Date   
Re: Shipping rant

 

Good to hear you refused to pay for his mistake.  More people need to protest when this happens.  Perhaps negligent sellers will learn the lesson.  I think many of the failed shipping occurs when a seller just drops the item off at one of the pack n ship stores.  There are many who have no idea how to ship electronic instruments.  Its exacerbated by sellers who think if the guts are solid state they don't need to pay extra for "Fragile" shipping.

From: "microwyatt@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Tuesday, January 3, 2017 3:04 PM
Subject: [TekScopes] Re: Shipping rant

  Paul,

I had the same thing happen to me a few weeks ago. I purchased a "working" 2215. It arrived in a box with no packing at all. The crt was broken. I asked the seller for a refund. He emailed me that the description also stated as-is and would not refund the purchase. I went through Ebays dispute process and it was decided in my favor. Ebay emailed a shipping label and I returned the scope. The day the scope was received by the seller Ebay refunded my purchase including the shipping costs.

Hopefully the seller will realize that refunds cost more than bubble wrap !

Michael

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

Re: TDS754D CRT

David Wilson
 

I took a picture of this power supply, other than being a little dusty nothing looks out of the ordinary so far. See photos in this Tek group to find the picture

Re: New Member Dead 7704

volvoboy242@...
 

Re: 2445: character breakthrough on trace

Siggi
 

Hey Jeremy,

look around A1U400. The channel switch doesn't have an internal switch for
the readout (CH5), so the switching is done externally. For details on the
channel switch, you can see a spec on it in this document <
http://w140.com/tek_made_sm.pdf>, search for "203-0211-90".
The transistor networks that are used to switch the readout and turn it
differential from single-ended (U475/U485) are 4 transistor arrays in a DIP
(IIRC). I remember at least one report of those failing, so that'd be my
first port of call. You should be able to buzz them out with your DMMs
diode test.

Siggi

On Tue, 3 Jan 2017 at 12:56 jezzer3@... [TekScopes] <
TekScopes@...> wrote:



My recently acquired and repaired 2445 (psu caps) is now showing data-like
bursts on any trace. Fixed height - not affected by input sensitivity.
I finally worked out it's something to do with the readout display. With
display disabled (knob to left) there is no problem on the display.
Since the readout and main traces are otherwise very clean I suspect
something like a display blanking issue.
Before I dive into unfamiliar territory, any suggestions on where I should
start looking? (I do have the service manual).

Many thanks
Jeremy

Re: TDS754D CRT

David Wilson
 

I will open it up to check the capacitors, thanks for the advice

Re: TDS754D CRT

 

I have seen this happen. It is usually a capacitor with high ESR. As the cap heats up due to the high ESR, the ESR drops. Then the scope starts working. Most of the time this happens with switching supplies.

Regards.

----- Original Message -----
From: Tom Gardner tggzzz@... [TekScopes]
To: TekScopes@...
Sent: Tuesday, January 03, 2017 4:09 PM
Subject: Re: [TekScopes] TDS754D CRT



On 03/01/17 19:32, david.wilson92@... [TekScopes] wrote:
>
> The problem I am having is with a cold instrument turn on, occasionally there
> is no picture. Waiting a few minutes the picture comes in.
>
> During period of no picture the LCD rapidly flickers.
>
> Ever since I got the instrument there is a slight wine from the CRT and the
> display is a little dim. I opened up the instrument to brighten it slightly
> though that makes it a little blurry.
>
> I wonder if I have a tired CRT with a tired CRT driver board. If this really
> becomes a issue I can find parts or get the NewScope display kit.
>
I saw a vaguely similar problem on a 485.

Turn it on and nothing would happen for 5 minutes, then the everything would
spring to life.
Turn it off then on, and it instantly sprang into life.
Leave off for 1 hour, turn on, it would take 30s to spring to life.
Leave off overnight, back to the 5 mins delay.

One test per 6 hours made life tedious!

I traced the problem to an electrolytic in the switching PSU that was used to
kickstart the switching. Presumably the "electrolyte was almost dry", so the
dielectric took a few minutes to form. Once formed, it gradually decayed over 6
hours.




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

Tektronix 475 issue

thery2@...
 

Re: New Member Dead 7704

volvoboy242@...
 

My new 7B53A came in the mail today. Had to double check the eBay listing because of the heavy drop check damage.
The picture that would have shown such damage was conspicuously missing, but for $20 shipped........Meh!
I plugged it in with the 7A18 and, for a minute, I had a readout and was able to watch time and volt values change with the knobs. No dots though.
I pushed the beam finder and it all went away.
With the beam finder locked, I have everything and can move the dots X and Y but, without the beam finder, it's all off screen. Up, I think.


So now I'm pretty sure most of this scope works.
Just need to figure out what's loose or cracked.

Re: Update on 2465

Tom Gardner
 

On 03/01/17 16:46, tatumj1@... [TekScopes] wrote:

Thanks Dave, I turned it off for a while and when back on the symptoms returned but went away in a few minutes.
As I've just noted elsewhere in another context, I've seen something similar with an aluminium electrolytic in a 485. There were "recovery delays" proportional to the off time between 1 and 6 hours.

It was a bugger to trace, since one test every six hours encourages thought and understanding :(

Re: TDS754D CRT

Tom Gardner
 

On 03/01/17 19:32, david.wilson92@... [TekScopes] wrote:

The problem I am having is with a cold instrument turn on, occasionally there is no picture. Waiting a few minutes the picture comes in.

During period of no picture the LCD rapidly flickers.

Ever since I got the instrument there is a slight wine from the CRT and the display is a little dim. I opened up the instrument to brighten it slightly though that makes it a little blurry.

I wonder if I have a tired CRT with a tired CRT driver board. If this really becomes a issue I can find parts or get the NewScope display kit.
I saw a vaguely similar problem on a 485.

Turn it on and nothing would happen for 5 minutes, then the everything would spring to life.
Turn it off then on, and it instantly sprang into life.
Leave off for 1 hour, turn on, it would take 30s to spring to life.
Leave off overnight, back to the 5 mins delay.

One test per 6 hours made life tedious!

I traced the problem to an electrolytic in the switching PSU that was used to kickstart the switching. Presumably the "electrolyte was almost dry", so the dielectric took a few minutes to form. Once formed, it gradually decayed over 6 hours.

Re: Shipping rant

Michael Wyatt
 

Paul,

I had the same thing happen to me a few weeks ago. I purchased a "working" 2215. It arrived in a box with no packing at all. The crt was broken. I asked the seller for a refund. He emailed me that the description also stated as-is and would not refund the purchase. I went through Ebays dispute process and it was decided in my favor. Ebay emailed a shipping label and I returned the scope. The day the scope was received by the seller Ebay refunded my purchase including the shipping costs.

Hopefully the seller will realize that refunds cost more than bubble wrap !

Michael

Re: Update on 2465

Siggi
 

On Tue, 3 Jan 2017 at 11:46 tatumj1@... [TekScopes] <
TekScopes@...> wrote:



Thanks Dave, I turned it off for a while and when back on the symptoms
returned but went away in a few minutes.

I understand that drying electrolytic capacitors can come good with
temperature, to a degree. One possible way to hunt this down is with freeze
spray, or it might be simpler to just change out the electrolytics in the
power supply.

Another possible fault that can manifest similarly is contact oxidation.
While you have her open, it makes sense to undo and re-seat all connectors,
jiggle or pull and restore all socketed ICs as well as the hybrids.
My 2467 was all kinds of glitchy and jumpy until I pulled, cleaned and
re-seated the hybrids...

Good luck,
Siggi

TDS754D CRT

David Wilson
 

The problem I am having is with a cold instrument turn on, occasionally there is no picture. Waiting a few minutes the picture comes in.

During period of no picture the LCD rapidly flickers.

Ever since I got the instrument there is a slight wine from the CRT and the display is a little dim. I opened up the instrument to brighten it slightly though that makes it a little blurry.

I wonder if I have a tired CRT with a tired CRT driver board. If this really becomes a issue I can find parts or get the NewScope display kit.

Re: Update on 2465

Joseph Tatum
 

Thanks Richard. Fortunately most capacitor failures I have encountered have been bad enough to be pretty straightforward. I am thinking the real problem with this one may be pretty elusive. Thanks to help here I have several good leads and likely will eventually find out what is going on with this scope.

Shipping rant

Paul Amaranth
 

Just received a 213 I bought off of ebay. It was nonfunctioning,
but looked to be in pretty good shape. I included a note to the
seller to pack it in bubble wrap and foam since they are somewhat
fagile.

Well, I received it today and it was the absolute worst packing job
I have ever seen.

The scope was in a paper grocery sack inside a medium flat rate box.
That was it, no other packing. The box was a little crushed looking.

The scope looks intact, but who knows about the CRT. I've had other
perfectly repairable scopes had their CRTs destroyed through bad
packing and the 200 series CRTs are particularly fragile.

Way to start the new year :-)

--
Paul Amaranth, GCIH | Rochester MI, USA
Aurora Group, Inc. | Security, Systems & Software
paul@... | Unix & Windows

Re: Update on 2465

Richard Knoppow
 

Sometimes the problem with a capacitor is "leakage" or _parallel_
resistance. In other words they pass some DC. Such capacitors can test
OK for value and for ESR or dissipation factor (they are the same
thing). High ESR makes the cap less effective as a capacitor but does
not pass DC, leakage does and is why some paper coupling caps cause
distortion. Not many capacitance meters or bridges measure parallel
resistance. Many capacitor checkers do and you can check for it with an
ohm meter although sometimes the voltage from an ohm meter is not high
enough.
Electrolytic caps always have some leakage but bad ones can have a
great deal to where they become essentially low value resistors.

On 1/3/2017 8:46 AM, tatumj1@... [TekScopes] wrote:

Thanks Dave, I turned it off for a while and when back on the symptoms
returned but went away in a few minutes.

I have always been a bit dubious of ESR meters but have found one
useful at times.Most electrolytic caps I have had to replay had the
distinguishing oval top. Don't run into all that many that actually
have leaked. I can see why they would be hard to find since when it is
working the fault would be gone. Do you find that the temp test works
even when symptoms are not present but the cap is failing?

I do have a temp probe and thanks for that suggestion.

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

--
Richard Knoppow
dickburk@...
WB6KBL



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

2445: character breakthrough on trace

Jeremy Owen
 

My recently acquired and repaired 2445 (psu caps) is now showing data-like bursts on any trace. Fixed height - not affected by input sensitivity.
I finally worked out it's something to do with the readout display. With display disabled (knob to left) there is no problem on the display.
Since the readout and main traces are otherwise very clean I suspect something like a display blanking issue.
Before I dive into unfamiliar territory, any suggestions on where I should start looking? (I do have the service manual).

Many thanks
Jeremy

Re: Update on 2465

Joseph Tatum
 

Thanks Dave, I turned it off for a while and when back on the symptoms returned but went away in a few minutes.

I have always been a bit dubious of ESR meters but have found one useful at times.Most electrolytic caps I have had to replay had the distinguishing oval top. Don't run into all that many that actually have leaked. I can see why they would be hard to find since when it is working the fault would be gone. Do you find that the temp test works even when symptoms are not present but the cap is failing?

I do have a temp probe and thanks for that suggestion.

Re: Update on 2465

ArtekManuals
 

This occurs not infrequently in older gear. Typically ( but not always)
a sign of weak electrolytic and tantalum caps "reforming". Which they
are known to do with voltage applied for long periods of time.
Eventually these will fail and can be really hard to find them until
they do fail.

Things you can do

1) Check the electrolytic's & tants with an ESR meter ( not always
conclusive) but a "bad" one is usually really bad, but a "good" one is
not always good.

2) If you have a temperature probe such as you find with the DM50x
series DMMs you can check the larger caps to see if any of them are
getting noticeably warmer than their brothers. I also use one of those
infrared pistol grip cooking thermometers for this. This is a typical
gun I am talking about http://en-us.fluke.com/products/thermometers/.
Much less expensive ones can be found all over the internet and evil-bay

3) Do nothing .... wait until the "reforming cap" eventually fails.
Could take a few days or a few years and can be quite spectacular when
it occurs including the ritual release of the "magic smoke" that makes
everything work.

Good luck

Dave

manuals@...




On 1/3/2017 9:28 AM, tatumj1@... [TekScopes] wrote:

Hello Siggi,

I started to check the levels at the TPs. As I probed the scope the
reading began to improve on their own. As it ran it gradually got
better and now the trace works normally. The voltages are right at the
TPs and the signal I was seeing is now gone. This all stated when I
noticed that the random trace (the pics) suddenly synced on the screen
into a stable pattern and its amplitude gradually (over maybe 5 min)
decreased until the trace was flat.

The only problem I see now is that the trace is just a little fuzzy. I
does not focus down to the sharpness I expect. Also am seeing for the
first time a voltage reading in the upper left screen. When it first
appeared it read .010 v. It gradually went down to .005 V. I think
this is why the trace looks a bit fuzzy. The trace would be deflected
by that amount.

Have you ever seen one fix itself? I do not know how long it was
stored in the box. My friend had packed it away under a counter in the
shipping box. Is it likely that just not being used for a long while
caused it to act up?



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

Re: Update on 2465

Joseph Tatum
 

Hello Siggi,

I started to check the levels at the TPs. As I probed the scope the reading began to improve on their own. As it ran it gradually got better and now the trace works normally. The voltages are right at the TPs and the signal I was seeing is now gone. This all stated when I noticed that the random trace (the pics) suddenly synced on the screen into a stable pattern and its amplitude gradually (over maybe 5 min) decreased until the trace was flat.

The only problem I see now is that the trace is just a little fuzzy. I does not focus down to the sharpness I expect. Also am seeing for the first time a voltage reading in the upper left screen. When it first appeared it read .010 v. It gradually went down to .005 V. I think this is why the trace looks a bit fuzzy. The trace would be deflected by that amount.

Have you ever seen one fix itself? I do not know how long it was stored in the box. My friend had packed it away under a counter in the shipping box. Is it likely that just not being used for a long while caused it to act up?