Date   

Re: 547 scope HV transformer problem. One practical solution.

 

Hi Doug,

"That old test equipment"... "OLD" is not an adjective that should be used with test equipment or tools in general. The basic tools I have (hammer, pliers, etc) are incredibly old, and working fine. As for electronics, I have a relatively new multimeter with digital display, auto-ranging and advanced features, precise, economical. But I use more my old cheap Radio Shack MICRONTA 22-221, which I found junked in the garage and restored it. I rarely need precision, like when measuring continuity, and I prefer to see the needle move than the digits flicker with the auto-ranging. Maybe because my eyes are old too? LOL.


Re: CRT rebuilding

victor.silva
 

During all my years refurbishing Tek 24xx series I have been able to trade/barter/buy(when within reason) a large collection of NIB CRTs for the 2465x/45x and even 2 NIB 2467B CRTs. If ThomasElectronics comes back with "$300-400 dollars, maybe more" I would certainly consider selling a few NIB 154-0850-01 CRTs for that.

--Victor


Re: Modifications to 577 Curve Tracer Main Power Supply

 

On Mon, Mar 2, 2020 at 04:34 AM, Gary Robert Bosworth wrote:


Thank you to everyone. I now have ideas of where to look. I probably have
more than one problem. I will continue to troubleshoot in a few days.
Good luck, Gary. I'm curious to know what you'll find.

Raymond


Re: CRT rebuilding

Eric
 

Interesting thought. I wonder if they would work on 576 crts I have 2 -5
tubes that could use a rejuvenation. Or possable rebuild. For the 1 off
tubes like that I would not mind paying for a rebuild.

On Sun, Mar 1, 2020, 10:22 PM Roy Thistle <roy.thistle@mail.utoronto.ca>
wrote:

Hi All:
I ran into a guy who owned one of the service companies that used to
supply rebuilt CRTs for televisions... it was a good business for about 15
years. Basically, he would rebuild (install a new gun assembly) onto a unit
with a failed one (either filament damaged, or emitter components damaged)…
he did not do any re-phosphor. He could charge T.V. repair shops about 20%
less than the manufacturer supplied CRT.
My guess is... if the guns for Tek CRTs are not available (and where would
they be?)... or unless possibly one wanted burn-in repair on the screen (so
re-depositing the phosphor) on an otherwise strong CRT... then rebuilding
is not going to happen. Guns for popular television tubes where
manufactured by the 100's of millions... and maybe still are available in
China, of the former C.C.C.P. countries. Tek guns... not so much.
Best cheers and wishes.
Roy




FS: Late serial 7104 with 2x7A29, 7B15, 7B10 in UK

 

I've not used this more than 3-4 times since I bought it a few years back
from an estate sale in the Manchester area.

The person who owned it was a collector and had HUGE amounts of stuff, all
in almost new condition.

Serial B052922 which is very late AFAIK, and it is in very fine condition.

It has minor screen burn in the readout area, and no obvious signs of burn
in the rest of the CRT screen.

I only broke the calibration seals to have a look inside!

It comes complete with a "dead tree" service manual.

I'm not really sure what to ask for it so make me an offer (off list).

Given the risk of shipping damage, this is for collection only from
Kenilworth, GB

David


Re: 547 scope HV transformer problem. One practical solution.

tek_547
 

On Wed, Feb 26, 2020 at 07:41 PM, Ernesto wrote:


It has now inside an added little centrifugal blower fan that cools the HV
supply. This has solved the classical HV transformer problem, that caused it
to fail after 10 minutes.
Effective solution Ernesto to put a fan on the HV section, I did the same with my 647A. Worked good before the fan but better safe then sorry. The temp from the core of the transformer is lowering about
2°C with no holes in the HV box so there is room for more improvement.


Re: Wanted Tektronix 2756P / 2794

Ron
 

Marc,

Have a Tektronix 2753P on the bench, but available.

regards, Ron


Tek 214 vertical amplifier problems

Harvey White
 

I have a 214 I got quite a while back, and have replaced the batteries, the mode switch (store/norm/single sweep, etc).

However, the vertical amp on channel 1 seems to be off by a lot. IIRC (and it's been a while), some of the attenuation settings are off, very off.  I'm thinking it might be the switch, but the way the thing is constructed makes it difficult to troubleshoot (it's a wrap around style that hides all the interesting parts).

I'd be interested in a new vertical amp board, if there are any available at a (to me) reasonable price.  Getting the probes would be nice as well, but I'd also be able to print a back plate and put in two BNC jacks with peltoler connectors, and that would allow me to do standard probes.  That would defeat running it from the line and having isolation, but that's not been a need for me.

Anyone have any repair tips either?

What I think I do want is something around a 225 or so, digital scope would be good, not that I have to have it, but it's cute....

I really do need the two channels...

Harvey


Re: Modifications to 577 Curve Tracer Main Power Supply

Gary Robert Bosworth
 

Thank you to everyone. I now have ideas of where to look. I probably have
more than one problem. I will continue to troubleshoot in a few days. Gary

On Sun, Mar 1, 2020, 17:29 Raymond Domp Frank <hewpatek@gmail.com> wrote:

On Mon, Mar 2, 2020 at 02:01 AM, Ed Breya wrote:


while those made on caps and transistors may not reflect how they behave
in
actual operation.
I thought about that, especially re. Q722 just being two diodes. Next,
since Gary mentioned he had checked all parts, I thought he'd checked them
for what they are supposed to be. That left the possibility of a continuity
problem with said point being a nice candidate.

Raymond




Re: CRT rebuilding

Roy Thistle
 

Hi All:
I ran into a guy who owned one of the service companies that used to supply rebuilt CRTs for televisions... it was a good business for about 15 years. Basically, he would rebuild (install a new gun assembly) onto a unit with a failed one (either filament damaged, or emitter components damaged)… he did not do any re-phosphor. He could charge T.V. repair shops about 20% less than the manufacturer supplied CRT.
My guess is... if the guns for Tek CRTs are not available (and where would they be?)... or unless possibly one wanted burn-in repair on the screen (so re-depositing the phosphor) on an otherwise strong CRT... then rebuilding is not going to happen. Guns for popular television tubes where manufactured by the 100's of millions... and maybe still are available in China, of the former C.C.C.P. countries. Tek guns... not so much.
Best cheers and wishes.
Roy


Re: DS1742W-120 replacement adapter?

amirb
 

Does anybody know at which addresses the number of power cycles and hours of operation (in TDS3000B series) are stored in the DS1742W NVRAM?
and what is the format?
I remember I saw that information somewhere a while back but I cannot locate it


Re: CRT rebuilding

BW
 

For what it's worth, the Early Television museum has the facilities to do rebuilding, just not the staff nor time to do it full-time.

If they get that online though, odds are the Tek folks will be behind a mile long queue of folks wanting to get their TV CRTs rebuilt...

http://earlytelevision.org/crt_rebuilding_at_museum.html


Re: CRT rebuilding

stevenhorii
 

Those who have been posting about replacement Tek CRTs, you may know of the
Sphere Research "Stuff Day" sale. Walt Shawlee has Tek CRTs available both
used and new. Here's the URL:

https://mail.google.com/mail/u/0/?tab=wm&ogbl#search/walter/FMfcgxwGDWxRnBcXTgjWpdfSKwbFhgCV


I have no financial connection with Sphere, though I have been a customer
(slide rules!).

Steve

On Sun, Mar 1, 2020 at 6:54 PM Jeff Kruth via Groups.Io <kmec=
aol.com@groups.io> wrote:

Long ago, I did business with Thomas, a first class outfit. They needed
glass for re-building a special tube they sold and I had a lot of it, so I
traded twenty duds for two rebuilt tubes. They re-gun the tube as far as I
know, cut off the old gun, re-phosphor and put in a new gun. Relabeled and
everything. I dont know how they will do with custom CRTs from Tek. What if
they break the CRT envelope? Maybe they would do it on a "If it works out,
we will charge you" kind of effort. However, expect to pay something real.
$300-400 dollars, maybe more, would not surprise me.

Jeff Kruth
In a message dated 3/1/2020 6:05:21 PM Eastern Standard Time, donfrasher=
yahoo.com@groups.io writes:
Looking over their web page FAQ they claim to do around 50 different
phosphors.I also sent them a note from there contact listing. I'm thinking
at this point that cost will be the big factor.

On Sunday, March 1, 2020, 05:56:19 PM EST, John Williams <
books4you@telus.net> wrote:

Interesting. I am going to contact them. If they can redo the phosphore
maybe they could change it to a different one. Depending on cost of course.
Thanks.







Re: Modifications to 577 Curve Tracer Main Power Supply

 

On Mon, Mar 2, 2020 at 02:01 AM, Ed Breya wrote:


while those made on caps and transistors may not reflect how they behave in
actual operation.
I thought about that, especially re. Q722 just being two diodes. Next, since Gary mentioned he had checked all parts, I thought he'd checked them for what they are supposed to be. That left the possibility of a continuity problem with said point being a nice candidate.

Raymond


Re: 555 Attributes, facets, benefits and General Discussion

fiftythreebuick <ae5i@...>
 

Hi Bob-

Thanks for adding all of that good info! Good assessment of the weigh-1-or-2 piece issue. I can move the two pieces of a 555 much easier than the single piece of the 556. I need to have an overhead crane installed in my shop... <laughing>

The Type O trick has been useful to me on more than one project when trying to trigger on something difficult to lock onto. Depending on what the problem is as far as obtaining a stable lock, you can easily have an adjustable differentiator, and adjustable integrator or a trigger amp with non-linear gain, etc, etc, etc. By building your own module to plug into the Type O, you can get even more creative. And the nice thing is that you have a complete oscilloscope sitting right there to monitor the "trigger processor" output with... Then considering that you can trigger the the A timebase from your "conditioned" trigger and then delay the B timebase, you have another tool with which to isolate what you want to see.

Tom AE5I

On Sat, Feb 29, 2020 at 09:01 AM, bobkrassa wrote:


Tom's mention of using a Type O as a trigger conditioner is interesting. I'd
appreciate hearing more about this. Modern scopes have menus for this but
they are opaque.

The 556 is a wonderful scope but when it needs work, access is quite difficult
for people with larger hands.

The display on a 556 is 6 x 10 cm per beam with a 4 cm overlap while on a 555
it is 4 x 10 per beam with a 2 cm overlap.

Some time ago there was a very informative message in this group about not
mixing A and non-A time base plug ins in a 555. As mentioned, they are
designed for access not swapping.

Weights are different. The 556 is a single compact unit that weighs 83 pounds
even without plug ins. This is fine if you can handle the weight without
damaging yourself or the scope. On the 555, the indicator weighs 68 lbs and
the power supply 45 lbs. You certainly need more bench space to work on them
because you can't do much diagnosis without having the two parts connected,
but the somewhat lower weight and the accessibility make a difference.

Bob Krassa AC0JL


Re: Modifications to 577 Curve Tracer Main Power Supply

Ed Breya
 

Raymond wrote: "What about my suspicion of R776 or its connection to R775 being open? It would result in about - 7V (6.2 + 0.7) V at the output, which Gary has observed."

Yup, that would do it too - the R or the end of the pot could be open. But, considering that all of the parts were checked, it's more likely that any resistance and connection measurements would still be valid, while those made on caps and transistors may not reflect how they behave in actual operation.

Ed


Re: Modifications to 577 Curve Tracer Main Power Supply

 

On Mon, Mar 2, 2020 at 01:08 AM, Ed Breya wrote:


OK, so with partial output to -7V, then it's likely the voltage on VR772 is
stuck way too low (failed or dumped by C772), or Q772 is breaking down or
leaking. If Q772 went open, it would go open loop overall, and the no-load
output would be near the 40V raw supply. There are a number of ways it could
have failed and makes -7V output, but I'd suspect the "772" parts at this
point.
Ed,
What about my suspicion of R776 or its connection to R775 being open? It would result in about - 7V (6.2 + 0.7) V at the output, which Gary has observed.

Raymond


Re: Modifications to 577 Curve Tracer Main Power Supply

 

Gary,
I believe this is easily explained by looking back at the parts list where it says R773 and C773 were discontinued at Serial Number B049999.

There is a discrepancy between this PDF of the manual I have and a later paper original manual I have. The earlier PDF says it is:
070-1414-00, First Printing JUN 1973, Revised DEC 1981. On Schematic 12 it says REV E, MAR, 1978. In this PDF R773 and C773 are visible. They are a little fainter than the other parts around them but that appears to be a side effect of the scanner that was used to convert the manual into a PDF.

In the original manual I have which is more recent it says:
070-1414-00, First Printing JUN 1973, Revised SEP 1986. On Schematic 12 it says REV JAN 1985. In this manual R773 and C773 are drawn in faintly. That is not an accident. It appears deliberate.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Gary Robert Bosworth
Sent: Sunday, March 01, 2020 2:04 PM
To: TekScopes@groups io <TekScopes@groups.io>
Subject: Re: [TekScopes] Modifications to 577 Curve Tracer Main Power Supply

Dennis: The parts in faded print are R773 and C773. They are not on the circuit board.
The circuit design is not well described in the service manual. No normal voltages and currents are mentioned in the print.
The +40V and -40V unregulated are fine.
ALL of the components measured perfectly good including the rectifier bridges and filter capacitors.
The power supply behaves the same whether the loading connectors are attached or not.
All of the other supply voltages are good including +200V, +12V, -12V, and
+5V.
I momentarily disconnected the short-circuit feedback diode CR785 when the loads were not attached and it had no effect.
The reason why I do not like this design is because of the fact that the -30V output is used to bias the 6.2V reference diode VR772. This poses a classic lock-up condition in that if the -30V does not exist, then the reference diode is never turned on.
I have measured every circuit trace from beginning to end and there are no micro-cracks to open them up, and there are no solder bridges causing short circuits.
This is a perplexing problem that I have not seen in 56 years of working in electronics.

Gary

On Sun, Mar 1, 2020 at 11:53 AM Dennis Tillman W7PF <dennis@ridesoft.com>
wrote:

Hi Gary,
Which parts on which schematics are shown in shaded text?

Dennis Tillman W7pF
TekScopes Moderator



--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247





--
Dennis Tillman W7PF
TekScopes Moderator


Re: TDS2000 brightness control

Mark Jordan
 

Or you can replace the backlight with white LEDs.

    Mark Jordan

On 01-Mar-20 19:49, Tom B wrote:
Unfortunately, it does not appear that there is any way to adjust the brightness.  They built the main power supply and CCFL inverter all on one board.  There is nothing to adjust.  The service manual specs the inverter output at 1400V P-P @5mA load.

I don't know if there is enough room inside to put a separate inverter for the backlight.  It might be better just to live with it the way it is.

Tom

On 3/1/2020 4:25 PM, Harvey White wrote:
You can do that, possibly.  It depends on whether or not the display has an easily replaceable CCFL bulb.

What you'd need would be an LED strip, the appropriate resistors and LEDs.  You'd need a variable PWM source or perhaps an additional resistor/variable voltage regulator to give you the brightness you want, or just adjust the resistors (which can get messy if you do it too many times).  You can adjust the resistors to work profitably on a 5 volt supply, for instance.

Another option is to replace the inverter with a variable brightness one, and put a small pot in to control that brightness.  If the existing configuration has the provisions for bright/dim the inverter, you may want to mess with that instead of putting LEDS in or replacing the inverter.

I have replaced CCFL lamps with LED strips, and do have LEDS and the blank PC boards, though.  You'll want to be able to do surface mount soldering, the parts are 1206 and 805 in size.

I'd look at messing with the control of the inverter first.  I would NOT mess with the high voltage part at all, you're talking 1600 volts at 8 ma or so to light that little CCFL lamp.

Likely the first thing would be to see what the inverter has in the way of a control voltage, for the ones I've seen, it's a simple voltage from, say, 0 to 4 volts.  Don't remember if more is less here, but that depends on the inverter.  Some are not brightness controlled, some are.


Re: Modifications to 577 Curve Tracer Main Power Supply

Ed Breya
 

OK, so with partial output to -7V, then it's likely the voltage on VR772 is stuck way too low (failed or dumped by C772), or Q772 is breaking down or leaking. If Q772 went open, it would go open loop overall, and the no-load output would be near the 40V raw supply. There are a number of ways it could have failed and makes -7V output, but I'd suspect the "772" parts at this point.

Yes of course Raymond, the output transistor would be turned on fully if it went open loop. I'm presuming it's still closed loop, with the failure limiting how high it can go. This appears to be the better kind of failure - not enough output rather than way too much, which could do some damage.

Ed

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