开云体育

Hi Rich:

I don’t have the manual here in front of me, but I did a lot of troubleshooting and calibration of the 2440 series. What you describe, reminds me of the current sense resistors going out of tolerance. If I recall these are very low value resistors, with tight tolerances. If they drift the PSU will start acting very similar to what you describe.

Hopefully, someone can tell you which resistors these are.

Rich Miller

I recently purchased a 2440 with a 4000 code, battery weak. Everything else appeared to be working. That was the only fault code. I replaced the two ram modules with new. The original were obsolete (DS1235BWL-120) so I purchased DS1230-100+. When I first turned on the scope everything powered up and there were plenty of fault codes so I started a self calibration. It never completed the self calibration. The scope went blank. I was able to power it up only occasionally until it stopped completely. It no longer tries to test when it is powered on the only lights on are the three GPIB lights. The screen will start with some erroneous dots and then go blank. I have tested the low power board and have some readings that do not match the schematics The voltage reading according to the power supply overcurrent check page 478 of the manual do not match. The voltages on the side board are correct so I am not sure where to proceed. I have attached a - of the readings I got from the power supply. Any help is greatly appreciated. Thank you, Rich
/g/TekScopes/files/015-0282-00/TEK%202440%20Power%20supply%20test/TEK2440%20Curret%20test20180627_12351992.pdf

Doing more clean up at Sphere, I found a factory bag full of the 2.5 inch black fan turbine blade assemblies used in many Tek scopes (465, 475, 2465, etc.). sorry, no fan motors to go with them, but if you have a damaged fan assembly, I can help with that! i think they are too fragile to send in a padded bag, probably needs a box to ship safely. There's 4 new turbines in the bag, US$5 each if anybody can use them.

Lots of over-stocked Tek, HP and Fluke bits to clean out, if you will be up this way (Kelowna, BC, Canada) please stop by, we can load you up with cheap and free stuff, and tons of factory manuals. Just WAY too much stuff here. There's not another stuff day scheduled for the rest of this year, but we have extra stuff all the time, so visitors are welcome!

All the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.

Including production-line hand blowing of tube envelopes:


<> &t=405s



Albert

Hi Musicamex,

You might find this video helpful, from the YT channel "the Radio Shop", posted just 4 days ago.
Chap is fixing a 465 with similar LV issues.



You might have to skip the first 20 minutes to get to the start of his repair.

IIRC he had bad filter caps (the cans), then bad pass/power transistor, then bad small signal transistor, the one that's between the op-amp and the pass transistor.

Hope this helps,

Vincent Trouilliez

--------------------------------------------

Ten 10 meg resistors in series. The same stack can be used to multiply your voltmeter range.

Sorry. that should read "NONE of them can short it out"

The sources are only using the 55 volts for reference, it does not feed them. If all of them are out, it is unlikely that they all just got that way and that the problem is with the 55 volts.

You should see some of my other typos.

Ok. I read a post on 485 troubleshooting recently that suggested to wait at least 6 hours to let the
CRT
charge fall off before pulling the lead to prevent killing that IC. It is more than possible that
I
misunderstood.

U660 is the vertical output amplifier in a 485. You must mean U1600, which is the x6 voltage
multiplier. Can't think of a mechanism by which unplugging the CRT could zap it. Internally it is
protected by a series resistor in the tens of megohms range so that if the output is totally shorted
out, the current is sufficiently low to not damage the internal components.

But let's do some what-if sums. I'm not sure what the capacitance of the DAG coating is, but let's
assume 100pF. Accelerating voltage is 18kV. Let's say we wait those 6 hours before we unplug the HT
connector - what sort of leakage resistance will we need to reduce the voltage?

6 hours is ~20,000 seconds. Let's say that is ten time constants, so the voltage will decay to ~100V
and let's say, for argument's sake, that is low enough. So one time constant has to be less than 2000
seconds, which is the product of the CRT capacitance and the leakage resistance. Which works out at a
leakage resistance has to be less than 2e13 ohms, and an initial discharge current of 0.9 nA.

I would say that is entirely possible. Reverse leakage of the multiplier diodes should be more than
enough in itself, not counting other leakage paths. So waiting 6 hours should indeed discharge the
CRT. But it makes fault finding the restorer circuits a bear - wait 6 hours, try something, turn on
scope - oops it wasn't that, wait 6 hours etc etc. And whether or not it is necessary to wait that
length is time is anyway moot.

The other way to see if the multiplier is faulty is to disconnect the input. The main symptom of a
dead multiplier is that it loads down the high voltage transformer, so the -3kV test point reads low -
a few hundred volts typically. If disconnecting the multiplier input results in the -3kV coming back
up and reading correctly, then the multiplier is dead.

Craig

On Wed, Jun 27, 2018 at 05:30 am, Craig Sawyers wrote:

I have read here that discharging the CRT to the frame on the 485 has been

know to kill U660 so that

is
one reason I would like to learn of another way to do it.

AAAAGHHHH! Switch scope off. You unplug the darned connector first. Said it
three times already!!!!!!!
There is absolutely no way on God's green earth you are going to blow anything
up.

Craig.

Ok. I read a post on 485 troubleshooting recently that suggested to wait at least 6 hours to let the CRT charge fall off before pulling the lead to prevent killing that IC. It is more than possible that I misunderstood.

I have read here that discharging the CRT to the frame on the 485 has been know to kill U660 so that
is
one reason I would like to learn of another way to do it.

AAAAGHHHH! Switch scope off. You unplug the darned connector first. Said it three times already!!!!!!!
There is absolutely no way on God's green earth you are going to blow anything up.

Craig.

Hi all,

I couldn't help myself and got (another) 2465 on "the Bay"
This time it was a 2465DMM, shown with the beamfinder button pressed (while nobody was pressing it :-)

Still, shipping from the States to Europe is not cheap, but they accepted my offer, and I am happy with what I paid.

Long story short: unpacking cost more time than the actual repair: Contact cleaner on the beamfinder switch and it was good to go :-)
When the time comes I will re-cap the PS and calibrate the scope, but for now I am happy (again).

Nice touch: I could be fined 1000$ US or be sentenced to one year jail time because I unauthorized removed a label :-) :-)

Pictures can be found here: /g/TekScopes/album?id=61275

Un saludo,

Leo

P.S. I could use the rear rubber feet for this DMM scope.

On Tue, Jun 26, 2018 at 11:02 pm, Jeff Urban wrote:

On Mon, Jun 25, 2018 at 10:37 pm, Craig Sawyers wrote:

THEN YOU SHORT THE EXPOSED TIP OF THE CRT WIRE TO GROUND

Sorry, I didn't take that as meaning the lead from the CRT, I thought you
meant the lead out of the multiplier.

Doing that after it is powered up and down, if it has an arc you have cleared
the CRT and the multiplier, but don't yet know which one is bad if it doesn't.


So you didn't say to turn it on and arc the anode lead (output of the
multiplier) to ground. This appears to be my mistake. You probably agree that
it is not a good idea to arc the source while running to ground, but you never
said that it was.

I'm sorry, it's my mistake.

I have read here that discharging the CRT to the frame on the 485 has been know to kill U660 so that is one reason I would like to learn of another way to do it.

The +, +5 and -8 are all referenced from the +55 volt line. One of them can short it out, but if it is gone, they are gone.

On Wed, Jun 20, 2018 at 04:33 pm, musicamex wrote:

My sn is B 317000. But i am not having much luck in finding the downloads for
this later version.

The one on this page says SN B 250000 and up



I can't give you the exact URL because I had to "upgrade" my browser and now instead of just saving the file it insists on displaying it. Another function I used GONE.

But it says 465.pdf, noting else. Then there are some other versions, M, B whatever. But I got the one and it does say 250000 and up.

On Mon, Jun 25, 2018 at 10:37 pm, Craig Sawyers wrote:

THEN YOU SHORT THE EXPOSED TIP OF THE CRT WIRE TO GROUND

Sorry, I didn't take that as meaning the lead from the CRT, I thought you meant the lead out of the multiplier.

Doing that after it is powered up and down, if it has an arc you have cleared the CRT and the multiplier, but don't yet know which one is bad if it doesn't.

So you didn't say to turn it on and arc the anode lead (output of the multiplier) to ground. This appears to be my mistake. You probably agree that it is not a good idea to arc the source while running to ground, but you never said that it was.

I'm sorry, it's my mistake.

Hi Fabio,

Thank you so very much for this information! I will make some time tomorrow afternoon to put this all to use, or to the test in the real and figurative sense. I have been truly bewildered by the complexity of this circuit and the high probability that anything that I need will have to be part of my early October trip to the states. Although I have an inventory to repair 95% of all tube amps that find their way here, I dont have much at all for this attempt. Tube amps are so logical and similar that they might have given me a false sense of my abilities. But I am determined not to relegate this highly regarded and clean 465 to the bone yard.
I was feeling like I was lost in a big city without a map and with your pinpoint instructions I hope to start to find my way.

For some reason 3 of my posts never showed up here. It might be my cobbled together internet connection. I live about 4 km outside of our town and there was no internet at all before. And marginal cell service on top of a nearby hill. I rigged a few solutions, but now that we are in the monsoon season it can have its challenges. One attempted post had some measurements including voltages on the main filters. I'll pull out my notes and try to repost along with the results of the suggestions and guidance you just gave.

Thank you again. Russ

Btw, I just bought a TDS 460A with a "passed self test" screen. I want to have at least 1 working scope for each 2 work station bench and one for me to demo with. I probably should stick with analog scopes from the same family like my 465 and 485, but I was browsing ebay late one night recently and the 460a popped up with minutes to go . I had a GAS attack and shot a low bid and got it. I just know it will get me additional scrutiny as my carryon just like the last 2. At least this one is lighter?

On Mon, Jun 25, 2018 at 09:38 pm, lop pol wrote:

Ok. You can't just leave it there. How do you discharge the CRT? ?\_(ツ)_/?

When dag was no longer ground in TVs we used a HV probe, usually 1090 meg which with the meter made 1100 meg.

But the capacitance, (Leyden jar) is to ground, not the cathode. With it OFF you can just arc it. It is a problem when you do it when on. When you short the ON "top" (+) HV to ground the "bottom" of that transformer winding shifts all its voltage to the cathode circuit.

It has a quadrupler, that means the 3 KV on the cathode end is simply rectified, but quadrupled into the + so0urce for the ultor. If the + shorts that will cause double the voltage to the cathode circuit. That is just about the right amount to blow a bunch of shit before the rectifier or filter shorts out.

I am not looking right now but many Teks have a shunt regulator tube for the cathode end, if you burn that out, where do you get one ?

I have worked on some damn expensive equipment and have learned to be careful. Had some sort of car diagnostic machine once, them people will work on anything, or actually have me do it. no red. the other guy, normally competent, decided to rejuv the CRT. I said no. they did it anyway and still no red. I had to go to the video subsystem of a computer and find a bad gate IC. then we got red, but not the formally pristine cathode has now been stripped so guess which gun is going to go first.

I INVENTED the dim bulb test., I do not claim to have invented it first, but when I figured it out I had never heard of one. It was house wiring, a fuse kept blowing. I screwed a light bulb into the fuse socket and it lit and I started disconnecting things until it went out. Non destructive testing. You don't want to know my age but, I hadn't yet gotten my first hardon.

Point is, destructive testing is only for when it is absolutely necessary.

Hello Russ,
I've already suggested some vague, not quite specific, approaches... and then kept following this topic from a distance for a few days to see if someone with more specific knowledge on the 465 would jump in, but it seems there's silence on the radio for a while.
Maybe everybody is expecting you to produce some more information with the hints you already got, and maybe you're waiting to be "taken by the hand" a little bit further before proceeding... so this is stalling.
I`m not particularly experienced with the 465. I have a 464, whose Low Voltage Power Supplies (hereby on, just LV, or LVPS) are quite similar to the 465, so I hope this will suffice.
By looking at the name of the test points you reported earlier, I assume that I`m looking to the same schematics that you have but, to avoid further misunderstandings, I`m looking at the manual whose part number is 070-1861-00 (written on the lower left side of the cover) which states "SN B250000 & UP".
When I mentioned the current sense resistor on my previous post (message #149051), I was talking about R1549, of 1.1 Ohm and, answering to your question, no it's not individual to each tantalum capacitor.
The voltage drop on this resistor, when exceeded a given amount of current, turns on the fold-back current limiting transistor (Q1548, R1456 and R1457) which steals away bias from the +15V pass transistor, Q1546.
So, from several things that may cause the voltage of the +15 LVPS to be zero, one of them could be the +15V shorted to ground.
From all possible causes for the +15V to be shorted to ground, the various dipped tantalum decoupling capacitors are the most common causes, almost a chronic disease on scopes of this vintage. *** dipped = a radial tantalum capacitor that looks like a color striped epoxy blob, not the more rare wet tantalum that looks like a metallic cylinder with axial terminals.
Only to serve you as an example, it can be C1559, right on the +15V output, or C1339 on diagram 8 (SWEEP & Z AXIS LOGIC) connected to the +15V via a 22R resistor, or C891 on diagram 5 (A & B TRIGGER GENARATORS) conneted to the +15V via a 2.7uH inductor, or C4498 on diagram 4 (VERTICAL OUTPUT AMPLIFIER, discrete version) connected to the +15V via L4498//R4498, or C346 or C358, both on diagram 3 (VERTICAL SWITCHING), etc, etc...
What sucks about finding shorted decoupling capacitors is that they're - sort of - all in parallel, and if one is shorted, it takes the whole rail down.
Of course, some of them can be ruled out right away, like C1339 above, which is not connected directly to the +15V, but through a resistor, and in that case, it wouldn't be able to short the rail down to an absolute 0V like you measured.
As a matter of fact, for the +15V to be reading a dead zero volt (as you measured), it's unlikely the problem to be a shorted tantalum alone (because the voltage drop on the PCB's copper tracks, plugs and connectors, would make some small voltage to be present at the +15V TP),
But a shorted tantalum may have caused something else to burn open, and in that case, you may be looking at two problems, and not just one.
Measuring the voltage drop at R1549 (the current sense resistor) is a good way to see if the +15V supply is sourcing any current (which may be shorted to ground) or if it's sourcing no current at all, or if R1549 is open altogether.
If you measure a very low voltage (say < 0.1 V) across this resistor, probably the +15V power supply itself has a problem (an opened pass transistor Q1546, or lack of drive from U1524B) which will need to be troubleshoot further.
If you measure something between 0.7V and 1V, then it means the +15V power supply is trying to source its juice, but it's being turned down by the over-current protection (an indication of a short circuit downstream).
Finally, if you measure a higher voltage across this resistor, maybe up to the full unregulated voltage (say 24V), it may be R1549 itself open.
You can probe a few things to help troubleshoot further:
1. Voltage across R1549 for a starter.
2. Voltage (in relation to ground) at pin 8 of U1524B. There must be 22V there. Lack of such and the +15V will fail.
3. Voltage at pin 5 of U1524B must be a 15/55th proportion of the +55V power supply (at the current state of affairs, it must be at 12.79).
4. Voltage at pin 6 of U1524B must be whatever voltage you're measuring at TP1548, in other words, it should be reflecting the actual +15V PS voltage.
5. If all voltages at topics 2, 3 and 4 above check, then the OpAmp should be at full thrust. i.e. anything from around 2.4V (the sum of Vbe of Q1544 + Q1546 + Voltade drop on R1549) up to about 21V (whatever volttage is at pin 8 (the IC + supply pin) minus 1V.
6. Voltage at the collector of Q1544 and Q1546 must be the same as the +15V UNREG voltage. As per your very preliminary messages, this should be at about 24.5V (it's the voltage that you measured on both sides of the internal fuse, F1419, which is fed from the same voltage.
*** There's a missing piece of information on the schematics... The +15V UNREG voltage that feeds the high voltage inverter IS INDEED, the voltage that is going into the +15V PS regulator (the collectors of Q1544 and Q1546), but this information is not mentioned anywhere in the PS diagram.
From the 6 measurements above, you will be able to draw a conclusion, or report back and someone here surely will.

KRgrds,

Fabio

They are trained NOT to tell you. You have to ASK for it or as the previous poster said it is available through PayPal shipping includes tracking. Tell them it just a "manuscript" and DO NOT INCLUDE any correspondence. You put a one page letter in there and suddenly it is a 1st class mail

For a description google is your friend

-DC
ArtekManuals.com

--
Dave
Manuals@...
www.ArtekManuals.com