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Re: 465 No Horizontal Sweep
Cap C1220 is wet Tantalum, all caps in 465 are tantalum except for Filter Caps in power supply section. I replaced C1220 with a Aluminum electrolytic, and all is working correctly. Also replaced R1220 which was burned black. All voltage readings in Horizontal Amp section correct except for Collector of Transistor Q1226. Measures -0.36v, should be -0.45v ,20% low, I believe the -0.45v is the forward voltage of Diode CR1253, but scope is working well so I am not concerned. If it's not broke don't fix it.
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Re: 7A15A issue or limitation??
Chuck Harris
Simple explanation, I think:
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"Vertical mode" triggering is only valid when there is a single vertical signal displayed on the screen, or you are in ALT (alternate) mode. It gets more complicated if I try to tell you why: The only modes where the traces on the screen are exactly what they appear is when there is only a single channel displayed on the screen. Whenever there is more than one channel on the screen, there is some form of eye trickery going on. This is because there is only a single beam in the CRT to draw on the screen. A couple of scope models have multiple beams, but they are the exception, rather than the rule... In ALT (alternate) mode, it may appear to the eye that there are two signals on the screen at the same time, but in reality, the two signals are being shown singly, alternating: A, B, A, B... If the sweep time is fast enough, the eye merges the alternating images so they appear to the brain to be simultaneous. At the slower sweeps, the eye can easily see the traces alternate. In CHOP (chopped) mode, it may appear to the eye that there are two signals on the screen at the same time, but in reality, the two signals are chopped up into alternating tidbits.... a tidbit of A, a tidbit of B, a tidbit of A, a tidbit of B...all the while the sweep marches on, making a sort of square wave with the tops being the tidbits of one channel, and the bottoms being the tidbits of the other channel. Because the chopping of the A and B signals is faster than the sweep speed, and with no time relationship to the sweep speed, or the signals, the eye sees the chopped up signal to have merged into what looks like simultaneous display. But the trigger isn't a human eye, so it isn't fooled by this trickery. When the trigger mode is in "Vertical", the trigger is given the exact signal the plugin is trying to display on the screen: Single channel mode, gives the single channel. Alternate mode, gives an alternation of Channel A and Channel B. Chop mode gives a composite signal of a little bit of A, B, and their vertical positions... A real dog's breakfast. "Vertical mode" triggering is only valid when there is a single vertical signal displayed on the screen, or you in ALT (alternate) mode. -Chuck Harris tinkera123 wrote: Hi, |
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Re: Tek 3c66 Carrier Amplifier Bridge plug-in for the Tek 560 series scope
From Tim P (UK)
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As you may have gathered from the manual, the 3C66, and 'big brother' Type Q are very specialised plug-ins. The only use is with transducers like pressure sensors and foil strain ga(u)ges. I have one in a 564 with a Statham pressure transducer and a pneumotachometer, but TBH it lacks sensitivity here. I have also seen a 564 storage 'scope with two 3C66s in X/Y configuration for displaying stress / strain curves. It's a 'fun' thing if you have the transducers, and probably useful for teaching about certain engineering concepts, but yes, it's a 'one-trick-pony' Tim On Mon, 25 Nov 2019 at 20:07, garp66 <hrgerson@...> wrote:
hi, |
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Re: Yet another 7L5 issue (7L5 / 7854) below 10 kHz
Hi Cliff,
I wrote about a related problem in this message: /g/TekScopes/message/149400 I also have the same issues with my 7L5/7854 as you reported (improper reset and CF display below 10kHz), and my conclusion is that 7854 readout processing does not conform to specification, so it's the 7854 firmware issue. I summarized a part of it in the conversion document posted here: /g/TekScopes/message/150089 So until someone dares to do brain surgery on 7854 ROMs, I doubt there's much we can do. Tek did not touch it back in '82, so I figure it wasn't an easy fix. These recent microfiche scanning operations might reveal some project documentation on 7854 firmware, though I'd be amazed if somebody fixed a 30 year old bug :) 7854 is still hard to beat even today. Best Regards, Nenad Filipovic |
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Early 515a schematic?
Hello,
I have an early production 515a, which uses some 6U8s and 6BQ7s. At serial number 4804, Tek introduced a bunch of tweaks including replacing them with 6DJ8s. My paper manual's circuit diagrams depict the newer design, with the old components in red. I've come across a couple of mistakes in the red annotations, and also wonder if the voltage values are correct for the older design. Some of the old circuitry is omitted entirely in the new circuit diagram, for instance where in the calibrator a single 6AU6 pentode replaced the original 6U8 triode-pentode, but as far as I can tell, doesn't show the function of the 6U8's triode section. I've searched without success for a PDF of the original 515 or pre-4804 515a schematics, without success. Do you have a 515 or early production 515a manual or PDF showing *only* the old circuits? |
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7A15A issue or limitation??
Hi,
I have been playing around with my 7A15A's, in different 7603 Mainframes, and have a 'jittering' or 'flickering' of the 4V Calibration signal. The 'jittering' is a movement, always to the left, of the trace along the horizontal axis and return to the correct position. I can define this issue or limitation as follows:- Independent of Mainframe - 2 x 7603's used Independent of Timebases - 7B53 and 7B92A used Only occurs in TRIG SOURCE/VERT MODE with VERT MODE/ALT - both traces are stable in all other Modes Only one of the traces becomes unstable Only occurs when traces from each Vert Amp are 'un-overlapped' - when the two traces are overlapped, both traces are stable The Manual states that in TRIG SOURCE/VERT MODE .... "each sweep is triggered by the signal being displayed on the CRT" This suggests to me that when I dive into the Circuit Descriptions, that I should be looking for some 'switching mechanism' which is swapping the Triggering mechanism between the signals from each Vert Amp. If this 'switching mechanism' is faulty or receiving a weak signal, then this maybe causing poor triggering, hence the 'jittering'. However, this 'switching' between Vert Amp signals would occur in the Timebase or Mainframe. But that doesn't make sense because the 'jittering' occurs in both 7A15A's, independently (ie. 7A15A + 7A26 + 7B92A etc), and in 2 different Mainframes, and with different Timebases. So .... where have I gone wrong here???? ..... or is this a limitation of the 7A15A??? Any guidance is appreciated. -- Cheers, Ian, Melbourne, Australia |
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Re: Trying to save a 576
Hi Ryan,
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That was a very generous offer. Hi to Kim! Dennis Tillman W7PF -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Ryan Scott via Groups.Io Sent: Saturday, December 07, 2019 12:13 PM Subject: Re: [TekScopes] Trying to save a 576 Hello, I have a 154-0563-05 CRT which came from the estate of a Tek collector. I don't have a 576 so it's of no use to me. You can have it for the cost of shipping from 97229 and take the gamble as it's in unknown condition. Regards, Ryan Scott On Saturday, December 7, 2019, 09:49:50 AM PST, Bob Koller via Groups.Io <testtech@...> wrote: Dennis, no other instrument used the 154-0563-xx CRT, unfortunately. -- Dennis Tillman W7PF TekScopes Moderator |
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Re: 7L5 dot frequency reset bug - any clues or a fix?
I can test mine out tomorrow and let you know if it does the same thing.
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Dave Casey On Sat, Dec 7, 2019 at 4:46 PM Cliff Carrie <cliffcarrie@...> wrote:
The 7L5 manuals say the Dot Frequency should reset to 0.000 kHz at power |
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Yet another 7L5 issue (7L5 / 7854) below 10 kHz
The dot frequency displays with the decimal point in the wrong place below 10 kHz (Fine mode on); the displayed number must be multiplied by 10. The 7L5 tunes correctly to 9.750 kHz, for example, but displays 0.975 kHz
Tek documented this in Service TekNotes in November of 1982. Strangely, they never produced or published a fix as far as I can discover. Does anyone have a solution, or ideas for one? Cliff Carrie. |
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Re: 577 D1 function won't turn off
I have an update
I performed the 370V calibration on TP 2 to ground from the D1 storage board. I was about 365 so i put it right at 370 I took pictures of the adjustments on the D1 board and very carefully moved each one slightly back and forth and noted the display. I fixed my problem by carefully turning down SENS COR from the 3 o'clock position to near the 12 o'clock position, the ghosting problem disappeared and the D1 storage appears to work correctly and turn off when I don't want it. I turned off the instrument and back on, a brief flash of the screen but the display came on free of storage display artifacts All the other settings are default except 370V and SENS COR Hopefully this might help anyone out by trying this, maybe reply with your results to see if this is my particular case or perhaps it is a fix hopefully for some people |
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Re: 577 AC collector supply not reading zero on display
Reading the manual I notice the following for the collector supply
120 Volts is fed to T101 autotransformer (Variable collector) K125 turns T101 on or off The wiper of T101 goes to what appears to be a filter L101 R101 and C101, and then it goes to the primary of T102 From T102 it appears this is where I get 6.5 25 100 400 and 1600V from for the collector For 6.5 to 100V rectifier CR107 is used and above that CR103-106 is used Since different rectifiers are used at higher volts I decided to test my problem at higher voltages, the problem appears to get much worse At 1600V 8kOhms 5V Division 0 collector volts the line is 4 divisions across which should be 20V, not good The collector supply appears somewhat simple if i look at certain sections of it. I feel like I simply have a T101 autotransformer issue. The wiper is making contact to the very edge but yet it acts like i have it turned up partially. Maybe a issue with T101 or maybe K125 or perhaps C101 is bad? I feel this problem is occurring at the beginning of the collector supply stage. |
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Re: Trying to save a 576
I have a very early and a very late model 576. The CRT in the later one is an -05 at the end of the part number. The early one is a -00 or -01 if Memory serves me. The older one suffers from a bad HV transformer, which I am currently trying to get a replacement for.
-- Michael Lynch Dardanelle, AR |
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Re: Trying to save a 576
On Sat, Dec 7, 2019 at 12:37 PM, Ed Breya wrote:
CRT voltages tested at the neck pins. 1) -3815 Vdc 2) -3841 Vdc 3) -3840 Vdc 4) -2667 Vdc 5) NC 6) NC 7) 100 Vdc 8) 100 Vdc 9) 100 Vdc 10) 109 Vdc 11) 52 Vdc 12) NC 13) -3814 Vdc 14) - 3814 Vdc Heater voltage ping 1-14) 5.9Vac |
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7L5 dot frequency reset bug - any clues or a fix?
The 7L5 manuals say the Dot Frequency should reset to 0.000 kHz at power on. There have been previous posts about this not happening, but no mention of a fix. I have personally seen two 7L5s, including the one I am currently using in my 7854, that reset to a varying frequency near 3778 kHz. I have forced a reset using a jumper to trigger the power-on reset timer. The Dot Frequency goes to 0.000 kHz during the reset but goes back to 3778.xxx kHz when the reset timer ends. All other modes and indicators reset as expected. I don't think this is unique to the 7854 power on since the mainframe was already powered up before I did my test. I suspect a timing race in U830 as the reset pulse turns off. I know this is a minor annoyance, but the circuitry is there, and I'd like to make it work properly. My 7L5 service manual is 070-2184-01. The reset timer is Q621 on Drawing 5 lower left. U830 is on Drawing 8 (see pins 4 and 17).
1: Has anyone experienced this on the 7L5 in a mainframe other than the 7854? 2: Who else is experiencing this in a 7854? 3: Does anyone have a fix? Cliff Carrie |
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Re: Trying to save a 576
Bob Koller
Eric,
Too bad the tube is weak, but very typical, I probably at least a dozen bad 576 tubes up in the loft, that I can't quite bring myself to toss. You have the later HV transformer, so no worries there. As for the dash number on the CRT, don't worry about that, all are usable, install any CRT that works! |
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Re: Trying to save a 576
Bob you hit the behavior exactly square on the head. 0-75% intensity control the trace brightens then dims and brighten again and at full intensity it loses all resemblance of focus. So I think this tube is toast. Also this tube has a weird model number it is a 154-0563-05 I cant seem to find any reference to a tube version higher then 2. The High voltage transformer is the black silicone one.
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Re: Trying to save a 576
On 7 Dec 2019, at 21:18, Tam Hanna <tamhan@...> wrote:
on the risk of sounding like a broken record: please hang onto the DANAHER 576, 577 and 575 instruments with damaged screens.Why do you call them _Danaher_ 576, 577, etc.? I thought Tek wasn¡¯t acquired by Danaher until 2007. Tek was still under independent ownership at the time the 575, 576, and 577 were made, wasn¡¯t it? If you¡¯re naming it by current ownership, then wouldn¡¯t it be more correct to call it Fortive? Ownership often doesn¡¯t reflect branding, anyway. E.g., a Vauxhall Corsa or Chevrolet Corvette is a Vauxhall Corsa or Chevrolet Corvette, not a General Motors Company Corsa or General Motors Company Corvette. Or am I missing something here? |
Mlynch001
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