2465B 5v Digital ripple and other issues


Allan
 

HI All

I have recapped my 2465B and all voltages on J119 are spot on and all ripples very low except for Pin 2 (+5V Digital) which reads around 1.9mVAC ripple instead of <1mVAC. Any ideas on where to look now?

Also and Im not sure if this is related but my Intensity control does not work and I cant do the Cal 08 as turning down the Grid Bias dims the entire display...not just the dot. All other functions etc on the scope seem fine. Any help would be appreciated.

cheers...Allan


Mark Vincent
 

Allan,

The filters on the power supply need to be a high temperature low ESR type. Examples are Nichicon ULD/UHE. I do not know what brand and series you used. Condor Audio says to increase the capacitance of the filters for the 180 and 250mfd to 330mfd. Mouser has 470mfd 16V types in stock in the UHE version at the time of this post. These would be ones to use for the 5V supplies and any 8V supply. If you have used this or equal quality caps, move on. The TO-220 rectifier is suspect as these can go bad. The 47mfd types on the boards should be changed. I used ULD types in mine.

The intensity should go from 0 to 1,36V at the wiper and pin 16 on P120. You may not have put this back in fully. Reseat this. That may be all that is wrong. See if there is a bad solder joint to the control or flex cable. I am assuming the readout intensity is working by your post. You may have to trace the voltage back through the 10,000 ohm resistor back to the IC it goes to. The IC could be bad. This is an unlikely case.

What you said and looking at the schematic is the best I can do for now. You may find the problem easily. Let us know what you find as your problem(s).

Mark


Allan
 

Hi Mark

Thanks for the reply. I have used caps supplied by Condor Audio throughout. The voltage on the wiper and Pin 16 on P120 is 0-1.36 as you specified. I have checked quite a few of the component specs on the A5 board namely the resistors etc. and all look within spec. The readout intensity sort of works but is flakey when you get around the centre of the rotation. ie: 0v It acts more like an on/off as the actual intensity does not seem to vary. The focus works as does scale illumination. I have made a short video of the startup and what I get on screen at:

https://schoolsnsw-my.sharepoint.com/:v:/g/personal/allan_meredith_det_nsw_edu_au/Ef2xp0sYF9pLlCKUQlHqJjUBq0--tV-ck9zl0PzcwvQRwA?e=l9wnuR

i am new to this so really do appreciate the help. Thanks.

cheers...Allan


Mark Vincent
 

Allan,

Turn the readout control some times. It does not need to be on when rotating the control. That may clean the element so it will vary as it is rotated. That may be the only thing wrong. The caps you got from Condor Audio is a great kit.

Mark


Jean-Paul
 

Allan: BRAVO for you new scope and rework. 2465B was the LAST Tek CRT scope and a classic, remarkable they are STILL in everyday service 30-40 years later. Bought my first 2465 in late 1980s....
The 2467B and various OPT are also very interesting. We have a few of each...

1/ Ripple 5V: unlikely any issue re C or ESR of the Condor caps.

Measuring the PSU ripple of 1 mV is not trivial! It requires a 1:1 probe connected DIRECT from the GR to +5 pins of U119 header!
With a 10X probe and normal ground lead, 2 -3 mV is going to be seen.
We use a RG/198/U thin coax to BNC direct to the observing scope input.

2/ RE: Intensity, CAL 08, and other issues:
ANY 2465B MUST have the A5 SMD lytics REPLACED as they ALL leak corrosive electrolyte that damage the DAC and other sections of the board, causing many strange symptoms.

3/NVRAM Dallas Semi should be removed, place low profie machined pin socket, read CAL data, replace with NEW FRESH Dallas NV RAM, THEN recalibrate.
See the many threads on 2465B A5, NVRAM, Dallas Semiconductor on this forum and in EEVBLOG, check the 60 pages "Tektronix 2465B teardown" for more tips.

4/ A FULL CAL is recommended, with proper CAL test gear. Takes a day the first time, a steep but useful learning curve !

Bon Chance,


Jon

PS: Menachem at Condor is and expert, and very generous to respond to 2465B restoration problems.


Jean-Paul
 

Hello again

See the Tek manual for the PSU ripple V spec on U119.

Is the 5V ripple is specified in mV RMS or mV peak to peak?

How did you measure, tRMS meter, scope, VOM ?

Enjoy

Jon



Jon


 

Jon

Thank you, but I am very far from an expert.
I try to learn from every man, give my best, and share what I can.

Menahem


Jean-Paul
 

Menahem, how are you doing? What's news in Israël?

All fine in Paris, super busy....

the wisest man is also the most modest....

כֹּל הַכָּבוֹד

All honors to you!

Jon


Allan
 

Hi Jean-Paul (and all)

Thanks for the reply. I am measuring ripple with my Siglent 3065X DMM and all seem to be well within specification except for Pin 12 (Analog +5v) which is 1.5mV I have replaced all caps as noted before and also a couple of SMD caps and linked a couple of tracks that were damaged. All traces etc now show continuity between parts etc. so I am hoping that is now all ok. I have checked multiple components around the A5 board and all check out ok. The video I linked below shows the display issues and besides the Intensity not doing anything, the Readout Intensity is very flaky as you rotate it through the 12 o'clock position (shown in video). All voltages on these pots seem to be within spec also. I am really at a bit of a loss as to where to go next with this. Any ideas will be greatly appreciated.

https://schoolsnsw-my.sharepoint.com/:v:/g/personal/allan_meredith_det_nsw_edu_au/EYzZagaZt6VPqvE2G7kR-fcBsWZDXxBMX_goVLsdZ6JxIA?e=SYZ8im

cheers...Allan


Siggi
 

On Wed, Jun 30, 2021 at 9:36 PM Allan <saj507@gmail.com> wrote:

The video I linked below shows the display issues and besides the
Intensity not doing anything, the Readout Intensity is very flaky as you
rotate it through the 12 o'clock position (shown in video). All voltages
on these pots seem to be within spec also. I am really at a bit of a loss
as to where to go next with this. Any ideas will be greatly appreciated.
The readout looks to be working as intended to my eye, the problem is the
intensity control. The 12 o'clock position is where the readout is off,
clockwise from there you get the scale factors etc, whereas
counterclockwise you only get delta readouts.

You need to look at the intensity signal, see where it's going awry. There
are test points (65/66?) in the vicinity of U950 where you should be able
to see whether the intensity is coming out right from the Z axis hybrid. If
so, likely you'll have a bad DC restorer or some kind of trouble on the HV
board.

Good luck!
Siggi


Jean-Paul
 

Looks suspiciously like a system wide issue that affects many functions.

Perhaps the control DAC ckt , which affects almost every control and function.

If the PSU voltages on U119 are 100% OK, have you checked every connector and reworked the A5 control board for NVRAM and leaky SMD caps?


Jon


Allan
 

Hi

Thanks for the tips. The screen issue was resolved finally by replacing the U950 Z Axis IC. As soon as that went in all was good, well as far as the screen goes. Now I will need to look at the NVRAM as after a Calibrate, although all went through without issue, I now get Test 04 Fail 02. Moving forward I guess. At least it is getting close to being usable.

cheers...Allan