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"Lee Gleason" <lee.gleason@comcast.net>: Dec 20 04:03PM -0600 I have a crusty old TEK 465 I saved from going into the garbage a few years back. Finally got time to pull it off the shelf and see what's going on with it.   I was told it was completely dead and not repairable when I salvaged it - I thought, I'll be the judge of that. Initially it was stone dead - no trace, no lights, no fan nothing. I found a 1.5 A fuse (F1419) blown, and when replaced, it would blow again immediately. None of the panel lights or the fan would come on, and all the power supply voltages were low.   I found one bad capacitor that was grounding the +15, when it started smoking (some faults are easier to locate than others). Replaced it and then found another cap, C1419, that was shorted that was blowing F1419. Replaced it and now the lights and scale illumination and fan come on.   When I press the beam finder, I get a large dot flash and then nothing. Letting off the beam finder and adjusting the controls for a normal trace, I noticed that the whole screen is sort of illuminated. If I slow the sweep way down, I see that a dim 3/4 inch wide by whole screen tall bar goes across the screen, at about the rate you'd expect on the slow sweep settings - so that looks like the HV and the time base stuff is more or less working.   I'm guessing I have some sort of vertical amplifier problem. Before diving back into the schematics, I thought I'd ask, anyone ever seen this symptom before?   -- Lee K. Gleason N5ZMR Control-G Consultants lee.gleason@comcast.net

Phil Hobbs <hobbs@electrooptical.net>: Dec 20 05:22PM -0500 On 12/20/2014 5:03 PM, Lee Gleason wrote:   > I'm guessing I have some sort of vertical amplifier problem. Before > diving back into the schematics, I thought I'd ask, anyone ever seen > this symptom before?   Re-capping the whole thing would be a good start, I expect. I have a 475 that I'll have to do that to one of these days.     Cheers   Phil Hobbs     -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics   160 North State Road #203 Briarcliff Manor NY 10510   hobbs at electrooptical dot net http://electrooptical.net

amdx <nojunk@knology.net>: Dec 20 04:23PM -0600 On 12/20/2014 4:03 PM, Lee Gleason wrote: > Lee K. Gleason N5ZMR > Control-G Consultants > lee.gleason@comcast.net   There's a good TEK yahoo group that might be helpful.   Mikek

mike <ham789@netzero.net>: Dec 20 02:23PM -0800 On 12/20/2014 2:03 PM, Lee Gleason wrote: > Lee K. Gleason N5ZMR > Control-G Consultants > lee.gleason@comcast.net   I'd go check all the caps. Over the last few years, I've had more and more caps fail in tek stuff. Originally was the teardrop tantalums, but more recently, all types. I don't have a schematic handy, but if you can check the bleeder resistors in the HV supply, I'd do that. There should be HV test point that you can check with a normal multimeter.

"Tom Miller" <tmiller11147@verizon.net>: Dec 20 06:43PM -0500 "Lee Gleason" <lee.gleason@comcast.net> wrote in message news:5495f247$0$13196$882e7ee2@usenet-news.net... > Lee K. Gleason N5ZMR > Control-G Consultants > lee.gleason@comcast.net I would recommend going through the adjustments section of the service manual. That will offer you a chance to find any out-of-spec parts. The Tek manuals are very complete and include a theory of operation section that will answer most questions. Pay attention to the ripple/noise specs on the power supply test points. The +55 volt rail serves as the main reference for the rest of the supplies.   Regards

mike <ham789@netzero.net>: Dec 20 09:06PM -0800 On 12/20/2014 3:43 PM, Tom Miller wrote: > The +55 volt rail serves as the main reference for the rest of the > supplies.   > Regards   That's a good idea, but concentrate on getting the numbers close by fixing busted stuff. I'd recommend against randomly tweaking stuff in an attempt to fix hardware problems. That assumes that the previous owner exercised similar restraint when he tried to fix it.

jurb6006@gmail.com: Dec 21 08:40AM -0800 Are the voltages on the vertical plates close ?

RobertMacy <robert.a.macy@gmail.com>: Dec 21 09:48AM -0700 On Sat, 20 Dec 2014 15:03:27 -0700, Lee Gleason <lee.gleason@comcast.net> wrote:   > Lee K. Gleason N5ZMR > Control-G Consultants > lee.gleason@comcast.net     Did you ask the TEK group?   <TekScopes@yahoogroups.com>   I saw some detailed info go by there, often.

Phil Allison <pallison49@gmail.com>: Dec 20 06:11PM -0800 Mike wrote: Phil Allison wrote: : > > drive belts) are made from soft rubber in the first place ?   > > You ever serviced a tape recorder in your life ?   > No need to be rude!     ** Nothing rude about what I posted.   You clearly have no idea how a capstan tape drive works.   > I said why I thought the pinch roller needed to be resilient; just a > matter of physics and pinch pressure.   ** Makes no sense.   > on an unstated but reasonable assumption: that the pinch roller is wider > than the tape so gets driven by the capstan on its margins and drives the > tape between those margins.     ** Whaaaaattt - so you have never seen a capstan drive tape machine ?   Yet you still decided to argue with me about my clearly written, totally correct post, by snipping and ignoring the bits you completely misunderstood.     > You could, of course, have explained that instead of ranting...     ** The one rating is YOU - pal.   FFS - YOU could have admitted that YOU had no idea how a capstan tape dive worked instead of making guesses and bullshitting.   FYI:   The pinch roller is CRUCIAL to the operation - it traps the tape against the capstan shaft and resists tensions coming from the supply and take up reels. The roller's height is about twice the width of the tape so it contacts the capstan directly and is driven around by it.   The pinch roller is generally mounted on a spring loaded arm, which is held back opening a small gap unless the machine is in play or record mode. When in play or record mode, the spring loaded arm is released and holds the pinch roller firmly against the capstan trapping the tape in between.   The roller must have a flat surface, with a good amount of grip to the capstan shaft when engaged. It must also grip the tape and the shaft it turns on must be exactly parallel with the capstan itself.   A worn or old pinch roller typically has a "glazed" surface that has almost no grip to the capstan or tape - or else it may become barrel shaped. A barrel shaped roller skews the tape up or down the capstan, causing the tape to spill or wind around the roller.   With a cassette deck or VCR, the capstan drive mechanism is hidden from the operator - but with a reel to reel recorder or tape echo it is highly visible cos the tape must be manually threaded through the capstan gate.   As Pete Townshend famously said " .. the simple thing you see are all complicated ... "   Capice ?     ... Phil

Cydrome Leader <presence@MUNGEpanix.com>: Dec 21 07:21AM > ** Got some news for you - pal.   > The exact diameter of an idler wheel is irrelevant.   > Cos all any idler does to transfer the surface speed of one rotating object to another.   I have to admit that your explanations for pinch rollers is dead on. A worn or dry roller would cause slippage though, so rough it up and try again.   As for the OP, Not sure how much I'd trust a 400 year old tach. It may be time for a cardboard disc and a neon light to check for speed problems with the motor. You don't need as many lines as on a turntable either.

Tim Schwartz <tim@bristolnj.com>: Dec 21 08:49AM -0500 > So I next got out the Strobeotac and put it on the motor capstan. The motor is rated for 1850 RPM at 115V, and it's running rock solid at 1795. I tried loading it while watching the speed and it remains steady, so it doesn't appear to be a load problem. Could such a slight motor speed reduction cause a 25 percent reduction in the frequency of my 1KHZ test tone off the tape? It doesn't seem possible, but I don't know.   > The motor has a label that reads that it uses a 3.0UF 330V capacitor. I haven't investigated this yet, but with four wires going into it I figure that the cap must be on the chassis somewhere. I wouldn't think that a cap problem though would cause my RPM's to drop 55RPM would it? Oh and I have no service manual, however I don't think that service manual would do me much good with this problem anyway.   > If anyone has any thoughts on this I'd sure appreciate hearing them. Thanks, Lenny   Hello everybody,   I doubt that his issue is a pinch roller no matter how badly glazed it is as his machine is running SLOW, and it the tape is being pulled ahead by the take-up torque overpowering the capstan/pinch roller, it would be running fast.   Regards, Tim Schwartz Bristol Electronics

Cydrome Leader <presence@MUNGEpanix.com>: Dec 21 07:28AM > Hi all,   > recently I replaced a toroidal mains transformer in a 5 or 6 year old Crown XLS602 power amplifier. This was a 240V, 800VA size tranny with the secondary winding giving of 75-18-0-18-75 volts.   > http://cdn.avsforum.com/3/38/38365662_vbattach143596.jpeg   That thing looks awful. nasty silicone-looking glue and sloppy cable ties parts buried under other parts. It is amazing fans cost less than real heatsinks these days.     > But then there WAS a big surprise underneath - the toroidal core itself. Normally there are precision made, tape wound cores with molded plastic caps covering the sharp edges. Not this one.   > The corner edges had simply been ground off by hand and covered in cloth tape. The core itself looked rough and uneven - then I realised it was made from dozens of separate strips of steel, spot welded to each other, end to end and of varying thicknesses and widths. The tranny was made from scraps !!   > Some dirt poor Chinese had hand assembled the core using rusty off cuts and sweepings from the floor from some transformer factory. The centre hole was perfectly round but the outside diameter varied by 3mm due to all the joins.   fascinating.   > One would reasonably suspect such a "Frankenstein" core of having poor magnetic performance - but all my testing showed it was perfectly OK.   > The Chinese are getting desperate.   such a crappy transformer is slightly brilliant though. Somebody took the time to try that hack.

Phil Allison <pallison49@gmail.com>: Dec 21 12:54AM -0800 Cydrome Leader wrote:   > Phil Allison   > > http://cdn.avsforum.com/3/38/38365662_vbattach143596.jpeg   > That thing looks awful.   ** Its actually rather well made - Crown Audio are not mugs.   nasty silicone-looking glue   ** Huh ?   and sloppy cable ties parts buried under other parts   ** Not true.     > It is amazing fans cost less than real heatsinks these days.   ** It has always been so.       > > The Chinese are getting desperate.   > such a crappy transformer is slightly brilliant though. Somebody took the time to try that hack.   ** Yeah - I came to the same conclusion.   The Chinese guy who discovered you *could* wind perfectly usable and sellable cores using scraps welded end to end must have got a few big pats on the back - or an extra bowl of rice & fish.   BTW:   The same amp has a novel feature not seen by me before. In faulty condition, it drew about 10mA of AC current while having no DC rails and there was a faint smell of something hot.   Turns out, it has a soft start circuit consisting of a relay and a PTC in parallel. No, not an NTC - a *PTC* !!   A coin sized device made by "Epcos" that has 6 ohms cold resistance and jumps to circa 20kohms if overheated - and it can tolerate 240VAC.   So, if the DC supply does not come up in the first 100mS, the PTC goes high and that is that. Brilliant.     .... Phil

"hrhofmann@sbcglobal.net" <hrhofmann@sbcglobal.net>: Dec 20 08:38PM -0800 I repair donated for recycling incandescent miniature Christmas lights and donate to the local Goodwill. A couple of strings that I have gotten have every single miniature light bulb burned out. Apparently the owner/user never replaced the burned out bulbs, and as the voltage across the lit bulbs increased due to the shunts on the filaments of the burned-out bulbs, there was an escalating burn-out. It must have made a spectacular flash at the final failure<g>.

"David Farber" <farberbear.unspam@aol.com>: Dec 20 05:51PM -0800 "David K. Bryant" <dbryant_94585@earthlink.net> wrote in message news:m6itbj$1qko$1@adenine.netfront.net...   > Certainly not worth the effort and > possibly not even serviceable.   > --- news://freenews.netfront.net/ - complaints: news@netfront.net ---   Hi David,   I finally disassembled the printer again to look at the electromagnetic clutch and the related components. I put DC on the clutch terminals and manually turned the gear that the engine normally turns. I could feel the magnetic field pushing on the opposite end but the gear near the clutch did not engage. It seemed like something should have changed after energizing the clutch. Then I removed the gears and clutch from the shaft that held them. That's when I found that same type of sticky grease on the shaft that was present on the solenoids that caused a paper jam failure months ago. I cleaned the grease off with some alcohol, reinstalled the clutch and gears, and this time both gears turned when the clutch was energized with DC. I reassembled the printer and now paper processed through tray 1 works properly every time. It turned out to be an easy fix but I never would have thought to look in that area of the printer without your suggestion so thanks very much for that. (-:   -- David Farber Los Osos, CA

Michael Black <et472@ncf.ca>: Dec 20 12:48PM -0500

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