Re: Intermittent power on problems with 2465B
Hi Mark,
I would start by recapping the PS, the intermittend not starting makes me feel it's in there.
The SMD caps on the A5 board would cause all sorts of funtions on the frontpanel not working as they should, including brightness, trace position, even calibration, etc.
Just my 2 cts,
Leo
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Intermittent power on problems with 2465B
I have a tek 2465B (serial# B077725, so could have the infamous SMD cap issues) that sometimes does not start.
Typically, this is in the morning, and after I hit the switch 2-3 times, it starts. This afternoon, I fetched it from my workshead where it had to live for a few days (it has been raining in No Cal last few days), and I must have had to pound on the button at least 30x before it finally started. Subsequently, no problems, started up the first time after ever power down. (tried this about 8x tonight).
When it doesn't power on, no fan, no front LED's nothing.... Made me think that I had not plugged it in. Read about the "ticking" state on startup, but could not hear any ticking (but perhaps I should ask someone with better hearing...)
As far as I know, there has been no power supply re-cap. Once it starts, seems to work fine for its age.
I saw where some folks had to replace the power switch, but that sounds like a hard failure to me and not an intermittent problems.
Suggestions to start?
Thanks
Mark
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It is a pretty well known phenomenon... well discussed
on this group over the years... often by me.
Around about the time the 547/545B scopes got designed,
tektronix decided to make a universal HV compartment that
was plastic, contained the EHT, the 5642 rectifiers, and the
capacitors and resistors. The compartment was sealed to
help keep dirt, critters, and carbon dust out.
The sealing also prevented good cooling due to air motion.
This required the transformer to run at a higher temperature
than was allowed in the earlier 500 series scopes.
The earlier scopes used beeswax to impregnate the transformer
windings and tektronix was afraid that the wax would melt in
the new sealed compartments (newsflash: it doesn't to any great
degree... but I digress.)
Instead of using beeswax to improve the HV breakdown characteristics
of the EHT, they used an epoxy varnish to coat the windings.
Because epoxy is rigid, and the tiny wires used in the EHT were
easily broken, they added something to the epoxy to soften it,
and probably also something to act as a fire retardant.
The epoxy degraded over time, and greatly increased the losses
inside of the EHT, making it thermally runaway.
This has been dubbed the transformer epoxy disease.
Some improvement has been witnessed from long baking at high
temperatures, but it is only temporary, as the epoxy truly has
changed. The only real answer is to replace the winding with
new. Beeswax works better than the epoxy as when it gets laden
with moisture, it gets hot, melts the beeswax, and releases the
water vapor. Once the water vapor is gone, the EHT goes back
to its usual warm self.
The 560 series transformers were epoxy varnished, and then potted
in an aluminum can using a clear silicon RTV. They still fail
at about the same rate as the open core transformers in the
545B/547.
Some have opined that the failure mechanism is due to the fire
retardant that was added to the epoxy... if there was a fire
retardant added to the epoxy. This opinion comes from a long
history of problems that have come from fire retardant additives.
-Chuck Harris
petertech99h via groups.io wrote:
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Chuck,
Please tell me more about the 564B HV transformer epoxy disease!
Thanks!
Pete On Sunday, January 3, 2021, 8:07:20 a.m. EST, Chuck Harris <cfharris@...> wrote:
It is a cute little scope, but very low bandwidth,
something like 10MHz.? Its HV transformer suffers
from the epoxy disease that affects 547 scopes.
They are quiet, not having a fan, and the plugins
contain all the deflection circuitry (as I recall).
I used to like them quite a lot back in the day, for
audio work.
The storage functions are finicky.
-Chuck Harris
Stephen wrote:
Hi all, and Happy New Year 2021,
Is a 564B a good grab, is it desirable at all?
It¡¯s not considered a 500 series, right?
56x family I suppose...
Thanks ?
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Chuck,
Please tell me more about the 564B HV transformer epoxy disease!
Thanks!
Pete On Sunday, January 3, 2021, 8:07:20 a.m. EST, Chuck Harris <cfharris@...> wrote:
It is a cute little scope, but very low bandwidth,
something like 10MHz.? Its HV transformer suffers
from the epoxy disease that affects 547 scopes.
They are quiet, not having a fan, and the plugins
contain all the deflection circuitry (as I recall).
I used to like them quite a lot back in the day, for
audio work.
The storage functions are finicky.
-Chuck Harris
Stephen wrote:
toggle quoted message
Show quoted text
Hi all, and Happy New Year 2021,
Is a 564B a good grab, is it desirable at all?
It¡¯s not considered a 500 series, right?
56x family I suppose...
Thanks ?
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Re: 7613 Mainframe - Readout problem
If I remember the threads properly, the thermal compensation (dancing readouts) fixed a small wobbling problem.? This sounded like a much larger deviation, and the picture I was thinking of was, say, the character height or more (in both X and Y) rather than a fraction of it.? I have seen the readouts vary, but that was when the vertical amp had been overdriven.? Reduce that, and that particular wobble went away.
Very few designs are completely immune to power supply variations (unless great care is taken, IMHO, but I'm not an analog expert). My thought was that if power supply ripple is large enough, then that can couple to the output voltages, and make the readout (and all else, I might add) wobble on the screen.? If it's JUST the readouts, and the rest of the screen is steady (trace, hor sweep, etc.), then I'd be looking for another problem.
Harvey
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On 1/4/2021 7:53 PM, teamlarryohio wrote: and I must be thinking of another 7K frame as I couldn't find it in the manual I have. It's also been called thermal compensation, or it may not be there on this model. But the symptom was dancing readouts, usually
moving about as high as one of the characters. I'll keep looking.
-ls-
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Re: 7613 Mainframe - Readout problem
and I must be thinking of another 7K frame as I couldn't find it in the manual I have. It's also been called thermal compensation, or it may not be there on this model. But the symptom was dancing readouts, usually
moving about as high as one of the characters. I'll keep looking.
-ls-
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Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
No problem, Attilio! :)
As to tuning the filter, it's very important to take a good picture (or several) showing clearly the initial state of all of the adjustments before you started adjusting them. That way, if you get into trouble,? you can always return to the beginning state.
To avoid getting into trouble at all, only make small changes. Keep in mind that your goal is to change the center frequency by less than 5%, so only minor adjustments will be needed. Make only the smallest change that produces a visible effect. If the effect is in the right direction, but not big enough, keep going. If not, go the other way. If you stick to this strategy, you should have no trouble. And if by some misfortune you do run into big problems that prevent you from going back to the initial state, remember that the nanoVNA will still allow you to finish the job. You'll want the nanoVNA anyway. :)
Good luck!
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 1/4/2021 16:28, Attilio wrote: Thanks Tom,
sorry, but I'm a little old and sometimes I miss something. I have read the cavity filter tuning procedure, the note that warns me that if you lose the signal it becomes almost impossible to recover it makes me a little anxious.
We'll see, now I have to retrieve the 52.5 MHz crystal and a TR503 Tracking Generator to modify.
Thanks for your help.
--Cheers
Attilio
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Re: 7613 Mainframe - Readout problem
There is a low frequency compensation adjustment on the vertical output amplifier. If your power supplies are ok, check that next.
-ls-
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Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
Thanks Tom,
sorry, but I'm a little old and sometimes I miss something. I have read the cavity filter tuning procedure, the note that warns me that if you lose the signal it becomes almost impossible to recover it makes me a little anxious.
We'll see, now I have to retrieve the 52.5 MHz crystal and a TR503 Tracking Generator to modify.
Thanks for your help.
--Cheers
Attilio
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Re: 7613 Mainframe - Readout problem
Thanks Harvey,
I have not yet tested the voltages and their ripple on the power supply, I thought it was a fault on the Readout board, but I replaced it and the defect remained.
Tomorrow I'll check the voltages on the power supply.
--Cheers
Attilio
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Re: 7613 Mainframe - Readout problem
Have you checked power supply voltages and ripple with the two sets of plugins inserted?? Wandering across the screen suggests both X and Y problems, and changing with load suggests power supply.? May be the main DC filter capacitors not giving enough "depth" for the drain.
Harvey
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On 1/4/2021 4:27 PM, Attilio wrote: Greetings to all,
I brought home a 7613 mainframe to insert the 7L13 (SA) plug-in, but it has a problem in readout. It currently has a 7A16A vertical plug-in and a 7B70 plug-in timebase installed.
Without input signal (solid line on CRT) the readout is correct, but by inserting for example a sinusoidal signal the characters of the readout follow the movement of the signal dancing up and down around the stable position they should have.
By inserting the plug-in 7L13 (SA) the situation worsens and the characters wander on the CRT.
I tried to replace the readout board, but without resolving.
I ask for your help in identifying the defective component or components.
Thanks.
-- Cheers,
Attilio
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Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
Hi Attilio,
I encourage you to read the article I linked you to earlier. You do have to retune the filter only a few percent. You cannot skip that step¡ªthe filter has a very steep rolloff so a few percent makes a big difference. As I said before you don¡¯t need extra instruments to do it. Again please read my previous messages in full. It¡¯s all there.
Cheers
Tom
Sent from my iThing, so please forgive brevity and typos
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On Jan 4, 2021, at 13:03, Attilio <a.alovisetti@...> wrote:
Thanks Tom,
you still give me hope to find the 52.5 MHz crystal third overtone.
Just one question: if I understand correctly I don't have to touch the calibration of the four cavity filter, is that so?
The coupling of the mixer I was already intending not to touch it.
Thanks again Tom
-- Cheers,
Attilio
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7613 Mainframe - Readout problem
Greetings to all,
I brought home a 7613 mainframe to insert the 7L13 (SA) plug-in, but it has a problem in readout. It currently has a 7A16A vertical plug-in and a 7B70 plug-in timebase installed.
Without input signal (solid line on CRT) the readout is correct, but by inserting for example a sinusoidal signal the characters of the readout follow the movement of the signal dancing up and down around the stable position they should have.
By inserting the plug-in 7L13 (SA) the situation worsens and the characters wander on the CRT.
I tried to replace the readout board, but without resolving.
I ask for your help in identifying the defective component or components.
Thanks.
-- Cheers,
Attilio
|
Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603
Thanks Tom,
you still give me hope to find the 52.5 MHz crystal third overtone.
Just one question: if I understand correctly I don't have to touch the calibration of the four cavity filter, is that so?
The coupling of the mixer I was already intending not to touch it.
Thanks again Tom
-- Cheers,
Attilio
|
Tek logic analyzer probes free to a good home.
I have 10 or more Tek analyzer probes, wires, and clips that I have no use for.
These are 92a96 probes with breakout cables and clips.
Time to clean up my shop.?? Free for the postage.
Send a private message and they are yours.
Pete.
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Don't expect them to plug in, they're not keyed right.
Vince.
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On 01/04/2021 01:11 PM, Larry McDavid wrote: Vince, that would be helpful. I don't have a Tek 5000 scope; can anyone
independently confirm this?
Larry
On 1/4/2021 9:46 AM, Vince Vielhaber wrote:
A frame and front panel from a 5000 series scope plugin is the same as
the TM500[0] plugins. Sometimes they can be found for under $20 on ebay.
Vince.
On 01/04/2021 02:17 AM, Brian Cockburn wrote:
Ladies and Gents,
Don't forget that you'll need a chassis to put this in. And there
are now 50 people all trying to buy such a thing right now. Get your
skates on!
Brian.
--
K8ZW
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Re: 7L5 shaft encoder disassembly
Photos in album 7L5 encoder knobs
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Re: 11801C T2325 error diagnostic repair
Hi Reg,
By checking out the error codes in the "Tektronix 11801, 11802, and SM11 Diagnostics" document (on TekWiki, 11801 scope page), it shows from page 431 onward that the Time Base error index T232X points to the strobe generator. But then on page 435, only the error codes T2321-T2324 are indicated. Apparently, T2325 is added for a later 11801 model scope.
Maybe this helps you further.
Kind regards,
Gerard
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
From a side by side examination, it would appear that Vince is quite correct.
Jack
toggle quoted message
Show quoted text
On 1/4/2021 1:11 PM, Larry McDavid wrote: Vince, that would be helpful. I don't have a Tek 5000 scope; can anyone independently confirm this?
Larry
On 1/4/2021 9:46 AM, Vince Vielhaber wrote:
A frame and front panel from a 5000 series scope plugin is the same as the TM500[0] plugins.? Sometimes they can be found for under $20 on ebay.
Vince.
On 01/04/2021 02:17 AM, Brian Cockburn wrote:
Ladies and Gents,
? Don't forget that you'll need a chassis to put this in.? And there are now 50 people all trying to buy such a thing right now.? Get your skates on!
? Brian.
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Vince, that would be helpful. I don't have a Tek 5000 scope; can anyone independently confirm this?
Larry
toggle quoted message
Show quoted text
On 1/4/2021 9:46 AM, Vince Vielhaber wrote: A frame and front panel from a 5000 series scope plugin is the same as the TM500[0] plugins.? Sometimes they can be found for under $20 on ebay.
Vince.
On 01/04/2021 02:17 AM, Brian Cockburn wrote:
Ladies and Gents,
? Don't forget that you'll need a chassis to put this in.? And there are now 50 people all trying to buy such a thing right now.? Get your skates on!
? Brian.
--
Best wishes,
Larry McDavid W6FUB
Anaheim, California (SE of Los Angeles, near Disneyland)
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satbeginner
Attilio
Jean-Paul