November 14, 2011 at 9:59 pm #2641Ed KrausharCVRS Member
This was an easy restoration. I picked the radio up some time ago at a club auction and it had been well cleaned up for sale. It did not work though. The finish was left as found.
This Thomson is another one of those radios that has very little information available on it. The Thompson plant was in Jersey City, New Jersey, USA.
When the chassis was pulled three problems were found. The first audio interstage transformer was open, the bypass capacitor was leaking badly and the grid leak resistor was open.
It is interesting to note the two jacks on the left side of the chassis just under the tubes. They allow one to choose between one and two stages of audio amplification by moving the plug from one to the other.
The chassis underside.
The open audio transformer was repaired first. I normally rewind these but this one had a relatively small coil on a 1/2 inch square leg. I was worried about a rewound coil being too big to fit in the steel so I took the easy way out and installed a Hammond 124C coil on the old steel. The Hammond core was a little tight so I left one lamination off. I learned the hard way by opening up a rewound coil by forcing too much steel into it.
The leads are brought out of the top plate of the transformer and soldered to the lugs. The center tap of the coil was not needed so it was covered with a shrink tube.
The bypass capacitor was pulled apart next. It was potted in wax and sealed with tar and came out of the housing easily when heated with a heat gun.
The metal straps which connect to the bottom of the foil pack are cut short and a replacement cap is soldered in place and the assembly held together with hot melt adhesive. The insulating paper is wraped around the assembly and more hot melt holds it in place when it is inserted into the can.
The completed parts ready for installation.
With a good grid leak installed the radio plays quite well. Thompson has a set of unmarked terminals for hook-up at the rear of the chassis and their chart is a help in hooking the radio up.
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