Zenith TransOceanic Y-600 Refurb
Built the Same Year I Was Born
After a busy month where I found time for an alignment on the S-38B, a recap on the S-120, and clean-up, refurb, and calibration of some test gear, it was time to move on with some shelf projects. The knobs on the S-38E showed some resistance, so after doing what I should've done long, long ago: order some Bristol Wrenches. While I waited for them to come in, I couldn't work on the S-38E until I got the cabinet off, so I started on the Zenith TransOceanic Y-600.
The Y-600 is a 1957 model, with chassis 6T40Z, part of the last series of TransOceanics with tubes. In fact, 1957 marks the overlap with the start of the first transistorized model Royal 1000 which started manufacture that fall. Production of tube models continued until 1962.
This was such a high-end radio in it's time. As the book says, it's "The Royalty of Radios", and you might have one of these if you owned a sailboat or a yacht. Originally priced at around $200 (1957), this would've been about 1/10th the price of a new car around that time - think now about paying $2000 (2009) for a portable radio! I paid $50 to a local fellow. The radio was playing on AM Broadcast, but needed a dial-restring.
But after all, except for the quirky current regulating 50A1 and a couple of other rare miniature tubes, it's pretty much a very sophisticated All-American 5 radio, with a hot chassis.
Mothers Mag and Aluminum polish makes the brass and nickle parts of this radio shine. I thought the dial pointer was lost to corrosion, but it shined up bright and new. I can see that care needs to be taken in determining what's brass and what's plastic.
The 50A1 tube was missing in action; probably borrowed to repair another radio or just went out, so the 'patch' is the socket is shorted at pins 2 and 7 and R3 is replaced with a large wattage 2000-ohm resistor.
What's inside a Wave Magnet
After a polish with Novus #2, and a quick repaint with a Testors Enamel Paint marker, a swell little tool which has a flat marker tip, The wave magnet looks as nice as it's going to get. It's smooth and shiny enough it now picks up fingerprints.
I always have an interest in antennas and combined with a strong desire to see what's inside
things, I opened up the famous Zenith Wave Magnet to find a flat ferrite bar (pretty light!), wound
with two sets of turns, 32 to a side (not including the half-turn back to the solder point) for
a total of 64 turns. The yellow wire at top brings the far end back to the red lead-in.
I'll try to calculate the permiability of the ferrite, but whatever it is, it measures out at the end of the 300 ohm lead at 92 microHenries. The Paint isn't yellowed; it's the original paint that normally faces down towards the radio except when the suction-cups are used to hang it up.
Replacing the missing 50A1 with a solid-state substitute allowed some voltages to be measured in order to prepare for the replacement of the old selenium rectifier.
Power Calculations and Selenium Rectifier Replacement
First Some Measurements — arrival of the solid-state 50A1 allowed me to test using a 'final configuration'. I removed the old changes that had allowed the radio to play without the 50A1. Using a variac, I started it up.
- Current and Power
- R2 (130 ohms on the schematic) is 133.9 ohms
- Voltage drop across R2 (130 ohms / 133.9 measured) is 8.4V
- Calculated Current: I = V / R = 8.4 / 133.9 = .0627 A
- Calculated Power: Power = V * I = 8.4 * .0627 = .53 Watts
Replacing the selenium rectifier with an 1N4005 would result in a higher DC voltage (lower voltage drop across the rectifier). According to the datasheet, Forward Characteristics graph, at about .06A, the voltage drop would be just over .7V.
- Voltage Calculations
- AC Input is 120VAC (RMS)
- Peak VAC = VRMS / 0.707 = 120RMS / .707 = 170 VPEAK
- Rectifier Average DC Out (after the rectifier, but before R2 is measured at 107VDC
- Calculated Half-Wave DC = 170 * .318 = 54.06
And 54.06 is what it is when the switch is off. Switching on, the filter caps are added
in line and the voltage smooths to a higher average level.
Starting with a higher resistance for R2 - 570 ohms / 5W - and backing down until we have just about 100V after (new) R2. Schematic specifies 105, but I'm setting a conservative level of 100V DC. That number for R2 comes out to 200 Ohms / 5W. At this point, the resistor is hot, but not terribly so and, amazingly, the radio plays fine on all 7 bands!
Results and Operating
The resulting power measurement at R2: voltage drop is around 12.7 volts, at 200 ohms results in .0635 amps (63.5 milliamps). Power consumption at 120 VAC is 7.6 watts. In fact, our house current is 125 VAC, so it turns out the conservative choice for R2 was good, making the resulting DC voltage after R2 to be 107 volts.
The TransOceanic is now at the office, replacing the S-38B (and before it, the S-120) which will retire for a bit. In addition to good local AM Broadcast reception, I've received Radio Havana's Daytime signal at around 11.8 Mhz in English and in French — amazing once you consider the radio is on the north side of a steel and marble-faced building, using it's own Wave-Rod antenna.
Certain AM Broadcast stations are much stronger and clear when rotating the Wave-Magnet.
- Cleaned and polished (with Novus #2) the WaveMagnet, and repainted the letters in white
- Cleaned and touched up the 'Black Stag' cabinet, tighting down some loose edges; wiped with mink oil.
- Polished the dial pointer (brass), and the front cabinet latch (all brass).
- Reversed-out the 'big-resistor' patch that someone previously put in place of the missing 50A1. Replaced with two 5-watt 360 in series (for a total of 710 measured) for R3. Installed a new solid-state 50A1.
- Ordered two knob brights (Part Num P-K985) from Antique Electronic Supply. Both were missing, although the knobs are in good shape.
- Also ordered some
Type #48 bulbs. These didn't work. They're too long to fit behind the dial. Types that are small enough to work are: Type 14 (2.47V/300ma), a round, but still small bulb, Type 222 (2.33V/270ma), and the one I found, a type 112 - 1.2V / 250ma. This works great with a D-Cell and fits behind the little dome in the dial sheet. When it lights, it washes the entire dial with light, edge-lit through the clear-plastic dial sheet.
- Replaced the Rectifier with a 1N4005 diode, increasing R2 from 130 ohm to 200 ohm.
- Replaced ALL the tubular and a few of the waxy, round ceramic capacitors. This improved and increased the audio quite a bit and the tone switches now sound much better. Replaced the 12uf electrolytic AVC capacitor with a 10uf (measuring about 10.8uf) electrolytic.
- Decided against restuffing the 4-in-1 electrolytic; bypassed with 4 individual electrolytics under the chassis.
- Checked all of the resistors and found them to be within 10% tolerance (always a bit high).
- Cleaned the cabinet and wiped down with Kiwi Black Paste Polish.
Mostly capacitors, one resistor, plus the old selenium rectifier. The large 4-in-1 filter cap was left on, but bypassed with modern electrolytics under the chassis.
Finished and working with strong reception on all bands. Oddly enough it works better with it's own internal antenna than on a 75' longwire.
Front Panel outer plastic was cleaned and polished with Novus #2. Everything was slightly foggy from filth, but also the outer panel was a bit scratched. Knobs were undamaged, but missing center brights (replacements from AES - tubesandmore.com). Note that the latch logo is polished but needs cleaning out - heh.
The case turned out nice. It was mostly intact, with a few edges where the 'Black Stag' covering was barked. Heh - darn that latch still has some polish in it.
This is nicely kept - no torn or worn pages and the little prop-lever on the right is not broken.