Document pBYw0YKqE7Ka0Z9p5bx88QX7d

I-' j. Ttlanufacturers "' ' ''" * lfe i if.-. -. .ijj/.;.,;;." v ,-f. =--- 'i-r'.'iT -*.'.ij ;'. v- - RADIO ERAL RADIO COMPANY AND ELECTRICAL LABORATORY FOUNDED 1915. APPARATUS . QENRADCO.BOSTON tley's code TROWBRIDGE 4400 THIRTY STATE STREET CAMBRIDGE 39, MASSACHUSETTS March 11, 1944 f. Monsanto Chemical Company Anniston Alabama . . ' '. , Gentlemen: Attention of Mr F. A. Barker. Chief Chemist . This acknowledges the receipt of your letter of February 29 concerning the difficulty that you have experienced with your Type 716-A ' ' Capacitance Bridge which you have been attempting to use with your Type *-r; 608-A Oscillator and the Type 707-A Cathode-Ray Null Detector. We are enclosing the Service Notes for this bridge and we hope, that these will enable you to locate and correct the difficulty. The information which you have given seems to indicate that there is an open circuit at some point in the bridge and it should not be too difficult to locate and repair it. With the aid of an ohmmeter it should be quite simple to make a rough check on the circuit to determine where the difficulty lies. Measuring between the high detector terminal and the high parallel con denser terminal should give a resistance of 20,000 ohms regardless of the setting of the capacitance multiplier switch. From the same high detector terminal to the high unknown condenser terminal an ohmmeter should measure the resistances of 20 ohms, 200 ohms, 2,000 ohms or 20,000 ohms, depending upon the setting of the capacitance multiplier switch. In order to make these measurements, however, a piece of paper should be inserted under the switch blade at the end opposite the connections which you wish to measure. With both sides of the switch insulated a check for continuity of the transformer secondary can be made from the unknown condenser terminal directly to the unknown detector terminal. A final check can be made on the input of the transformer by checking with your ohmmeter across the two generator terminals. It is hoped that this information with that in the Service Notes will enable you to easily locate and repair the difficulty in your bridge. If more complete information is required, however, please let us know the results of these tests with complete details concerning the manner in which they were made. This we believe will enable us to analyze the difficulty and to let you know how it can best be corrected. KA:MEC Enc. Yours very truly, ^ji ~ J M 4*4* Cipling /Adams Service Department 0S\N 33A401 STLCOPCB4078045