October 21, 2009 at 12:36 am #1221Ed KrausharCVRS Member
I just finished this OEM-7. It was picked up a collectors estate sale and had seen pretty poor storage. It had been a mouse-house and in fact part of the aluminum label on the back of the chassis had been eaten away by mouse urine.
The wood case had to be washed with Murphy’s Oil Soap inside and out to get it clean and deordorize it. The shellac finish was dull and stained but fortunately did not have major dings and scrapes.
The chassis had to be washed with citrus cleaner and hot water to get down to the bakelite. Many metal parts had a white or green crust that was brushed off with a wire brush in a Dremel. The coils are dull and faded but have continuity and the aluminum tuning caps have some dull and pitted areas.
Both interstage transformers were open. I find this common on radios that have had poor storage. The steel laminations rust, swell and break at least the primary windings. The transformers were disasembled and the rust on each lamination removed by careful sanding on a table top belt sander. They were then sprayed with a product called Rust Check. This stops further rusting and gives a primer coat which will act as an insulation for the laminations.
Coil formers were made and the transformers rewound on the forms using a mini lathe. I had a quantity of #40 wire in stock so it was used. #42 may be closer to the original but it takes a day of travel to get it. Primary was 4,000 turns and the secondary was 12,000. That is my standard rewind and care must be taken with large diameter wire like #40 otherwise the dimensions of the coil will be too big for the iron. The benefit of #40 wire is that it is strong enough to be wound at a fairly high speed without breaking.
After assembly and testing the cabinet was tackled. I have be trending away from automatic stripping and refinishing and have been trying to retain as much of the original finish as possible lately. This is easy on shellac finished cabinets. To even the colour out I tinted the shellac with an aniline stain. The shellac was then applied using a "French polishing" method. It is easy to build up a good finish in very little time on these small cabinets and the amount of build up can be varied by the needs of the area being done. The results are not perfect but the original finish was retained and refurbished, the process taking a little more than an hour.
For a four tube radio the performance is quite good.
Download oem7open.jpg. (Caution: This file may not be virus scanned.)
Download oem7top.jpg. (Caution: This file may not be virus scanned.)
Download oem7front.jpg. (Caution: This file may not be virus scanned.)October 22, 2009 at 8:47 am #1216radionutForum Participant
That is a lovely job. How long did it take to do that. I have a couple like that but am just starting to learn how to fix radios. I acquired some 300 to 500 old radios from my dad when he died 3 years ago. He wanted to do a Museum, so I am trying to do that. He has a big house with lots of basement room. I poured a cement floor, then patched cement blocks and painted the walls white twice. Then I put up 32feet of shelving 6 high about 1 foot apart. Then I started working on the radios. I have done some 85, but not perfect as some need cabinet re-done or some missing knobs,grill-cloth,glass with stations on it.I hope with time and help from experienced people I will get this done right.Thank you for showing how it should look like and how you got it looking like that.
Bruce Ruttan (radionut)
613-542-3179October 22, 2009 at 3:15 pm #1217Ed KrausharCVRS Member
Your time queation. I work on radios as I have spare time or as the operation allows. I usually have a pile of chassis restored waiting for the cabinets to be done depending on weather. If I lacquer them it is done outside with a HVLP sprayer. I probably spent about two days or so on the OEM-7 if I put all of the times together that I worked on it. Since I prefer to work on 20’s radios the actual electronics often do not take as much time as the cleanup and cabinet repair/refinishing.
Rewinding the interstage transformers can take a lot of time. I can do a rewind in an hour but dissasembly, cleaning up the steel if needed, making a coil form and reassembly takes much more time. Sometimes I will use a Hammond 124A if it will fit in a can or 124C if the old steel will accept it. Unfortunately a lot of the old steel is 5/8" or 3/4" square and Hammond have chosen not to offer a coil that size so I rewind them to duplicate the original appearance.
Campbellford, Ontario.October 24, 2009 at 8:30 pm #786Ed StoneForum Participant
I agree that looks a great job on the Day Fan Ed – and some good comments on the techniques used. I am not familiar with the Day Fan models, having only seen one ‘in the flesh’ at a CVRS meeting/SPARC museum (it had a speaker built-in so was likley a later model?). From the angle of the coils on the OEM-7 I presume it is a Neutrodyne design?
I have also tried to preserve the original finish where I can – though I have found that sometimes this is not as much of a time-saver as it may appear at the onset. However, quite often a combined approach can work well (avoiding stripping the entire cabinet) – instead stripping (scraping) the often plant pot-damaged top and then re-finishing the top from the bare wood, but restoring the original finish on the sides/front using a combination of touching-up scratches, light sanding with superfine steel wool and then using toned lacquers applied with an airbrush for small areas and larger spray gun for larger areas. A couple of examples are shown here of lacquered cabinets that have been restored this way.
Some more detail on your coil re-winding efforts would be appreciated.
Download DSC00086 [1024×768].JPG. (Caution: This file may not be virus scanned.)
Download DSC00119 [1024×768].JPG. (Caution: This file may not be virus scanned.)
- You must be logged in to reply to this topic.