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mjb@signal11.invalid (Mike): May 18 08:05PM +0100 In article <168027cfc3d16763$1$2112880$6edd246a@news.thundernews.com>, >Turns out these use the problematic Astec power supplies identical to >the ones used in the Osborne 01. There is a 0.1uF 250V polymer cap that >tends to blow.   Is it a RIFA Yellow/clear/foil looking thing, wired across Live/Neutral as part of the incoming filtration?   If so, these infest other stuff, like ICL One Per Desk PSUs, Apple II+ PSUs, SYMBFile 5.25" external harddrive enclosures etc. and they fail with a crackle, hiss, bang and smoke. In each case, removing the charred remains stops the smoke and allows the device to work just fine. Replacing them with appropriate modern caps is possible too, but not essential to operation.   https://eevblog.com/forum/chat/old-rifa-capacitors-and-a-disaster-story/   >The Westwind, on the other hand, will not recognize the hard disk. >However the built-in ramdisk does work.   Did the power cut out suddenly when the capacitor went (blown fuse?), or did you power off in a panic? Could unexpected loss of power have upset an "old" hard drive (no time to head park?)     -- --------------------------------------+------------------------------------ Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk

John Crane <john_crane_59@yahoo.com>: May 18 03:27PM -0500 On 5/18/21 2:05 PM, Mike wrote: >> tends to blow.   > Is it a RIFA Yellow/clear/foil looking thing, wired across Live/Neutral > as part of the incoming filtration?   Exactly! It is a RIFA.     > Did the power cut out suddenly when the capacitor went (blown fuse?), > or did you power off in a panic? Could unexpected loss of power have > upset an "old" hard drive (no time to head park?)   That's an excellent point. As soon as I saw the smoke, I hit the power switch. I may have just lost the data and need to reformat. Of course, I don't see any utilities to do that. So more exploration is needed.   -John

Rayner Lucas <usenet202101@magic-cookie.co.ukNOSPAMPLEASE>: May 18 11:34PM +0100 In article <168043217a113e0f$1$2262039$72dd386b@news.thundernews.com>, john_crane_59@yahoo.com says...   > > Is it a RIFA Yellow/clear/foil looking thing, wired across Live/Neutral > > as part of the incoming filtration?   > Exactly! It is a RIFA.   RIFA filter caps are evil little devices. They don't just tend to blow, they *will* blow, with a thick plume of absolutely foul clinging smoke. They can turn up in just about any mains-powered equipment from the 80s or 90s, from kitchen appliances to computers to high-end test gear. Any vintage equipment that plugs into the wall should be considered suspect until you've checked its power supply to make absolutely certain of the absence of the damned things.   They should be replaced with equivalent safety capacitors with the same X or Y rating, never with a normal capacitor. The equipment will also generally work without them, though without the associated protection against generating or receiving EMI.   I once dug *eight* RIFA caps out of the power supply in a Tektronix VM700T test set, only for the back end of the Schaffner branded power inlet to explode instead. It turns out that Schaffner filtered power inlets *also* contain RIFA capacitors, concealed inside a metal casing and some sort of potting material for an especially unwelcome surprise.   I've also seen a near-identical type of cap under the WIMA brand. These seem much rarer but are just as treacherous.   I expect Mike's right about the drive, I'm only posting because I've developed a very specific grudge against these things.   R

mjb@signal11.invalid (Mike): May 19 02:21PM +0100 In article <MPG.3b0e514ef8134b798968f@news.eternal-september.org>,   >with a thick plume of absolutely foul clinging smoke.   I must have got the alternate-flavour ones, somewhere between burnt toast and toffee. Although 100% unwanted when coming out of a piece of electronic equipment, it's not *that* bad. :)   If the hard drive is an old shoe-box style one (5.25", full height) that uses stepper motors to trundle the head out over the disk and back, then they don't tend to like having the head dropped on the active disk -- any sign of diagnostic LEDs on the drive, as these can start giving blink-codes to say "Didn't spin up, there's a head holding me back!" etc.   -- --------------------------------------+------------------------------------ Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk

Ralph Mowery <rmowery42@charter.net>: May 18 01:09PM -0400 In article <s80omu$95r$1@dont-email.me>, jayson1@stiger.com says... > harmonic emission requirements for spectral purity for HF radio > transceivers in the US? I *think* its either -30 or -40db below, but > it's been years since I've used these transceivers. Thanks.   Look in the FCC part 97 rules. Such as here:   http://www.arrl.org/files/file/Regulatory/March%208,%202018.pdf         (d) For transmitters installed after January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission. For transmitters installed on or before January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must not exceed 50 mW and must be at least 40 dB below the mean power of the fundamental emission. For a transmitter of mean power less than 5 W installed on or before January 1, 2003, the attenuation must be at least 30 dB. A transmitter built before April 15, 1977, or first marketed before January 1, 1978, is exempt from this requirement. (e) The mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency between 30-225 MHz must be at least 60 dB below the mean power of the fundamental. For a transmitter having a mean power of 25 W or less, the mean power of any spurious emission supplied to the antenna transmission line must not exceed 25 µW and must be at least 40 dB below the mean power of the fundamental emission, but need not be reduced below the power of 10 µW. A transmitt

Phil Allison <pallison49@gmail.com>: May 18 07:24PM -0700 Jason wrote: ============= Phil Allison wrote:   > for RG-8 (this is RG-58 I'm using now). It's not tight around the RG-58 > of course, but output stays well within the analyzer limit. However, > harmonics vary depending on where I move the loop.   ** You using a proper 50 ohm dummy load or your antenna ?   Cos that result sounds like you have standing waves on the co-ax at harmonic frequencies.     ...... Phil

T i m <news@spaced.me.uk>: May 18 07:16PM +0100 >>they seem to be a good 2mm apart.   >>https://ibb.co/YQg7Lp4   >The wires without magnet wire enamel look pretty close to me.   I think it may be my bad picture, IF we are talking about either of the pairs of wires as they pass in and out of the ring choke?   >You should be concerned that wires exiting core in different >directions are not visibly or physically separated.   Ah, right, then yes, there is a good 2mm between them.   >Force >these apart with a flat screw driver and insert biz card >thick paper stock.   A stack of 5 biz cars would fall out. ;-)   Can I just confirm something please? The output choke seems to be bi-wound, two wires wound side-by-side so in parallel, both going to the same pad at each end so carrying the output current between them?   So, it wouldn't matter if the 'pairs' of wires touched as such, as long as the input and output wires didn't as they will be at a different potential / phase?   >>Measurable just with my DMM? (if so, I can't measure anything).   >You're looking for discoloration, crumbling of core where magnet >wires are forced against core edges due to winding force.   Check.   >Discoloration is sign of point-contact heating.   Well I think the output choke windings have been running hot as the enamel looks darkened compared to those bits that were likely cooler as they were in the air and had heatsinks in the form of the soldered connections to the board but I can see no obvious signs of failure of the enamel. >>it?)) and if so, not that I can easily see?   >If you don't hear grinding noise or see shifting, when manipulated, >then there's probably no issue.   There doesn't seem to be?   <snip>   >>The ones near C18? (just for reference, C16 is 100uF, 25V and C17 is >>4.7uF, 50V). I have one of those automatic component testers. Would an >>'ok' from one of those be ok?   Ok, I just pulled these had found:   The 100uF, 25V: VLoss= 1.8% Capacity= 90uF ESR= initially 2.1 ohm then dropped to .69 when repeating the test.   The 4.7uF, 50V: VLoss= 3.0% Capacity 4755nF ESR= 5.5 Ohm and stayed around that after several repeats of the test.   So, is that our 'bad' cap? <snip>     >>Sorry, you have lost me on that one. ;-(   >Main transformer primary inductance of a forward converter >running off mains will be more than 400uH - typically 2mH.   Ok, I'll try that now ('strike whilst the iron is hot'). ;-)   https://ibb.co/N33cKSf   >Lower values suggest shorting of windings or terminal >connections/traces.   Understood.   What I think is the primary (marked in red) was: .4 ohms, 17.4mH.   Another winding on the primary side (marked yellow and going to the small caps etc) showed: .3 ohms, .08mH   FWIW, the output seems to be made of 3 windings in parallel (marked in green and tested wired that way) measured: .02 ohm, .25mH.   Does any of that help?   Cheers, T i m

legg <legg@nospam.magma.ca>: May 18 04:03PM -0400 >So, it wouldn't matter if the 'pairs' of wires touched as such, as >long as the input and output wires didn't as they will be at a >different potential / phase?   They're shorted on the printed wiring, so just simple 2wires in parallel.   On closer examination of choke, I see it's been impregnated, so there's little likelihood of fault due to enamel failure or vibration.     >>If you don't hear grinding noise or see shifting, when manipulated, >>then there's probably no issue.   >There doesn't seem to be?   Anything serious would have showed up measuring Lp.   <snip> >VLoss= 1.8% >Capacity= 90uF >ESR= initially 2.1 ohm then dropped to .69 when repeating the test.   These are often part of feedback network for simplest integrated switcher ICs. Probably not the culprit, but low side of tolerance on an electrolytic is indication of end-of-life. Changing esr can indicated corroded/intermitent inner contact.   >Capacity 4755nF >ESR= 5.5 Ohm and stayed around that after several repeats of the test.   >So, is that our 'bad' cap? <snip> Small 4u7 can have esr in the mid-ohms range. Probably not an issue on housekeeping supply, but parts with <1R esr will allow start up always in cold weather. Check rectifier feeding it for typical forward voltage. If open or shorted, the unit would only run intermittently (short would affect Lp measurement, but only if in-circuit)     >Understood.   >What I think is the primary (marked in red) was: >.4 ohms, 17.4mH.   That's ok as long as measuring units are correct (common mistake). Fairly high value for this power level and topology, but only low side limit is important.   >FWIW, the output seems to be made of 3 windings in parallel (marked in >green and tested wired that way) measured: >.02 ohm, .25mH.   No surprises.   Integrated switchers can be finicky when it comes to self-generated noise. This makes snubbers and clamps pretty important. As a last resort, check primary parts wired across main primary winding and secondary side RC before replacing the big integrated switch.   RL

T i m <news@spaced.me.uk>: May 18 11:17PM +0100 On Tue, 18 May 2021 16:03:31 -0400, legg <legg@nospam.magma.ca> wrote:   <snip>   >They're shorted on the printed wiring, so just simple 2wires in >parallel.   Ok, so just to increase the current carrying capacity or something more subtle? I'm more of a DC / LV / serial datastream sorta guy and know 'frequencies' can do weird stuff sometimes (skin effect etc). ;-)   >On closer examination of choke, I see it's been impregnated, so >there's little likelihood of fault due to enamel failure or >vibration.   Good news, thanks.   <snip>     >These are often part of feedback network for simplest integrated >switcher ICs. Probably not the culprit, but low side of tolerance >on an electrolytic is indication of end-of-life.   Noted.   >Changing esr can >indicated corroded/intermitent inner contact.   Ok, and cheap / easy enough to replace so ... >Small 4u7 can have esr in the mid-ohms range. Probably not an issue >on housekeeping supply, but parts with <1R esr will allow start up >always in cold weather.   Ok.   >forward voltage. If open or shorted, the unit would only run >intermittently (short would affect Lp measurement, but only if >in-circuit)   D7 checks out as a std rectifier on my DMM (ohms Diode test).   >>What I think is the primary (marked in red) was: >>.4 ohms, 17.4mH.   >That's ok as long as measuring units are correct (common mistake).   My tester actually displays the values as quoted so I'm happy there. ;-)   >Fairly high value for this power level and topology, but only >low side limit is important.   Ok. >>green and tested wired that way) measured: >>.02 ohm, .25mH.   >No surprises.   Good news. The txfmr also 'looks' ok FWIW, no burn marks etc.   >Integrated switchers can be finicky when it comes to self-generated >noise.   So that's the 5 pin TOxxx case device?   >This makes snubbers and clamps pretty important.   Do you mean the small electrolytic's, diode and other caps (is that what they are / doing)?   >As a last >resort, check primary parts wired across main primary winding and >secondary side RC before replacing the big integrated switch.   So are we still on for replacing the opto device RL? I don't think my tester can do that, other than the opto side as a diode possibly and if it wasn't so cheap and already fairly old, I'd set up a test for it myself on some breadboard. ;-)   Just to give me a better visualisation on all this, could you point me to a schematic of something similar perchance please?   Cheers, T i m

legg <legg@nospam.magma.ca>: May 18 09:58PM -0400 >On Tue, 18 May 2021 16:03:31 -0400, legg <legg@nospam.magma.ca> wrote:   ><snip> <snip> >tester can do that, other than the opto side as a diode possibly and >if it wasn't so cheap and already fairly old, I'd set up a test for it >myself on some breadboard. ;-)   Optos get leaky, light seals break. - in most feedback loops that means it's turning the circuit off without assistance from the TL431.     >Just to give me a better visualisation on all this, could you point me >to a schematic of something similar perchance please?   >Cheers, T i m   https://www.power.com/design-support/application-notes/an-30-topswitch-gx-forward-design-methodology   You'd probably get better app notes chasing down the actual part number in the unit.   RL

bitrex <user@example.net>: May 18 03:28PM -0400 Any guitarists?   I'm wiring a 3 humbucker "super Strat" like this:   <https://res.cloudinary.com/phostenix/image/upload/GuitarWiring/StratHHHHotRailsSeries.jpg>   Two Seymour Duncan mini-humbuckers in the neck and middle position as per the diagram, and one Bill & Becky Lawrence regular humbucker in the bridge.   <https://www.wildepickups.com/>   The SD wire codes are black - north start, white - north finish, red - south finish, green - south start   The Bill Lawrence is black - north start, white - south start, red - north finish, green - south finish   (ref: <https://cdn11.bigcommerce.com/s-fxdzp2uudp/product_images/uploaded_images/bill-lawrence-original-xl.jpg>)   I have it wired up as per the diagram except on the BL since the color code is different I have white on that one to ground, red to top left of 5 way switch pin 1, green to top right of five way switch pin 1.   Switch position 1, 3, and 5 give the quiet powerful hum-bucking sound I'm used to. Something seems wrong with positions 2 and 4, though, but as I've only played a Les Paul or SG for 20 years I don't have any idea how splitting coils across humbuckers and running them in series is supposed to sound. I was under the impression that it gave a "virtual humbucker" kind of sound but it sounds thin and nasally more like a Strat single coil. Maybe that's how it is, don't know.   Anyone see an error in how I've wired this up or in the diagram that could be causing the symptoms?

bitrex <user@example.net>: May 18 07:37PM -0400 On 5/18/2021 3:28 PM, bitrex wrote: > Strat single coil. Maybe that's how it is, don't know.   > Anyone see an error in how I've wired this up or in the diagram that > could be causing the symptoms?   Think I found the problem, black and green look to be reversed on my particular model of mini-buckers. Would be nice if manufacturers could agree on an industry-wide standard with respect to this stuff but that's probably wishful thinking....

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