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4125 W. Jefferson Blvd. Dept. 73-56 AREA 213, 731-2251

LOS ANGELES, CALIF, TWX 21 3-737-1 31 5

It blanks out the retrace and intensifies the trace whenever a signal deflection takes place,

Conversion Details

The pan adaptor power supply is designed for 38011000 cycles. It will be necessary to replace the power transformer with a 60 cycle oscilloscope power trans former. The one used by the author was a replacement transformer for a Heath 0-11 oscilloscope. See modified schematic diagram. Most transformers do not provide for a 1B3 filament winding. The transformer used in this conversion used a IV3 high voltage rectifier, The author also wished to remove the power connector, name tag, fuse liolder, handle and mounting fasteners from the front panel to give the unit a commercial appearance.

Each individual will have ideas that suit his own needs or that utilizes a particular "junk box'* part that he wishes to make use of in the conversion of the pan adaptor, The steps outlined in the article will serve as a guide to help get started.

A brief reason will be given for the part that was changed or replaced to help in the understanding of the conversion. This wTill be particularly helpful in the advent of trouble and also help you to determine if the change is unnecessary or fits your particular application.

The unit that was converted by the author was very clearly marked with respect to component identification. Reference to a resistor for example, R125, upon inspection of the unit, is very easy to locate. Hallicrafters did an admirable job when they built this unit for the Air Force.

Conversion Steps

Step 1. Replace power transformer with 60 cycle version. Remove 400 cycle transformer. See schematic diagram for transformer details. ! lie author, in order to mount the transformer he had available, cut a hole in the chassis and mounted the transformer on two small angle brackets.

Step 2. Replace the 1B3 with a 1V2 tube. This is only necessary if the replacement transformer does not have a 1.25 volt high voltage rectifier filament winding. Most inexpensive oscilloscope transformers have a 0,625

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<■■ .-..Hi JTnf,—M ííl filament winding, and will only operate a IV2 satisfactorily.

Step 3. Replace the following resistors in the high voltage power supply section and accompanying voltage divider circuit (Note; Throughout the conversion, many of the resistors removed may be used again in the conversion. Therefore treat the leads with respect) In order to provide the 800 to 1000 volts needed for the high voltage with the ripple component low enough, and still use the high voltage filter capacitors CI24A and C124B? it is necessary to:

1. Increase the value of R147 from 22K to 220K 1 watt

2. Increase the value of the high-voltage divider network to limit the current drain.

Remove R159 220K 1 w. Replace with 1,0 meg ] watt. Remove HI47 22K 1 w. Replace with 220 K (use R159). Remove 156 L50K lw. Replace with 680 K 1 watt, Remove yellow wire from R155. Add in series a 22K 1 watt (use R147) between yellow wire and connection of Intensity control Remove R160 56K w. Replace with 150K (use R156). This improves the astigmatism of the electron beam.

Step 4, In the authors unit, it was found necessary to add a small 8 henry—'70 to 100 milliamp choke in series with 13-plus. In addi-

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