Date   

Dang'd old electrolytics again?

Howard Matthews
 

Risking turning this group from a Tek scopes group to an
electrolytic capacitor group, I have questions.

I bought a "fixer" 454. Initial review showed chan 1 working okay,
but chan 2 not. After it sat a few months in my "shop", I started
working on it. First I checked and set all the voltage supplies.
They were all within spec, and now right on. However, now both chan
1 and chan 2 were visible ONLY using the beam finder. They were
both offscreen high.

So, I started tracing the voltage levels and signals in the chan 1
preamp first. A number of DC levels were off enough to throw the
trace off screen. And there was disturbing noise on top of the
signal. But before I could pin-point the source of the problem(s),
chan 1 starts working! It drifts around a bit, but the bias and
noise problems are gone.

Turning to chan 2 - guess what. After a few hours of trying to get
consistent readings and find the source of the problem, BINGO - chan
2 is working.

I left the scope powered off over night. The next day, both
channels are still working and now quite stable. No noise, no drift
after warmup.

The power supplies had and have NO problems. There are a number of
small bypass electrolytics in the preamp circuits which I did not
get around to checking.

Questions:
1. Is it likely that some electrolytics were "reformed" while I was
looking for the problem.

2. If so, is it likely the electrolytics will fail again soon, if
not used frequently? Might they have poor ESR, or high leakage now?

3. Should I pull the little electrolytics in the preamp and
check/replace them? I'm thinking modern tantalums might be good
replacements.

Anyone have similar experiences? Opinions? Advice?

TNX
-Howard


Re: 2215

Craig Sawyers <c.sawyers@...>
 

It is just as
expensive to ship something from Europe/UK over to the States.
It is horribly expensive to send stuff from the UK to the US. Taking a 30lb
package as a for instance, USPS tells me that this is $107 air parcel, and
$66 surface. The same weight by Royal Mail costs the same numbers in UK
pounds - �107 and �72 respectively. IOW it is 84% more expensive to ship
from the UK to the USA as it is in the other direction (on today's exchange
rate).

Craig

PS just been fighting another capacitor death problem. This time a shorted
tant in a Racal true RMS voltmeter. Took out the +15V reg too and a couple
of resistors. Tant was 47u 16V, on a 15V line. Posts to the list from
Miroslav indicates that this is sailing *very* close to the wind - so I'll
be changing out all dozen or so of these beasts now.

Racal volmeter is very interesting. Goes from 10kHz to 1.5GHz at 1mV full
scale max sensitivity. Does it with a random sampling probe, then analog
computer to calculate rms (squarer, integrator, log, halve then anti-log to
get square root). Accuracy 1% to 500MHz and 5% to 1.5GHz.


Re: 2215

Miroslav Pokorni
 

Do not think that Burma gets special treatment in shipping. It is just as
expensive to ship something from Europe/UK over to the States. Perhaps, hand
carrying the scope (as carry on-board luggage), when you go to the next
vacation might prove cheaper than to ship and certainly much better for the
health of the instrument.

Regards

Miroslav Pokorni

----- Original Message -----
From: "aakmoe" <aakmoe@yahoo.com>
To: <TekScopes@yahoogroups.com>
Sent: Monday, January 12, 2004 11:20 AM
Subject: [TekScopes] Re: 2215


Thanks Jeff

I saw one on uk ebay and I was wondering about it.
I have a 465B but I am thinking of getting a smaller & lighter scope.

I mean another one and may be ship back to Burma(Myanmar) so that I
can use when I go home on holiday.
Shipping costs from uk to Burma cost as much as a scope.

I am only a hobbyist and there don't have the full knowledge of
various models of tek scopes.
Scopes are really scarce in Burma outside the service centres and
government establishments.

Aung Moe








--- In TekScopes@yahoogroups.com, "Jeff W" <vwthingy@c...> wrote:
aakmoe wrote:

what do you think of 2215 scope.Is it 60Mhz any more information?
How does it compare to 465 series.
The 2215 (& 2213) were Tek's first foray into cheapie scopes. And
they made one, by gosh! They had a horrible power supply that used a
complex triac prereg scheme with current sensing, which didn't work
well & caused a loud 60Hz buzz from the smoothing choke. Tek
realized they screwed up, and released a modification kit that
replaced the prereg with a PWM switcher; a much better scheme. If
you are looking to buy a 2215, make sure it has this kit, or you will
think something is wrong with the scope from the loud buzzing noise
it will make. (the kit is no longer available)

I have a 2215 that I will sell really cheap, as it doesn't have this
kit :)

Yes; they are 60 Mhz bandwidth, but just that. I have worked on two
2215's, and both units barely met it, whereas most other Tek scopes
are rated more conservatively.

The 465 (especially a 465B) is a much better scope. You must keep in
mind that when the 2215 came out in 1982, it sold for $ 1,400, versus
the 465B which sold for $ 2,995 at that time. Bottom line: the 2215
sold for less than half the price of a 465B in 1982, it is less of a
scope then as now performance-wise, and usually sells for less today.

The only good thing about a 2215 is that it is fairly easy to work
on. Also, please keep in mind that the 2215A is better than the
2215; it uses the same mainboard & CRT as the 2235. (I had a 2215A
once and it was a nice little scope)

Jeff


Re: 2215

aakmoe <aakmoe@...>
 

Thanks Jeff

I saw one on uk ebay and I was wondering about it.
I have a 465B but I am thinking of getting a smaller & lighter scope.

I mean another one and may be ship back to Burma(Myanmar) so that I
can use when I go home on holiday.
Shipping costs from uk to Burma cost as much as a scope.

I am only a hobbyist and there don't have the full knowledge of
various models of tek scopes.
Scopes are really scarce in Burma outside the service centres and
government establishments.

Aung Moe

--- In TekScopes@yahoogroups.com, "Jeff W" <vwthingy@c...> wrote:
aakmoe wrote:

what do you think of 2215 scope.Is it 60Mhz any more information?
How does it compare to 465 series.
The 2215 (& 2213) were Tek's first foray into cheapie scopes. And
they made one, by gosh! They had a horrible power supply that used a
complex triac prereg scheme with current sensing, which didn't work
well & caused a loud 60Hz buzz from the smoothing choke. Tek
realized they screwed up, and released a modification kit that
replaced the prereg with a PWM switcher; a much better scheme. If
you are looking to buy a 2215, make sure it has this kit, or you will
think something is wrong with the scope from the loud buzzing noise
it will make. (the kit is no longer available)

I have a 2215 that I will sell really cheap, as it doesn't have this
kit :)

Yes; they are 60 Mhz bandwidth, but just that. I have worked on two
2215's, and both units barely met it, whereas most other Tek scopes
are rated more conservatively.

The 465 (especially a 465B) is a much better scope. You must keep in
mind that when the 2215 came out in 1982, it sold for $ 1,400, versus
the 465B which sold for $ 2,995 at that time. Bottom line: the 2215
sold for less than half the price of a 465B in 1982, it is less of a
scope then as now performance-wise, and usually sells for less today.

The only good thing about a 2215 is that it is fairly easy to work
on. Also, please keep in mind that the 2215A is better than the
2215; it uses the same mainboard & CRT as the 2235. (I had a 2215A
once and it was a nice little scope)

Jeff


125mF 450V Capacitor

wireless_paul <paul_earland@...>
 

Have a 545A Oscilloscope. There is a large metal electrolytic 125mF
450V capacitor in it. It has a leak and wants replacing. What and
where do I replace it with.
Thanks.
Paul


Cab-to-Rak adaptor for 5000 scopes

Tim Phillips <t.phillips@...>
 

Hi, all;
I have a couple of 5103Ns, one of which I would like to rack-mount.
Seems Tek once provided a kit of parts to adapt a 'boxed' 5xxx
to a rackmount. part# 040-0583-03. Anyone ever come across such
a thing? Never seen one on ebay.
Kindest regards
Tim.


Re: 2215

Jeff W <vwthingy@...>
 

aakmoe wrote:

what do you think of 2215 scope.Is it 60Mhz any more information?
How does it compare to 465 series.
The 2215 (& 2213) were Tek's first foray into cheapie scopes. And
they made one, by gosh! They had a horrible power supply that used a
complex triac prereg scheme with current sensing, which didn't work
well & caused a loud 60Hz buzz from the smoothing choke. Tek
realized they screwed up, and released a modification kit that
replaced the prereg with a PWM switcher; a much better scheme. If
you are looking to buy a 2215, make sure it has this kit, or you will
think something is wrong with the scope from the loud buzzing noise
it will make. (the kit is no longer available)

I have a 2215 that I will sell really cheap, as it doesn't have this
kit :)

Yes; they are 60 Mhz bandwidth, but just that. I have worked on two
2215's, and both units barely met it, whereas most other Tek scopes
are rated more conservatively.

The 465 (especially a 465B) is a much better scope. You must keep in
mind that when the 2215 came out in 1982, it sold for $ 1,400, versus
the 465B which sold for $ 2,995 at that time. Bottom line: the 2215
sold for less than half the price of a 465B in 1982, it is less of a
scope then as now performance-wise, and usually sells for less today.

The only good thing about a 2215 is that it is fairly easy to work
on. Also, please keep in mind that the 2215A is better than the
2215; it uses the same mainboard & CRT as the 2235. (I had a 2215A
once and it was a nice little scope)

Jeff


Single-sweep mod for 531/541

Tim Phillips <t.phillips@...>
 

Hi, all;
I have a 531A (with it's service manual), and
I recently saw on ebay what looked like a 531 with a
single-sweep feature added; (switch on front panel.)
Is this easy to implement? The photo I saw looked like
a genuine Tek mod, with a small photo-etched plate for the
switch.
kindest regards
Tim.


WANTED! 3L10 Spectrum analyser

petertech99h
 

Hi All,

I looking for a nice 3L10 analyser!!! They made them, they gotta be out
there!! Who can let one go??

Pls let me know!

Take care,

Peter


Looking for TG501 parts

eboytoronto
 

Hi,

Can anybody help ?

I am looking for a knob for the TG501 time marker generator.

I am also looking for a display board with the LEDs on it.

Thanks,

John Barnes


Re: What's the best manual?

maddisassembler
 

January 12th, 2004


Albert and all others who care for this issue,

even if one has a complete collection of
microfiche (which would be well above 10,000
microfiche I estimate) he would have to spend
appr. USD 2,000 (0.20 times 10,000) just to
have them digitized.

All this is worthless (or at least the same level
as putting microfiche into a reader) if this whole
action cannot give immediate answers to questions
like (just examples):
What is a 067-0542-99 good for? Where was part
120-0612-01 used and what was the serial number
range? Under which modification falls my 7A24
serial B116058?
etc etc etc

From my point of view such answers can only be
found in reasonable time if the contents of all
microfiche are linked into some kind of data base
or retrieval system.

To build up such a system it would need a big
effort of labour - too much for single a person
with only 24 hours a day to spend on this...

Comments welcome.

Best regards
-Roland



--- In TekScopes@yahoogroups.com, "Albert LaFrance" <lafrance@a...>
wrote:
Another option which might be worth considering is to have the
microfiche
scanned onto a CD-ROM. I looked into this a while ago for some
Bell System
Practice manuals, and several service companies estimated prices of
15-35
cents per image, depending on quantity, fiche quality, need for
post-scanning image cleanup, etc.

Albert

----- Original Message -----
From: "Stan & Patricia Griffiths" <w7ni@e...>
To: "maddisassembler" <320041677522-0001@t...>
Cc: "TekScopes" <TekScopes@yahoogroups.com>
Sent: Monday, November 03, 2003 4:43 PM
Subject: [TekScopes] What's the best manual?


<SNIP>
Our local library has microfiche readers that can read either
fiche sheets
or 35mm filmed images and convert any image to hard copy on
excellent copy
paper similar to what you use in your own laserjet printer. It
costs 10
cents per image to do prints and I sometimes use that service.
<SNIP>


Re: tek 475 sweep probleem

benclarke_uk
 

Hi Henny
I have just fixed a 465 with a very similar problem, in my case certain
sectors of the timebase control would produce a sweep whilst other sectors
would not.
The problem turned out to be the Zener that feeds the negative supply to
the Monolithic Sweep Control IC going short circuit. The IC needs +5v and
-5v but the scope only has +5v and -8V available. The negative supply is
therefore derived from the -8v line by feeding it through a 3v Zener. With
-8v instead of -5v the IC would work happily on certain ranges, but not at
all on others.
The 475 and 465 circuitry is identical in the area that failed so it may be
worth a check on your unit.
Cheers,
Ben

At 18:42 08/01/04, hi1vld wrote:
I just bought this scope, but have the following problem:
Wen using the scope with a setting of 1ms or shorter, i got a trace.
But when using 2ms and longer i got no trace.
What could be the problem?
I have a service manual, but don't know were to begin.
I will start with measuring the voltages from the supply, but when i
take the scope appart, i also want to look at this sweep problem.

Thank you.

Henny



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2215

aakmoe <aakmoe@...>
 

HELLO ALL

what do you think of 2215 scope.Is it 60Mhz any more information?
How does it compare to 465 series.

thanks

AKM


Re: tek 475 sweep probleem

Stan & Patricia Griffiths <w7ni@...>
 

Hello Henny,

Here is place to start on your 475 after you are certain the power supplies
are working correctly.

Go to the Timing Switch schematic diagram and look for changes that occur
when you switch from 1 ms to 2 ms, like a part that is switched in the
circuit right at that point.

That is where I would start on this problem.

Stan
w7ni@easystreet.com

----- Original Message -----
From: "hi1vld" <intersound@zonnet.nl>
To: <TekScopes@yahoogroups.com>
Sent: Thursday, January 08, 2004 10:42 AM
Subject: [TekScopes] tek 475 sweep probleem


I just bought this scope, but have the following problem:
Wen using the scope with a setting of 1ms or shorter, i got a trace.
But when using 2ms and longer i got no trace.
What could be the problem?
I have a service manual, but don't know were to begin.
I will start with measuring the voltages from the supply, but when i
take the scope appart, i also want to look at this sweep problem.

Thank you.

Henny




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To visit your group on the web, go to:
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To unsubscribe from this group, send an email to:
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Re: Fuzzy 465B trace revisited, final report

donlcramer@...
 

This is follow up for posts made about a year and half ago (has it been that
long?) asking for help with an odd behaviour, fat-ish trace on a 465B of
vintage B048 SN prefix. See posts #2024, #2008 and related for additional details
of the symptoms.

I'd run the scope by an ex-Tek CRT inspector, and she thought the symptoms
looked like "low cathode". I interpreted this to mean that, although emission
is still good, it is coming predominantly from parts of the cathode structure
that are not optimum for a nicely focused beam. Another CRT related
possibility mentioned at the time was some kind of mechanical damage that affected the
internal alignment of the elements. Whatever the root cause, it turned out the
problem was indeed with the CRT itself, and not the electronics. A new CRT
(actually for a 465M) from ebay, a new blue filter from Walter at Sphere
Research, and a recal, and it seems to be as good as rain again. With the new tube,
the traces are nicely crisp. Not as good as I remember a 485 mind you, but
quite nice, and certainly not worse than any other common Tek scope of the 80's
and 90's that I'm familiar with.

Don Cramer
Beaverton, OR


504 scope for sale

Charles <charlesmorris@...>
 

Having had an attack of collecting last year, I now have too many
Tek scopes fixed up and doing nothing but collecting dust. I have
a nice 504 looking for a good home. Cosmetically it is in great
shape and it works too (reformed electrolytics, power supply
voltages correct, etc). Can email pics. Best offer.

thanks
Charles

ps this is NOT the "modular" SC504 scope plugin.


2467, 2467A, 2467B: differences and preferences?

donlcramer@...
 

Any comments from the knowledgeable regarding what differences exist between
the 2467 (non-letter) MCP CRT portable and the subsequent '67A and '67B models
(other than bandwidth)? I didn't know there was an 'A version, but one
website lists one (perhaps a mistake?).

Is one preferred over the other? Anything in particular to watch out for in
buying one of these used?

Thanks,

Don Cramer


Re: Darned capacitors again!

ehsjr@...
 

Uhhh... I tried to post my reply to Tekscopes yesterday - let me try again.

Miroslav Pokorni wrote:

I was to stick to my New Years resolution and not get mixed into every
thread started here, but this description of problem and conclusions beg for
another view.

Thank you! I am so glad you posted the info - an excellent post!
Most of it was information I did not know. I can say that this is
an old clock - we've had it for may years - and you mention that
modern chips avoid the problem. I doubt the chip in this clock
is modern! So it is highly probable that your analysis is exactly
right.

A quiescent current of 100 mmA is not completely out of line for a CMOS
circuit. Most of those circuits, regardless of complexity, be that CD4007
with six transistors or a microcontroller with thousands of them, have 100
mmA placed as upper limit. That value seems to be maximum die leakage when a
reasonable life expectancy of IC can be still obtained and certainly is a
cut off point in testing packaged ICs.
At any rate, a run-of-the-mill 9 V battery has capacity of 450 mA, what at
90 mmA gives you 5000 hours or 208 days without line power (battery is a
back up). Replacement battery did not last that long. My guess is that IC
was going into SCR mode, shorting Vcc and ground pins; if it was not that
battery limited the current, chip would have been destroyed. When current
was measured with meter, and extra 1 kOhm or so was inserted in the battery
path (meter burden), so probably SCR holding current could not be reached
and that is what limited the current to only 90 mmA.
The most common way to form an SCR in a CMOS IC is when output line goes
above supply line by more than a diode voltage drop. In this conditions,
pair of parasitic transistors in the walls of the well containing output P
transistor are biased and that latches the SCR. All CMOS ICs are vulnerable
to SCR mode but more modern and carefully designed one have added
conductivity in the base of parasitic transistors so their gain is killed
and it is harder to trigger that SCR, but still, a good ringing on the
output line can do the trick.
One of the ICs most notorious for SCR was Motorola's Time of Year Clock,
MC16688 (if I still remember that number right), used by me one of my
designs and one that gave me education on one of the many aspects of CMOS IC
vulnerabilities. Strangely, that particular IC would go to SCR mode through
input lines manipulation, a functionality of 'MOTEL' [MO(torolaIn)TEL]
circuit.
The Motorola's MC16688 also enhanced business of Tadiran (Li battery
manufacturer, common supplier for PCs). Not all of those ICs were
vulnerable, but there were batches. Those lucky people who had one from the
batch would have message 'CMOS memory failure' appear during boot and
battery would be replaced every few weeks. That was not uncommon during 80s,
before Time of Year Clock function was switched to National's I/O IC.
To get back to alarm clock, my guess is that electrolytic held Vcc pin
propped up, so the short load pulse did not collapse Vcc pin below the level
of output pins. Open wired electrolytic did quite poor job of propping up
the pin and the IC ended up as an SCR.
Regards
Miroslav Pokorni
----- Original Message -----
From: <ehsjr@bellatlantic.net>
To: "Dan Kerl" <dlkerl@knology.net>
Cc: "TekScopes" <TekScopes@yahoogroups.com>
Sent: Monday, January 05, 2004 1:57 PM
Subject: Re: [TekScopes] Darned capacitors again!

Dan Kerl wrote:

I have a similar tale to share about an oven controller.
<snip>

This episode reminded me of the subtle ways that electrolytic caps can
cause problems that are not obvious, particularly the noise. If erratic
behavior in an electronic device is a problem, there's a good chance
that an electrolytic is at the bottom of it.
-Dan
Another tale: we have a his/hers digital alarm clock (2 alarms).
A few months back, it "went crazy" running much faster than
normal. I investigated, and found that the 9V battery backup
was only ~ 4 volts, so I replaced the battery, and all was well.
The damn thing failed again last Friday - same symprom. Sure
enough, the battery was below 5 volts. Another symptom was
thatt he clock display blinked at a very fast rate when the battery
was unplugged (I thought that was normal) .*This* time, I knew it
wasn't a simple battery failue due to old age. I metered the current
drawn from the new battery - sure enough, I found ~90 ua draw.
The clock is nothing more than a big LSI chip, some wires and
buttons, a couple of resistors - and 1 electrolytic cap.
I replaced the cap, which showed over 16 meg resistance.
Now the clock does not blink when the battery is out, and my DMM
cannot detect any current draw from the battery, and the clock is
working. This was a case where the battery hid the failure - as long
as it was in and good, the clock performed flawlessly, even with
the bad cap, (220uf 16v) I probably would not have thought of
the cap being bad had it not been for the ongoing discussion here.


General Question...and maybe suggestion.

Mark Anton
 

Why is a TV damper tube not suitable for normal DC rectifier applications? From some of the ratings it looks as if would be nearly ideal for that service, but the tube manual usually cautions that not recommended for that use.

Im asking it here because there are many knowledgeable people here. A couple of other discussion groups i belong to are mostly for beginners.

Which actually brings up another point was thinking that would be cool if most of us could be part of another group disscussing general electronics and other brands of test equipment too. I think some general questions get asked here instead of other groups because most of us fairly knowledegable.

Mark

_________________________________________________________________
Tired of slow downloads? Compare online deals from your local high-speed providers now. https://broadband.msn.com


Re: General Question...and maybe suggestion.

donlcramer@...
 

They are. For example, see the fine article "Dumpster Rectifiers" by John
Atwood in issue 12 of Vacuum Tube Valley.

Don Cramer
KA7CEV

In a message dated 1/9/04 11:23:50 AM Pacific Standard Time,
heightstv@hotmail.com writes:
Why is a TV damper tube not suitable for normal DC rectifier applications?

From some of the ratings it looks as if would be nearly ideal for that
service, but the tube manual usually cautions that not recommended for that
use.

178541 - 178560 of 184732