- crappy laptop company - 2 Updates
- Another old-timer tube/valve question - 4 Updates
- humming CFL - 1 Update
| bitrex <user@example.net>: Jun 05 11:35AM -0400 I had to hound Lenovo for months to get a warranty service on my failed less than 1 year old laptop from them, because there was never a serial number installed on the enclosure anywhere when it was manufactured, and the BIOS was inaccessible due to it being a internal PSU failure where the PC wouldn't even power on. Eventually after harassing them for a long time, being denied service by their local brick-and-mortar service center who treated me like a criminal, filing a dispute with my credit card company, etc. I managed to get someone's attention who didn't completely treat me like a criminal just for wanting the contractual repair I'm obligated to on their failed product. so it's finally on its way back and here's part of what they wrote: "The system board was replaced along with the base cover. We are not able to provide a serial number sticker, but my technician wrote the serial number: (redacted) on the base cover." Lol they can't even print up a real replacement sticker they used marker or something. Also: "During his diagnosis of your machine, he says it looks like you may have tried to install Linux or some other non-Windows operating system. Installing an operating system other than Windows10 (Lenovo Preload) is not supported." Yeah, that's why the PSU board fucking failed, Linux made it happen. be the last machine I buy from this company just avoid these shit heads. |
| bitrex <user@example.net>: Jun 05 11:37AM -0400 On 6/5/19 11:35 AM, bitrex wrote: > not supported." > Yeah, that's why the PSU board fucking failed, Linux made it happen. > be the last machine I buy from this company just avoid these shit heads. It's too bad ThinkPad used to be a quality product when IBM made them but it's just bargain basement zombie-brand China junk, now. |
| three_jeeps <jjhudak@gmail.com>: Jun 04 10:50AM -0700 On Sunday, June 2, 2019 at 11:57:25 AM UTC-4, Cursitor Doom wrote: > protocols, whether for profit or not, is conditional upon a charge of > GBP10.00 per reproduction. Publication in this manner via non-Usenet > protocols constitutes acceptance of this condition. From the Radiotron Designers Handbook, RCA, 1952: pages 1164-1168 (I could not paste in a number of curves, one of which is Direct Voltage at input of filter versus DC Load in mA.) (This book is in my library but also in .pdf's around the web...) Equivalent circuit of high vacuum rectifier: The high vacuum rectifier can be considered as being an ideal switch in series with a non-linear resistance and a source of potential which is connected by the switch to the load when the polarity is that required by the load (Ref. 7). As the switching gives rise to pulsating currents (and voltages) it is necessary to assume a linear resistance which is equivalent to the non-linear effective resistance of the rectifier during this pulsating or conduction period. The conduction period (1)), and therefore also the magnitude of the current pulse, will depend on the loading and the type of filter connected to the rectified supply. Certain approximations which must be made for the first calculation should be readjusted when the results are known, in order that a second and more accurate calculation can be made. Mercury vapor rectifiers In the case of mercury vapor rectifiers the voltage drop in the valve is a constant value of the order of 10 to 15 volts over a wide range of currents. These rectifiers are generally used with choke input filters to provide good regulation for class B amplifiers. The direct voltage output of such a system is equal to 0.9 times the r.m.s. value of the input voltage minus the valve voltage drop. g. Output voltage = (0.9 Erma - 15) volts. (ii) Rectifier valves and types of service Rectifier valves may be subdivided into the following groups :( 1) High vacuum (a) High impedance (e.g. 5Y3-GT) (b) Medium impedance (e.g. 6X4, 5R4-GY) (c) Low impedance (e.g. 5V4-G, 35Z5-GT) (2) Mercury vapor-(e.g. 82, 83). The choice of a rectifier valve for a particular service must take into account the maximum permissible ratings for peak current, average current, and peak inverse voltage. The design of the following filter will influence these last two factors particularly; the type of filter, either choke or condenser input, will be determined partly by the demands of power supply regulation. In supplies feeding Class A output stages the choice will probably be a condenser input filter, but where Class ABsub1 and ABsub2 output stages are to be supplied, the regulation of the power supply becomes a significant feature and choke input filters with low impedance rectifiers must be used. The following examples represent typical practice. c. radio receivers with Class A power stage :High vacuum full wave (e.g. 6X4, SY3-GT, SU4-G). A.C. radio receivers with Class ABsub1 power stage :- 116S With self bias-high vacuum full wave (e.g. SY3-GT, SU4-G, SR4-GY, SV4-G) With fixed bias-low impedance high vacuum full wave (e.g. SV4-G). A.C./D.C. radio receivers:- Indirectly-heated low impedance high vacuum half-wave types with heaters operating at 0.3 A or O.IS A (e.g. 2SZ6-GT or 3SZS-GT). In England, heaters operating at 100 rnA are widely used. Battery operated radio receivers with non-synchronous vibrators:Indirectly- heated low or medium impedance high vacuum full-wave types (e.g. 6X4). Amplifiers :- As for radio receivers except that mercury vapour types may also be used. In general for radio receiver and small amplifier design high vacuum rectifiers are to be preferred to mercury vapour types because of- (1) long and trouble-free service; (2) the lower transformer voltage which can be used for the same d.c. output voltage when a condenser input filter may be used; (3) self protection against accidental over-load due to the fairly high internal impedance of the rectifier. Use can only be made of this last point when the supply is for use with a Class A output stage, when good regulation is not a major consideration and a high impedance rectifier may be used. With directly-heated rectifiers it is generally found preferable to connect the positive supply lead to one side of the filament rather than to add the further complication of a centre-tap on the filament circuit. Parallel operation of similar types of vacuum rectifiers is possible but it is preferable to connect together the two sections of a single full wave rectifier and to use a second similar valve as the other half-rectifier if full-wave rectification is required. With low impedance rectifiers as used in a.c.jd.c. receivers (e.g. 2SZ6-GT) it is desirable to limit the peak current by some series resistance. When two units are connected in parallel it is also desirable to obtain equal sharing, and in such cases a resistance of SO or 100 ohms should be connected in series with each plate, then the two units are connected in parallel. Mercury vapour rectifiers may only be connected in parallel if a resistance sufficient to give a voltage drop of about 2S volts is connected in series with each plate, in order to secure equal sharing of the load current. |
| Al <iqbalali898@noreply.com>: Jun 04 09:15PM On Tue, 04 Jun 2019 10:50:27 -0700, three_jeeps wrote: > could not paste in a number of curves, one of which is Direct Voltage at > input of filter versus DC Load in mA.) > (This book is in my library but also in .pdf's around the web...) Clear as mud! |
| tabbypurr@gmail.com: Jun 04 02:26PM -0700 On Tuesday, 4 June 2019 22:15:20 UTC+1, Al wrote: > > input of filter versus DC Load in mA.) > > (This book is in my library but also in .pdf's around the web...) > Clear as mud! which bit/concept is not clear? NT |
| Sjouke Burry <burrynulnulfour@ppllaanneett.nnll>: Jun 05 01:47AM +0200 On 04.06.19 19:50, three_jeeps wrote: >> protocols constitutes acceptance of this condition. > From the Radiotron Designers Handbook, RCA, 1952: pages 1164-1168 (I could not paste in a number of curves, one of which is Direct Voltage at input of filter versus DC Load in mA.) > (This book is in my library but also in .pdf's around the web...) Cut Googled...downloaded..... checking. (Thanks) |
| micky <NONONOmisc07@bigfoot.com>: Jun 04 04:27PM -0400 In sci.electronics.repair, on Tue, 4 Jun 2019 11:08:26 -0500, Mark Lloyd >setting it to channel 7 and misadjusting the fine tuning, I could get >channel 22 (cable midband, frequency just below that of ch. 7). >BTW, you could get ch. 6 sound on an FM radio. Wow. Unrelated but you remind me, Our first TV was a Dumont, with magic eye tuning. It had continuous tuning like a radio (both gross? and fine tuning) and the channels 2 to 13 were marked in their approximate location on the dial, 2 where 1 o'clock would be, and 13 where 11 o'clock would be. I think 2, 3, 4, and 5 were grouped together, then a space and 6 and 7, then 8 to 13 in a group. Between 7 and 8 were the FM radio stations, and a swich on the TV would turn off the picture so you could listen to the radio without running the TV. Unfortunately there were no FM stations in New Castle, Pa. or even Pittsburgh in 1953 or 1960, none in Indianapolis from 1960 to 64, none in Chicago afaik from 64 to 70, but by the time I got to NYC in '71, they had FM radio. Unfortunately I didn't still have that television. |
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