sci.electronics.repair@googlegroups.com

Google Groups

Andy Burns <usenet@andyburns.uk>: Feb 09 03:17PM > Wait, did you mean the stick as the gizmo or the player in the car as > the gizmo ? I assumed the stick as the gizmo so take my statement > accordingly. From previous descriptions (here or elsewhere) the gizmo is a 3rd party device, the USB memory stick loaded with MP3s is plugged into the gizmo, gizmo is plugged into the car's cigar lighter and the gizmo acts like an iTrip broadcasting FM which the car's radio receives.   I suppose the gizmo could store the position on the stick rather than internally, but AFAIK there's no standard for this. My car has a built-in SD card reader rather than needing a gizmo, I don't think it ever writes to the SD card.

tabbypurr@gmail.com: Feb 09 12:24PM -0800 On Friday, 9 February 2018 16:31:37 UTC, John-Del wrote:   > > I'm not clear on the details of what you're suggesting, but anything that reduces horiz scan power also reduces EHT, and vertical scan too if that runs on a LOPT derived rail.   > > NT   > I'm assuming he's trying to reduce horizontal overscan as vertical overscan is always adjustable and he knows that. Any modification to horiz width that causes vertical height changes can be adjusted out. By adding capacitance to the Horizontal Output Transistor (I believe you call it Line Output), the horizontal width will be affected. The HV (EHT?) will change a bit but it shouldn't be enough to cause issues.   It's only reasonable to assume he wants to tweak because he's out of adjustment.   But you're not understanding something. If you decrease the voltages out of the LOPTF by eg 10%, ie both scan voltage & EHT, the scan size remains exactly the same. Think about why.     NT

jurb6006@gmail.com: Feb 09 12:41PM -0800 >"Reducing B+ reduces EHT too, which is derived from B+, so picture size doesn't change."   In my experience it does get smaller with less B+. Apparently the pulse to the yoke had a greater effect than the deflectiion sensitivity of the CRT.   Here's an interesting thing maybe. (because this is all academic, I'll get this one any which way once I get the thing on the bench)It was an NAP PTV 310 I think, it was the one with the flyack on the power board on the right and the deflection board on the left, viewed from the rear.   It used a regulation scheme somewhat like IRC a C3 chassis. The H drive comes from the filter choke off the chopper regulator which is locked to the horizontal sync. This means the H output duty cycle increases with increased load on the PS. I guess it was a way to tighten up the H and HV regulation.   So this thing uses about the same circuit but there is a sub regulator for the B+ going only to the flyback. Looking at the circuit I could tell that the regulation was not rock solid, and I mean by design. Well one time I had one that was shorted and since it only drops a few volts the set did not shutdown, or there was something not right in the shutdown circuit. But the B+ nto the flyback was rock solid then. This does NOT feed the yoke, that is a separate transformer and output all together on the other board.   Well when the beam current increased, the raster size shrunk. +This must have had to do with the actual density of the electron beam. There could be no other reason. I saw the effect one other time only and thar was on a high ed Soy direct view moitor, I think a Profeel. It had separate hV and H as well. A few other models had it as well.   But this NAP apparently they had to let the B+ and therefore the HV drop slightly to keep the raster size constant. But so much for that.   This little shit is nothing like that, the only thing the same is the name. It is an elcheapo, model KV1396R and I am surprised it even has video in. That is good because the IF strip is whacked out and since my convertor box is defective and doesn't put out sound on video, only on RF, I have to use a VCR to tune it in. I'll probably fix that IF when I have it apart, but it works for now the way it is. The RF probably doesn't put out stereo so it picks off the mono signal before it becomes stereo in the box. I am NOT fixing the box. I refuse.   >"Don't increase B+ on failing tubes, it increases xray output. "   Don't worry.   1. I am old and I don't care if I glow in the dark. 2. The CRT is nice and strong. 3. Increasing B+ would not do what I want at all.   So I am safe.

jurb6006@gmail.com: Feb 09 12:45PM -0800 >"By adding capacitance to the Horizontal Output Transistor (I believe you call it Line Output), the horizontal width will be affected. The HV (EHT?) will change a bit but it shouldn't be enough to cause issues. "   Adding capacitance across the primary (or any winding) of the flyback will decrease the HV, which I don't care. I watch at night and could turn it down. I only got it set bright so it doesn't shut down after startup. Adding that capacitance also will lengthen retrace time which would make the APPARENT overscan worse. I mean, with the increased retrace time it would SEEM to overscan more.

jurb6006@gmail.com: Feb 09 12:53PM -0800 >"It's only reasonable to assume he wants to tweak because he's out of adjustment. "   No, this is an elcheapo and there is no adjustment for H width at all. There is not even a pincushion circuit. If it was a matter of adjustment there would be no discussion.   >"ut you're not understanding something. If you decrease the voltages out of the LOPTF by eg 10%, ie both scan voltage & EHT, the scan size remains exactly the same. Think about why. "   That is simply not true on this type of unit. I have seen it 100s if times. When the regulator, which is a pass transistor, not switching, goes open the set runs on a ballast resistor that is there to decrease dissipation in the regulator transistor. In those cases the H width is small and the vertical has a distortion somewhat like a foldover at the top because it is not getting enough of a retrace boost. That is what that cap and diode do on the vertical IC. The supply is scan derived so it is also low when the main B+ is low.   I understand your reasoning, but in practice that is not how it is, the picture shrink when the B+ drops. I can prove it, want pics ? (have to borrow a camera, lost it)

jurb6006@gmail.com: Feb 09 01:01PM -0800 >"but anything that reduces horiz scan power also reduces EHT, and vertical scan too if that runs on a LOPT derived rail"   True, but it does not stay linear. The vertical in this vintage of sets is like an amp that simply compares the current output with a ramp waveform. Frequently, the ramp waveform stays the same amplitude because it is further regulated, which then overdrives the vertical because the B+ to it is low. They cut it pretty close to keep the dissipation down. A smaller heat sink is cheaper. And most of these ICs are in a family, like LA 7830, 7831, 7832, 7833 with the highest number having the best max ratings. I would always replace them with the highest rated one in the family since they are otherwise identical and with a quantity price break the better part may actually cost less, but on a manufacturing level it pays to custom choose only as much as you need because on a million units a small saving adds up. Possibly to a bonus for someone.

tabbypurr@gmail.com: Feb 09 02:39PM -0800 > >"ut you're not understanding something. If you decrease the voltages out of the LOPTF by eg 10%, ie both scan voltage & EHT, the scan size remains exactly the same. Think about why. "   > That is simply not true on this type of unit. I have seen it 100s if times. When the regulator, which is a pass transistor, not switching, goes open the set runs on a ballast resistor that is there to decrease dissipation in the regulator transistor. In those cases the H width is small and the vertical has a distortion somewhat like a foldover at the top because it is not getting enough of a retrace boost. That is what that cap and diode do on the vertical IC. The supply is scan derived so it is also low when the main B+ is low.   > I understand your reasoning, but in practice that is not how it is, the picture shrink when the B+ drops. I can prove it, want pics ? (have to borrow a camera, lost it)   There are 2 types of sets. Some will keep all picture geometry as B+ varies, these don't have regulated supplies. Then there are sets that do need regulation because it all goes pear shaped if B+ fluctuates. I didn't tell you which type you had.     NT

Jeroni Paul <JERONI.PAUL@terra.es>: Feb 09 05:30PM -0800 I once slightly reduced the horizontal size inserting a small inductor in series with the yoke.

jurb6006@gmail.com: Feb 09 10:19PM -0800 >"Some will keep all picture geometry as B+ varies,"   Those have pincusion ciruits with a feedback system that responds to the width and adjusts the pincusion output accordingly.   >"Then there are sets that do need regulation because it all goes pear shaped if B+ fluctuates."   Those do not compensate.   >"I didn't tell you which type you had. "   I told you. The pincusion in this one is built into the CRT and there is no active circuitry. You can do this with a little 13". This set has regulation, a pass transistor with a ballast across it. These are usually controlled by a small hybrid module but this one might be newer than that vintage.   There were some early GE sets that had automatic pincusion and no regulation, and while the raster stayed straight, the size would vary directly with the AC line input. In these the H output ws a critical safety component because shutdown dependd on its faiiurre. Sometime in the late 1970s or early 1980s sychg circuits were disapproved and they had to go to an active shutdown circuit. The requirement, law whatever stated in no uncertain terms that the HV protection cannot depend on the failure of a component. Some of the set built right after this mandate used four lead caps across the H output because its failure was the chief cause of excessive HV.

jurb6006@gmail.com: Feb 09 10:25PM -0800 >"I once slightly reduced the horizontal size inserting a small inductor in series with the yoke. "   That method affect the linearity. Sometimes it is acceptable and other times it is not.The only way is with a bucking winding. Sometimes you can find a trace positive winding on the flyback feeding a scan derived source but this is a direct line set, no power transformer. Hot chassis. That means it would cross cold and hot grounds and that is a big nono. Finding the right coil might be a problem as well, but with a tertiary winding on the flyback you can add or subtract turns to get it right where you want it.   Note that this also lengthens retrace time but not as much as adding capacitance across the primary.

Jeff Liebermann <jeffl@cruzio.com>: Feb 09 05:09PM -0800 >> Ummm... right.   >What? If you sprayed it in your ear it would shield you >against noise.   Ummm... It uses a brush or swap applicator (for maximum waste and evaporation) and is not a spray. A Q-tip might be best for swabbing in your ear. Let us know if it reduces the noise level and improves the SNR (signal to noise ratio) in this newsgroup.   >And when were you last hassled by Robert Fred or Ian? See it does >shield you from R,F&I.   Cute, clever, and I like that.       -- 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

"pfjw@aol.com" <pfjw@aol.com>: Feb 09 10:25AM -0800 On Friday, February 9, 2018 at 2:00:26 AM UTC-5, micky wrote: > development of standardized wire gauges rationalized selection of wire > for a particular purpose. -- Wikip   > Did all know this?   A-merican W-ire G-auge   Somewhere between Caliber (which is fractions of an inch) and arbitrary convention. Once upon a time, wire was measured in fractions-of-whatever, much as railway timetables were arbitrary and based on local time. After a large number of crashes, railroads created a convention which is now GMT.   And, US wire manufacturers adopted a similar convention so as to be able to sell products beyond their back yards - somewhere just before the Civil War as I remember - mid 1850s or so.   https://www.rapidtables.com/calc/wire/wire-gauge-chart.html   Peter Wieck Melrose Park, PA

Fox's Mercantile <jdangus@att.net>: Feb 09 01:54PM -0600 > A-merican W-ire G-auge   Micky, if you've paid any attention at all, the AWG numbers follow a logarithmic pattern.   The "gauge" refers to the cross section area of the wire. Moving the "gauges" 3 numbers either doubles or halves the area.   In doing so, it doubles or halves the current carrying capacity of the wire.   #1 can carry twice the current as #4. #12 can carry half the current of #9; And so forth.       -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

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.