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Sounds like an insulation failure in the HV section. With sound, my guess is the wire that brings HV to the CRT.

HTH,
Dave Wise
________________________________________
From: [email protected] <[email protected]> on behalf of thespin@... <thespin@...>
Sent: Monday, September 03, 2018 7:51 AM
To: [email protected]
Subject: [TekScopes] Intermittent crackle when turning on 547

Hey all,

When I turn on my 547, occasionally once the thermal relay clicks on, the fan will slow down more than usual, and I'll hear a loud crackle and hiss and the CRT won't come on. Any ideas what this could be? Usually when I try again in a few hours it comes up just fine.

Evan

There is a very decent PDF manual at w140.com/tekwiki/wiki/466. For serious fault finding I print off a few pages, sometimes as two sheets stuck together, and make a note on these where to find other schematics and layout pages. It looks like all the lower voltages get their reference from the +65V that you will find just below the +140V supply on schematic <11> Power Supply and Distribution. If all of your lower voltages are off by the same fraction eg all low by 20% it could just be that the +65V is off spec and everything else is OK. If you want I can talk you through some of the stages but I am far from being an expert and you will have to wait until after our holiday!

Roger

Is the -05 a later replacement/suitable for my mainframe or is the -05 a typo?

For your scope any revision of the CRT will work.

There were four revisions of 154-0644-0x, -00, -04, -05 and -09. Only -00 (< B040600) and -05 (repl for -00 and used from B040600)
were used in 7704A. The other two were used by 7854 and 790x series opt 78 i.e P11 phosphor. For some reason 7704A opt 78 used another CRT.
If the CRT was replaced on 7704A below B221300 a Part Replacement kit (050-1732-01) was required. It contained the -05 CRT and two resistors
(one for 7704A and one for 7904/R7903) used to reduce the heater voltage to extend CRT life.
Kit instructions here:

/H?kan

Hey all,

When I turn on my 547, occasionally once the thermal relay clicks on, the fan will slow down more than usual, and I'll hear a loud crackle and hiss and the CRT won't come on. Any ideas what this could be? Usually when I try again in a few hours it comes up just fine.

Evan

My TDS3032 (original version) works fine. When I turn it off, it seems to
retain its settings except it doesn't remember the GPIB address configured
in the I/O Setting. I set it to GPIB Address 2, and it reverts to "1".

Is there a lithium battery in the scope or in the I/O Module (I have the
I/O module with VGA, RS232 and GPIB).

I use the scope with GPIB in a test system.

This isn't a major problem, but rather a nuance.

Thanks much,

Dave

Oh, right. That hadn't occurred to me to be honest. I've removed the 'CRT fuse' as you suggested and run the rest of the scope up to 230VAC without anything going *bang* so that's a plus, anyway. However, being realistic I don't think there's much more I can do at this stage. Only one of the PSU output voltages tallies up with the schematic (the 140V TP is reading 141V) but the rest are not within what I would describe as normal. I'm hampered by the lack of a physical, hands-on manual. The scanned copy I'm using is hard to read in places and the pages are hell to find with page/up/down buttons. On top of which what little I can see of the schematic is seriously unfamiliar circuitry to me. If you can understand that rat's nest you must be a genius, that's all I can say.
Reckon I'll just have to mothball it for a few more years until I have the time to get to grips with it with a better chance of success. :(
Many thanks indeed for your assistance, anyway.

Hey Kerry,

Nice to know that it worked. Such a pity that you had to replace U310. ECL logic ICs are usually very robust and don't seem to fail very often.
But definitely, better this than having to replace a Custom Tek IC.
Rgrds,
Fabio

Hello Fabio

i replaced U310 (with the help of another Tekscopes member) and this solved the problem. The 20ns, 10 ns and 5ns timing is now correct. I made most of the adjustments in the manual to maximise the amplitude of the waveforms and these seem to be in spec. The amplitude of the 2ns appears down slightly, but this is probably to be expected when using a Tek 2465A with only 350MHz bandwidth to measure it. I can't of course check the 1ns output without a wider bandwidth scope.

Thank you once again for your assistance.

Regards

Kerry

The circuitry around the high voltage transformer T1501 constitutes a power oscillator running at around 50kHz, there is feedback from the CRT cathode to Q1472 that controls the drive to the power transistor Q1486 and stabilises the cathode voltage. There is a theory of operation section in the manual.

Roger

Ok Chris,

Let me get the scales out and do some weighing! It would be much preferable to send the entire module, as I know it works, and includes the driver power transistors. I have things on over the next two days, but first thing Wednesday, i’ll Get you some costs.

Cheers,
Mel

--
you can never have enough oscilloscopes, DMMs, valve testers or soldering irons . . .

That’s good to hear Colin,

As an aside, the connector will dismantle into the body, sides and the connector pins. However, getting it back together is a right pig’s ear! If your rigid extender is just missing it’s sides, you can remove them from the new connector, but be prepared for all of the connecting pins dropping out! Yes, a tenner will be fine. My PayPal address is the same as my email address.
Many thanks,
Mel

--
you can never have enough oscilloscopes, DMMs, valve testers or soldering irons . . .

Dennis Tillman W7PF
Aug 30 #150747

Hi Dave,

"The internet is rapidly eroding the privacy of individuals everywhere on earth. Each of our members is entitled to the protections of, and governed by, their nation's privacy laws. But we are an organization comprised of members worldwide so it may be unclear what is allowed and not allowed. Another way to summarize what I was trying to say would be this:"

We hope that the revelation of email addresses is not abused. However as long as non-members can view, we cannot trust them. If someone doesn't get it right and say make a new email for this, they are vulnerable. Luckily, this is not Facespace or Mybook or any of that. Personally I got to the point where I do not care, and that is because I get very little spam. I found out where it came from and took care of it. Now I am getting spammed by the Trump people, and while I do support him to some extent I am not ready to "join". And they all do that. Trump didn't some other whatever entity did it.

I got more spam from places that are "safe" than "unsafe" except for a few.

"Becoming a member of TekScopes does not give a member permission to contact another member outside of TekScopes without prior permission."

OK, then it reconciles with what you said about taking some things off group. So if someone is selling something, well first of all we don't need to know the details, especially if they use Paypal or something like that. We REALY don't want that info in the open forum because it is not secured. And I am not bitching about that, it is good for people with a genuine interest in Tek etc. to find us, and interesting and join. Even if they have stuff to sell, WE WANT IT. But the details of the sale go private. Sounds good to me.

"Dennis Tillman W7PF"

Yes sir, you are pretty good at this.

I have not read the rest of the responses yet, but I will and be back with whatever. Then you can take it or leave it.

For some reason this quoting thing is not working well for me, might be my browser, but whatever.

Many thanks for that; good idea!
I'm just a bit bamboozled by the fact that the schematic you mention shows that line from the fuse going to the primary winding of a transformer. If it's +15V unreg as stated, I can't see how this 15V DC to a transformer primary is going to give any outputs from the secondary side! Maybe I'm reading it wrong (don't have my glasses so it makes following schematics very difficult!)

You have 135th one off the production line. Your deduction on the part
number is correct the last two digits are the major rev level. For your
scope any revision of the CRT will work.



On Sun, Sep 2, 2018, 1:06 PM ulf_r_k via Groups.Io <ulf_r_k=
[email protected]> wrote:

Gentlemen,

I am considering replacing the CRT on an old 7704A
that is worn out. According to Sphere, the part number
is 154-0644-05, but my mainframe S/N B010136 has a
CRT labeled 154-0644-00

Before I go hunting:

Is the -05 a later replacement/suitable
for my mainframe or is the -05 a typo?

Cheers

Ulf Kylenfall / SM6GXV

Gentlemen,

I am considering replacing the CRT on an old 7704A
that is worn out. According to Sphere, the part number
is 154-0644-05, but my mainframe S/N B010136 has a
CRT labeled 154-0644-00

Before I go hunting:

Is the -05 a later replacement/suitable
for my mainframe or is the -05 a typo?

Cheers

Ulf Kylenfall / SM6GXV

If you remove the fuse in the 15V unregulated supply to the high voltage inverter (z-axis / crt schematic) you remove both the high voltage to the CRT and the CRT filament supply so that should keep the CRT safe.

I would then power up on full line voltage and check all the low voltage supplies are within spec. If they look ok then replace the fuse, move the vertical position controls to move the beam away from the visible area, intensity to minimum, and power up again on full supply voltage, ready to turn off quickly if anything is amiss.

The manual will have instructions for the setting of the storage controls for first time use.

Roger

These PDFs were by made possible by Deane Kidd and his family and friends.

Sorry about that, Mel.? Let me try filing down the epoxied bowed connector first.?
Thanks.
Jim


Sent from my Verizon, Samsung Galaxy smartphone

That would be fine. The only other part that is difficult to test for me is the tripler module with the hv lead. If you like you can include that also. Let me know the cost and method of payment you prefer.
Chris

I'm perfectly sure it will cause "some oddities" - I don't dispute that. I'm just very wary about winding that variac up more when the display is already brighter than IMO it should be (although I have only my limited experience with Telequipment analog storage scopes to go by which may be of no help at all here).