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Input w 12y output 400v/ also used on I 111 96 brand new .Ba SYNCHROSCOPES MODEL TS -34 /AP t'tui,. - a 2a cathode y tube with a optical megolIt tj .fr y Le used ulsedr informs- ... microsecond to 'ring. ation. Mar used for observing sine w from 30 cycles to 1 megacycle. This nnit la supplied with carrying case and accessory cables. Condition Is ex sellent. All equipment hat checked $95.00 - GREATEST SURPLUS BARGAINS. -SCATALOGREE $5.00 Order Minimum. 25 Deposit on C.O.D: s Pric. s arc F.O.B. New Haven, Conn. 133 HAMILTON ST. NEW HAVEN, CONN. 4:4 SALES CO. positive! Now we come to what ought to be a dead end, a 300 -µµtd. capacitor (Crc). The capacitor has the same voltage at both ends, so I guess he's the culprit." "Dead on the ball," approved Tommy, "and that's the best way to approach a fault like that too. Put a decent capacitor in there, one of those 750 -volt types. I'd better give the rest of the set a check over I guess. Hey!" he erupted a few minutes later, Who checked these tubes." "I did," admitted John, "what's wrong ?" "See those shields ?" Tommy pointed to the i.f. strip. "You must tuck those little grounding strips inside the shield (Fig. 3) when you replace it, especially on this particular model. It has a tendency to take off into oscillation if those tubes aren't properly shielded." The Second G -E Chassis Jack had been quietly making a voltage check of the second chassis and now came up with a list that practically matched the figures on the schematic. "That doesn't get us far, does it ?" he observed disappointedly. "I guess this one needs a different approach -and I was looking forward to playing Sherlock Holmes myself on this one." "Don't worry," said Tommy, "there are other ways of bringing the fault to justice without tracking him everywhere he goes. Let's look for some more evidence." He picked up the low - capacitance probe and turned up the intensity control on the scope above the bench. "Let's have a look for the sync pips coming through from the clipper circuit." He attached the probe to pin 8 of the phase detector in Fig. 1. "Note we have plenty of spike from the sync department which disappears when we tune off- channel. Always a good idea to remove the signal temporarily to make sure it is the sync pulse you are looking at, rather than some induced signal from the high - voltage section. And you can see the saw -tooth there from the horizontal - discharge tube. Better check along that line as John did with the other set. We'd look rather foolish if it was the same thing and we went batting off on some other tack." This was done, but it turned up nothing. "Now look here," said Tommy, "I think the best way here would be to sift the evidence through, exhibit -byexhibit in the routine. component - check method. Check each part in the grid circuit of the reactance tube and then those between the reactance tube and the oscillator grid. I'm going to nip out for an early lunch." When Tommy returned, the set was working merrily on the bench, its horizontal hold as stable as a rock. "It was this 470 -µpfd. capacitor, C,.,," reported Jack. "It has no capacitance at all according to your checker." "What does that capacitor do in the circuit anyway ?" asked John. "I don't know much about this reactance -tube business." "Well," explained Tommy, "you can regard the reactance tube as being in parallel with the oscillator tuned circuit, like this (see Fig. 5). Now the capacitor that went open was coupling the reactance tube to the circuit so, with it open, the reactance tube might as well not be there for all the good it does. Under such conditions, when the oscillator drifts off- frequency, the reactance tube is not able to change the phase of the circulating currents in the oscillator tuning network to compensate for the drift ... what was that you said, John ?" "I just said, 'I pass,' " mumbled John. SOLDER GUN WIRE STRIPPER By FRITZ C. HOFFMAN WHEN INSULATION must be removed from wire, an irritating situation usually results, especially when the wire involved is in a cramped working space. A slender knife might work, but even the slight nicks that inevitably result weaken the wire and thus tend to invite breakage. The little device shown in parts (A) and (B) of the accompanying illustration, made from a miniature, copper alligator clip of the "Minigator" type, solves the problem neatly. To make up the wire stripper, cut a "V" into the very tip of the clip, and then bend this tip over 90 degrees as shown in (A). The entire unit is then clipped onto the tip of the soldering gun, as shown in (B). Now all you have to do is press the trigger of the gun and rotate the adapted tip around the wire to be stripped. With the help of the applied heat, insulation comes off cleanly and quickly. Where a considerable amount of stripping is to be done, as in wiring up kits, a stripping clip can be made up for use on a regular or pencil type iron. Shown in part (C), this adapter can be fashioned front copper and left per- manently in place on the iron. While this version may not work quite as well as the gun adapter in close quarters, it is more practical for extensive work and is always at band when needed. -30- ELECTRONICS WORLD

Hi -Fi Control Center (Continued from page 65) Treble Control: -16 db, +16.2 db at 15 kc. Loudness Control: Designed to affect the low- frequency end only and is effective in its operation. Channel Separation: 41 db at 1000 cps. IM Distortion: Measurements were taken under two separate conditions and through the high -level stages only. For 1 volt in and 1 volt out, IM distortion was .12c/r. For .5 volt in and 2 volts out, IM distortion was .13", . These measurements were taken at 60 and 6000 cps mixed 4:1. Harmonic Distortion: Tests were made under two separate conditions through the high level stages. For 1 volt in and 1 volt out, harmonic distortion was .11% at 30 cps, .1r/r at 1000 cps, and .07'4 at 15,000 cps. For .5 volt in and 2 volts out, it was .07% at 30 cps, .067r at 1000 cps, and .05e/r at 15 cps. If we were to subtract the residual distortion in the test equipment for both the IM and HD tests, one would have to report that distortion was entirely negligible. This unit should not add in any way any coloration to the sound reproduction. Hum and Noise: -56 db on magnetic phono input with .006 volt input and level controls adjusted for 1 volt output. One point worthy of mention is that both tone controls have a flat taper at their centers of rotation and this, coupled with the use of Baxandall tone control circuits, provides a fairly broad center adjustment for flat response. The over -all design of the front panel and cabinet is neat and attractive although it is not as elaborate as many of the preamplifiers on the market today. This unit is available in either assembled or kit form. The one we tested was a wired version and therefore we did not have the opportunity of actually constructing and checking it out as a kit. In going through the construction manual, however, we found no reason why anyone should have problems in assembling the kit. There is one point very much in the builder's favor and that is the use of printed circuit boards. This obviously minimizes possible errors and certainly simplifies the construction. COTTON -TIPPED TIP D01 BLE- TIPPED canon .s.ah., such as "Q- Tips," originally designed for the nursery, may be used for the maintenance of recording and other electronic equipment. Dipped in carbon tet or other cleaning fluid, the cotton swabs are handy for cleaning recording, bias, and playback heads; wiping oil from driver wheels; and cleaning hard -to -reach contact points of all kinds. They arc also useful for applying talc to drive wheels to prevent slippage and for applying oil to switches and moving parts. -- May, 1959 111 I11111 1_'! I`%i WAN 1I I ::: II IM IlM 1_!1 ma1 If m 111111 1L\1 Ifli ILION MOM ULM nun 111111 IMO IP`1 1I IN 1111 W11 ILA1 1/I1 1111111 IllM M` 11111M 111111 W II min IVAN 1111111 It 1P`1 111M II 1M 1\\11 IF11 WW1 111 II 1M W11 II M1 111M Il\11 was IriI Ir1 III "Most- used" law -power THYRATRONS RCA is the leading manufacturer of thyratron types 2050 and 2D21. These types have an enviable record of performance in demanding industrial applications. RCA- 2050's and -2D21's, as well as all RCA Thyratrons, are available at your RCA Industrial Tube Distributor. RADIO CORPORATION OF AMERICA Electron Tube Division Yours for the asking -Free booklet (PGIOI-C) on electrical characteristics of RCA Thyratrons, os well os other RCA Gas and Power Tubes. Write RCA Commercial Engineering, Section E -sl -T Harrison, N. J. Harrison, N.J. 135

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