sci.electronics.repair@googlegroups.com

Google Groups

Cursitor Doom <curd@notformail.com>: May 12 11:04AM Gentlemen,   I've got this RF sig gen I'm testing at the moment. It was made in 1955 and is all valve (I say "all valve" but there are only two tubes in it and only one of those generates the RF - the other's 400Hz for the modulation). Anyway, it has 8 ranges in total covering 100KHz to 240Mhz. The oscillator tube is a double triode, a 12AT7. One half handles range from 100Khz to 30Mhz and the other takes care of 30 - 240Mhz. Now, it all works great EXCEPT for one range (the 3rd lowest) which has appreciable distortion present on the output. It looks a bit like it's being over- driven on my scope. My question is, does a valve like a 12AT7 require different DC biasing points for every range of frequencies? Obviously the range switch is switching in different combinations of coils and capacitors, but is it likely to be also switching in different cathode- grid DC biasing at the same time?   TIA       -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other 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.

Fox's Mercantile <jdangus@att.net>: May 12 06:44AM -0500 On 5/12/19 6:04 AM, Cursitor Doom wrote: > range switch is switching in different combinations of coils and > capacitors, but is it likely to be also switching in different cathode- > grid DC biasing at the same time?   A make and model would help considerably. But, I'm gonna generalize here, if it's cheap enough to only have two tubes, they certainly didn't waste any money on complications like switchable bias.   -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

"pfjw@aol.com" <peterwieck33@gmail.com>: May 12 04:55AM -0700 Keep in mind that a 2-tube SG is, was and ever will be a hobby device. With that in mind, a little, even a lot of distortion which is still "on frequency" hardly matters to a hobbyist aligning a consumer grade radio.   Peter Wieck Melrose Park, PA

Cursitor Doom <curd@notformail.com>: May 12 01:05PM On Sun, 12 May 2019 11:04:06 +0000, Cursitor Doom wrote:   [...]   Sorry, guys, it's a Taylor 68A/M. I can't find the exact model on line but this one is as close as it gets:   https://www.radiomuseum.org/r/taylor_afrf_signal_generator_68a_2.html   The grid/Cathode bias does change with range selection; I just measured it. There doesn't seem anything obviously amiss with the readings:   Range 8 (lowest frequency) -25V 7: -7V 6: -3.4V 5: -1V 4: -0.3V 3: -1.6V 2: -1.8V 1: -1.0   Anode is +80 to +90VDC vs. Cathode over all ranges.         -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other 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.

John Robertson <spam@flippers.com>: May 12 07:34AM -0700 On 2019/05/12 6:05 a.m., Cursitor Doom wrote:   > Anode is +80 to +90VDC vs. Cathode over all ranges.   If you are troubleshooting this then be aware that plate resistors often fail high and are (after capacitors) the next suspects in repairing old tube/valve equipment. Schematics are a huge help of course to be able to verify meeting manufacturers BOM as older parts colours have usually faded to obscurity....antique radio societies will be an aid in tracking down schematics...   If you can't find a match check out EICO or Heathkit of the same vintage as chances are someone may have copied the schematics to their product.   John :-#)#   -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."

tabbypurr@gmail.com: May 12 08:46AM -0700 On Sunday, 12 May 2019 14:05:35 UTC+1, Cursitor Doom wrote: > 2: -1.8V > 1: -1.0   > Anode is +80 to +90VDC vs. Cathode over all ranges.   If you've eliminated other faults as possible then time to adjust the bias on the iffy range.     NT

Cursitor Doom <curd@notformail.com>: May 12 03:53PM On Sun, 12 May 2019 08:46:42 -0700, tabbypurr wrote:   > If you've eliminated other faults as possible then time to adjust the > bias on the iffy range.   It breaks my heart to do this, but I think it's a junker. On further inspection some screwdriver jockey's fucked around with it and since I only paid a fiver for it, it's time to consign it to recycling.           -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other 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.

Mike Coon <gravity@mjcoon.plus.com>: May 12 05:02PM +0100 In article <qb9fhd$gun$2@dont-email.me>, curd@notformail.com says...   > It breaks my heart to do this, but I think it's a junker. On further > inspection some screwdriver jockey's fucked around with it and since I > only paid a fiver for it, it's time to consign it to recycling.   The computer museum at Bletchley Park has (or had) a valve re-cycling exchange. I bequeathed (or dumped) my father's collection of valves and his (Taylor?) big wooden-cased valve tester to them and they made appropriate gratitude noises...   Mike.

Cursitor Doom <curd@notformail.com>: May 12 04:26PM On Sun, 12 May 2019 17:02:11 +0100, Mike Coon wrote:   > exchange. I bequeathed (or dumped) my father's collection of valves and > his (Taylor?) big wooden-cased valve tester to them and they made > appropriate gratitude noises...   Oh, I save the tubes alright; I'm not that much of a philistine. That valve tester of yours was probably an AVO. I've got a couple of those in my collection.           -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other 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.

Prouvost <Prouvost12345@aol.com>: May 11 07:56PM -0600 I need to know better how the booster water pump pressure switch is tested & adjusted I think, where I ask your advice to help me figure it out. [http://img4.imagetitan.com/img.php?image=19_relay00.jpg]   Is there a way to better test or adjust that booster pump switch?   All I know, so far, is that when I manually press down on the complicated intermeshed switch levers with a stick, the switch sparks green and instantly activates the booster pump which stays running for about 4 minutes which gives the house water pressure for about three or four showers worth of water.   But the switch no longer turns on by itself anymore.   What else can I test or adjust?

Rheilly Phoull <rheilly@bigslong.com>: May 12 10:35AM +0800 On 12/05/2019 9:56 am, Prouvost wrote: > showers worth of water.   > But the switch no longer turns on by itself anymore.   > What else can I test or adjust?   We used to test and set such with a variable air supply (Like the control valve on a spray booth paint gun setup) in your case it would be a good idea to remove the switch and check the usually small orifice that is in the water inlet of the switch, it is a common fault for those to become blocked. While you are on the job it looks like the system could use a coat of paint !!

"pfjw@aol.com" <peterwieck33@gmail.com>: May 12 04:50AM -0700 If reliability is critical, replace it immediately. Then, if you must, troubleshoot the old one and then put it on the shelf as a *temporary* spare.   Peter Wieck Melrose Park, PA

Prouvost <Prouvost12345@aol.com>: May 12 09:07AM -0600 Pondering that which Rheilly Phoull wrote:     > that is in the water inlet of the switch, it is a common fault for those > to become blocked. While you are on the job it looks like the system > could use a coat of paint !!   Thank you for showing how to test the switch instead of just blindly replacing it, where I try to never replace a part that I can't prove is broken.   I only blindly replace things when I don't understand how the system works, which means I can't test it properly due to my ignorance of the system.   I researched how the system works overnight where I wrote up this troubleshooting flow chart that I'd like to ask for review.   I'll likely do the work today but this is what I figured out overnight.   Non-inventory parts & tools needed: (1) Water pressure tester GHT fitting (at least 0 psi to about 75 psi) (2) Pressure gauge (NPT fitting) (at least 0 psi to about 75 psi) (3) Pressure switch (Double-D brand, preset to the correct range)   Normal inventory parts & tools needed: (1) Air compressor & hand-held Shrader gauge (2) 220VAC voltmeter or DMM (3) Wrenches, flat file, pipe dope, screwdrivers, Sharpie, and so forth   Basics of normal operation: (30-50 psi for homes with 20 pound differential) (1) The bladder is pressurized to about 28 psi in most homes (or 38) (2) The pressure switch is set to close 4 pump contacts at 30 psi (or 40) (3) The pressure switch is set to open 4 pump contacts at 50 psi (or 60)   Basics if the pump isn't turning on: (1) The pressure to the pressure switch may be faulty (2) The pressure switch contacts can be pitted or corroded or sticking (3) The water line or the screen on the pressure switch may be clogged   Determine the design cut-in & cut-out pressure range (1) Read pressure written on the tank & on the cap of the pressure switch (2) Measure pressure in the tank at the cut-in & cut-off points (3) Read the pressure gauge at the cut-in & cut-off points   Check bladder pressure (1) Shut off the input/output to/from the pressure tank & drain (2) Read pressure on tank when empty & full (3) Bladder should be 2-4 psi below cut-in pressure (30-2 = 28 psi)   Clean debris clogging the pressure to the pressure switch: (1) Clean the four contact switch points with a flat file. (2) Clean debris from the screen on the bottom of the pressure switch (3) Clean out the water tube connected to the pressure switch   What do the four contacts do (1) Usually the inside two contacts generally obtain input line power (2) Usually the outside two contacts generally output to the pump (3) There are generally two ground screws, one each for the input & output   Safety concerns before removing components (1) Turn off the power (2) Shut off the nearest water valves to and from the pressure tank (3) Drain the pressure tank of water until the pump gauge reads 0 psi   Adjust the pressure in the bladder & pressure switch if necessary (1) Pressurize bladder to 28 psi (2) Center large nut (3/8") adjusts the cut-in/cut-out 20-degree range 1 clockwise rotation tightening the large spring adds 2-3 psi Example values are 35-55 psi, 40-60 psi, 45-65 psi, and so on (3) Side small nut adults the cut-out pressure only (widens the range) 1 clockwise rotation = 2-3 psi Example values are 35-55+2 psi, 40-60+2 psi, 45-65+2 psi, and so on   System overview videos (1) [https://youtu.be/X4TZoFIsE2w] (2) [https://youtu.be/CQayY5FTNKk] (3) [https://youtu.be/Rb8k7xoBNSI] (4) [https://youtu.be/2WGlRaTmvbM] (5) [https://youtu.be/gJxjA5eDOS8]   Pressure tank videos (1) [https://youtu.be/AH4H9mpwhnY] (2) [https://youtu.be/w21qa2bMUh8] (3) [https://youtu.be/9fTzXVIQDBY] (4) [https://youtu.be/IhBifh7nCtg] (5) [https://youtu.be/NzZI7WOnMMQ]   Pressure switch videos (1) [https://youtu.be/Vq-8RCCeh3k] (2) [https://youtu.be/1VNSv7xVzzU] (3) [https://youtu.be/D1QAkfbIclo] (4) [https://youtu.be/DmCoc4e2gyI] (5) [https://youtu.be/8TI98cs85ew]

root <NoEMail@home.org>: May 11 09:41PM Neither Denon nor NVidia has been able to resolve a problem I have. My system consists of a Linux Box running MPlayer through an NVidia GeForce 610 video card. The HDMI output of the card goes to the DVD input to a Denon AVR-3313CI receiver. The output of the Denon goes to a 65" LG 4K oled display. The resulting display on the LG is as if there is a serious interlace mismatch.   If the HDMI signal goes directly to the LG the picture is perfect.   I have tried other NVidia cards, several versions of the 610 and all show the same problem. Other NVidia cards such as the 210 and 710 do not show the interlace problem.   As with any receiver, I would expect the Denon would query the display for its edid capability and forward that information to any source connected to the Denon's input. Apparently not so.   For the time being I have put a 2-way HDMI splitter in the line coming from the computer to the Denon. One output of the splitter goes to the Denon while the other output goes directly to the HDMI1 of the LG display. Simultaneously the HDMI output of the Denon goes to HDMI2 of the LG.   This arrangement works, and nvidia-settings shows the display characteristics are set by the LG, but Denon is mentioned in the nvidia-settings output.   Starting with power off on all three components, I first turn on the LG, then the Denon, then I boot the computer. The computer runs 24/7 thereafter.   Could there be a simple solution for connecting the components together which might correct the problem?

jjhudak4@gmail.com: May 11 11:44AM -0700 > > augur using a big wrench. That's how it was done in 1939 on > > inexpensive tractors.   > Were transistors or semi-conductors also around back then? Incidentally, I know little about science, math and technology, so you know: I'm just curious.   Google is your friend....Google knows all...(more or less, a little fuzzy around the edges sometimes, but mostly in the ballpark..)   Semiconductor transistors? No, not in 1939. 1946, 1947 depending on what you want to call invented? - actual semiconductor effect? patented? demonstrated? Dec 23, 1947 is the most cited date. IIRC there was about 6-10 months from the time the actual device worked in the lab till when it was announced to the world (Dec 1947) Actually the field effect transistor was discovered in 1925. A vacuum tube (valve) diode was invented in 1904, semiconductor version was developed in the early 40's.   Silicon crystals that exhibited the 'diode effect' were used in the 1920,1930 as detectors in the crystal radios. https://en.wikipedia.org/wiki/Transistor#History

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.