tektronix 2215 Beam intensity  problem - Page 1
Forum section: electronics / testgear

author: soldo63
author_rank: Contributor
timestamp: April 05, 2014, 05:08:42 pm
content: I am having a problem with a 2215 I am trying to get goingI have it set up for both channels and alternate mode, but will only display 1 or 2 channel sweeps not both at the same time.switching through ch.1, both, ch.2 and back. In both mode it stays in the last channel that it was in. never displays bothat the same time.can someone give me any hints?soldo63

author: Nermash
author_rank: Frequent Contributor
timestamp: April 05, 2014, 06:18:55 pm
content: Maybe "chop" is the right solution for your problem

author: soldo63
author_rank: Contributor
timestamp: April 05, 2014, 09:22:46 pm
content: I have tried chopped.I have read the manual and followed the instructions on how to seetwo traces, but i think something is wrong with the alternate sweep circuit,I thought someone might know which components to check.thanksfor you help.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 05, 2014, 09:41:46 pm
content: It's not 100% clear what the problem is from your question.Alternate sweep does just that - first ch1 does a complete sweep, then ch2 does a complete sweep. At longer sweep times (approx 5ms/div or slower) this becomes very obvious. With sweep speeds faster than the "flicker fusion" rate you will perceive two steady traces.With chop mode rather than doing a complete sweep first one channel is shown for a short period, then the other, then the first.At slow sweep speeds you should choose "chop", at faster sweep speeds (100uS/div or below) choose "alt"To tell you whether there is a fault or whether your 'scope is operating correctly could you tell us what sweep an trigger settings you have set up?

author: soldo63
author_rank: Contributor
timestamp: April 05, 2014, 10:13:08 pm
content: I have tried all combinationsVertical mode: both Alt and ChopHorizontal Mode: alt,trigger: autoA&B Int Ch.1, Ch.2, vert modeA source: int, lineI can see each channel individually when i set the vertical mode to ch1 or ch2 and when i select add i can see the total waveforfrom both channels but it will not display both at the same time no matter which combinations i use.thanks for you interest.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 05, 2014, 10:19:36 pm
content: OK but what speed have you set the timebase to?QuoteThis is for the delayed sweep - set it to "A" until you are comfortable with the 'scopeQuoteLeave it on Int

author: soldo63
author_rank: Contributor
timestamp: April 05, 2014, 11:08:02 pm
content: I have tried all time basesI can see wave forms on ch 1 and ch2 when it is set to add I can see the result wave but alt does not show bothwaves at the same time.when i set both from ch1 I still see ch1. when I switch to both from ch2 I only see ch2.I have tried all combinations of settings.I was hoping someone had some some idea of what is wrong.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 05, 2014, 11:22:00 pm
content: Rather than wildly trying "all combinations of settings" I suggest you try something which has a fighting chance of displaying your signals.Talking of which what signals are you trying to display?Can you:a) set horizontal mode = AA source = IntA&B Int = Vert ModeTrigger = AutoSlope = upgoingTrig level = mid pointVar Holdoff = fully anticlockwiseCh1&Ch2 position = mid positionb) pick a time-base appropriate to the input signals andtell us what it isc) set Vertical mode = Ch1- do you see the signal on Ch1?d) set vert mode = Ch2- do you see the signal on Ch2?e) set vert mode = both+chop- what do you see?Photos and videos, if you are able to post them, can be helpful.

author: soldo63
author_rank: Contributor
timestamp: April 06, 2014, 12:18:09 am
content: a) set horizontal mode = AA source = IntA&B Int = Vert ModeTrigger = AutoSlope = upgoingTrig level = mid pointVar Holdoff = fully anticlockwiseCh1&Ch2 position = mid positionb) pick a time-base appropriate to the input signals and tell us what it is: 20 micro secc) set Vertical mode = Ch1- do you see the signal on Ch1? Yesd) set vert mode = Ch2- do you see the signal on Ch2? Yese) set vert mode = both+chop- what do you see? Ch2I will post pic soon

author: soldo63
author_rank: Contributor
timestamp: April 06, 2014, 12:25:12 am
content: here another picI am having trouble posting more than 1 pic at a time

author: miguelvp
author_rank: Super Contributor
timestamp: April 06, 2014, 12:26:48 am
content: Is it me or are those cal buttons supposed to be in?Not that it will help with the OP problem but just noticing.

author: soldo63
author_rank: Contributor
timestamp: April 06, 2014, 12:27:52 am
content: here is vert mode: both

author: soldo63
author_rank: Contributor
timestamp: April 06, 2014, 12:31:55 am
content: I don't know what you mean by "in" other than the time base they don't go in or out.her is another pic of x/y 10200hz/5100hz

author: miguelvp
author_rank: Super Contributor
timestamp: April 06, 2014, 12:46:12 am
content: Quote from: soldo63 on April 06, 2014, 12:31:55 amMy analogue is a bit older and the call knob is pushable.

author: David Hess
author_rank: Super Contributor
timestamp: April 06, 2014, 01:58:19 am
content: On the 22xx series the variable adjustment controls have a detent instead of being push on-off. They should be turned fully clockwise for calibrated operation but be careful not to overtighten them because the flexible coupling is easily damaged. The horizontal variable adjustment pulls out for x10 horizontal mode.soldo63, I do not see a picture in ALT mode to go with CHOP mode but that is probably unimportant. It does look like there is a problem with the channel select logic.ALT mode uses the ALT SYNC pulse from the sweep to switch channels. CHOP mode uses a separately generated chop signal. The fact that both appear to be missing tells me that either one of them is getting stuck low disabling the other or there is a problem at U310A at D3 on schematic 3 where they are combined.

author: soldo63
author_rank: Contributor
timestamp: April 06, 2014, 04:03:19 am
content: Thanks for you help.I did some testing on it at test point 1 i got the right waveform and you will see in the diagramsthe output waveform in test location 2 is not as it should be, but, behind cr320 I get the right waveform.is there something wrong with the diode?

author: soldo63
author_rank: Contributor
timestamp: April 06, 2014, 11:37:50 am
content: Or is it something on the end of cr320 that could be keeping the signal from going hi to low.I checked all the voltages around Q841, they were all right.I changed the cr320.Now I have the right waveform, and the trace is slightly brighter in chop mode, but still only one trace at a time

author: grumpydoc
author_rank: Super Contributor
timestamp: April 06, 2014, 01:29:23 pm
content: The first thing i'd check would be the vert mode switch itself - had a 2213 recently with odd problems (don't remember the details) which was down to a faulty contact on the vertical mode switch. It responded very nicely to some switch cleaner.

author: oldway
author_rank: Super Contributor
timestamp: April 06, 2014, 07:42:07 pm
content: You are not looking at the right place: it's not a blanking problem.There is nothing wrong with cr320, put the original diode in his place again.Comutation of canals is done by U317A (74ls74 - D flip flop) and diodes 177, 178, 187, 188, 277, 278, 287, 288.First thing to check is the signal you have on pins 5 and 6 of U317.In alternate, you must have a square wave of 1/2 the frequency of time base and in chopp an high frequency square wave (more or less 500Khz) on pin 5 and the same signal with 180° phase delay on pin 6.U310 (74ls132) or U317 (74ls74) is probably defective.

author: soldo63
author_rank: Contributor
timestamp: April 07, 2014, 01:52:29 am
content: I tried contact cleaner, it didn't help thanks for the suggestionPins 5 is at 5v and 6 of U317 are at 1vdc in vertical mode both, alt or chop.Pin1 of U310 is is at 4.4vdc in alt and a 0-3.5v square at 420Khz regardless of timebase in chop and 0vdc in alt mode.From the schem. doesnt U317 get its signal from 310 pin 3, which gets its signal from U640 pin9when I checked U640 pin 9 was giving a pulse varying with the time base. but it wasn't getting past CR644.?

author: oldway
author_rank: Super Contributor
timestamp: April 07, 2014, 02:56:11 am
content: Ok, that's it: U310 (74ls132) or U317 (74ls74) is defective.Replace both, it's easier.When you replace an IC, always use a socket.Without socket, you will damage the board if you have to replace the same IC a second time.

author: David Hess
author_rank: Super Contributor
timestamp: April 07, 2014, 05:24:55 am
content: Quote from: oldway on April 07, 2014, 02:56:11 amI always use a socket when replacing ICs. If you have the time, you can clip the collet pins out of a socket or SIP and use them directly on the printed circuit board to make a low profile high performance socket.

author: soldo63
author_rank: Contributor
timestamp: April 07, 2014, 08:34:23 am
content: You are right, it is easy and faster just to replace both ICs, and I will try that but,it just seems to me that neither IC is supposed to make the pulses on their own,they are just relaying a signal which it seems that they are not getting.Unless they might be holding a signal low or High?I don't have that much experience with this.Thanks for your help.

author: oldway
author_rank: Super Contributor
timestamp: April 07, 2014, 09:33:03 am
content: Quote from: soldo63 on April 07, 2014, 08:34:23 amFirst, they are not "relaying" a signal, they are logic IC's.Second, they have input signals:U310A:- on pin 1, 4.4vdc in alt and a 0-3.5v square at 420Khz regardless of timebase in chop and 0vdc in alt mode. That seems correct.- on pin 2, same signal as U640 pin 9 (they are connected together) , a pulse varying with the time base. That seems correct.You should then have clock pulses at pin 3 of U317A and, in position "both" of S317, a square wave of on both pins 5 and 6 of U317A. You don't have: that's not correct.I did not make the measurements, you did...but you give very poor informations.Of course, levels of signals are very important too, you did not give any details.But it seems that replacing both U310 and U317 will give you 90% luck to solve the problem.

author: soldo63
author_rank: Contributor
timestamp: April 08, 2014, 01:40:10 am
content: I replaced u317 and u310 and it didn't change anything.Maybe I didn't make it very clear when I said that the signal from u640 pin 9 wasn't getting to U310 pin 2, but that's what i meantwhen I wrote"when I checked U640 pin 9 was giving a pulse varying with the time base. but it wasn't getting past CR644".So I followed the path from U310 pin 2 to U640 Pin9 and came across the screw that holds the cover for the power supply.and found that the screw made contact with the trace on the board( grounding it). Check picWhen I loosened the screw Both channels worked, but I got some bad noise on signal that i put in and it's not coming fromthe signal generator. check pic.

author: David Hess
author_rank: Super Contributor
timestamp: April 08, 2014, 04:22:37 am
content: So you fixed the ALT and CHOP dual trace problem which was caused by that screw shorting the trace but a new triggering problem developed? I would retrace my steps and make sure I reassembled the oscilloscope correctly and did not damage something.What does the calibrator signal look like?

author: oldway
author_rank: Super Contributor
timestamp: April 08, 2014, 05:19:47 am
content: @soldo63: Why did you replaced U317 and U310 if you know that the informations I used to make the diagnostic where wrong?Short circuit of the trace happened after reasembling the scope forgetting insulating washer.What's the story of this scope?It seems to be a scope salved from scrap.

author: soldo63
author_rank: Contributor
timestamp: April 08, 2014, 08:57:41 am
content: Oldway: It wasn't working when I got it. the power supply board had been worked on by someone els and some components missingI installed the missing components and the scope worked. When I assembled it i noticed that the dual trace wasn'tworking, but the signal was clean in both channels, as you can see in the previous pics.The reason I changed the ICs was that it seemed like it might be the problem. U310 if faulty, could have been holding down the pin2 inputplus you seemed very certain.I appreciate the help anyway,thanks.any Ideas about the noise on the display? what area could cause that?

author: grumpydoc
author_rank: Super Contributor
timestamp: April 08, 2014, 09:47:20 am
content: QuoteActually your earlier photos struck me as either poorly focussed or noisy, though it's difficult to photograph oscilloscope screens. Your latest photo does look worse though.It looks as though there is "noise" in X and Y directions, or poor focus.With no signal and the 'scope in X-Y mode can you get the beam focussed in a single sharp spot.Have you checked the power supply rails for ripple as well as correct voltage?

author: soldo63
author_rank: Contributor
timestamp: April 09, 2014, 02:12:18 am
content: I checked the power distribution voltages. I didn't notice any noise in them.I put the scope in X/Y mode and the dot was spread horizontally two more than 1-1/2 divisions but vertically it was .2 divisionsIs it something in the horizontal amp.?I didn't have time to take a pic.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 09, 2014, 08:31:44 am
content: QuoteThere's usually a bit, and there's a spec in the service manual to check against.QuoteI believe you have a 2nd 'scope as you posted pics of some waveforms, so you can check the X and Y drives to the CRT to see if there is noise or oscillation on them.I would make sure the chain of resistors in the focus circuit is OK (notorious for going O/C or drifting in value) and I'd check the grid bias and astigmatism adjustment.

author: soldo63
author_rank: Contributor
timestamp: April 10, 2014, 01:03:05 am
content: Thankswhen I get a chance I'll do that.

author: soldo63
author_rank: Contributor
timestamp: April 15, 2014, 08:50:01 pm
content: I found the source of the horizontal noise. It was in the C971 and C975 in the+8.6v supply, after I changed those capacitors there was no more noise in thehorizontal signal. Circled in BlueThere was a slight noise in the intensity of the trace. And as I was checking other capacitors I accidentally touched a high voltage area of the board, circled in red and there was as small arch of current to the test probe. After that the beam intensity is very low.I cant figure out what the problem is, I don’t remember exactly what I touched. I have removed C990, C992 and C995.Even though they are labelled as 0.02uf they are all 0.01uf 4000v , maybe someone hadChanged them and did a very nice job because the solder looks original.I tested they crudely, I don’t have a capacitor meter yet. They seem to behave like 0.01uf caps. What I mean is that they charge up and discharge like a good capacitor, but I can only test up to 30v. I checked the diodes, they are fine I checked the resistors, they are within limits.My question is, what In this circuit would cause the beam intensity to be so dim? Could it be U990Any Ideas?

author: David Hess
author_rank: Super Contributor
timestamp: April 16, 2014, 12:29:48 am
content: I doubt you damaged one of the DC restorer diodes but that is possible. The high voltage capacitors and diodes are practically impossible to test without a high voltage power supply unless they show a short or high leakage at low voltages. It is usually safer and less expensive to just replace them.The likely problem is damage to the z-axis output stage shown on schematic 6 and specifically Q850 or Q847 or both. Q841, Q844, and Q845 should be checked as well.

author: soldo63
author_rank: Contributor
timestamp: April 16, 2014, 02:43:30 am
content: at your advice I have checked Q850 & Q847.They are OK. I have ordered the high voltage capacitors.in the mean time I'll Check the other transistors.thanks

author: soldo63
author_rank: Contributor
timestamp: April 16, 2014, 01:30:48 pm
content: Another thing, I don't have any specs. for what the voltage at the Cathode or is it the heater element of the CRT should be but when I measured itit was only 4vac. it seems low?does anyone know what it should be?

author: grumpydoc
author_rank: Super Contributor
timestamp: April 16, 2014, 01:37:45 pm
content: Don't forget that it comes off the main PSU transformer so it will be at (iirc) about 20kHz and your multimeter might be reading low at that frequency.Also don't forget, when probing around that area, that it's about -2kV relative to the chassis.

author: David Hess
author_rank: Super Contributor
timestamp: April 16, 2014, 01:45:46 pm
content: I think the heater voltage is 6.3 volts but the waveform is *not* a sine wave and is high frequency.The cathode voltage is about -2000 volts so you almost certainly need a high voltage probe to measure it. Keep in mind that the heater is also kept at the -2000 volt cathode potential so measuring the 6.3 volt heater voltage safely should not be taken for granted either.There was a design flaw in the original 2213 and 2215 involving too high a heater voltage which caused the CRTs to fail early. Tektronix issued a change notice to fix this which involved an extra winding on the transformer.

author: grumpydoc
author_rank: Super Contributor
timestamp: April 16, 2014, 01:53:46 pm
content: QuoteTo correct David slightly the field fix is actually to remove one turn from the heater winding on the transformer.

author: David Hess
author_rank: Super Contributor
timestamp: April 16, 2014, 02:28:43 pm
content: Quote from: grumpydoc on April 16, 2014, 01:53:46 pmThanks. I have not had to deal with it myself despite repairing a 2213 for a friend and I gather that it is rare to find one of these oscilloscopes with the heater voltage problem.When asked, I always recommend people avoid the 2213 and 2215 in favor of the A versions although for additional and different reasons.

author: soldo63
author_rank: Contributor
timestamp: April 16, 2014, 02:34:29 pm
content: Thanks guys,I found a troubleshooting guide i will checkouthttp://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf

author: soldo63
author_rank: Contributor
timestamp: April 18, 2014, 12:16:00 pm
content: I have a Quick question.what is the purpose of C990,C992 and C995, in the HV cuicuit?

author: tautech
author_rank: Super Contributor
timestamp: April 18, 2014, 12:30:05 pm
content: My view is snubber, smoothing, snubber.

author: David Hess
author_rank: Super Contributor
timestamp: April 18, 2014, 01:31:23 pm
content: Quote from: soldo63 on April 18, 2014, 12:16:00 pmThey are the output filtering capacitors for the -2 kilovolt cathode supply voltage. I am not sure why they included the series resistors since the other 22xx oscilloscopes lack them. Maybe they needed to limit the startup current.The -2 kilovolt output is not part of the regulator's feedback loop unlike some other Tektronix designs which regulate it directly so the series resistors are not there for frequency compensation.

author: soldo63
author_rank: Contributor
timestamp: April 18, 2014, 02:46:13 pm
content: I have another question!I am assuming that the intensity is controlled by the the difference in potential from 8Kv to -2Kand the -2K is being raise to control intensity.so I removed Q877 to see if that was bringing up the -2kv.when I powered it on The beam was still there at the same low intensity, but the intensity control stillcould lower the intensityHow can that be if the intensity level is coming from other side of Q877?

author: David Hess
author_rank: Super Contributor
timestamp: April 18, 2014, 03:37:39 pm
content: Quote from: soldo63 on April 18, 2014, 02:46:13 pmQ877 controls the automatic focus which changes with intensity. Removing it just disables automatic focusing.Intensity is controlled by by the grid to cathode potential with grid voltages lower than the cathode producing lower intensity. The grid voltage range only extends from the cathode voltage of about -2 kilovolts to 10s of volts lower with a hard limit set by series connected neon bulbs DS867 and DS868 which prevent the grid to cathode voltage from becoming too large because that could damage the grid.The intensity control signal originates from the z-axis amplifier shown on schematic 6.

author: soldo63
author_rank: Contributor
timestamp: April 18, 2014, 05:33:02 pm
content: Everything in z axis amp seemed to be workingIt must be In the high voltage HV multiplier or CRTany way to know for sure without a HV meter?

author: David Hess
author_rank: Super Contributor
timestamp: April 18, 2014, 05:53:14 pm
content: Quote from: soldo63 on April 18, 2014, 05:33:02 pmIf there was a problem with the high voltage multiplier or the cathode high voltage, then the display deflection would be altered.The problem is in the z-axis amplifier, z-axis DC restorer, or in the CRT. Maybe the short you caused damaged the CRT grid but I hope not.

author: soldo63
author_rank: Contributor
timestamp: April 19, 2014, 10:11:11 am
content: Thanks David,I have gone through the Z axis amp twice with power on and all the voltages are as they should be in the diagram,It also seems like there is high voltage,because the beam responds normally except for the brightness.any way to confirm that its the CRT?

author: David Hess
author_rank: Super Contributor
timestamp: April 19, 2014, 12:42:24 pm
content: Quote from: soldo63 on April 19, 2014, 10:11:11 amI made a mistake in the above: the PDA (post deflection acceleration) voltage from the high voltage multiplier will affect the brightness but not the deflection. The cathode voltage will affect both.You could check the CRT grid to cathode resistance which should be open.There are other things which can dim the intensity like x10 horizontal mode. I have been caught by that often enough that I remember to check it now.The high voltage parts in the DC restorer can be difficult to test because they may only have high leakage at high voltages.If the multiplier was damaged then I would expect the cathode voltage to be wrong which would alter the deflection but in this particular case, I would try to make a direct measurement of the multiplier output voltage but that requires a high voltage probe.

author: David Hess
author_rank: Super Contributor
timestamp: April 20, 2014, 02:36:53 am
content: Weird. Did you delete your last reply?The power supply is adjusted for a -8.6 volt output on the secondary side at test point TP500. There is a headroom adjustment that changes the output voltage of the preregulator measured between test points TP934 and TP952. Essentially it is a switching preregulator followed by a linear regulator and inverter that provides isolation.All of the power supply voltages including the -2000 volt cathode and +8000 volt anode supply follow the -8.6 volt output and there is only one adjustment. If you fiddle with it, the horizontal and vertical calibration of the oscilloscope will change.There is no indication that the problem is on the primary side of the power supply unless it is overloading and shutting down.

author: soldo63
author_rank: Contributor
timestamp: April 20, 2014, 10:13:56 am
content: Yes I removed the last post. when I went back to look at wave form 32 in noticed that the diagram said 0.8v witch i was gettingnot 8.0v which I thought I saw.So I didn't really find anything wrong. then I just removed the whole post.then after that I went through the z axis amp. all the voltages and waveforms were were right.In x/y mode and horizontal mode the intensity is almost right, but at full setting. the brightest doesn't come at the fullclockwise position of the intensity control or grid bias pot, but at around 3/4 full cw and middle setting the beam is invisible.I was wondering if there was high voltage leaking to ground wouldn't there be heat. I have had it running for about 1/2 hour or moreand it doesn't get very hot. After turn it off, I touch the caps and resistors. and they all just feel warm nothing is really hot.Another thing. when in horiz mag mode, where the beam is most visible, as i go through the time scale it will loose intensity but i canget some back with the auto intensity control. If I monitor the wave output of zamp at R865, I noticed that the intensity is highest atat 30v peak, also the peak varies with time setting but does not vary when switching to x/y or horiz mag mode.you (David) said that the z amp out put should change when switched to horiz mag mode?so is it somthing in the z amp?

author: David Hess
author_rank: Super Contributor
timestamp: April 20, 2014, 04:52:34 pm
content: Quote from: soldo63 on April 20, 2014, 10:13:56 amHigh voltage leaks do not usually remain leaks for long and often solve themselves by turning into shorts or failures.QuoteThe peak should be constant in X-Y mode. Horizontal magnification mode should not affect it at all.How does the intensity behave at slower sweep speeds? Is there some sweep speed where it gets brighter toward the right side? I am thinking that maybe the z-axis amplifier is damaged such that is is simply slow and not unblanking the CRT quickly enough.Quotex10 Horizontal magnification mode should leave the trace significantly dimmer, 1/10th as bright actually, and not brighter. There is no connection between the x10 switch and the z-axis amplifier.

author: soldo63
author_rank: Contributor
timestamp: April 21, 2014, 01:59:17 am
content: I just can't stop until I find the cause,I found something, I don't know if it's significant.I was just following wherever the z goes.I checked all the test waveforms on diagram 5they were all pretty good except 3 and 43, I got 0.0v 4 I got 4.3vdcwhat do you think David?

author: David Hess
author_rank: Super Contributor
timestamp: April 21, 2014, 04:05:55 am
content: Quote from: soldo63 on April 21, 2014, 01:59:17 amIt is not significant.That is the logic which controls the sweep. Normally the sweep is started and the CRT is unblanked after a trigger is received. You already have a sweep and in AUTO mode, the sweep may occur without a trigger.The reason 3 and 4 are static DC values is that there are no trigger events occurring.Is it possible that nothing is wrong at this point? Maybe it would be worthwhile to do the z-axis adjustment procedures and then the performance check procedures.

author: soldo63
author_rank: Contributor
timestamp: April 21, 2014, 11:42:00 am
content: all I can find in the service manual is the external z axis operation or the grid bias adjustment, and that starts off with checking the -2500v supply.I don't have a HV meter.Nothing happens when I apply any kind of input in the ext. z axis input -10v to +10vIn the troubleshooting manual, it says if the unblanking is not working, that can cause a dim display.Is there anything that I can do to, disable unblanking or to bypass the intensity control to see if I can get full intensity. just to eliminatethe CRT as the cause?

author: David Hess
author_rank: Super Contributor
timestamp: April 21, 2014, 05:59:23 pm
content: Quote from: soldo63 on April 21, 2014, 11:42:00 amMaybe it is time to pickup a high voltage probe to use with your multimeter. I bought a used Fluke 80k-6 cheap for just this sort of thing.QuoteThat is a pretty big clue that something is very wrong.QuoteDisconnecting the AC drive to the DC restorer by removing C863 or R863 and disconnecting the z-axis amplifier should make the CRT operate with full brightness. If you do this, deliberately defocus the CRT to prevent damage. You should do that anyway when working with the z-axis and DC restorer circuits anyway to prevent damage to the CRT.If that does not cause high intensity, then either the grid is not at the cathode potential because of leakage or the CRT is damaged.The CRT grid is driven *negative*, below the cathode voltage, to lower the intensity. If it is held at the cathode voltage, then intensity is maximum.

author: soldo63
author_rank: Contributor
timestamp: April 21, 2014, 10:51:17 pm
content: Disconnecting the AC drive to the DC restorer by removing C863 or R863 and disconnecting the z-axis amplifier should make the CRT operate with full brightness. If you do this, deliberately defocus the CRT to prevent damage. You should do that anyway when working with the z-axis and DC restorer circuits anyway to prevent damage to the CRT.I did that and nothing happened. No increase in brightness.I will look for a HV probethanks

author: David Hess
author_rank: Super Contributor
timestamp: April 22, 2014, 12:22:18 am
content: Quote from: soldo63 on April 21, 2014, 10:51:17 pmOne thing you can try without a high voltage probe is to measure the grid to cathode voltage with a voltmeter. The cathode is at -2000 volts but the grid is right around that voltage as well so with care, you can make an isolated voltage measurement between them. This is the kind of thing to do by hooking the meter up, then powering up the oscilloscope, making the reading, and then powering down the oscilloscope. The meter and meter leads need to be kept away from any conductors.I have a different question though. Is the normal sweep length about the correct length? It should extend from 10 to 11 divisions without the x10 magnifier turned on.You might want to try joining the TekScopes@yahoogroups.com email list and asking. There are others there who have more experience with the 22xx series and CRT circuits. Z-axis problems are common. If you do this, include a summary of your diagnostics.

author: soldo63
author_rank: Contributor
timestamp: April 22, 2014, 03:14:02 am
content: Cathode to grid voltage 55v intensity set to max and 80v intensity set to min.the beam takes up the whole width of the screen in both modes.and shows undistorted signals it's just very dim.

author: David Hess
author_rank: Super Contributor
timestamp: April 22, 2014, 03:57:38 am
content: Quote from: soldo63 on April 22, 2014, 03:14:02 amSo the grid voltage was more negative than the cathode voltage in all cases? If it is varying from -55 to -80 volts compared to the cathode and was dimmest at -80 volts, then that indicates that the CRT works fine and there is some problem with either the z-axis amplifier, DC restorer, or grid bias adjustment.

author: soldo63
author_rank: Contributor
timestamp: April 22, 2014, 11:27:04 am
content: I don't have a lot of experience, from what I know the grid is right in front of the cathode which is in front of the heaterand that's what I Measured.I don't know what is that plate in the front of the crt, circled in blueQuoteDoes the grid bias adjustment vary the voltage between the grid and the cathode?What should the voltage be?Should it keep going higher than -55I removed the z amp from the circuit and also removed the dc restorer by removing R863. and it didn't make any difference in brightness. and I also removed R884, and that didn't make any difference in intensity.and when I did all that the grid bias pot had no effect.But I didn't remove the circuit from the front plate in circled in blue (what is that )

author: David Hess
author_rank: Super Contributor
timestamp: April 22, 2014, 05:19:15 pm
content: Quote from: soldo63 on April 22, 2014, 11:27:04 amThe grid is the screen element closest to the cathode and it controls the CRT intensity.QuoteYes.QuoteIt is not a fixed value and varies significantly between CRTs which is why there is a grid bias adjustment. I suspect it should be higher than -55 volts (closer to 0 volts between the grid and cathode) which is just another indication that the CRT is not damaged.QuoteDoes the grid bias pot do anything with everything connected?QuoteThat is the expansion mesh screen. It increases the deflection sensitivity of the CRT allowing higher bandwidth, a shorter CRT, or both at the cost of increasing the spot size.I may have to add another chapter to my Tektronix notebook for the 2215.

author: soldo63
author_rank: Contributor
timestamp: April 22, 2014, 06:37:41 pm
content: The grid bias pot does does effect the intensity when everything is connected.turning it clockwise increases intensityalso the intensity control does the same thingin normal mode the trace is very dim in 10x mode it is barley visible in dim light.and when I add chan2 it seems like the intensity is half as much.

author: David Hess
author_rank: Super Contributor
timestamp: April 24, 2014, 05:02:30 am
content: Quote from: soldo63 on April 22, 2014, 06:37:41 pmDual channel mode reduces the CRT intensity simply because the beam is spending half as much time on each trace. x10 horizontal magnification reduces the CRT intensity to 1/10th because the beam is only on the CRT 10% of the time. Neither of these are usually a problem because the CRT should be more than bright enough to perform well but in your case, the low brightness is a problem.There are two things that could cause this; either the beam intensity is low which is what we have assumed or the sweep is not occurring as often as it should. You can distinguish between these two by switching the oscilloscope to X-Y mode or using a very slow sweep speed so that instead of a trace, a spot is displayed. If the maximum brightness of the spot is low, then the problem is not the sweep.

author: soldo63
author_rank: Contributor
timestamp: April 24, 2014, 08:40:14 am
content: In /xy move with just the dot it is still very dim.I guess there not much more I can do until I get a HV probe.Thanks for your help David

author: w2aew
author_rank: Super Contributor
timestamp: April 24, 2014, 09:59:27 pm
content: Quote from: soldo63 on April 24, 2014, 08:40:14 amYour discussion of getting and using an HV probe prompted me to get off my butt and fullfil a longstanding required to put together a short video on the basics of HV probes, showing how they work and the basics of using them. There are some subtle things to be aware of that you might not think about...

author: soldo63
author_rank: Contributor
timestamp: April 25, 2014, 12:43:02 am
content: Thanks for everyone's help, But I solved the Problem. It turned out to be the crt.I got a hold of a working 2215 and swapped crt's and the problem followed the crt

author: David Hess
author_rank: Super Contributor
timestamp: April 25, 2014, 01:49:16 am
content: That is to bad that the CRT was damaged. That is difficult to test unless an element shorts to another element or the heater filament is open.Sometimes they can be repaired by blowing out a short using a high power pulse but that assumes one knows where the problem is.

author: ulyanoff
author_rank: Contributor
timestamp: April 04, 2015, 07:04:06 pm
content: Hello, guys!Please somebody knows that the inside unit of the multiplier U990 ? -2kV +8kV is associated voltage or not ? To get them used one secondary winding T940 . I am repair Tektronix 2215 - issue no beam. Thanks for the reply.

author: tautech
author_rank: Super Contributor
timestamp: April 04, 2015, 07:41:56 pm
content: Welcome to the forum.Triplers/quadruplers/quimtuplers just use a number of capacitor and diode doubler stages for the PDA voltages.It is quite rare for any troubles with them in CRO's, normally the surrounding -2 kVor lack ofis the problem.Do you have the Tek guide:http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdfSphere is also a good source for Tek parts.

author: ulyanoff
author_rank: Contributor
timestamp: April 05, 2015, 06:42:30 am
content: Thankstautech!Thanks for the link, Yes I have this document. Also I forgot to specify that the secondary voltage is normal , the secondary circuit capacitors replaced. +100V,+30V, +5V, +8,6, -8,6 is normal. On the right circuit on the output U990 voltage is present , I can't measure it accurately, but my multimeter goes into overload by showing somewhere 1180 V. Using the divider I also could not measure it because of the high frequency conversion. From this I assume that-2kV present.Also I have signal on horizontal plates(see photo). The glow of the filament of the CRT is yellow light inside. Continue search...

author: tautech
author_rank: Super Contributor
timestamp: April 05, 2015, 07:42:16 am
content: Check the SM for DC check points.On the schematic the should be various voltages at certain test points. They may or may not be numbered, normally only the waveform check points are labeled.To use the DC voltage test points there will be instruction as to how the scope must be set for the DC voltages to apply.Good to see the Sweep seems to be working.You could also check the Vertical amp in the same way using the 1 KHz Cal output.Often in CRO's the resistive dividers around the -2kV fail open or values drift.You could do this check to see if the PDA has recently worked.Caution needed.10+ kVPDA's hold a residual charge, this can be used to determine if it has been working.With the scope powered off, gently slide a well grounded and insulated screwdriver under the grommet on the CRT. You should hear a click/crack as it discharges.This should be done if you plan to remove the CRT or the PDA and other than using this method to establish recent operation or part removal there is no other reason to remove the CRT Anode lead EVER.Does the "Beam Find" work?

author: ulyanoff
author_rank: Contributor
timestamp: April 06, 2015, 11:10:35 am
content: Hi, Unfortunately beam finder does not work, I do not see any activity or beam spot on the screen at any position of regulators. Nevertheless, the first multiplier stage operating voltage is present -2kv.

author: ulyanoff
author_rank: Contributor
timestamp: April 21, 2015, 09:50:54 am
content: Hello ! I did measure the voltage divider and the anode in 7650 as well as the voltage at -1900v. Can someone suggest the correct voltage at the crt? measurement scheme is shown below. In general, I can not see the beam. In the darkness I could see a flare or as it is right to say, the reflected signal from the left edge of the screen. As if the beam is located outside of the screen and I can only see its afterglow. Afterglow varies with sweep mode. Maximum seen in slow-sweep.

author: tautech
author_rank: Super Contributor
timestamp: April 21, 2015, 10:21:44 am
content: CRT HV Supply -1900 to -2100 V at pin 2 CRT socket.As specified in SM Section 5, P 5.

author: ulyanoff
author_rank: Contributor
timestamp: April 22, 2015, 08:03:44 pm
content: Good evening! I think after these pics of my "quest" fault will be completed.Photo taken by the camera in total darkness, found the most "bright" focus and brightness. Moreover, the intensity of this screen varies even when uncoupled from the plates when switching the duration of the sweep. Plate completely disabled horizontal and vertical. Transistor Q877 deleted. That's the "point" happened. Let me remind you that in the dark, the shutter speed of my camera for about 10 seconds.p/s/ During the rotation of p on Board AUTO FOCUS and GRID BIAS of improvements is not received. all stronger eroded and faded.

author: ulyanoff
author_rank: Contributor
timestamp: May 20, 2015, 09:01:25 am
content: Hello guys,Somebody has a schemeCurrent Limit Board Configuration for Tektronix 2213serial number is belowB020100, (B016612). I need scheme without Preregulator board, a input circuit.I have burnt resistor and capacitor (C926,R926) on the input of all the manuals in network without the power supply circuit.Thanks for prompt replay,

author: ostap
author_rank: Newbie
timestamp: September 01, 2015, 06:46:54 pm
content: Quote from: ulyanoff on May 20, 2015, 09:01:25 amTektronix 2213 Current Limit Board schematicYellow label all components need to replace :-)

author: ostap
author_rank: Newbie
timestamp: October 05, 2015, 03:51:32 pm
content: Quote from: ulyanoff on April 04, 2015, 07:04:06 pmMaybe someone help this circuit )Theory (Tektronix 22XX HV MULTIPLIER x4 (-2Kv / +8kV))Praktik & InstallCheck -2kV / +8kV