Re: TDS744A tick tick tick when power on (and something smelling)
Hi Evan,
The cable looks actually really clean so I doubt that is the cause here. In fact, the complete CRT supply looks really tidy compared to some other instruments I have opened. Very little black powder anywhere really.
Regards,
Staffan
|
Re: TDS744A tick tick tick when power on (and something smelling)
Hi Staffan,
Did you check if there is contamination on the CRT flyback cable?
Sometimes it can get dirty and arc to the chassis causing a power
supply fault. I have never seen this scope but I have seen it happen
in others from Tek (and in TV sets of the era).
Obviously all normal precautions for working around high voltage apply.
-Evan
toggle quoted message
Show quoted text
On Thu, Apr 4, 2024 at 7:18?PM Staffan <testjarfalla63@...> wrote:
Hello,
Starting my trusty 744A today, it seems to have given up. There is a ticking sound (once every second?) from something likely trying to restart within the power supply?
There was a distinct smell, but not as bad as when a cap on the primary has given up. Not wanting to destroy anything else, I disconnected power as fast as I could.
Now I have opened the unit down to the power supply.
Nothing visible at first sight, but -phew- it doesn't look trivial.
Any suggestions on how to go about in pinpointing the faulty component would be very much appreciated. Are schematics available anywhere?
Searching the message history I found some discussions regarding the CRT board. There are four transistors on the neck board of the CRT, but none of those is visibly burnt at least.
Very much hoping for hints and suggestions!
Regards,
Staffan
--
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v2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=Ta4p
-----END PGP PUBLIC KEY BLOCK-----
|
TDS744A tick tick tick when power on (and something smelling)
Hello,
Starting my trusty 744A today, it seems to have given up. There is a ticking sound (once every second?) from something likely trying to restart within the power supply?
There was a distinct smell, but not as bad as when a cap on the primary has given up. Not wanting to destroy anything else, I disconnected power as fast as I could.
Now I have opened the unit down to the power supply.
Nothing visible at first sight, but -phew- it doesn't look trivial.
Any suggestions on how to go about in pinpointing the faulty component would be very much appreciated. Are schematics available anywhere?
Searching the message history I found some discussions regarding the CRT board. There are four transistors on the neck board of the CRT, but none of those is visibly burnt at least.
Very much hoping for hints and suggestions!
Regards,
Staffan
|
Re: 7904A--Horizontal and Power Supply Seem Ok, but Not Much Else
Check if the readout is working at all.
You can do that by probing the X-Y outputs with a scope in xy mode. The text may be upside down, but still you will see the readout.
If you get a dot or unreadable gibberish, the readout system is bad or not getting power.
Benjamin
|
Re: Help! I bricked a perfectly functioning 2467B!
Don,
Where are you located? The lab might be able to help in this situation as I can do a full calibration on a 2467B as a last resort I might be able to help run it through a calibration process.
Zen
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Don via groups.io Sent: Thursday, April 4, 2024 1:20 PM To: [email protected]Subject: [TekScopes] Help! I bricked a perfectly functioning 2467B! Hello all, I had a perfectly functioning 2467B scope (1989 vintage). After reading about possible loss of calibration data due to the NVRAM battery dying, I decided to put in a new battery (mine is the older version, below 50000 serial #) which has the battery separate from the NVRAM. The battery had a date code of 2689, so the battery is 35 years old. I did hook up a backup battery before removing the Lithium battery and confirmed that pin 28 of the RAM chip had at least 3 V on it from the backup battery after removal of the original battery. After putting in the new replacement battery, I also changed out the 4 electrolytic capacitors on the A5 board. When I put the scope back together and fired her up, I got the dreaded " Test 04 Fail 13" message indicating corrupted or lost calibration data. Not sure how this happened since I hooked up a backup battery before removing the original battery. So, the very thing I was hoping to prevent happened by my being proactive! Before doing all this, I had made a copy of the RAM contents by running through the Exercise 02 option, so I have the original calibration data available. My question is: how to write this data to the RAM? (my scope does not have the GPIB option). I look forward to your suggestions and hope to get this fine scope functioning again!
|
Help! I bricked a perfectly functioning 2467B!
Hello all,
I had a perfectly functioning 2467B scope (1989 vintage). After reading about possible loss of calibration data due to the NVRAM battery dying, I decided to put in a new battery (mine is the older version, below 50000 serial #) which has the battery separate from the NVRAM. The battery had a date code of 2689, so the battery is 35 years old. I did hook up a backup battery before removing the Lithium battery and confirmed that pin 28 of the RAM chip had at least 3 V on it from the backup battery after removal of the original battery. After putting in the new replacement battery, I also changed out the 4 electrolytic capacitors on the A5 board. When I put the scope back together and fired her up, I got the dreaded " Test 04 Fail 13" message indicating corrupted or lost calibration data. Not sure how this happened since I hooked up a backup battery before removing the original battery. So, the very thing I was hoping to prevent happened by my being proactive!
Before doing all this, I had made a copy of the RAM contents by running through the Exercise 02 option, so I have the original calibration data available. My question is: how to write this data to the RAM? (my scope does not have the GPIB option).
I look forward to your suggestions and hope to get this fine scope functioning again!
|
Re: FS: Tektronix 012-0884-00 calibration / direct output cable for the Tek CG5XXX scope calibrators
Replied to both Nick and Rubens about purchase of cables. Hope you got my private messages?
Craig
|
Re: 7904A--Horizontal and Power Supply Seem Ok, but Not Much Else
Thank you Roger.
I'll double check the low voltage supplies. I did check the voltages with a DVM, but did not check for ripple.
I've had the scope for a while, and it did work properly when I acquired it. A few years ago while I was using it the vertical stopped responding. I turned it off, put the scope away and have since been using a 7603. I decided to see if I could get the 7904A working again, and seem to be in over my head!
|
Re: trigger problem with 7B70
I'll second Ozan's helpfulness with this sort of thing. He has helped me a few times isolate a problem like that whcih I'm pretty sure I would not have found on my own. Glad you have something going and hope the correct transistors will fix the rest of the issues with this.
Barry - N4BUQ
toggle quoted message
Show quoted text
Thanks to Ozan for helping off-list with some additional measurement advice and
insight on expected values. I continue to be amazed at what some of you can
understand from a schematic.
He suggested replacing Q309/Q317 in the trigger pulse generator with the pair
from my working 7B70, and that did the trick: stable waveform with
sine/triangle/square, and controls work as expected.
I had previously tried replacing them individually with a 2N3906 (one of the few
PNP transistors I have on hand), with no luck. Replacing both Q309 and Q317
with 2N3906s actually shows a waveform instead of a blank screen, but it
stutters so I've ordered some 151-0220-00 replacements.
Adam
|
Slightly off topic, but I'm getting desperate. Looking for the Adjustment Program for the HP/Agilent 4263B
Hi all,
A little off topic, but I'm getting desperate....
I'm on the hunt for a copy of the Adjustment Program to enable calibration of the HP/Agilent 4263B LCR meter, part number 04263-65005
It's just a BASIC program but Keysight Japan have given me a solid NOPE for any support regarding this instrument.
I've also emailed a few service/cal houses and they all have turned up dry too.
If anyone has this software, I'd greatly appreciate a copy! I want to calibrate my unit and also wouldn't mind having a go at porting it to Python and open-sourcing it to allow for easier use on modern PC's...
Thanks!
Jared
|
The HV supply is in the right-hand-rear of the scope and the HV line runs from there to the front of the scope around again to the side of the CRT. If that cable is arcing, it might sound like it's coming from the left-hand side.
If you still hear the arcing, you could remove the top covers and power the scope in a dark room. That might help show where it's coming from.
Barry - N4BUQ
toggle quoted message
Show quoted text
My beloved 7704A started arcing internally the other day, At least that's what
it sounded like. It seems to be coming from the LH front side next to the CRT.
Looking at the explosion diagram, this corresponds to the HT section. Also the
display has shrunk by 50% in both directions., so e.g. the readouts are at
25%/75% of height instead of 100%/100%.
Being more than reluctant to enter into an HT section untutored, I am wondering
if there are any hints as to what specifically I should be looking for. Scope
has been working flawlessly for 15 year, and the problem occurs in both A and
B/V and H, so it isn't a plugin.
TIA
EJP
|
Re: 7904A--Horizontal and Power Supply Seem Ok, but Not Much Else
Sorry, just noticed the 'no readout' in your post.
If you also have a problem with lack of intensity control then checking all the low voltage supplies moves to the top of the list.
Roger
|
My beloved 7704A started arcing internally the other day, At least that's what it sounded like. It seems to be coming from the LH front side next to the CRT. Looking at the explosion diagram, this corresponds to the HT section. Also the display has shrunk by 50% in both directions., so e.g. the readouts are at 25%/75% of height instead of 100%/100%.
Being more than reluctant to enter into an HT section untutored, I am wondering if there are any hints as to what specifically I should be looking for. Scope has been working flawlessly for 15 year, and the problem occurs in both A and B/V and H, so it isn't a plugin.
TIA
EJP
|
Re: 7904A--Horizontal and Power Supply Seem Ok, but Not Much Else
Do you get the readout displayed correctly at top and bottom of the display? That would imply the vertical amplifier was basically OK and you might need to look for a fault in the vertical switching.
Is the scope new to you? If so try exercising the mainframe vertical mode switches several times, they may need cleaning and last but not least check that the vertical deflection plates are connected!
Roger
|
Re: trigger problem with 7B70
Thanks to Ozan for helping off-list with some additional measurement advice and insight on expected values. I continue to be amazed at what some of you can understand from a schematic.
He suggested replacing Q309/Q317 in the trigger pulse generator with the pair from my working 7B70, and that did the trick: stable waveform with sine/triangle/square, and controls work as expected.
I had previously tried replacing them individually with a 2N3906 (one of the few PNP transistors I have on hand), with no luck. Replacing both Q309 and Q317 with 2N3906s actually shows a waveform instead of a blank screen, but it stutters so I've ordered some 151-0220-00 replacements.
Adam
|
7904A--Horizontal and Power Supply Seem Ok, but Not Much Else
Hello.
My 7904A has several problems.
With a time base in either horizontal slot, I am getting a horizontally adjustable trace in the middle of the screen. I am getting a good, adjustable sawtooth signal on the front panel sawtooth output. Horizontal seeks to be working fine.
With a known good vertical plug-in in a vertical slot, the trace will not adjust up or down. At first, turning the position control did affect the triggering somewhat, but after a few minutes, the position control had no affect on triggering. I am using a 7A26--regardless whether it is in alt or chop there is only one trace and the position controls have no affect on the trace. Moving the plug-in between the two vertical slots makes no difference.
The trace remains in the middle of the screen with the beamfinder pressed.
The trace focuses, but the intensity controls have no affect on A or B. The intensity controls are at minimum and the trace is normal brightness, but the controls do not change the brightness at all.
There is no read out.
Any thoughts on what may be the cause of no vertical trace movement, and/or which of these issues may be related to one another and how I might be able to tackle them would be greatly appreciated.
Thanks.
Dave
|
Re: FS: Tektronix 012-0884-00 calibration / direct output cable for the Tek CG5XXX scope calibrators
Please let me know if anyone got stock Cheers
Nick,
I have several available some used and new. If you want to contact me online with your needs.
electronixtoolbox@...
|
Re: FS: Tektronix 012-0884-00 calibration / direct output cable for the Tek CG5XXX scope calibrators
Any of these cables still around?. Please let me know if anyone got stock Cheers
|
Re: 2465A Power Supply Issues
Did you follow up on Satbeginner's post (#203616)?
Raymond
Yes, I followed up on that post to no avail.
|
Re: trigger problem with 7B70
On Sun, Mar 31, 2024 at 04:09 AM, Adam R. Maxwell wrote:
With 7A26 on 0.5V/div, EXT trigger displays a stable waveform with a 1.25 Vpp
square wave. INT trigger displays a stable waveform with 2Vpp from the FG502.
With the 7A26 on 1V/div, EXT works with 1.25Vpp, but INT requires 4Vpp to
display the waveform. I do not understand this interaction with the vertical
amplifier, but the INT trigger only gives a stable waveform if the signal is
4x the vertical V/div setting. EXT only requires 1.25 Vpp.
Adam, In the 7A26 all attenuation is done is by the input attenuators. Hence after that the same signal is sent to the Vertical amp chain and the trigger amp chain. This means that the signal amplitude at the CRT is important for triggering. In both cases you mentioned here the amplitudes at the CRT are the same. Albert
|
Benjamin Badrakh
Craig Cramb
Jared Cabot