sci.electronics.repair@googlegroups.com

Google Groups

avagadro7@gmail.com: Jan 06 06:52AM -0800 using http://www.powerstream.com/Wire_Size.htm   is there a functional difference, other factors ie metal purity equal,   between 8-12-14> gauge wire having 10 strands and 25 strands ?   does covering each copper strand with aluminum coating increase conductivity ?   or increase conductivity eliminating corrosion ....

"pfjw@aol.com" <pfjw@aol.com>: Jan 06 07:17AM -0800 >>SNIPPAGE<<   a) Wire conductivity, irrespective of material, is a function of surface area and gauge amongst other factors. So, if 14-gauge wire is then divided into strands, the final product with the most strands will have the most surface area, and so by some factor greater conductivity.   b) Using material conductivity hierarchy, the most conductive material wants to be on the surface. Aluminum is a much poorer conductor than copper. All other things being equal, aluminum coated copper will be a poorer conductor than copper-coated aluminum (or steel: c.f. CopperWeld).   c) Corrosion is a factor, but not much of one. Alumina (AKA Aluminum Oxide) is an excellent insulator, as well as being quite inert. As aluminum wire acquires an oxide coating very nearly immediately upon exposure to air, that will reduce conductivity on the immediate surface of the wire. But as that coating is only a very few nanometers thick, the effect is near-zero overall. Copper oxides and sulfates as well as various other 'salts' are variously conductive, but also can be rectifiers, so there will be some effect on overall conductivity in the presence of these materials. BUT, copper is not a very active metal, so oxidation under normal atmospheric and environmental conditions is low and slow. Similar to Aluminum, but for different reasons. d) Electrolysis is always a factor when dissimilar metals are forced into a conductive connection in the presence of oxygen or other oxidizers. For an interesting experiment, take an ordinary 16D nail, wrap a bit of copper wire around it, and place it in a glass of ordinary tap water. In an adjacent glass place a similar nail, no copper. Then a bit of copper, no nail. Do the same with an aluminum wire bonded to a copper wire (mere wrapping may not insure sufficient connectivity for electrolysis to take place. Copper clad materials generally do not suffer as there is very limited surface area exposed.   Enjoy!   Peter Wieck Melrose Park, PA

Jean-Pierre Coulon <coulon@cacas.pam.obs-nice.fr>: Jan 06 02:38PM +0100 Finally I succeded after removing the 3 large boards and unscrewing the 6 screws at the bottom of the cavity. Aftewards there are screws at the borrom of the analyzer and you can pull the mother board which has right-angle soldered BNCs.   Bye, -- Jean-Pierre Coulon

Jon Elson <elson@pico-systems.com>: Jan 06 12:42AM -0600 We have a Kenmore 110.28082700 washing machine that I've done a lot of work on over the years. These seem to be famous for getting an "LF" long-fill error. Well, we started getting that again, and after a good deal of fooling around and false starts, the problem came down to valves operating at the wrong time. I STILL have no idea why, but I know what it isn't.   There's a pressure sensor used to detect water level. I took it off the board and tested it, and it appears to work as desired. it has a part number that doesn't match anything on Digi-Key, but it is clearly an NXM sensor similar to a bunch of models Digi-Key does carry, and that was enough to be able to power it and test it.   The design of the water valves is this: There is a hot and a cold inlet valve, and a thermistor. Then, this goes to a manifold with 4 valves. It can dispense directly into the basket, and this works fine at a fast flow. Or, it can dispense into the detergent cup, the softener cup or the bleach cup, to send those solutions into the wash. These run very slow, so as not to overflow the cups.   So, what we see is the basket fills for a while with the direct valve, then that shuts off, and it fills the rest of the required water level from the detergent cup, ONLY. This takes so long (it can take up to 45 MINUTES!!) that the machine stops with the LF error several times before it gets to the washing stage. I can see why it turns on the detergent valve, to add the detergent to the load, but I do NOT see why it shuts off the direct fill valve. After trying many tests, replacing the relay for the direct fill valve, etc. and not fixing it, I finally kludged it. I tied a wire from the detergent valve to the direct valve so that when EITHER relay is turned on, it will open both valves. I can't really see a downside to this hack, and it seems to have solved the problem.   The controller board is $264, and has a VFD for the basket spin/agitate motor, the pressure sensor and a whole raft of relays to control the two pumps, 6 valves, heater and door lock. One other relay failed before, and I replaced that with an SSR. So, I really don't want to replace the thing if I don't have to. The only things I can come up with that could cause this behavior are:   1. defect in the microprocessor (seems unlikely) 2. defect in the relay driver chip (I'm guesing it is some house-labeled Allegro chip) that causes it to shut down the relay output after several minutes. 3. intermittent connection in the wiring to the valve The relay has been replaced, and I now have accumulated 3 sets of the valve manifold assembly trying to keep this machine working. So, it isn't a defective solenoid coil or valve. (They all fail the same way.)   Anyway, the machine seems to be back working at a reasonable speed per load without having to keep checking if it stopped.   Any comments?   Jon

"pfjw@aol.com" <pfjw@aol.com>: Jan 06 04:28AM -0800 On Friday, January 6, 2017 at 1:43:02 AM UTC-5, Jon Elson wrote:   >>Snippage<<   > Any comments?   > Jon   A couple.   a) Some sort of restriction in the flow through the detergent cup. We have an LG that splits the flow when filling, running water through the detergent cup *and* the drum when filling. If yours is different, make sure that the flow through the detergent cup from the pump is unrestricted. b) The valve that switches from cup to drum may be sticking such that it does not permit full flow when in the detergent position.   I try to look for simple mechanical issues before looking to software/electronic problems. As you state you have additional valve assemblies, I would suggest you tear one down via destructive demolition and see how it 'goes'. That may give you a clue as to what is going on now.   Good luck with it!   Peter Wieck Melrose Park, PA

"pfjw@aol.com" <pfjw@aol.com>: Jan 06 04:30AM -0800 Whoops! One more thing. Set the level control higher on the initial fill, if that is in any way adjustable. Then there would be less time required for the remaining fill. If this is a timing fault, that might cure it.   Peter Wieck Melrose Park, PA

Jeroni Paul <JERONI.PAUL@terra.es>: Jan 05 05:05PM -0800 Thanks for all the replies. The storage room is quite stable in humidity around 50% relative humidity. Here is the drum and paper after another stop-in-the-middle print test:   http://imgur.com/97Fc62n   As you can see there is some background toner, that could be due to a failed wiper blade, still the black text does not seem to transfer to the paper. The text "HP Explorer" and "Information" has already passed over the paper and most toner remains in the drum, so the text in the paper is almost indistinguishable.   There may be two different problems, a failed wiper blade and something else and I'm not sure if they are related. I would not mind some gray background as long as the text was readable, so I am more interested in fixing the second problem than the first.   The printer and cartridge contacts are clean and all three posts in the printer have a working spring pushing them against the cartridge contacts.

Jeroni Paul <JERONI.PAUL@terra.es>: Jan 05 05:14PM -0800 Here is the drum and the paper:   http://imgur.com/a/5O5xi

Bob Engelhardt <BobEngelhardt@comcast.net>: Jan 05 11:58AM -0500 On 1/5/2017 11:38 AM, amdx wrote: ... > If you change only the transistor to (0.6V) you will probably never > develop enough voltage on the transistor to start it conducting.   > Mikek   Ah! That makes perfect sense. Thank you.

Bob Engelhardt <BobEngelhardt@comcast.net>: Jan 05 12:07PM -0500 > If the transistor you need is a DTG600, NTE179 is a substitute and is germanium. I have one in stock if you want it. This is a TO-3 style transistor right?   > The posted schematic was a bit fuzy, so if I have the part number wrong, please post the correct one.     The transistor is a DLG600. I remember seeing that the NTE179 was a substitute, but the NTE179's that I found were just about as expensive. Especially compared to the $0.48 for the TIP32C.   Thanks just the same.   Bob

Bob Engelhardt <BobEngelhardt@comcast.net>: Jan 05 12:46PM -0500 On 1/5/2017 12:07 PM, Bob Engelhardt wrote: > The transistor is a DLG600. ...   Oops - D _T_ G, as you said

Jeff Liebermann <jeffl@cruzio.com>: Jan 05 10:04AM -0800 On Thu, 05 Jan 2017 12:07:25 -0500, Bob Engelhardt   >The transistor is a DLG600. I remember seeing that the NTE179 was a >substitute, but the NTE179's that I found were just about as expensive. > Especially compared to the $0.48 for the TIP32C.   Try eBay for an NTE179: <http://www.ebay.com/sch/i.html?_nkw=nte179> Yep, expensive.   DLG600 is rated at 90V/25A, while the TIP32C at 100V/3A. That would seem to be a rather poor choice for a substitute.   If you substitute silicon, you'll need to change some component values to deal with the Vbe change from 0.3v to 0.6v. Probably doubling the resistance of the 8.2 ohm sense resistor, and changing D7 from germanium to silicon. Hopefully, the current ranges will remain the same. The silicon device will have a better gain-bandwidth product, so a few ferrite beads to keep the power xsistor from oscillating. If you choose to use a different package, you'll need to do some creative mounting and heat sinking. The analog series current limiting transistor will dissipate considerable heat at high loads.   Sounds like too much work. I'll see if can find one in my junk pile. I've been hoarding germanium devices for years for use in repairs.   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

"Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com>: Jan 05 07:39PM "Bob Engelhardt" <BobEngelhardt@comcast.net> wrote in message news:o4m0p20vlf@news3.newsguy.com... > On 1/5/2017 12:07 PM, Bob Engelhardt wrote: >> The transistor is a DLG600. ...   > Oops - D _T_ G, as you said   TBH: I'd strip out the original current limiter circuit and rebuild with one from a more modern linear PSU.   Its usual practice to use a separate small signal transistor who's B/E threshold detects the volt drop across the current sense resistor. Its collector shunts away base current from the pass transistor. If you go that far - a Darlington pass transistor has a number of advantages.   The B/E threshold is different between silicon and germanium, so you need to re calculate the current sense resistors. There's various online archives of test gear schematics - you can probably find a circuit that you can pretty much copy.

"Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com>: Jan 05 07:44PM "Ralph Mowery" <rmowery28146@earthlink.net> wrote in message news:MPG.32d8422c7b566649897e1@news.east.earthlink.net...   > Without looking, I would say the diode is a form of temperature > compensation and the material of the 2 devices should be the same. > That would be true if they are mounted on the same heat sink.   It looks like a very simplistic version of the current limiting circuit. The diode Vf is pretty much a reference voltage generator that the sense resistor volt drop is compared to - the fact that the diode also provides dome degree of temp-comp, is probably incidental.

Bob Engelhardt <BobEngelhardt@comcast.net>: Jan 05 03:56PM -0500 On 1/5/2017 2:39 PM, Benderthe.evilrobot wrote: > TBH: I'd strip out the original current limiter circuit and rebuild with > one from a more modern linear PSU. ...   Too much. I could even live without the limiter, but for a couple of cheap parts, I'll fix it. But not anything more.

Bob Engelhardt <BobEngelhardt@comcast.net>: Jan 05 04:03PM -0500 On 1/5/2017 1:04 PM, Jeff Liebermann wrote: ... > DLG600 is rated at 90V/25A, while the TIP32C at 100V/3A. That would > seem to be a rather poor choice for a substitute.   What you don't know, cause I didn't say, is that the supply is 50v, 1.5A.   > you choose to use a different package, you'll need to do some creative > mounting and heat sinking. The analog series current limiting > transistor will dissipate considerable heat at high loads.   There is no calibration in the circuit - the current limit is picked by rotating a pot until the current is limited where you want it. Hopefully this will be able to account for the different device. There was a poster who did this, so I'm probably OK.   I will mount it, isolated, to the steel frame. And at 1.5A that "should" be enough sinking.   > Sounds like too much work. I'll see if can find one in my junk pile. > I've been hoarding germanium devices for years for use in repairs.   My order is in, but thanks anyhow.   Bob

Bob Engelhardt <BobEngelhardt@comcast.net>: Jan 05 04:05PM -0500 On 1/5/2017 2:44 PM, Benderthe.evilrobot wrote: >...- the fact that the diode also > provides dome degree of temp-comp, is probably incidental.   Yeah - the diode and transistor are very thermally independent.

"Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com>: Jan 05 09:45PM "Bob Engelhardt" <BobEngelhardt@comcast.net> wrote in message news:o4mbt4016j3@news3.newsguy.com... >> one from a more modern linear PSU. ...   > Too much. I could even live without the limiter, but for a couple of > cheap parts, I'll fix it. But not anything more.   I've knocked a complete current limiter together in an evening - basically just a scrap of sheet aluminium and a few components that were laying around.   You could use a Si transistor and fit the matching Si diode, but you'll probably have to recalculate all the sense resistors - which is most of the work.

John Robertson <spam@flippers.com>: Jan 05 02:14PM -0800 On 2017/01/05 8:38 AM, amdx wrote: > If you change only the transistor to (0.6V) you will probably never > develop enough voltage on the transistor to start it conducting.   > Mikek   Mikek, would replacing the germanium diode with a silicon one fix the voltage drop you speak of?   John :-#)#     -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

amdx <nojunk@knology.net>: Jan 05 06:31PM -0600 On 1/5/2017 4:14 PM, John Robertson wrote:   > Mikek, would replacing the germanium diode with a silicon one fix the > voltage drop you speak of?   > John :-#)#   There are twenty regulars here that could give you all the details with the math, I'm not one of them. If it were me, I'd change both diode and transistor to silicon and see how it works. I think it will. Mikek         --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com.