Tips and Tricks, A Few Rants

How It All Started

It all started with a Zenith H500 TransOceanic that I picked up at the Berlin Flea Market, Berlin, New Jersey for $75 in 1981. A lot of money back then, but I had never seen a T/O before, this one was near-perfect, had all its paperwork, spare tubes, suction cups, hang-tag, everything. Sadly, that radio is now gone, but it started me on a long, slippery slope that now has me holding nearly 50 radios, of which nearly 20 are TransOceanics. Many have come and gone in the intervening years, but that one started it all.

Tips and Tricks

The tube TransOceanics from the 7G605 to the B600 are not much more than a typical AA5 transformerless radios with a fancy antenna array attached. With that in mind, one should not be intimidated by them, as they are (really) no more difficult to service than any other radio with an overly crowded chassis, and much simpler than many.

Vaccuum Rectifier Models (7G605 and 8G001XX):

1. These are Hot Chassis radios. Be sure to use an isolation transformer and/or extreme caution when servicing this radio outside of the case. Lethal voltages can exist on any exposed metal part.
2. The 7G605 often suffers from rubber-insulation disease. Certain critical connections such as to the tone switches may have been made with natural-rubber insulated wire, which by now has become brittle and is crumbling. Be very cautious when flexing these leads, as threading new wires through the braided shield is difficult. If you need to do it, take your time, obtain a good quality and brand of replacement wire and be prepared to do the entire harness, not just individual conductors. This will take some creativity in removing and replacing cardboard covers and the like.

Tip: Use cloth tape to repair cardboard covers if damaged. When the tape is in place, paint it over with a strong, flexible sealing glue such as "Seal-All" or similar.

3. The 7G case is often lined with asbestos under the chassis. Asbestos is very dangerous, but only when it becomes airborne and is breathed into the lungs. Unless you are an abatement contractor, you are simply NOT QUALIFIED to remove it, and any attempt to do so could have horrendous consequences. So, the goal will be to make it impossible to become airborne.

Tip: Obtain a tube of AMBROID Model Cement, and a pint of Acetone. Obtain a small soft-spray bottle, fill it with a 5-parts water to 1 part dishwashing liquid soap. Obtain two large plastic garbage bags, two small plastic garbage bags, a roll of soft paper towels, and two soft 1" paint brushes (to throw away). Mix a small dish (about a pint) of the same soap mix. Obtain a 1-micron-filter or-smaller particle-capture breathing mask.

Working outdoors and wearing the mask, place the radio on a worksurface such that it is surrounded by one of the trash bags. Open the back of the radio. Dampen with the soap and one of the brushes the exposed edge of the asbestos, working wherever it can be seen. Loosen the hold-down screws of the chassis and dampen the edges when the chassis is lifted up a bit. The idea is to prevent any asbestos-laden dust from becoming airborne. Remove the chassis from the radio. Looking at the bottom of the chassis, search for any bits of asbestos that may have stuck to it. With the sprayer, rinse these bits off the chassis onto a bed of paper towels. Saturate the chassis and the towels until you are sure that you have removed ALL the bits. Put aside to dry.

Mix the AMBROID glue with an equal amount of acetone. This should be a very thin mixture. Soak it into the asbestos mat on the case. Get all the edges, get the center, get everything. Allow to dry. Do it again. This soaks into the asbestos mat and prevents any of it from becoming friable, airborne, and therefore dangerous. The mat will still perform its insulation functions, yet no longer present a danger.

When you are done, collect all your leavings, paper towels, both brushes, everything, soak it in the remaining water, double-bag it, and dispose of it as HAZARDOUS WASTE.

4. Miniature T/Os use the expensive (but NOT rare) 1L6 tube.

Tip: When servicing these radios, use a 1R5 for testing and servicing purposes. It will work for AM and the lower SW bands, not affect alignment, and allow you to make repairs without risking a 1L6.
Tip: The European DK-92, and the 1U6 are both drop-in replacements for the 1L6.
Tip: The 1LA6 Locktal Tube was repackaged to make the 1L6. Bill Turner (dialcover@webtv.net) makes an adaptor fitting this tube for your T/O.
Fact: ONLY Sylvania EVER made the 1L6. True 1L6s labeled otherwise have been rebranded by the sellers.

Two Rants: Isolation Transformers & Metered Variacs

If anyone is at all serious about the vintage radio hobby, then they must invest in a proper isolation transformer capable of carrying the load of any item that might be on the bench.

What it does: An isolation transformer keeps the workpiece isolated from the household electrical system. So, the user is less able to insert themselves between Hot (power) and Ground. So, if one touches a hot-chassis radio while on a damp concrete floor, an isolation transformer will help against shocks.

What it does NOT do: Protect against idiocy. If one inserts oneself into the circuit, one WILL get a shock. Simple as that.

Variac (General Radio's trademark for a variable auto transformer): How many times have you heard the phrase: "I brought it up on the variac"? Or "Use a variac to reform the capacitors"? Both of the above phrases are complete twaddle. The former is bad, the latter is far worse. A variac has NO USEFUL PURPOSE other than light-dimming unless it is properly metered. Metering *must* include voltage AND a meaningful measure of current drawn by the workpiece, and in increments fine enough to give useful information. Without such meters, a Variac is actually worse than useless, gives no information on the state of a workpiece, and will instill a false sense of security in its user.

Tips: The average radio of less than 10 tubes or so draws from roughly 1 amp to perhaps as little as 1/3 of an amp (120 watts to about 40 watts). Therefore the current meter must be able to read accurately in 1-2 watt increments to be useful.
Example: A radio *should* draw 45 watts. In fact, it draws 53 watts. This is not enough to cause short-term excessive heat such that it can be detected by touch or by smell. But what it means is that the radio is dissipating 8 watts of heat (about as much as a night-light lamp) somewhere inside the radio. Not a good thing.

Next Tip: With such metering, one can reasonably put a radio of unknown antecedents on the Variac and do some basic tests. By watching the meter, one can determine more-or-less the state of the filter caps, some of the wax caps, the transformer (if any) and several other facts about the item. AND... if the meter starts to peg up, one can shut off the radio before damage is done.

So, PUT THAT VARIAC IN A CLOSET unless and until you have installed the proper metering. Use a dim-bulb tester instead! As crude as that is, at the very least it gives you some useful information.

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