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SX-28 Restoration

The RF deck was completely dismantled to get to the buried parts and allow thorough cleaning of the band switch wafers.

All transformers, chokes, electrolytics have been removed. The Power transformer will be repainted.

Replacing all those paper caps should be lot easier now!

The left side of the chassis had some corrosion which has been cleaned up with a Dremel.

I also drilled out several of the rivets which I replaced with Stainless #6 hardware.

I later painted this section of the chassis with chrome paint.

The RF deck modules and tuning gear assembly:

Here's the Power Supply side after rebuild:

And the IF side:

All the resistors and capacitors have been replaced (including the mica caps inside the IF transformers which I did not do at first but later found them to be bad). The switch wafers have been carefully cleaned with Deoxit and very small chamois swabs. The wiring harness is all original. 

A new power cord (3 wire). The binding posts have all been buffed up.

The Gear box was stripped down and cleaned. I used my usual hand cleaner approach. 

This is a much simpler task than many people think. Disassemble it in a kitchen tray to catch  all the bearings. I had 13 ball-bearings each on each end of the main tuning shaft and one other shaft. The rest of the gears have a single larger ball on each end. There's no need to loosen any of the bearing points. Mark the gears with a marker to remember where they go then simply remove all the screws and separate the 2 halves. Remove all the old grease etc - clean up the bearings. I used a thick synthetic grease for the reassembly. 

Remove the pinch springs from the pinch gears and store them. Ensure the 2 parts of these gears turn freely. 

Deposit grease in the bearing cups and place the ball bearings in there - the grease will hold them in place during reassembly.

Now its time for reassembly. The pinch gears should be adjusted for ~ 0.1 inch overlap and then located in the bearing cups on the plate as shown below. You'll need to place some spacers under the gears to help them stay in position (I used standoffs) - these will fall out when it is all back together.

At this point the other half of the gear box is carefully dropped in position and the screws tightened  (making sure all the gears are in place in their respective bearing cups). This is much easier than it sounds. At this point the gear box can be stood up and spacers allowed to fall out.

Adjust the bearing points if necessary - tighten to the point of just taking up any lateral play. Everything should turn freely. If the gears are stuck on the wrong side of the gear stops, back out the stops and rotate the gears to the correct side.

Now the fun part - reinstalling the pinch springs. Most of them are easy as the gears can be rotated to where they extend outside the envelope of the gearbox. 2 of the gears are not as accessible - I used a pair of long reach needle nose pliers to install these. It was  little tricky but I succeeded without loosing them.

The Hallicrafters website has a more detailed description and slightly different method of servicing this gear box but I think my method is simpler.

Here it is all back together and mounted in the Radio:

Here's it is all back together. You can see the chrome paint on the left side of the chassis, painted power transformer. I polished the cover for the RF deck. Painted the S-meter housing.

I have already aligned the IF chain (did this before reassembling the RF deck). I just got it all back together so next step is RF alignment.