sci.electronics.repair@googlegroups.com

Google Groups

"~misfit~" <shaun.at.pukekohe@gmail.com>: Jun 16 08:46PM +1200 Once upon a time on usenet Mr.E wrote:   > The fan on a 13n2951 is a Matsushita 2806KL-04W-B89.   > 12 Volt - 650 ma with a 42 cfm at 38dba rating.   > Dimensions are 70 x 70 x 15 mm and the third wire is a tach lead.   I've never known a ThinkPad fan to *not* be 5v before. I guess you learn something every day. -- Shaun.   "Humans will have advanced a long, long way when religious belief has a cozy little classification in the DSM*." David Melville (in r.a.s.f1) (*Diagnostic and Statistical Manual of Mental Disorders)

Mr.E <Mr.E@totally.invalid>: Jun 16 06:50AM -0400 On Thu, 16 Jun 2016 20:46:54 +1200, "~misfit~"   >> Dimensions are 70 x 70 x 15 mm and the third wire is a tach lead.   >I've never known a ThinkPad fan to *not* be 5v before. I guess you learn >something every day.   The FRU 13N2590 is a desktop FRU. The thinkpad group was "fishing" for a knowledgeable repair person for Lenovo. -- Mr.E

"Gareth Magennis" <soundserviceleeds@outlook.com>: Jun 16 12:07AM +0100 Aded back to back 4.7V zeners over the back to back 6.2V zener gate protectors of the audio amp, as owner only goes to 60% volume.         You might want to reconsider that. Isn't that restricting the amps headroom?       Gareth.

N_Cook <diverse@tcp.co.uk>: Jun 16 09:57AM +0100 On 16/06/2016 00:07, Gareth Magennis wrote:   > You might want to reconsider that. Isn't that restricting the amps > headroom?   > Gareth.   yes, going the wrong way, so removed. On the air-movement lack of design, instead of drilling small screws through the h/s for the pcb mounting screws, they deep milled off the corners so making it even less likely the air will pass through the restriction of the h/s vanes

jurb6006@gmail.com: Jun 15 07:24PM -0700 >"** So they are cheap and nasty piles of Chinese junk that sell for >like $40 ? "   No, they go for quite a bit more than that, but I bet you are probably close to the actual cost of them. And damnear everything is Chinese junk. Any company publicly traded in the US is pretty much governed by Dodge v Ford.   >"No way are they TRF cos that is impossible. "   Why ? I tellya I seen the cores lower in the adjustable coil/transformers lower in the channels with the lower frequency. Are you saying that is all front end and they still downconvert ?   Maybe they do, leaving little for the IF to do in the way of selectivity and letting the previous stages do it. When you have like an audio type FM tuner, they use superhetrodyne because the customer want to tune from channel to channel at will and the IF provides most of the selectivity. But these are fixed. I believe I have mentioned that the frequency readout on the front panel are burnt in.   Yup, cheap Chinese shit made by Apex. But what ain't ? Everything is junk these days.   >"** A 34.825MHz crystal can produce both 208.95 & 174.125 if >multiplied by 6 and 5. "   This chipset has no such function as far as I can tell. These are very simple units, and cheaply build. There is no chip on the board up front.   What I am going to do next is look at more of these and while I know I will find the cores buried deeper in the coils associated with the lower frequency, I am going to pay special attention to the last one, which would be a coil for the quadrature detector.   If those are buried deeper that indicates TRF. For fixed frequency TRF is not a bad approach. Saves money and there is absolutely no radiation to worry about. So the FCC or whatever you have as its equivalent will not give you any trouble.   Anyway, from the gist of this whole thread I get that the crystal frequency is not necessarily what is printed on it. What if resistors and capacitors were like that ?   I might just have to take a freq counter in there but that is above my pay scale. That may change.   The scope they gave me is like 20 MHz, so I could see 10.7 MHz IF on it. And the chipset datasheets do indicate they are for FM, mobile FM in fact.   It probably doesn't matter, I think the people who own that company are hobbyists, rich kids who want to feel useful. Of course folks like that can be useful to me.

Phil Allison <pallison49@gmail.com>: Jun 15 08:22PM -0700 > Why ? I tellya I seen the cores lower in the adjustable coil/ > transformers lower in the channels with the lower frequency. > Are you saying that is all front end and they still downconvert ?   ** A "TRF" receiver has no local oscillator, mixer or IF amplifier - which your examples clearly do.       > Yup, cheap Chinese shit made by Apex. But what ain't ? > Everything is junk these days.   ** Radio mic systems by the likes of Shure, Sennheiser and AKG are very well made products intended for professional use - all operating on UHF nowadays.   What you have is a Karioke / DJ system.     > >"** A 34.825MHz crystal can produce both 208.95 & 174.125 if multiplied by 6 > > and 5. "   > This chipset has no such function as far as I can tell.   ** Frequency multiplying is done with a tuned filter, often one transistor and a coil that selects a single harmonic from the crystal oscillator's output. The oscillator circuit is designed to be rich in harmonics.   > will find the cores buried deeper in the coils associated with the lower > frequency, I am going to pay special attention to the last one, which > would be a coil for the quadrature detector.   ** The quadrature coil should be next to the IF amplifier, the LA1140 chip.   http://obrazki.elektroda.pl/2812242800_1353270059.jpg     > is not a bad approach. Saves money and there is absolutely no radiation > to worry about. So the FCC or whatever you have as its equivalent will > not give you any trouble.   ** You said there WAS a crystal in each receiver, labelled with the same frequency as one of the mics, so the receiver is a superhet.   FYI:   Radio mics use such low power levels they cannot operate successfully unless a clear frequency exists at the location where they are being used - having that means they interfere with nothing.   A shit awful load of poot is spoken about radio mics *causing* interference.     .... Phil

Michael Black <et472@ncf.ca>: Jun 15 11:44PM -0400

jurb6006@gmail.com: Jun 15 10:09PM -0700 >"** You said there WAS a crystal in each receiver, labelled with the >same frequency as one of the mics, so the receiver is a superhet."   I might find out tomorrow or Friday. For what they pay I work when I damnwell please. I make three times as much at home actually. Actually, it is time for me to get back into that 465B and find a suitable replacement for Q4565. Thing is most of this stuff is stock which means it is really hard to put any pressure on them.   Anyway, so what you're saying is that the crystals are labelled for the assemblers with a number that is offset from the IF frequency, and since this is a standard chip with the quadrature detector that would mean it most likely operates at 10.7 MHz. Do I got that right ? If so, the frequency of the crystal should be off by 10.7 MHz then.   This is kinda just a matter of interest, the only use of it I might get is if I need to change frequencies. If I oculd just change the crystal that would be great but I doubt it. That 1186 or whatever is for the front end. That means that if I decide to change the frequency of one of the channels I have to align it. Ugh. I think it is time to find out what these things sell for. I'm sure it is not forty bucks but if it isn't at least close to $200 I have to think about how much time to put into them.   >"Radio mics use such low power levels they cannot operate >successfully unless a clear frequency exists at the location where >they are being used - having that means they interfere with >nothing.   >A shit awful load of poot is spoken about radio mics *causing* >interference. "   I think, at least with the VHF ones, more other interference fucks them up than the other way around. Security systems with wireless cameras and the like. We had one that knocked out all of the cordless phones in the house, had to get rid of it. That band around 200 MHz is not the place to be anymore.   Of course now they sell UHF wireless mics. That is my next stack to get into actually. But I am thinking of telling them just to sell the VHF ones locally so people can bring them back ad they can pick one up running on a different frequency. Of course that is gong to require a note or whatever on the box denoting that frequency.   Other than that they can throw them in the fucking dumpster. Can't be shipping these things to bumfukt Egypt for a trial to see if they work.

jurb6006@gmail.com: Jun 15 10:33PM -0700 >"I thought you said these could be changed to >another frequency,..."   No, exactly the opposite. Maybe I mistypoed or you misread, but these are absolutely fixed frequency as far as I can tell. The frequency readout in the front has all the segments connected.   I also got a bunch of UHF ones that sync to the receiver by IR. I told them to get me an IR card. Nothing happened so that stack, well there in nothing happening to that either.   If I work for you and come up and say "We need this", it does not mean "Oh gee golly wiz it would really cool if we have this. It means EVERY DAY WE DO NOT HAVE THIS COSTS YOU MONEY. I do not play at work.   If they ever say "How come these units are not fixed" I am right there with "Because I asked for this and that and did not get it". And this has already happened at other places so I am starting to think I work for a bunch of hobbyists, I mean hobbyists in business. Probably got a ton of money and just want to get out of the house.   Personally I would rather work for a place that wants to make money. In fact HAS to make money because that makes me more valuable.

jurb6006@gmail.com: Jun 15 10:47PM -0700 >"How wide is the deviation? "   If you mean the base carrier frequencies they range from about 174 to 210 MHz on these models. I do not now the modulation but I know each frequency ends in a 0.05. Every one of them, like 210.95, 174,15, they all end in a 0.05. That leads me to believe they run maybe 50 KHz deviation ? Europe uses it for FM radio. The US runs 75 KHz. Of course there are sidebands but what are the odds ? And the ones I have seen, the two channels are displaced by about 10 MHz or more.   I am probably going to become much bigger in that company. We got other problems that are dropped in my lap. Three year old unit we can't get any parts for, and there are still sellers on Amazon and eBay selling them. WTF.

Phil Allison <pallison49@gmail.com>: Jun 16 01:48AM -0700 > each frequency ends in a 0.05. Every one of them, like 210.95, > 174,15, they all end in a 0.05. That leads me to believe they run maybe > 50KHz deviation ? Europe uses it for FM radio. The US runs 75 KHz.   ** Europe also uses 75kHz deviation, its the pre-emphasis that differs.   50uS in Europe and most other places, 75uS in the US, Canada and Japan.     > Of course there are sidebands but what are the odds ? And the ones I > have seen, the two channels are displaced by about 10 MHz or more.   ** The channel spacing coincides with US, VHF TV stations.   In a given location, prior to digital broadcasting, every second channel was blank. So you had chs 7,9,11 & 13 on the air OR chs 8,10 & 12. This allowed the class licensed use of several radio mics in each of the black bands.   The deviation on such models was usually 30kHz with 75uS pre-emphasis and some form of audio companding.   The best models from Shure, Nady or Vega had exceptional audio quality.       .... Phil

kaeckman <f6ceedb9c75b52f7fcc0a55cf0cfbf5d_1041@example.com>: Jun 15 10:37PM i have a Robbins & Myers motor 3/4 hp 115/230 volts 3450 rpm 60 cycle wired for 230 and i need it wired for 115 volts how do i do that?       --

Sjouke Burry <burrynulnulfour@ppllaanneett.nnll>: Jun 16 01:10AM +0200 On 16.06.16 0:37, kaeckman wrote: > i have a Robbins & Myers motor 3/4 hp 115/230 volts 3450 rpm 60 cycle wired > for 230 and i need it wired for 115 volts how do i do that?   carefully.

"pfjw@aol.com" <pfjw@aol.com>: Jun 15 05:12PM -0700 On Wednesday, June 15, 2016 at 6:37:05 PM UTC-4, kaeckman wrote: > i have a Robbins & Myers motor 3/4 hp 115/230 volts 3450 rpm 60 cycle wired > for 230 and i need it wired for 115 volts how do i do that?   > --   There should be a diagram inside the connector box or on the nameplate. If not, you will need to go to a motor-winder or similar service to ohm out the windings and determine which are connected for 115V. It is not rocket science, but unless you are quite familiar with motors, a mistake could be spectacular.   Peter Wieck Melrose Park, PA

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.