScopes] Looking for Tek 2445x 2465x Fan assembly parts etc.

?

Hi Group,

I bought a Tek 2445 scope at the Dayton Hamvention. One of the previous owners had removed the complete fan cooling system ;-(

I am in need of the following parts:

The A10 circuit board assembly 670-7390-00

This includes the motor.

This part is common to 400 series scopes like the 465, 475 etc.

The fan blades 369-0043-01

The collet 343-1040-01

Any help would be appreciated.

John VE3XRY
132621 - 132640 of 208740