开云体育

Hi Dennis, can u email me pls? I need some info for sending the SG504 head.
thx
Ancel

Hello all: I am looking for 1..2 Probe P6156, it is the wide band Zo probe for 50 Ohm input scopes and plugins.

There are a few on eapy, at rather high price or questionable condition.

If any group members have one (or 2?) to spare, please let me know.

I have a rather large collection of may other TEK scope probes, both passive and active, so we might be able to arrange a swap. I am in the USA.

Many thanks for looking!

With Kind Regards,

Jon

Hi All: I recently purchased a used 577 form eBay, It is in good shape although I couldn't yet even plug it on. It miss the safety plastic cover and recently the following appears in eBay:


Tektronix 576 577 Safety Shield cover for Curve tracers OLD STOCK





Tektronix 576 577 Safety Shield cover for Curve trace... US $150.00 New in Business & Industrial, Electrical & Test Equipment, Test Equipment



View on www.ebay.com
Preview by Yahoo




I looked at other 577's photo's and this one looks similar but not the same, it has a right shoulder that i did not see in other 577/76's and the tektronix logo has the (R) for registered missing. Dimensions seems to be right but for some reason I suspect this is not an original piece. My specific questions for the group are:


1) Does anybody recognize this plastic as a Tek part?
2) If so to which equipment belongs and most importantly if it would work on 577.


Thanks in advance,


Raul


PD: The packaging for the 577 was great, I will later post the photos of it in the context of tek packaging in this forum recently active.

Raymond,
You are correct the Q850 was bad and a replacement MJE800 restored the +15v.
Now I can try and fix the lack of a sweep.
When the beam finder is depressed I get a centered intense sweep of about 1/3 the width of the CRT. Just above it there is a short sweep. I suspect that what I am seeing is the horz. sweep and the readout . My diagrams do not show any normal voltages or waveform s. If someone could give me some idea what the unblanking should be and the voltage. Is there a source to find the expected wave forms and voltages?

Charlie



crpederson@...

From: hewpatek@... [TekScopes]
Date: 2016-03-24 20:16
To: TekScopes@...
Subject: [TekScopes] Re: 5440 low-voltage power supply

Charlie,
It's just after 3 AM where I live so I'll have to keep this short.
Base and emitter (and collector) of Q850 are both at 21.3 volt so it shouldn't conduct: Vbe should be at least 1.3 V.
I don't see any other alternative path than through R850.
Did you check if the plug-ins actually receive the 21.3 V? If they do, I really suspect Q850. It's not a good idea to run these plugins on > 15 V for any length of time, even if only because of the dipped tantalum C's they contain and which probably have a 15 WV rating. Unless you're certain, maybe you could solder in a resistor to load the 15 V with say 100 mA, like a >= 2 W 220 Ohm resistor.
There could be a short elsewhere, downstream "+20 V", actually causing 21.3 V to be *supplied to* the +15V PS output.

Raymond

7904 fixed! On this one it turned out to be the same type of Ta cap on the -17V unregulated supply, right next to the +17V one, as in the similar 7844 layout. This was a little weirder though. I didn't bother to power up the 7904 at first, and went directly to curve tracer measurements - it ticked when powered up that way. Then I did the CT checks on the supplies as I described on the 7844 repair, but didn't find anything wrong. But, I erred in rushing through it (promised to do a sink installation this PM), and didn't run the raw voltages all the way up, since I was expecting a shorted part.

Since I couldn't blame anything yet, I just powered it up regular and started probing around with a scope to see the various supply lines coming up part way. Then I noticed the CRT screen flashed, and things came on for a moment, then snuffed out and kept ticking. I let it run this way for about twenty minutes while I was poking around making measurements, then started to smell burnt part, but couldn't tell where it was from. I started sniffing around the scope, the CRT, and the PS, but no luck. Then, all of a sudden, all the voltages came up like normal, and right before my eyes, a huge jet of magic smoke shot out of a vent hole from under the regulator board - that narrowed it down a bit.

I opened it up and found the bad cap obviously darkened from heat, with a hole blown out one end - it had shot out right at the vent hole. As I mentioned on the 7844 fix, I have a very limited parts assortment up here, but managed to scrounge up four 6.8 uF, 35V ones to put in parallel. As hoped, the blown cap was the only problem - it fired up just fine. I'll let it burn in over night and report results tomorrow.

So, apparently this cap was partly failed and overloading the PS enough, but not fully shorted or burned open. Leaving it run ticking for a while was enough to finally heat it up and finish it off, and it's a good thing I happened to be watching at the right time.

In hindsight, if I had done my CT testing properly, I should have checked each raw supply at full voltage, and perhaps for extended times - this likely would have exposed the culprit right away. Gotta have patience in this stuff.

That's all for now - I've got a sink to install.

Ed

Hello,

I second both of the later opinions having had them for slightly over and
under 6 months for either.

The AVR gadget is very handy once you know its limitations, I use it almost
as much as a multimeter, it is quite accurate.
It will measure very large capacitors.
The downsides are the battery gauge being a bit erratic, capacity
measurements under 20pF get inaccurate. It will only test small SCRs for
lack of trigger current.

The DE-5000 I got from the bay, seller "akibashipping" it was selling a lot
cheaper than his current price.
It does kelvin measurements, the only think that could be better for the
price is the function calls but that's also quite subjective.

Paul





Le samedi 26 mars 2016, David DiGiacomo telists@... [TekScopes] <
TekScopes@...> a écrit :

On Sat, Mar 26, 2016 at 11:43 AM, Artek Manuals
<manuals@...> wrote:

I know over the years we have flogged the topic ESR meters to death but
it has been awhile

You might find this thread helpful:

've-seen-all-chinese-stuff-on-ebay/

I don't have one of the newer Chinese dedicated ESR meters (e.g.
"ESR01", very tempting at $10), but I have and can recommend either of
these options:

1. The German AVR "component tester" has evolved into a good ESR
tester, and does many other useful tests. The standard version
doesn't have charged capacitor protection... but you can add a simple
relay circuit for that if you like.

To see what version people are currently buying, check near the end of
this thread:

Or, any of these would be good options:

$19 kit, no case, with encoder:

$23 kit, with case, with encoder:

$32 assembled, with case, no encoder:

2. You could also consider upgrading to a DER-EE DE-5000, which is an
excellent full function 100kHz LCR meter, and of course measures ESR
as well. This will cost about $120, and you can just buy it from the
current cheapest eBay seller:

------------------------------------
Posted by: David DiGiacomo <telists@...>
------------------------------------


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

Yahoo Groups Links

[Non-text portions of this message have been removed]

I believe my S6 uncertainty calcs came out to 1.08% so there's no issue here at all. No 'correction' is required. My earlier post was about calculated cumulative uncertainty including the SG504 50Khz +/- 3% and connector uncertainty which Dennis raised (and is a valid point).
I'd just prefer not to use an averaging means of sampling for peak signal detection which are being measured for flatness across a span.

When I brought up using an S-4 or S-6 to measure the flatness of an
SG504, I think I came to the conclusion that it could make a
measurement to 1/10th of its rated bandwidth to 1% so no correction
was necessary. An S-2 sampling head or that Racal-Dana RMS RF
voltmeter would need (sin x)/x correction to get enough accuracy.
<<

On Sat, Mar 26, 2016 at 11:43 AM, Artek Manuals
<manuals@...> wrote:

I know over the years we have flogged the topic ESR meters to death but
it has been awhile

You might find this thread helpful:
've-seen-all-chinese-stuff-on-ebay/

I don't have one of the newer Chinese dedicated ESR meters (e.g.
"ESR01", very tempting at $10), but I have and can recommend either of
these options:

1. The German AVR "component tester" has evolved into a good ESR
tester, and does many other useful tests. The standard version
doesn't have charged capacitor protection... but you can add a simple
relay circuit for that if you like.

To see what version people are currently buying, check near the end of
this thread:



Or, any of these would be good options:

$19 kit, no case, with encoder:


$23 kit, with case, with encoder:


$32 assembled, with case, no encoder:


2. You could also consider upgrading to a DER-EE DE-5000, which is an
excellent full function 100kHz LCR meter, and of course measures ESR
as well. This will cost about $120, and you can just buy it from the
current cheapest eBay seller:

Dave,
I'm not sure how helpful I can be with my little knowledge (relative to most everyone else here) but I did purchase a Blue ESR meter kit just a few months ago and enjoyed putting it together myself. I have been successful in accurately testing caps while still in circuit with same results out of circuit so its claim of being able to accurately test caps in-circuit without energizing other components seems accurate in many cases. There obviously may be cases where out of circuit is still better.

The only thing I found that I didn't like about it was that the auto shutoff would activate too soon. As such, I'd have to re-zero it each time it auto shut off. There is an option to disable auto shut off when you build it by disconnecting R25, a 47ohm resistor. Instead of just doing that, I slightly modified a very small switch I bought from Mouser and added it to the top of the board, next to the on-off switch, and ran wires down to R25 so I now have the option to either make it stay on all the time if I'm testing multiple caps, or it can be in the auto shutoff mode for battery saving if I'm only testing one or two caps. A bit of extra work but makes it more versatile.

From the documentation: "The Blue ESR is an AC ohmmeter with an equivalent test frequency of about 100kHz and capable of measuring non-inductive resistances from 0.01 to 99 ohms. It creates a 500mV P-P (open circuit) burst of 8usec pulses at a 2kHz rate, repeated several times per second so it can also be used as a signal source." I was able to connect my 475 to it and see that signal.

One thing the instructions say is that it can produce unsteady indications if its test leads pick up strong horizontal deflection signals so you need to keep it away from CRTs when making measurements.

It has done what I've needed it to do but my requirements may be much more basic than yours. It's probably a little bit expensive compared to building one yourself...there are many home-made instructions out there...but this one is pretty nice.

John


To: tekscopes@...
From: TekScopes@...
Date: Sat, 26 Mar 2016 13:43:12 -0400
Subject: [TekScopes] ESR meters (again)


























I know over the years we have flogged the topic ESR meters to death but

it has been awhile



I am in the process after several moves in the last two years of getting

my lab set back up before I tackle a sick FG504. To my dismay my old ESR

meter has become the victim of battery leakage to the point of not

trusting it even if i could restore it , Several green and possibly

missing traces etc



I went out to Evil-Bay to look for a new one to a bewildering array of

"new and improved" models. Anyone have hands on experience with a an

ESR Meter they purchased in the last 6 months?



Please, please do not respond unless you have purchased something in

the last 6 months, Please reviews of recent purchases ONLY. No anecdotal

stories about how much you love your Geewhiz Model 300 you bought 5

years ago (Which is no longer available)



Dave



--

Dave

Manuals@...

www.ArtekManuals.com



---

This email has been checked for viruses by Avast antivirus software.





















[Non-text portions of this message have been removed]

On 26 Mar 2016 10:00:54 -0700, you wrote:

...

So anyway, I put it all back together, and it worked. I left it running overnight for burn-in, and it's still alive. I had to tweak the RO position, and the controls are kind of flakey, needing to be worked a bunch, but it seems to work, with both beams and all. BTW this one is also the P11 blue, like every other 7844 I've seen.

It makes sense that the 7844 would be more common with the P11 blue
phosphor than other mainframes. The dual beam capability is uniquely
useful for single sweep measurements which would require a camera
anyway.

Next on the agenda will be a 7904 up here that had been working until the last time I needed it - also in tick mode. I hope it's the same thing or less.

Something I noticed again with my 7904 a couple days ago when messing
with my 7CT1N and chop mode is that if I have higher power plug-ins
installed, then it will tick several times when first turned on but
then recover and operate normally. I assume marginally high capacitor
ESR and perhaps low capacitance is causing this. My older 7834 does
the same thing with a higher plug-in load.

Ed

Resolved.


Q920 B sweep JFET was defective. I replaced it with a 2N5245.

On 26 Mar 2016 09:29:48 -0700, you wrote:

I am no expert on these scopes, but it seems to me using RMS sampling to operate as a pseudo peak detector to limit jitter is somewhat of an oxymoron.I presume you're speaking of gaussian jitter and not deterministic jitter.
Usually If I am doing peak detection (as in an SA) , I will do just that, unless the signal is down in the noise floor that requires VBW and other noise reduction techniques. This isn't the case here.

I am not sure what you are referring to here. Random sampling is not
inherently RMS; it depends on what kind of measurement is made after
sampling and I did not suggest measuring the peak after random
sampling although that could be done.

If the signal cannot be triggered on, then an RMS (or peak)
measurement can still provide information about the amplitude while
taking advantage of the bandwidth and flatness of the sampling head.
Sampling RMS RF voltmeters work this way.

If the signal can be triggered on, then a better option is to make a
DC measurement and advance the manual scan control to only sample the
peak of the waveform to make a peak measurement because this reduces
noise from the sampling process itself. I am not sure what other type
of instrument would make a measurement like this but it could be
considered synchronous demodulation before measurement. Excessive
sampling jitter would bias the measurement but some fancy math can
remove this if it is a problem.

Since the issue is measurement flatness and uncertainty, artificially flattening the response more than absolutely necessary ought to be avoided. Again, I don't own a sampling scope so that's just how I do it. I can't compare the technique described.

Flatness depends on the sampling head RF performance (connector,
impedance match, etc.) and bandwidth do to the sampling gate width.
The later can be corrected for because it has a predictable (sin x)/x
response or ignored if the sampling head bandwidth do to the sampling
gate width is high enough. Since we are trying to make a leveling
measurement down into the single percents, the sampling head bandwidth
has to be very high compared to the signal frequency to be accurate
without correction. The Racal-Dana RMS RF sampling voltmeter I
mentioned only has a bandwidth in the low GHz range and includes a
correction curve for making accurate measurements in the UHF and
higher range.

When I brought up using an S-4 or S-6 to measure the flatness of an
SG504, I think I came to the conclusion that it could make a
measurement to 1/10th of its rated bandwidth to 1% so no correction
was necessary. An S-2 sampling head or that Racal-Dana RMS RF
voltmeter would need (sin x)/x correction to get enough accuracy.

Hi,can anybody tell me what the 465 MOD 950H implies?
Rens Tel

I know over the years we have flogged the topic ESR meters to death but it has been awhile

I am in the process after several moves in the last two years of getting my lab set back up before I tackle a sick FG504. To my dismay my old ESR meter has become the victim of battery leakage to the point of not trusting it even if i could restore it , Several green and possibly missing traces etc

I went out to Evil-Bay to look for a new one to a bewildering array of "new and improved" models. Anyone have hands on experience with a an ESR Meter they purchased in the last 6 months?

Please, please do not respond unless you have purchased something in the last 6 months, Please reviews of recent purchases ONLY. No anecdotal stories about how much you love your Geewhiz Model 300 you bought 5 years ago (Which is no longer available)

Dave

--
Dave
Manuals@...
www.ArtekManuals.com

I have a green phosphor R7844, nice scope for the shelf over a bench.

I recently got a 7844 DOA - it was in tick mode.

So anyway, I put it all back together, and it worked. I left it running overnight for burn-in,

and it's still

alive. I had to tweak the RO position, and the controls are kind of flakey, needing to be worked a
bunch, but it seems to work, with both beams and all. BTW this one is also the P11 blue, like

every

other 7844 I've seen.

Thanks for the write up - that was a relief that it wasn't some horrendous fault in the power supply
I'll bet. I agree on the P11 - but is there anyone on the list with a green phosphor 7844?

Next on the agenda will be a 7904 up here that had been working until the last time I needed it -

also

in tick mode. I hope it's the same thing or less.

Good luck!

Crai

I recently got a 7844 DOA - it was in tick mode. After some fooling around in the scope with unhooking various things, it looked like the problem was right in the PS unit. I dreaded that it might be the HV winding, and was not looking forward to yanking it out and tearing it down.



I decided to try the curve tracer to diagnose as much as possible from the outside access points. I propped up the PS outside the back of the scope, so I could get to as much as possible. I ran the scope from the curve tracer via the power cord to check for any gross problems on the input side. It looked OK, and charged the big caps up. The current was very low, and the ticking could be seen in the display pattern.


Then I checked each LV supply line output, but it was hard to interpret what was going on. I only tried unipolar sweeping, but later saw that each supply has reverse polarity protection diodes anyway, which is good. I could see the effect of the bypass caps on each line, and a sharp increase in current kind of like a diode curve as various semiconductor junctions activated. I didn't push any supply past a couple hundred mA, and only up to maybe 3-4 V, so it wouldn't break down anything backwards from the forced outputs. I was hoping to find a dead short somewhere, but no, it was definitely not past the LV regulators, so next the rectifiers.


From the schematic I figured out where each raw supply comes up to its respective pass transistor, and hooked up the CT wherever convenient. On these, I swept from zero up to a little over what the unregulated supply was supposed to be. Bingo - the +17V was shorted to ground. All of the others looked OK. So, digging down to the next layer of assembly, I started disconnecting first the rectifiers, then caps, still using the CT to check the status.


It turned out that I went on a bit of a wild goose chase - I had misidentified one of the caps, so had pulled what I thought were the only caps associated with this section, leaving no explanation for the short other than a solder bridge or lead bent over somewhere. This caused me to waste extra time taking apart even more stuff trying to see the solder side of the board, which can't really be done well without stripping almost the whole supply. Fortunately, before getting in too deep, I saw that there was another cap on that line right near the connector that goes to the regulator board. I confirmed the connection, pulled one end, and the short was gone. It was a large blue solid Ta dipped style, marked 47 uF, 20 V. My equipment facilities and parts are kind of sparse here at the farm, but I managed to scrounge up a 33 uF, 20V axial hermetic style Ta, so close enough.


One side benefit of my wild goose chase is that I also discovered that the safety ground wire that goes from inside the supply to the scope chassis was disconnected, just dangling loose in there - I saw it while trying to view the board. I was pretty sure it wasn't from my disassembly work, and wasn't sure where it should have attached in the first place, so I hooked it to the same screw that the line filter ground went to. If I hadn't noticed this, that lug could have eventually made contact with something in the guts with bad results - way beyond a bad cap.


So anyway, I put it all back together, and it worked. I left it running overnight for burn-in, and it's still alive. I had to tweak the RO position, and the controls are kind of flakey, needing to be worked a bunch, but it seems to work, with both beams and all. BTW this one is also the P11 blue, like every other 7844 I've seen.



Next on the agenda will be a 7904 up here that had been working until the last time I needed it - also in tick mode. I hope it's the same thing or less.


Ed

I am no expert on these scopes, but it seems to me using RMS sampling to operate as a pseudo peak detector to limit jitter is somewhat of an oxymoron.I presume you're speaking of gaussian jitter and not deterministic jitter.
Usually If I am doing peak detection (as in an SA) , I will do just that, unless the signal is down in the noise floor that requires VBW and other noise reduction techniques. This isn't the case here.

Since the issue is measurement flatness and uncertainty, artificially flattening the response more than absolutely necessary ought to be avoided. Again, I don't own a sampling scope so that's just how I do it. I can't compare the technique described.

Hi Guys,


bought a 576 few weeks ago in very dirty but basicly working condition. Solved almost all failures exept of two:


Number one are some defective IC's of the readout where I'm trying to find a cheaper and better way to replace them as just spending lots of money on eBay to buy hopefully/maybe/eventually "NOS" ones.
My first guess was to use the Schematics and doing some mapping for a PROM or PLD decoder, but as I am a lazy guy I first want to ask if someone else already spend effort into that.


The second failure is from the species "hard to find asshole".
Failure description is as follows: I put a Resistor, 1k for example between C and E terminals and add some collector voltage to it. Horizontal deflection is fine and in spec without any adjustment (checked this with freshly adjusted cal fixture). But when I try to increase the vertical deflection I got the following sympthomatic:
As the current sensitivity increases, I can see and hear that the amplifier gain switching relays are working properly. Also the Amplifier Gain itself is in cal and at the Step Gen setting I get the right response with 1 step per centimeter.
But when I increase the current sensitivity, I only see the amlifier gain switching but not the increase of voltage drop across the current sensing resistor. I tried to measure the resistances and all seems to be fine.
So does anyone have any guesses or hints how I can tackle that issue?


kind regards
Ben

On 26/03/2016 3:27 AM, Tom Gardner tggzzz@... [TekScopes] wrote:

Possible example: model train sets have started selling
like hot cakes again.

Ooops, sorry. That was me.