![]() With the 20V/div deflection factor available on most plug-in units and a 10x probe, waveforms up to 2kV p-p may be displayed, and slightly larger amplitude waveforms may be applied without risk of harming the scope. It's hard to top the old Tek scopes for servicing and analyzing tube systems. ![]() At that leakage current, the cap will dissipate 14.7mW due to leakage resistance at rated working voltage.Īnyone know why Tek specifies a 6.25A slo-blo fuse for 115V operation and 3.0A slo-blo for 230V instead of 6.0A and 3.0A? For a 125uF/350V, for example, that's 42uA or 837mV drop across a 20K series resistor. If I don't re-form the 'lytics every 2 years, I've noticed that it will eventually start blowing the line fuse after an hour of run time until I re-form them again, then it can run for 8 or more hours at a time without blowing its fuse after the caps have each been re-formed to the point of drawing less 1/5(sqrt(C*V)) uA of DC leakage current. The tube and transistor failures were also both caused by rough handling by movers, as both problems popped up a few days after setting the scopes up in new locations after a move. I've replaced one tube and one transistor in the time that I've owned it and those two breakdowns were preceded and followed by 4 or 5 years trouble-free. I've had very few problems with the 547, especially considering that the unit is older than I am. I prefer the extreme durability and ultra-sharp trace of the 547, but the 475A's portability is a plus at times. I learned from working as a lab tech for the university for 2 years that Tek scopes are virtually indestructible and will last practically forever with reasonable preventive maintenance.įor applications where I need more bandwidth or where the 547's size and weight might be an issue, I have a Tek 475A with the DM44 option. I started using Tek scopes exclusively in college. Just before I bought the 547, I was using a 531 that I bought from a TV repair shop. My first scope as an experimenter and student was an old Jackson CRO-2. I've had my 547 since '93 and periodically lift one side of and re-form each of the 'lytics with their rated working voltage and a 20K/5W series resistor just to make sure they're in good shape. (over 30+ years) the most memorable (to others, I don't remember much) was the laser start circuit that arced through a supposed insulator.įor general shop work, I use a Tek 547 with a 1A1 plug-in that I bought freshly serviced and calibrated from a vintage test gear restorer. I've been "bit" by scopes, lasers and whatnot. I don't remember how the old eico's etc that I worked with were set up. That's when I started to like magnetic deflection in crt's. Well the filament and the cathode are usually at or near the same potential so there is always the problem of moving a few watts way "uphill" to get that filament to glow.ĭid some 1" electrostatic deflection crt work for some military apps, and it was preferred that whatever voltages were used, that the electrostatic deflection plates were closest to ground potential, thus like tek we had -2kv to the cathode, and an isolated filament that we had to pump a couple of watts up to -2kv to light the filament, then we had the anode at +5 kv (tek 4xx is +15kv?). ![]() Moreover, these measurements may be made in a minimum of time, qulifying the Type 304-A as a quantitative as well as a qualitative instrument.IIRC, they were built the opposite of a TV, with the faceplate at ground and the cathode floating at (minus) high voltage. Unlike electro-mechanical devices, the Type 304-A is not restricted to rms or peak-to-peak readings of voltage, as any amplitude portion of the input signal may be measured with the instrument. "To obtain the utmost from the Type 304-A, full advantage should be taken of the novel amplitude calibrating system of the instrument which permits signal amplitude measurements in volts directly from the screen. The high gain assures that the Type 304-A can be used directly with most transducers, while d-c amplification provides that the lowest frequency portions of signal will be faithfully reproduced." Function Used to provide accurate time and amplitude of measurements of voltage signals over a wide range of frequencies.Īccording to the instruction manual, "The Du Mont Type 304-A is a general-purpose cathode-ray oscillograph that enables rapid, accurate amplitude measurements of any portion of a 0-to 1000-volt signal, from d-c to over 50,000 cps.
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