Westinghouse WR 116 - 1936
In 2011, the brothers Perini donated to the Museum of Radio, a radio Westinghouse Model WR 116, manufactured in the United States in 1936. It is a superheterodyne with 3 wave bands and IF 465 kHz. Valves 25Z6 K42C(Ballast) 25A6 6A8 6F5 6H6 6K7 have serial filaments connected. The speaker is electrodynamic.
Although my joy and gratitude for the valuable contribution to the Museum, the state of the wood cabinet and chassis were scare a seasoned restaurateur...
1.Visual inspection and cleaning
The termites had eaten the bottom of the box, leaving wood holes side by side and the circuit was quite "detonated". The photos illustrate the cabinet which had the task ahead:
A simple visual examination of the electronics, namely, chassis, components and wiring is demonstrated disrepair. Powder, disconnected wires and oxidation were widespread. After a severe cleaning with brush, vacuum cleaner and solvent can start a more accurate valuation.
It was observed that the output transformer and field coil speaker was interrupted. Similarly, the series circuit of the filaments had inadequate resistance due to defective Ballast likely. The chassis received did not come with a ballast K42C (original layout), but with a K8374-7, which can also be used. However, a "restoration" was placed above resistance (wire-mica) and warmed remaining point of charring and let wear on the bottom of the cabinet, which can be seen in the photos below.
3. The Speaker
The speaker field coil only had a tip! The other tip was broken and gone. To remove the coil was necessary to tear what was left of the cone because the screws were assembled before placing the paper and below this! What was destroyed was already ripped.
It has been a lot of work for the detection of outer loop coil, where the resistance measurement was similar to project (1800 ohms). After several hours, I found a 1690 ohms loop signaling was held where a weld millimeter. Finally, the coil was restored (in detail with green ribbon). The photo under shows the new speaker with output transformer, cone connections and painting.
4. The series circuit and filament lamps
As the reducing valve switching voltage K83747 presented in their higher resistance (here called A resistor) had to recalculate the entire circuit and filament lamps (resistors "A" and "B"). Beside, the circuit in series filament lamps and resistors. http://www.nostalgiaair.org
This was also done on the grounds that the operating voltage of the original Radio WR116 is for networks 110/117 VAC and the average current in my house is 125 VAC. A full explanation was very helpful to me, thanks to the help of good friend Jean-Yves Bourget (Quebec, Canada), which will transcribe below.
125 VAC = Heathers 25Z6 25A6 6K7 6A8 6H6 6F5 + resistor "A" + parallel (resistor "B" and 2 lamps 6.3V 150mA).
RB = (2 x 6.3 V) / 0.150 mA = 84 ohms
Vt = (25V x 2) + (4 x 6.3) + (6.3 x 2) = 87.8 V
VA = 125 V - 87.8 V = 37.2 V
RA = 37.2 / (0.150 mA x 2) = 124 ohms (threshold).
As a whole the ballast resistance presented existing value of 82 ohms, it was used as resistance "B". A new resistance "A" was placed on the chassis, with 50 watts of power and 160 ohms, increased value to protect the filaments of the valves. Detail next.
5. Final assembly and testing of the circuit
After the restoration of AF and circuit and filament lamps were replaced the 2 electrolytic capacitors, as well as most other common capacitors. Some resistances old wiring and ready, we go to the dynamic test! The radio worked, only requiring calibration IFs and adjusting the trimmers and padder. Strains were checked every filaments and were within a range of prevention (VCA 21 and 22 in tubes 25A6 and 25Z6 ; VAC 5 to 6 in the other). The operating voltage "B +" about 101 VDC. The first two photos show before and after. The last photo shows the chassis ready, running and painted with automotive paint.
6. The cabinet and termites
The "box" of WR 116 was almost over! Termites were stuck to the base and damage done on both inner sides, to the extent they stick to the timber. The pictures say:
I spent sandpaper around the office and left the show all the holes and ditches made by termites.
As certain parts of the wood were badly damaged and there were places with holes side by side, performed a phase stiffness of the wood with putty and catalyst. In a second step and fill the holes, put successive layers of bamboo barbecue skewers, phosphorus giant popsicles or more wood glue. The first pictures below show these two phases.
In follow-up, were put several layers of wood mass, interspersed with fine sandpaper until one level of smoothing that does not compromise the age and aim higher.
After the last layer of dough and sanding was reasonable appearance. Finally, I used a water based ink will dry and fast, like in the pictures that follow.
One last passage of sandpaper No. 400 in cash and two coats of clear lacquer submarine.
Superheterodyne receiver was ready WR116 model, manufactured in 1936 by Westinghouse Electric Corporation, Home Radio Division, Sunbury, Pennsylvania, USA.
It was the story of a restoration that lasted over two weeks and worked. It was worth it.
Daltro D’Arisbo april/2013