Component Tester Fault - Page 1
Forum section: electronics / testgear

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 01:02:04 am
content: When I first tested this feature out on the HM605 it appeared to work just fine. I followed the instructions in the manual, pushing the CT button, connecting the tester socket to one of the earth sockets by BNC socket and watched the horizontal line go vertical.Great I thought. As I had a few other things to do I left the scope turned on as I read in the manual that turning it on and off for short periods is not good for the CRT, but I turned the intensity right down so the trace was no longer visible.On returning, I went to repeat the test as I thought it was quite neat to see.Turned the intensity up to make the trace visible, pushed the CT button to be greeted with this image.....Also noting the overscan lights had illuminated.I released the switch, the messy image disappeared but the overscan lights stayed on.I thought dirty switch? So pushed the button in and out a few times and the lights went out.Pushing the button in again this time connecting the leads as I had before I see this mess.I can understand the overscan lights being illuminated in this instance.I can't think of anything I did different other from turning the intensity down for a few hours. Is this an open it up project or am I missing something obvious?

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 01:53:13 pm
content: This is what happens when I fed the scope 50kHz, auto triggering, 5v p-p, channel 1 and 2 tested individually, both set to AC.As can be seen no matter where the trace is put vertically the irregular fainter lines seem to emanate from the straight line that never leaves its position half way up the screen.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 02:10:10 pm
content: Measurements on the graticule seem to be correct for the main and brightest part of the image. 20kHz 10v

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 02:30:02 pm
content: I can get rid of some of the rubbish by turning off auto triggering and tuning into this but I can't get it to settle.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 03:05:37 pm
content: Following the instructions for probe adjustment this is what I get so I'm not blaming the source of the sine wave I gave it in the previous posts.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 03:34:58 pm
content: Removing probe from test socket but still connected to BNC shows this.....Trigger light on and lower overscan light on

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 03:51:27 pm
content: As I went to remove the probe I noticed the movement on the screen. On moving the probe around this is what happens...I wondered if it was the probe but both probes that I have behave the same

author: StillTrying
author_rank: Super Contributor
timestamp: October 20, 2019, 03:57:27 pm
content: It looks just like (or mostly) an intermittent connection in the probe or 1kHz socket to me, or somewhere else.I wouldn't worry about the 50kHz of open circuit noise.Having the trigger on DC coupled is probably better.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 04:26:31 pm
content: From the other source no probes attached

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 05:05:19 pm
content: Quote from: StillTrying on October 20, 2019, 03:57:27 pmI don't think it is either of the probes as both of them behave the same. Also when I unplug them completely the problem is still there as in the following image....As this only started after leaving it on with intensity turned right down is there any possibility of a link?Also if nothing is connected to the scope should it be triggering at all?

author: bob91343
author_rank: Super Contributor
timestamp: October 20, 2019, 05:18:14 pm
content: My guess is that you need to repair this unit. First check the power supply; this could easily be caused by bad filter capacitors or other faults. Get the service manual and verify integrity of the power rails.If that is good, I might think you have a bad CRT.

author: StillTrying
author_rank: Super Contributor
timestamp: October 20, 2019, 05:21:31 pm
content: Is the component tester off.Are you sure it's in single channel mode, ALT and CHOP can cause similar effects.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 20, 2019, 05:56:55 pm
content: Quote from: StillTrying on October 20, 2019, 05:21:31 pmComponent tester is in the off position. When it's on the first picture in the first post of this thread is still what can be seen. In single channel mode, ALT and CHOP button out.

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 20, 2019, 10:25:40 pm
content: Definitely check power first. (Always check power first...)If power hasn't failed, ideally you'd need another scope to follow a sine from input through to Y plates.

author: StillTrying
author_rank: Super Contributor
timestamp: October 22, 2019, 08:49:13 am
content: After that many tests it's not looking good, it looks like the Y amplitude keeps dropping back to the 0V position.We could imagine no decoupling on the Y's supply voltage, ...or something.Is CH 2 the same.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 28, 2019, 06:54:46 pm
content: Quote from: StillTrying on October 22, 2019, 08:49:13 amYes, both channels same

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 28, 2019, 07:22:28 pm
content: Unless I am going about this all wrong I think there may be a fault with the power supply.None of the secondary coils (I'm assuming it has multiple) are measuring anywhere near what they should, (if I am taking the measurements correctly of course).Here is what I'm looking at......ThisI assume relates to thisTaking these into account and the reading up I have been doing on primaries and secondaries, with the scope turned on I measured the V~ across each pair of same coloured wires (assuming rightly or wrongly this indicates they are all individual secondary coils in their own right).These are the results.Should bebk - 12v~gr - 8v~bn - 15v~rd - 15v~gn - 70v~bl - 68v~Actualbk - 7.1v~gr - 4.9v~bn - 8.8v~rd - 8.7v~gn - 40v~bl - 42.5v~

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 28, 2019, 07:32:51 pm
content: Also I found one of the black wires was not secured to the little post sticking up on the board so I re-soldered it back.I have made no tests regarding the CRT or the Z board.

author: SeanB
author_rank: Super Contributor
timestamp: October 28, 2019, 07:48:34 pm
content: Unsolder one end of each of the secondary wires and measure again. if they rise up to about correct then one of the bridge rectifiers is shorted, a capacitor is shorted or something after the bridges. If not the transformer is terminal, with shorted windings internally.If not the transformer connect secondaries back one by one to find which one is loading the rails down, and that at least gives you a start.My bets are on green, probably failed bridge rectifier, and if you change one of those little ones change the whole lot as a single operation, as they are all the same batch, and the 8V rail probably has the highest current in operation, and thus failed first from cooking. Use higher current rated devices, at least 2A over the 1A ones, though you will probably have to space them a little off the board and use sleeving to get the leads to fit the spacing, but they will run cooler.Had plenty of expensive failures from bridge rectifier faults, so got used ot running a scope probe over each power rail to see ripple before any other test, to see if there were any open or shorts, which would not cause an immediate fault, but would lead to transformer failure eventually.

author: StillTrying
author_rank: Super Contributor
timestamp: October 28, 2019, 07:52:09 pm
content: I can't imagine it working as well as it does ifallthe voltages were only 60% of what they should be, are you sure the DVM is accurate. None of those transformer connections look original to me.Beware the lethal voltages, do everything one handed, and don't get into the habit resting any fingers on the chassis, or anything else.Yes start with gn, then bl, perhaps.

author: bob91343
author_rank: Super Contributor
timestamp: October 29, 2019, 03:13:58 am
content: The fact that all the voltages are roughly half of what they should be makes me think you have the primary set to the incorrect power line voltage.

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 29, 2019, 07:09:49 am
content: Quote from: bob91343 on October 29, 2019, 03:13:58 amOP mentions that fault happened while turned on, was working normally on powering up. Usually line voltage selectors don't flip themselves.As suggested checking amount of AC on the DC side of the bridges could give you a clue to a defective bridge or overload on one power rail.With all those voltages measured so low, is CRT brightness lower than it was before the fault?Usually a secondary overload would cause significant heat somewhere, in this case probably enough for it to actually smell odd.A partial internal short on the transformer will usually give a very hot transformer, or noise if arcing on the HV winding.You may want to check over excessive resistance between plug and transformer primary, that could cause low secondaries without showing too much heat.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 29, 2019, 01:14:49 pm
content: Quote from: shakalnokturn on October 29, 2019, 07:09:49 amI'd have to say no, I don't think so.Since first using this scope I have never turned the intensity right up. It isVERYbright to the point where it is more like a torch. So to be kind to the screen I always keep intensity low, it mentions this in the manual.When leaving it for a few hours I even turned it all the way down, thinking I was being kind to it. On returning is when I noticed the above goings on.There does appear to be four more secondaries coming from the transformer to the Z board behind the CRT, but they are not colour coded pairs like the others. I haven't touched anything on this board at all (apart from moving it carefully to gain access to a screw when checking main power input (which is as you have already pointed out is on the correct input setting)).

author: StillTrying
author_rank: Super Contributor
timestamp: October 29, 2019, 06:29:03 pm
content: "There does appear to be four more secondaries coming from the transformer to the Z board behind the CRT, but they are not colour coded pairs like the others."There's another 3 wire winding supplying 6.3V and 30V to the CRT, but bewarethis winding and these voltages are at -1250V!The rd and bn 15VAC windings provide + and - 12V supplies, both with 7812s, your measurements of 8.8 and 8.7VAC wouldn't be enough for the 7812s to regulate, which is probably enough to explain the wobbly traces.But I don't know what's wrong with it! The schems in this German manual aren't very clear.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 29, 2019, 09:04:59 pm
content: Quote from: StillTrying on October 29, 2019, 06:29:03 pmI did notice something along those lines when I saw this, and thoughtcaution

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 29, 2019, 09:23:58 pm
content: While on the subject, I found some test points on the Y board.Thisand thisWhich I assume relates to thisPlease correct me if wrong. The +probe (to measure DCV) makes contact with whichever socket of the test strip?Where is the best place to maybe attach a -croc clip / -probe.I have been looking for a common. Either I'm looking for something that doesn't exist, looking at/in the wrong place or misunderstanding what the row of sockets are for and how to use them.

author: StillTrying
author_rank: Super Contributor
timestamp: October 29, 2019, 09:48:30 pm
content: "Where is the best place to maybe attach a -croc clip / -probe.I have been looking for a common."All the metalwork will be ground/0V.The 33Vpp @ 1250V will be the beam blanking during retrace and waiting for a trigger,I think.

author: Noidzoid
author_rank: Regular Contributor
timestamp: October 29, 2019, 10:24:11 pm
content: Does that mean that everything after the bridge rectifiers is DC and thereafter DC and Earth (top pin in UK wall socket) are the same?

author: StillTrying
author_rank: Super Contributor
timestamp: October 29, 2019, 11:11:22 pm
content: "Does that mean that everything after the bridge rectifiers is DC and thereafter DC and Earth (top pin in UK wall socket) are the same?"Yes there's chassis signs all over the schem. But that doesn't mean that the DC -Ve side of the BRs is chassis/0V, except for the +5v and +12V supplies. Have youcarefullymeasured the +5 +12 and -12 VDCs yet, I can't see how 8.8VAC before the BRs would be enough for the 12V 7812 regs.I can't think what could take enough power to lowerallthe supplies without getting VERY hot itself, there must be many Watts going somewhere. Is the CRT heater only a dim orange and not a bright white, you can usually see a glimpse of it somewhere, be careful around there.If it was 1 of these 6ACsupplies pulling the rest down I'd expect that 1 to be quite a bit lower % than the others, but there doesn't appear to be one.bk - 12v~ -> 7.1v -> 0.59gr - 8v~ -> 4.9v -> 0.59bn - 15v~ -> 8.8v -> 0.59rd - 15v~ -> 8.7v -> 0.58gn - 70v~ -> 40v -> 0.57bl - 68v~ -> 42.5 -> 0.62

author: AVGresponding
author_rank: Super Contributor
timestamp: October 30, 2019, 05:33:03 pm
content: If they use a common ground, and if this is bad, that would affect them all, and also might be harder to notice in terms of heat generation.

author: StillTrying
author_rank: Super Contributor
timestamp: November 01, 2019, 05:48:31 pm
content: Quote from: ThickPhilM on October 30, 2019, 05:33:03 pmThose voltages are the floating AC voltages from the secondaries as in Reply#16, thereshouldn'tbe any grounds involved in the ACV measurements.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 01, 2019, 10:22:19 pm
content: Haha okLooks like there is some commonality with the measured voltages though. That must surely narrow down the possible causes, though I believe the voltage select angle has already been explored, which would have been my first thought.I have a recently acquired 203-6, which I am in the process (LIES, I haven't lifted a finger) of fettling (just needs the pushrods on the switches sorting out).If I can be of any help by measuring voltages etc, please don't hesitate to ask.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 03, 2019, 04:12:48 pm
content: After reading replies here I think the transformer itself may be the problem.Before disconnecting the secondary windings from the Y board.......Then the following....Also in answer to a previous question, the back of the CRT is dull orange. I still have not taken any readings from the Z board.Also resistance of Primary Winding 40.2ohms

author: StillTrying
author_rank: Super Contributor
timestamp: November 03, 2019, 07:53:49 pm
content: Was 244 VAC the actual mains voltage, years ago I measured 255 and even 256 but it seem to be often as low as 232 these days.If there's definitely nothing overheating I'd be tempted to switch the mains voltage selection to 220V.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 03, 2019, 08:20:27 pm
content: Quote from: StillTrying on November 03, 2019, 07:53:49 pmI measured after the switch (black wire) and to the voltage selection fuse holder (transformer side) to the white primary wire that goes into the transformer (the one that gets connected when selector placed in 240V~ position). Is there any reason that would not be the actual mains voltage? Should I be taking a reading somewhere else maybe?Also I have no way of knowing how accurate my meter is/isn't.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 03, 2019, 08:49:55 pm
content: Unless you're waaaaay out in the sticks, you're unlikely to be lower than 240VAC in the UK, and often quite a bit higher than that, close to 250V sometimes.In any case, a sag big enough to affect the scope would be very noticeable in other appliances around the house; motors would run slow, incandescent lamps would dim, and even fluorescent and LED lamps might be affected, depending on the drive circuitry.It's worth checking, if you have a suitable meter and feel confident you can do it safely, but I'd be surprised if that is the culprit.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 03, 2019, 09:27:52 pm
content: Quote from: ThickPhilM on November 03, 2019, 08:49:55 pmAll other appliances seem to be working fine.Power from the socket scope is plugged into measures 244V~

author: StillTrying
author_rank: Super Contributor
timestamp: November 03, 2019, 09:30:39 pm
content: I just measured 2449:30 pm Sun, it's often a bit lower than that, but I'm not in the sticks.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 04, 2019, 04:48:56 pm
content: Something that just occurred to me...I was just looking back through the pics you've posted, and there are a number of very old looking electros on those boards...I would definitely consider sucking a few of them out to check.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 07, 2019, 12:51:11 pm
content: Not managed to look at this for a few days.I will check out the old electrolytic capacitors as mentioned, however does it make sense to assume my transformer has failed?The output on all the secondaries is lowThe input to the primary is correct (244V~)Could the fault be with the primary winding asallthe secondaries I have tested are wrong?I still have not touched the other 4 wires going to the Z board but does that matter (please forgive me if this is a stupid assumption) as the secondaries are individual coils not shared therefore the only thing they have in common is their relationship with the primary?

author: AVGresponding
author_rank: Super Contributor
timestamp: November 07, 2019, 04:32:28 pm
content: It certainly could be the primary, easy enough to check that, measuring the resistance of the primary and secondaries should give a ball-park idea.Alternatively, disconnect all the secondaries, and measure the current the primary uses.Should be very low with no load on the secondaries.Don't forget to mark them all up before you disconnect them all...I mentioned the caps simply because it's a classic failure mode, shorts or near shorts being common, though I'll grant you that all of them failing at the same time is less so, but given the circumstances (long unsupervised on period = cap-drying heat buildup?), it might have been the final straw on ones that were already tired and marginal.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 15, 2019, 01:32:26 am
content: Does something not look right here?The two top wires (purple and violet) are, I think, connected to the same track.It was suggested earlier in this thread that the soldering of the secondaries going to the Y board were not original. I agree, and I think the four going to the Z board are the same. I don't know if any damage has been done (looks like the insulation got pretty hot).Unless I am misunderstanding the diagrams and layout, there should only be 3 wires going from the transformer to the Z board. I appear to have 4.Also these four wires don't seem to be in pairs like the secondaries going to the Y board. Is this because they come from a shared coil?The transformer was I think foraHM605 but was maybe taken from adifferentmachine with a slightly different spec? However it does have an original looking label on which 605 is printed.

author: odium
author_rank: Contributor
timestamp: November 15, 2019, 04:31:03 am
content: disconnect all secondary windings from pcb and then apply power to primary and check secondaries off load voltagesalso check :- primary winding off load current if stable or fluctuating (magnetic core or winding isolation problems …)- is the magnetic core of transformer abnormally hot ? (if core sheets are soldered together check solder joints if cold/broken)- power off and check continuity between adjacent windings and also against magnetic core ! (>10M)cheers

author: StillTrying
author_rank: Super Contributor
timestamp: November 15, 2019, 01:11:10 pm
content: Quote from: odium on November 15, 2019, 04:31:03 amLooks about the best idea to me, of course don't let any of the secondary wires short.You couldcarefullymeasure the 6.3VAC and 31VAC, remembering that they're at -1200V, so at that voltage connect the DVM before switching on.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 15, 2019, 01:23:38 pm
content: I'll pull the casing off my 203-6 and see if it provides any useful information.EDIT: It's quite a bit different unfortunately. One similarity caught my eye...I wonder if mine is a centre tapped 3-wire, and yours is two separate secondaries, being used as a centre tapped 3-wire by shorting blue and purple. The double pad seems to suggest the possibility.Mine bells out as yellow-purple 1.1 ohms and purple-red 201 ohms, with yellow-red 202 ohms to check I had the phases the right way round lol (measured with 4-wire on calibrated Fluke 8840A, so high confidence).

author: StillTrying
author_rank: Super Contributor
timestamp: November 15, 2019, 03:29:40 pm
content: Quote from: ThickPhilM on November 15, 2019, 01:23:38 pmYes, the OP's look like 2 separate windings with the 6.3VAC and 31VAC windings in series to give 37VAC across the ends.Your 1.1 ohms and 201 ohms seem high.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 15, 2019, 05:14:32 pm
content: I'm inclined to believe my recently (end of July) calibrated 8840, especially using 4-wire resistance measurement, though I will admit I didn't warm it up before measuring.In my experience this can add up to 15 or so milliohms, but since I disregarded the last 2 digits it doesn't seem relevant.I would add that my 203-6 is 100% functional, the only repairs I've had to make are to the plastic links that connect the pushrods to the switches on a couple.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 16, 2019, 01:38:09 pm
content: Thanks to everyone who is helping me with this. I intend to take the advice with of course more questions along the way.I was just about to desolder the remaining secondary wires from the Y board (ones connected to the bridge rectifiers) and have two questions so far.Do I need to disconnect both ends of each secondary coloured pair to take measurements across them or can one remain attached to the board?Am I correct in assuming I don't need to be concerned about which way round each wire of the same colour goes to the AC~ pins on the bridge rectifiers?Also could I have an opinion on the following image. I don't think it is correct as shouldn't BR2502 have two AC~ wires going to it? It appears (to me) to only have one. The one I suspect should be going to it is sharing a track with brown going to BR2503.Whoever soldered this transformer in put the two red wires to BR2502 and the two brown wires to BR2503 which I assume is correct.

author: StillTrying
author_rank: Super Contributor
timestamp: November 16, 2019, 02:06:50 pm
content: Quote from: Noidzoid on November 16, 2019, 01:38:09 pmYou only have to disconnect one end of each secondary and no current will be able to flow anywhere, I think, I assume you're going to have all the secondaries disconnected at the same time to measure the no load AC values. For the 6.3V and 31v tapped winding disconnect the outside 2.https://www.eevblog.com/forum/testgear/component-tester-fault/msg2758742/#msg2758742QuoteYes, but not on the 0-6-31 winding, the phase there has to be kept because the 6.3VAC and 31VAC is in series."Also could I have an opinion on the following image. I don't think it is correct as shouldn't BR2502 have two AC~ wires going to it?"rd-rdandbn-bnare the 15VACs which produce the +12V and -12V so they could be swapped maybe, they look messed up on that last diagram.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 16, 2019, 02:33:08 pm
content: One other thing, I'm not sure that schematic you have is correct, the only one I could find for the 605 disagrees with yours, but makes more sense.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 16, 2019, 03:54:48 pm
content: Quote from: ThickPhilM on November 16, 2019, 02:33:08 pmI think there must have been a revision of something but there are differences.The tracks match up with the schematic I have taken from this book.As it was when first I saw it....

author: AVGresponding
author_rank: Super Contributor
timestamp: November 16, 2019, 05:27:47 pm
content: Hmm well ok, but the legend on your layout indicates 2 mixed colour pairs, each red/brown, which is a recipe for confusion.Since they seem to be for the +/- 12VDC rails, if they are implementing a centre tap by joining two secondaries, you better be 100% sure about the phase, or you're just making an impromptu space-heater...

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 16, 2019, 06:02:48 pm
content: As inexperienced as I am, the last picture (of the wires in place as I found them) of the three in my last post makes more sense to me as each bridge rectifier has two wires each of the same colour going to ~pins. However, I can't be sure that the right pairs are going to the correct rectifier. Yours looks very different.I wish mine was laid out like yours, it looks much tidier.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 16, 2019, 06:31:37 pm
content: @ThickPhilMJust a thought, do you also have a different schem for the Z board? If so, does yours show 4 wires coming from the transformer like my scope or 3 like my schem?

author: StillTrying
author_rank: Super Contributor
timestamp: November 16, 2019, 07:55:14 pm
content: I think I've got the same pdf as ThickPhilM,hameg_hm605_oscilloscope..........pdfthe Z board seems to have 3 power wires.If the tube heater current is flowing though thoseviandyetracks perhaps they're used as a fuse.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 16, 2019, 08:50:16 pm
content: Quote from: StillTrying on November 16, 2019, 07:55:14 pmWell, at the moment I am lost. You would think an official manual (assuming it is of course) would put wire colours in? Why is there such a difference between our schematics? How did whoever put in this transformer know which wires to put where without info from the schematic? (Unless of course like for like was done). If there isn't a different schematic out there what is the transformer and board I have?Also the board I have does seem to correspond to the schematic including the extra hole where the shared track is with two small posts with a purple on one and violet on the other.The Y board schematic I have although unlike ThickPhilM's one, does seem to have the same track pattern. Is it possible I have an early model and manual before they tidied both up a bit? The wires on mine look like afterthoughts that were drawn in just before being sent to the printers.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 16, 2019, 09:53:20 pm
content: Only three wires from this part of the transformer going to the Z board?The only place I am seeing the fourth wire is in the scope itself!

author: StillTrying
author_rank: Super Contributor
timestamp: November 16, 2019, 09:55:48 pm
content: I don't think the 6.3VAC and 31VAC windings are a very big problem. I can imagine it being shown on the schematic as just one 0-6-37 winding, but when they come to build the actual transformer it's made from a high current 6.3VAC winding and a low current 31VAC, at least they used the similar blue and violet colours for the center point.After correcting the misplacedrdwire on the drawn version, the three images in Reply#50 all look the same to me, thebnlooks veryorin the photo, and the soldering's terrible.I still think ThickPhilM's 1.1R and 201R for those windings seem high, the 240VAC primary winding might be only ~200R.Disconnect all the secondaries.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 16, 2019, 10:53:38 pm
content: Quote from: StillTrying on November 16, 2019, 09:55:48 pmIn regard to disconnecting the secondaries with reference to post #32 the measurements were taken with all the secondaries disconnected (well one from each coloured pair) but with the Z board four still connected at all times. Should I have disconnected those too? Will that be not giving me correct results? Should I disconnect the Z four and measure them all again?Also could I trouble you for a concise step by step instruction on how to test the Z board four once I have unsoldered them. I have been reluctant to mess with them so far as I understand this area should be treated with great caution. (I thought I needed a HV probe? Or would that be further into the Z circuit?) I am just trying to be respectful with regard to what I am unsure of.

author: StillTrying
author_rank: Super Contributor
timestamp: November 17, 2019, 12:35:19 am
content: Quote from: Noidzoid on November 16, 2019, 10:53:38 pmI've assumed you disconnected each secondary one by one, reconnecting the last one before disconnecting the next, which would be different thanwith all the secondaries disconnected.But still that should have been good enough to find which supply was pulling the rest down.The amount of power to pull all the secondaries down to only 60% should be more power than the whole scope uses,somethingshould be getting very hot in theory."Should I have disconnected those too? Will that be not giving me correct results? Should I disconnect the Z four and measure them all again?"Looking at the schem.I thinkit would be safe (for the scope!) to disconnect the 0V AND 37V ends of the 0-6-37 winding (rdandye), but if the other supplies are still connected these disconnectedrdandyeends would still be at -1200V because of the still connectedvi andbl."Also could I trouble you for a concise step by step instruction on how to test the Z board four once I have unsoldered them."You could disconnect the 0-6-37 's midviandbl as well, then you'd just have a 6.3VAC winding and a 31VAC winding that are isolated and not at -1200V, but the solder tags the 0-6-97 were disconnected from would still be at -1200V.I'd be happy to measure these 6.3VAC and 31VAC at -1200V, but I'd connect the DVM before switching on and not touch my toolbox DVM while it was at -1200V.I still think the best, safest and easiest idea is to haveallthe secondaries disconnected to see what the transformer does fully unloaded, and there'd be no HV then other than the mains.Quote from: Noidzoid on November 03, 2019, 04:12:48 pmA ThickPhilM's resistance measurement of his primary might be useful.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 17, 2019, 12:13:29 pm
content: The primary on mine measures 55.4 ohms, disregarding the last 2 digits (didn't warm the meter up).Bear in mind mine is a 203-6, with a manufacture date of 52/87.The layout I posted an excerpt from is the only one I could find for the 605, and all the text is in German. All the English manuals I could find were user only, not service. I suspect it might be a later version than yours.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 18, 2019, 12:39:56 am
content: Been doing some measuring with a different meter (TTi 1705) as I think my other one was being a bit odd.Just thought I would share what I have with those of you that have been helping so far before removing the Y board (which will be easier before putting the transformer wires back) to gain better access to the larger electrolytic capacitor legs.

author: StillTrying
author_rank: Super Contributor
timestamp: November 18, 2019, 08:37:40 am
content: Thoseall disconnectedreadings show the transformer is fine.It must be something else.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 18, 2019, 11:57:20 pm
content: Found two capacitors that seem bad.Can they become totally open circuit? They are not registering any change whatsoever on the ESR meter (MESR-100). Both these caps have the same values printed on them. 220μF 100vThe other three similar looking 1000μF 25v caps on the same board all tested good with the same meter.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 19, 2019, 06:08:41 am
content: Given the low cost, I'd replace them anyway. Sometimes they only exhibit the failure mode with a higher voltage applied than a tester can supply.Short or open circuits are both possible, with all points in between...EDIT: Failure can also be intermittently apparent due to thermal variation.

author: StillTrying
author_rank: Super Contributor
timestamp: November 19, 2019, 11:24:03 am
content: Quote from: Noidzoid on November 18, 2019, 11:57:20 pmNot often, but they can dry out and have very a low capacitance.Almost no smoothing capacitance on the +68 and +140 supplies would be enough to explain the wiggly traces, and maybe some of the low voltages if their discrete regulators were struggling.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 19, 2019, 02:08:48 pm
content: Just connected a 'bad' one up to a DMM as I was curious to see if it was totally open (20MΩ range) and it seemed to settle on a reading of 5.7So this is obviously just a straightforward resistance and not ESR. Does this throw any light on anything?Also could I have some advice regarding buying new caps.I have found several from RS and Farnell matching the μF, v, leg spacing and taking into account general cylinder dimensions.Is there anything else I should be considering like °C, hrs ESR (this last one when stated seems to be quite variable).I don't imagine any of the offerings from these outlets are 'rubish' and I don't need overkill as this is an old scope. I just want it to work properly.

author: StillTrying
author_rank: Super Contributor
timestamp: November 19, 2019, 02:57:50 pm
content: Yes they don't have to be too special or low ESR, but I nearly always buy 105C.I don't know why you can't get a proper ESR and capacitance measurement. It might be better to check a few others of the big electrolytics before ordering just 2 caps.I often use these for a few bits, £1.90 postage is not too bad for <24Hr delivery.https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=65_66_69&products_id=2511

author: AVGresponding
author_rank: Super Contributor
timestamp: November 19, 2019, 07:01:03 pm
content: It's dead.A good cap will show steadily climbing resistance until the resistance scale of the meter is exceeded, when using a normal meter.Technically it'll never have infinite resistance since there'll be a leakage current, but in practice this is usually much smaller than the resistance measurement current that the meter will supply.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 19, 2019, 07:32:37 pm
content: OK thanks good people. I've decided to replace all the aforementioned caps.Next I thought I'd test the bridge rectifiers while they are easy to get at. I'm pretty confident about how to go about it but need to know if they can be tested in circuit or should they be removed for testing?

author: AVGresponding
author_rank: Super Contributor
timestamp: November 19, 2019, 07:41:53 pm
content: It depends what else is in circuit. Often they can be tested in circuit, but occasionally other components can cause false readings.As long as you're sure nothing else is affecting your reading, there's no reason to remove them.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 20, 2019, 11:14:33 pm
content: Within the small sphere of my understanding the bridge rectifiers are ok.I've replaced the two 'bad" caps and the other three as it has been pointed out heat could make them unreliable intermittently. I also followed the example above and bought the 105°C ones. Thanks for the guidance.Along the way I have learned two lessons.When unsoldering one of the caps (with it hanging from the board pointing down), it fell out! It the dawned on me that I hadn't taken note of where the negative stripe was. So, first lesson was make notes and/or plenty of photos. Fortunately I managed to find one that just about showed the stripe on the wayward cap. (Pure luck!)Very pleased with myself after having soldered all five caps in place, I turned the board over, only then did I notice that two of the new ones looked physically taller than the old ones, so much so I wasn't sure the case would fit! After putting a straight edge where the case would rest I was relieved to find it didn't touch, though I think the only way to measure the gap would be with a feeler gauge. I just hope when the scope is working, any heat doesn't move anything due to expansion. So, second lesson for the idiot that should know better is physical size is just as important as other specifications when choosing components.After you guys have picked yourselves up off the floor or just rolling your eyes, here are some pictures of my handywork so far so you can do it again........I did cut the legs off

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 22, 2019, 08:56:05 pm
content: Thank you, so very very much to all who have helped me get this far. First tests are showing excellent results.The component tester test is doing exactly what it should, which is the reason this whole project started.Probes disconnectedProbes connectedAll that is left is putting the cover back on and learning how to actually use an oscilloscope.Did I say Thanks?Just to make sure, THANKS GUYS!

author: AVGresponding
author_rank: Super Contributor
timestamp: November 23, 2019, 05:23:53 pm
content: Glad to see it up and running again.Them lil' bastard caps cause soooo much trouble, not just in TE (have one/some failed in my TV, makes it lose settings, and lose ability to detect it has a signal so it triggers the 5-minute auto power off, too much hassle to chase it/them down)(at the moment xD)

author: StillTrying
author_rank: Super Contributor
timestamp: November 23, 2019, 09:23:32 pm
content: I/we were close in Reply#14."We could imagine no decoupling on the Y's supply voltage, ...or something."Where did you get the new caps from so quick, and how is it on other wave forms.An old one..Quote from: Noidzoid on November 07, 2019, 12:51:11 pmAs well as the primary the 1 magnetic field is common to all the windings, shorted turns anywhere would cause all the secondary voltages to be too low and the primary current to be too high.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 24, 2019, 12:55:00 am
content: Quote from: StillTrying on November 23, 2019, 09:23:32 pmRS Components. Ordered before 20.30, free P&P, received next afternoon. I am very impressed. Seemed good value too. (Although they couldn't send me the 60/40 solder I ordered. Restricted under some regulation I believe)Other waveforms seem to display fine on channel 1 but appear unstable on channel 2. If I'm right it looks like a triggering problem on that channel only, is that possible?

author: StillTrying
author_rank: Super Contributor
timestamp: November 24, 2019, 02:10:05 am
content: "If I'm right it looks like a triggering problem on that channel only, is that possible?"Often a dirty switch.There's 2 "Trig Drivers", one from each channel, and the CH1/2 selection in the middle of the block diagram, but I can't find them on the schems.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 24, 2019, 06:19:58 pm
content: Quote from: StillTrying on November 24, 2019, 02:10:05 amThe actual selection button/switch for CH1/2 on the front panel does seem a little stiff/slow. I shall investigate.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 24, 2019, 11:49:40 pm
content: Is there a universally accepted product/substance/method for cleaning switches etc.Servisol Super 10?Isopropyl/Isopropanol?WD40 Contact Cleaner?Halfords Electrical Contact Cleaner?Any or none of the above?

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 25, 2019, 05:01:36 pm
content: Reason channel switch was slow/stiff was the pushrod was 90° out and was fouling on the casework (button end where there is a bend in the rod not actual switch on the board end)......easy fix!Now though CH2 isn't picking upanysignal at all. Just a flat line.........?I thought maybe the misaligned rod may have upset the switch internals but jiggling it about didn't even cause the displayed line to flicker with a signal being fed in.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 25, 2019, 06:19:15 pm
content: I like plain WD40, from a 5 litre can, not the spray stuff, then a high melting point grease like white grease to lube afterwards.The bent pushrod might have put undue strain on the switch, which might now not be contacting properly, I reckon you'll have to jiggle it until you get a result.It seems a standard type if you have to replace it, just the stupid plastic adapter is a Hameg special

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 25, 2019, 07:42:00 pm
content: Quote from: Noidzoid on November 25, 2019, 05:01:36 pmQuote from: ThickPhilM on November 25, 2019, 06:19:15 pmThat's good. I have both of those on the shelf. (WD & whitegrease). Thanks.Already done the "jiggling" with a slight bias in all directions to hopefully make even the slightest contact and change in trace. Short of replacing the switch (which may not even be the problem of course), I wonder if there is a way to bypass the switch to make the connections necessary for CH2 to opperate. I will have a look to see if it is that simple.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 25, 2019, 09:39:24 pm
content: I think the CH1/2 switch is working. Using the common pins on the switch and testing for continuity to others, the changes between pins are quick and consistent.Following tracks, the signal is arriving at these sockets in the same fashion.Ch1 selectedCh2 selected

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 26, 2019, 12:34:59 am
content: Quote from: StillTrying on November 24, 2019, 02:10:05 amWill these drivers be actual physical components?

author: StillTrying
author_rank: Super Contributor
timestamp: November 26, 2019, 11:54:39 am
content: Quote from: Noidzoid on November 26, 2019, 12:34:59 amI would think they're active buffers, but I still can't find that diode switching on the schem. (too busy to study it ATM).If CH2 is still flat lined I think you must have disturbed something.

author: AVGresponding
author_rank: Super Contributor
timestamp: November 26, 2019, 06:40:19 pm
content: I suppose a place to start is looking for any measurable differences in the trigger stages, also I suppose it's possible IC270 or IC271 have been damaged by static discharge..?

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 26, 2019, 06:49:20 pm
content: Quote from: StillTrying on November 26, 2019, 11:54:39 amI would think they're active buffers, but I still can't find that diode switching on the schem. (too busy to study it ATM).If CH2 is still flat lined I think you must have disturbed something.I have very similar showing the same trigger drivers in my book.I think it makes perfect sense that I disturbed something, so I will be going over all the things I moved that I can remember. I thought/hoped I had found the problem, one of the long plastic ribbon plugs/sockets wasn't pushed fully home but it made no difference so I think it was probably pushed far enough to make good contact in the first place.Thank you for your help so far, and I appreciate your time has been given while you could have been busy doing other things.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 26, 2019, 06:52:34 pm
content: Quote from: ThickPhilM on November 26, 2019, 06:40:19 pmVery possible. I must confess to not being very careful about static, only going as far as to not touch the pins on the IC I removed.

author: StillTrying
author_rank: Super Contributor
timestamp: November 26, 2019, 08:49:17 pm
content: "Will these drivers be actual physical components?"There's the 2 Trig Drivers, the 2 TRs each, how they work with differential inputs I don't know.Nothing around the Trig CH1/CH2 SW or those Trig Drivers could explain the now flat lined CH2.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 27, 2019, 09:00:17 pm
content: Quote from: StillTrying on November 26, 2019, 08:49:17 pmI am trying to keep up but this learning curve I'm on isverysteep. I will revisit this and try to catch up.......While poking around I did notice a three leg component (I think it was a transistor) that was rubbing on the shaft of the X-Mag/X-Pos switch. One of the legs looked weak so I soldered the weak looking bit (just in case).Whether what I did next makes sense to more experienced fellows on here or not. It did to me..........sort of.......As I have a problem on CH2 and not on CH1 I thought what obvious physical parts could be swapped around? If the problem stays on CH2 or moves with the component/s it would give a clue. With this in mind I swapped the following....I did intend to swap the smaller plates on which are mounted the BNC sockets also but they, unlike the larger metal boxes, are handed.Everything soldered/fitted/screwed back in and fired up......... everything is the same, so at least that is a large number of the internals out no longer under suspicion.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 27, 2019, 10:11:30 pm
content: Also took the opportunity to replace another cap as I had easy access and surplus 1000μF 25v ones from earlier. It looked the same as the others I replaced so I thought it made sense.

author: StillTrying
author_rank: Super Contributor
timestamp: November 27, 2019, 10:47:56 pm
content: It's always worth having a look for dry joints while your there, sometimes they're almost impossible to see, but the component leg moves a bit.If those boxes are identical, after some checking you might be able to swap them to give some idea where the problem with CH2 is.

author: Noidzoid
author_rank: Regular Contributor
timestamp: November 27, 2019, 11:51:06 pm
content: Quote from: StillTrying on November 27, 2019, 10:47:56 pmOK. Will do. ThanksQuote from: StillTrying on November 27, 2019, 10:47:56 pmSorry, I didn't make myself clear :-(The two largest metal boxes in the above picture (each one of which are soldered together) with the amplitude knobs attached are what I did swap around. Before which I unsoldered these boxes and had a look inside for anything obvious, soldered the boards back in and the boxes back together (my inexperienced eye saw nothing).After putting/soldering everything back together I fired it up again and although the amplitude boxes had swapped places, there was no change in behaviour. My conclusion is that the problem is beyond these boxes.

author: StillTrying
author_rank: Super Contributor
timestamp: November 28, 2019, 08:56:39 am
content: "Sorry, I didn't make myself clear :-("You probably did,but it's hard for me to follow because I don't know the overall physical layout of the scope, and the pdf is low quality.If you're powering some parts up while disconnected, check they have a ground connection, it looks to me in some places there's no 0V on the connectors, and they're just relying on the metalwork for the 0V."everything is the same, so at least that is a large number of the internals out no longer under suspicion."Yep, I think the CH2 problem must be around the "Intermediate Amplifier" then, somewhere, maybe not the intermediate amplifier itself, maybe the 'Chopper Generator' and 'Ch. select' is preventing CH2's signal appearing at the input to the delay line. Good luck.