By Sindre Torp, LA6OP, Norway

Slug gage tools

DRAKE Slug Gages


Ever wonder if the ferrite slugs in the preselector rack of the 4-line products were the same length or even measured? And how did they set the depth of the slug on each transformer for each band?


The slugs came to Drake in bulk and were not all the exact same length. One of the jobs of the QC department was to sort the ferrite slugs. In the case of the slugs for the preselector racks, these were to be exactly the same length or at least the four that were used in a particular unit. So, the slugs were sorted, tagged, and sent to the appropriate product line.


The R-4 series receivers and the T-4X series products were built with several sub-assemblies. The sub-assemblies allowed better control of quality and insured operation once inserted in the end product. Each sub-assembly was fully tested by a technician in a fixture that simulated the end product. The sub-assembly would be fully functional before ever being bolted into a chassis.


The assembler making the preselector sub-assembly inserted one of the pre-measured slugs in each transformer and when finished with the sub-assembly, passed the sub-assembly on to the test department. There, a technician would place the subassembly into to a test fixture for alignment and testing. The test fixture was either a product missing that particular sub-assembly or a fixture produced in the test fixture department. In the early days, products were mainly used, the sub-assembly would be removed and the remains adapted to become a test fixture. This practice continued into the R-8 series receivers.


The slug gage provided the technician a quick and easy way to set the slug depth on each transformer and for each band as he tuned the trimmer capacitors. To begin the alignment procedure, the technician would set preselector pointer to the middle of the 80 meter segment and set each slug flush with the top of the white coil form. The R-4A slug gage provided five measurements, as can be seen in the photo of the slug gage. Each measurement is specified as well. In all cases, the measurement was from the top of the white coil form to the top of the slug, with the preselector pointer set to mid-range of the segment for that particular band.


The T-4X slug gage provided seven measurements. Six slug depths for each band, plus a 2- inch measurement, which if I remember correctly, was the length of the slug itself. If the technician had trouble with a trimmer not adjusting properly, he could remove a slug or all four slugs and check each slug length to ensure the lengths were exactly the same.


Once the technician had finished alignment of the sub-assembly and it had passed his/her test procedure. It was passed on to the production line of that particular product, where it would be installed in a chassis and put through another round of alignment and testing and finally on to Final Inspection.


One of my first jobs with Drake, as a technician, was the alignment and testing of sub-assemblies on the T-4X production line. Those were the days !!!!


Bill Frost 04/24/2012


Drawing of the slug gage

Slug gage for T-4X and R-4A

(c) 1998-2012 SINDRE TORP, LA6OP, Norway. - DRAKE is a registered trade mark of R.L. DRAKE COMPANY
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Last updated: April 30, 2012