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Rheilly Phoull <rheilly@bigslong.com>: Mar 13 01:09PM +0800 > 6. Rain-like water drops don't conduct electricity downward. You can stand under HV lines in the rain, the gaps between drops keep you safe. But this does NOT occur if you fire a water pistol up at it. > 5. Remove the lights now. People in bodies of water are extremely vulnerable to shock.   > NT   Yeah, mains voltages around pools are waiting for the above average idiot that no one can protect.

gregz <zekor@comcast.net>: Mar 13 08:44AM > In any event I'm going to install a GFCI on his pool circuit for him > before the start of swimming season which will be coming up in a couple > of months. Thanks, Lenny   Depends on isolation transformer type too. Some ground secondaries for noise.   Greg

makolber@yahoo.com: Mar 13 07:11AM -0700 I can't see how the motor could fail and become a shock hazard so > > I was more concerned about the lights.   be sure the motor frame and all metal pipes are well grounded.   m

Fox's Mercantile <jdangus@att.net>: Mar 12 12:05PM -0500 There's a reason they put a shielded transformer in there initially.     -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

tabbypurr@gmail.com: Mar 12 10:11AM -0700 On Monday, 12 March 2018 16:30:21 UTC, Jon wrote: > The 4700uF cap sits at 28V which given a measured consumption of 1.4A is fine giving a ripple of the order of a hundred millivolts. And as I said doubling it makes no difference.   Typically there are other smoothing/decoupling caps in there for low current rails.     NT

Jon Elson <jmelson@wustl.edu>: Mar 12 02:02PM -0500 > I have partially repaired an IBM mono monitor whose mains transformer had > failed.   http://minuszerodegrees.net/oa/OA%20-%20IBM%20Monochrome%20Display%20(5151).pdf   > Note I say moves. It does _not_ contract or expand which would indicate > insufficient headroom after the rectifier before the 15v regulator. I am > happy this isn't happening. Most likely it is magnetic radiation from the transformer. osme transformers have steel shields, others have copper shorting straps to reduce the external magnetic field. It REALLY doesn't take a lot of external field to affect the picture. You might be able to help by changing the orientation of the transformer, or getting it farter away from the neck of the CRT. Mu-metal shields might be fashioned to help, but if you bend the mu-metal, you have to re-anneal it.   Jon

whit3rd <whit3rd@gmail.com>: Mar 12 02:01PM -0700 On Monday, March 12, 2018 at 7:11:49 AM UTC-7, Jon wrote: > I have partially repaired an IBM mono monitor whose mains transformer had failed.   > ... the picture now sort of moves around but at a rate of 1-2Hz. Turning up the brightness shows a wavy left/right edge implying a few hundred Hz effect. But the effect is also vertical.   So, the 60 Hz magnetic field leakage from the new transformer is beating against the 62 Hz (or whatever) vertical sweep. Magnetic field from the transformer reaches through the glass into the electron beam path..   A conductive belt around the new transformer (can be made from copper tape, and soldered at the seam) would be a good start. Reorienting the transformer (if possible) might help. If the original transformer was shielded, now you know why...

tabbypurr@gmail.com: Mar 12 03:16PM -0700 On Monday, 12 March 2018 21:01:17 UTC, whit3rd wrote:   > A conductive belt around the new transformer (can be made from copper tape, and soldered > at the seam) would be a good start. Reorienting the transformer (if possible) might help. > If the original transformer was shielded, now you know why...   Rewinding the original might be what's needed.     NT

Phil Allison <pallison49@gmail.com>: Mar 12 05:42PM -0700 Jon wrote: ------------   > I am happy this isn't happening.   > Now I notice the original transformer was a solid metal screened thing with > an extra grounding wire.   ** That tranny has a very low external 60Hz field. Besides the steel box, it may have a copper flux strap around it and use more than usual primary turns.   The rest of your post is pure, wishful thinking.   Maybe the whole 15V supply can be placed at some distance from the monitor, in its own box.         ..... Phil

Phil Allison <pallison49@gmail.com>: Mar 12 06:13PM -0700 Jon wrote:   ----------   > I did try doubling up the 4700uF with another which yes I checked the > capacitance of first.   > Also what are R602 and D605 for ?   ** They de-couple the two electros, so the voltage on C604 does not follow the ripple on C603, allowing it to hold a higher average DC value.   Using your 1.4A load figure for the PSU with a 4700uF smoothing cap - the p-p ripple voltage works out at 1.9 volts.   I = C dv/dt ( where dt = 6.5mS )       ... Phil

Pimpom <Pimpom@invalid.invalid>: Mar 12 09:41PM +0530 > http://minuszerodegrees.net/oa/OA%20-%20IBM%20Monochrome%20Display%20(5151).pdf   > Driven from a genuine PC of the day which drives another such monitor perfectly well the picture now sort of moves around but at a rate of 1-2Hz. Turning up the brightness shows a wavy left/right edge implying a few hundred Hz effect. But the effect is also vertical.   > Note I say moves. It does _not_ contract or expand which would indicate insufficient headroom after the rectifier before the 15v regulator. I am happy this isn't happening.   Did you check to see if the regulator does have sufficient headroom? Maybe the replacement transformer has a lower output voltage or lower current capacity.     > Though generally experienced this baffles me somewhat so I'd appreciate your thoughts.   > Is the problem likely to be common mode noise ?   > Ideally I'd like to keep this transformer and not have to seek out a screened one.   My first suspect after the power transformer would be a filter capacitor that had become dry or leaky.   Considering that signal levels in a monitor are much higher than in sensitive analog systems like audio amplifiers, I doubt that the symptoms are caused by stray fields from an unshielded transformer.

Jon <jms019@gmail.com>: Mar 13 04:30AM -0700 We're 50Hz here as is the IBM MDA frame rate so beating is likely.

makolber@yahoo.com: Mar 13 07:07AM -0700 > A conductive belt around the new transformer (can be made from copper tape, and soldered > at the seam) would be a good start. Reorienting the transformer (if possible) might help. > If the original transformer was shielded, now you know why...     +1 you may have a magnetic field problem, not a circuit problem. Try moving and re -orienting the power xformer relative to the CRT. Often you can find a null point. Otherwise you need mu metal shield or copper strap bucking turn.   m

gregz <zekor@comcast.net>: Mar 13 03:53AM Been playing with this scope for some time. Original problem, blowing 10 ohm 2 watt surge resistors in supply. Replaced a couple caps so far, not sure if they had problems. I can bring up on variac and run, no problems. 200 ma. Draw on each of 3 resistors. I still burn resistors on full power up. Not sure if replacement resistors are suitable. Thinking now of upping power from 2 watt types.   Greg

Phil Allison <pallison49@gmail.com>: Mar 13 12:55AM -0700 GS wrote:   -------- > 200 ma. Draw on each of 3 resistors. I still burn resistors on full power > up. Not sure if replacement resistors are suitable. Thinking now of upping > power from 2 watt types.   ** Surge tolerant resistors rely on thermal inertia of the resistance material - so there is not much change in conductor temp during a short current surge.   Wire wound types are the obvious choice, though solid composition may do as well if you can find any.   If you have been blowing thick film resistors then try the same rating in WW.       .... Phil

gregz <zekor@comcast.net>: Mar 13 08:22AM > as well if you can find any.   > If you have been blowing thick film resistors then try the same rating in WW.   > .... Phil   Thanks. These things make a pop and a little hole.   Greg

Bo-Lennart <bo-lennart.karlsson@telia.com>: Mar 13 12:36AM -0700 Den onsdag 7 mars 2018 kl. 18:25:00 UTC+1 skrev Bo-Lennart:

Bo-Lennart <bo-lennart.karlsson@telia.com>: Mar 13 01:07AM -0700 Den torsdag 8 mars 2018 kl. 06:35:58 UTC+1 skrev Phil Allison: > However, I would clean and inspect the board first; a loose screw, tiny solder blob or metal fragment would do the same thing if lodged in a bad place.   > If you power the -14V from a bench supply, localised heating or a bit of smoke might direct your attention to the right area.   > .... Phil   Hi Phil--- Thanks for Your reply. Some nice guy send me schematics of the power supply board (B16) and board B15. Was that You??? I checked the Board B15 and found 3 shorted tantal-capacitors, C551, 548, 550. Changed these capacitors solved the problem. But there are some more problem with the instrument. In the 3 lowest range 300, 100, 30 micro Volt, the pointer of the movement is not stable. So I will continue foult-finding. The final problem seems to be in the board B11. This board includes both divider and amplifier. With combinations of these divider and amplifier gives the 15 ranges of +50dB to -90dB. OK, thanks once again for Your reply. I will continue the foult-finding. Best regards from SWEDEN Bo-Lennart Karlsson

Phil Allison <pallison49@gmail.com>: Mar 12 05:15PM -0700 pf...@aol.com wrote:   -------------------- > https://www.wd40.com/files/pdf/msds-wd482671453.pdf   > The above is the MSDS for WD40. And, yes, it is mostly > ultra-refined kerosene.   ** So no longer Kerosene at all, a myth WD-40 strongly deny.     > What it is not is Stoddard Solvent, although it has been accused > of being that in the past.   ** If you consider WD-40 to be a 5:1 mix of a Naptha like solvent or White Spirit and light mineral oil - you are very close.   Unlike most of its similar competitors, WD-40 is sold to the *public* at corner stores. So it suffers from being too commonplace.       .... Phil

Jeff Layman <jmlayman@invalid.invalid>: Mar 12 08:35PM On 11/03/18 09:31, Pimpom wrote:   > Unfortunately, yes, especially if you use the term "identical > model numbers" loosely, in which case there are often numerous > variants of the same basic model even in the same country.   Seems to me that Panasonic have muddied the waters even more. The seller of that service manual states on his Ebay page:   "This manual covers all worldwide models!   DMR-HWT130EB DMR-HWT230EB   Pages total: 102"   The manual I downloaded from Elektrotanya has only 60 pages, Both have the same Order No. on the top right of the cover page (the cover pages appear identical)! Strange...   > choose from, not only different models but also from the numerous > sub-variants of each model with slightly different suffixes. One > Samsung model alone had about twenty variants!!   I wonder if this sort of thing really makes business sense. Do they need that many variants?   --   Jeff

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