The Philco Tropic 46-888 E.Z. is a 9-band 11-tube AC Superhet circuit radio built in the USA for the export market. The radio is capable of operating on a range of mains voltages based on 115 or 230 volts, but having a HI, MED, and LOW setting for each basic line voltage. The radio receives the standard broadcast band and three short wave bands (from 1.5 to 22mHz). It also has five band spread bands for 31, 25, 19, 16, and 13 meters plus phono input capability.
The radio was purchased on eBay and was sold as "For Parts or Restoration" – it had no power cord. The only schematic diagram I could find was at Radio Museum Schematic. No other service information was found on-line. The Radio Museum schematic was from the Philco Home Radio Yearbook 1946-1947. I found a copy of that book at Amazon.com and purchased it. The book was somewhat disappointing. It did have the schematic diagram, parts list, and alignment instructions. But there was no dial cord stringing diagram, under-chassis component locations or circuit voltage readings. The capacitors in the parts list also had no voltage ratings (other than filter capacitors) and the resistors had no wattage ratings. Any parts references in this document will refer to the Radio Museum schematic, but membership is required for access.
The radio is unusual in that it uses a mix or Loctal, Octal, and Standard Base (big pin) tubes such as 76, 78, and 80. Perhaps that is due to the fact that this radio was built just after WWII, so parts may have been difficult to find. Or Philco may have been using up excess inventory.
According to an excellent article on Philco History found on Philcoradio.com, Philco Tropic radios were built for locations where super reception of short wave is necessary and where the radio and the cabinet are exposed to extreme conditions. The IF transformers in my radio were stamped “Tropicalized in Feb 45”. The radio has a tuned RF amplifier stage, two IF amplifier stages, push-pull 6V6 audio output tubes and should have excellent performance.
The radio appeared to be mostly original, with most original parts still in place. I decided to attempt to restore the radio and maintain the original chassis appearance to the extent possible. Two paper capacitors had been replaced (C100 and C101 – 80 rectifier plates to chassis). One tubular filter capacitor had been tacked in under the chassis. The original filter capacitors were still in place. Two tubes obviously had been replaced: the 80 rectifier and one 6V6 output tube. The rest were all branded Philco and could have been original. Only one of the tubes installed had the “E” (export) designation (78E).
Before I start work on the chassis I annotate an under-chassis photo with part number callouts from the schematic, and then compile a complete survey of the condition of all parts.
(This post was last modified: 06-19-2016, 12:06 PM by davemc.)
My next step is usually to check all of the parts I can and make a list of parts needed or repairs needed.
The cabinet was in good condition with only occasional scratches and finish loss. The knobs were original. The back cover was present and in good condition, but the retaining screws did not appear to be original. One knob spring was missing.
The chassis rubber corner bumpers were in poor condition, and one was missing. Fortunately these are available from Renovated Radios (PHS-COR).
Several parts that secure the two large vertical dials to the cabinet were missing. A key part of these four assemblies is a flanged bushing, shoulder bushing, or shoulder spacer (not sure what they are called). Two were missing. Fortunately I found two in my junk box which were slightly too long and could be cut down. These parts are often used in conjunction with rubber grommets to support tuning capacitors in radios. The other rubber parts used were two GPH-46-480 (a grommet with an offset groove) and 7/32” thick washers cut from a GPH-Sleeve from Renovated Radios. Two #8 x 1” round head black Philips head screws were also missing. I have not found a supplier for this screw, so I may have to use slotted zinc hardware.
The line cord had been removed. I assume that the original was likely rubber or vinyl vs. cloth covered.
One of the two dial pointer drive cords was off its pulley. The dial cord stringing in this radio is quite complex, and especially for the band spread dial.
The speaker field, cone, and output transformer were OK.
The power transformer was defective. It showed obvious signs of leaking wax. One of the two primary windings was open and one was shorted. After removal of the transformer for inspection, one primary winding was burned to a crisp. This may have been caused by shorted turns, or perhaps the radio had been connected to 230 volts when setup for 115 volts. When removed for inspection, it appeared that the transformer leads had been unsoldered and then reattached. So someone had been there before!
The three IF transformers were OK.
All of the RF coils and transformers were OK. I was unable to test two oscillator coils that were buried in the band switch – I could not safely access their connection points.
Eight resistors were out of tolerance – all were carbon composition types – all but one was ½ watt. Some original resistors that had to be replaced were rated at 20% tolerance. New 20% tolerance resistors are no longer made, and I will be forced to use 10% or 5% parts. I try to use vintage parts (vs. new) when available and in tolerance.
Five tubes were bad – either showing shorts or were weak. The original 80 tube was a tubular type which was good, but I prefer the ST or shouldered type so it will be replaced. One of the bad tubes was a 6V6 output tube (shorted) – its mate was OK but slightly weak. I picked two replacement 6V6’s from my parts stocks which had higher quality measurements and were closely matched. If the restoration goes well I may try to find two matched 6V6G tubes. The parts list calls for 6V6E GT/G so either G or GT types are acceptable.
The defective power transformer was obviously a showstopper if it could not be replaced. This had to be addressed before spending any time or money on restoration. The original transformer was quite unique, and there was not much chance of finding an exact replacement. It had two primary windings each rated at 115 volts. These winding could be arranged in either series (230 volts) or parallel (115 volts) by a switch on the rear chassis. Each winding also had three taps for HI, MED, and LOW voltages selected by another switch. My strategy (suggested by Ron Ramirez) was to find a suitable replacement for 115 volts only, which would be acceptable in the USA. I did not know the specifications of the original transformer. But I could calculate the total 6.3 volt filament current required based on the tubes and pilot lamps used (3.1 amps total). The rectifier tube was a type 80, so the rectifier filament winding rating was 5 volts at 2 amps. The maximum voltage and current for a type 80 rectifier is 350 volts max per plate and 125ma output current. So that should be the maximum high voltage winding rating required.
I first looked at the available new transformers at Radio Daze, who sells Hammond Mfg Transformers. I also looked at transformers available at Play Things Of Past. Here is what I found:
Play Things Of Past, Philco 32-8115, $18.50, used. Horizontal mounting, from a Philco model 41-295, 11 tubes, may fit chassis with minimum modifications needed. Filament current 41-295 3.8 amps, B+ 245v. The Philco 41-295 and 46-888 are similar radios except for the audio output tubes. The 41-295 uses two 42’s (6F6) while the 46-888 uses two 6V6’s.
Radio Daze Hammond 273CZ $109.41, Horizontal mounting, will fit chassis hole, no adapter needed, 5V@3A, 6.3v@5A, 650vct@173MA Much larger than needed and expensive, but it will fit the chassis hole.
Play Things Of Past, Philco 32-7080 NEW $35, Vertical mounting, would need an adapter plate, 5v@2A, 6.3v@5A, 720vct@123MA – a close match
Radio Daze Hammond 273X $82.64, Vertical mounting, would need an adapter plate would, 5V@2A, 6.3v@4A, 700vct@126ma – a close match
I ordered the Philco 32-8115 transformer from Play Things Of Past. When it arrived, I found that it fit the chassis exactly and all mounting holes even lined up! It even looked like the original transformer, and lead exit points were compatible with the chassis. So with all showstoppers resolved, I could proceed with the restoration. At this point I had to order some parts that I do not normally stock.
I assume that all paper and electrolytic capacitors are leaky and thus should be replaced. I always "restuff" the original components if possible. I normally stock only 630 volt axial film capacitors, and use these for restuffing the original paper tubular capacitors. Three capacitors in this radio were rated at 0.003mfd at 1500 volts. I have been unable to find new components rated at 1500 volts or more that would fit inside the original cases. Thus I had to use either disc ceramic capacitors or parts from my vintage Arco “color rated” capacitor kit which were likely dipped film capacitors rated at 1600 volts, and forgo restuffing. I do not replace mica capacitors, but may test them in place if possible (usually this requires disconnecting one end of the capacitor). In one case, a new 0.22mfd/630 volt axial film capacitor was too large to fit inside the original case of C103 (0.2mfd/200 volts). So I used a 0.15mfd part instead – likely close enough given the application.
When I replace a component, I always remove the original part completely from a terminal. Other good components connected at the terminal are protected from heat using old medical clamps (hemostats). Excess solder is then removed using a solder sucker in order to expose terminal holes for reattachment of the rebuilt or replaced component. My re-stuffing process for wax/paper capacitors is as follows:
The original capacitor is removed from the radio, and the required lead length and any use of insulating sleeving noted.
The low melting point wax from each end of the original capacitor is melted and removed using an old 25 watt soldering iron.
The original wire leads are removed, as well as any remaining wax.
While the internal wax is still molten, a small screwdriver is used to push out the original paper-foil roll. In some cases, the contents came out when the leads were pulled out.
The original cases are then cleaned out, and any wax and dirt on the outside removed by gently heating the body with a heat gun and wiping with a paper towel while still molten.
If the required lead length is longer than that of the replacement capacitor, a piece of bus wire is attached before restuffing. The splice is made close to the capacitor body so that the splice is hidden inside the cardboard tube after re-sealing.
The replacement capacitor is wrapped in a narrow strip of paper towel in order to keep the new capacitor centered and to keep it from falling out.
The finished capacitor is then sealed with melted rosin (salvaged from early RCA Superhet catacombs, and donated by or purchased from members on Antique Radio Forums).
I do NOT recoat the outside of the rebuilt capacitors with wax (I'm not sure what was originally used - probably beeswax).
While cleaning out some of the paper capacitors prior to restuffing, I was surprised to find a CD Dwarf Tiger capacitor inside an original Philco capacitor shell! I suppose Philco was unable to build enough original Philco parts due to shortages following the end of WWII, but wanted only Philco branded parts used in their radios. [Image: http://i261.photobucket.com/albums/ii80/...lcoCap.jpg]
Here are some restuffed Philco wax/papercapacitors using the method above: [Image: http://i261.photobucket.com/albums/ii80/...erCaps.jpg]
Filter Capacitors
The original filter capacitors were removed from the chassis for restuffing. C102 is a twist lock type capacitor rated at 40mfd with a cardboard cover. The parts list did not list the working voltage, and there was no marking on the cardboard capacitor case. The capacitor can inside was stamped as 40mfd/450 volts. The inner case was restuffed using a 47mfd 450 volt radial capacitor. C105/C105A/C205 is a twist lock type capacitor rated at 50mfd, 5mfd, and 5mfd all at 300 volts. It was restuffed using a 47mfd and two 4.7mfd radial capacitors at 450 volts.
My procedure for restuffing twist lock type can capacitors is as follows (there are many discussions and examples with photos using slightly different techniques on the various Antique Radio forums as well as YouTube. I generally use radial type electrolytics for restuffing, since they are usually much smaller than axial types. This is especially critical in cases where there are multiple capacitors inside the can.
Remove the cardboard cover (C102). In this case, I had to use a heat gun to soften the cement or tar holding it to the can. Sometimes the cover will pull off easily without heating. It is important not to pull using the capacitor's terminals, but rather the ground tabs, while the heated cover is held using an old wash towel or rag.
Clean the outside of the metal can using lacquer thinner.
Uncrimp the bottom of the metal can using a small screwdriver and small diagonal cutters. Try to minimize damage to the outside of the can, since it will be visible unless the capacitor has a cover.
Remove the mounting ring and the terminal board, cutting the aluminum leads to the capacitor body to free up the terminal assembly. I had to peel back a small area of the can in order to be able to insert a small screwdriver under the terminal board and start the removal process. One must be VERY careful and not break the terminal board, and to keep the terminals attached to both fiber boards (do not allow the terminals to pull free of either board). There was a layer of rubber sealing material between the two terminal boards, which was retained.
Clean the terminal board assembly using lacquer thinner and old toothbrushes.
Remove the can contents using a heat gun to release the tar, followed by a thorough cleaning. I first remove as much tar and other crud using mechanical means.
Connect the replacement capacitor leads to the original terminals by drilling small holes through the terminal board close to the terminals, passing a lead through the holes, and soldering them to the terminals on the inner side of the lug. I use small numbered drill bits and a Dremel Moto Tool - the drill bit used is only slightly larger than the component leads to be used.
The common ground lead of is passed through a small hole drilled near one of the three capacitor ground/mounting tabs. This lead is not soldered to the ground lug until after the capacitor is secured in the chassis mounting wafer (otherwise the solder would prevent the lug easily passing through the hole in the mounting wafer or could damage the wafer - ASK ME HOW I KNOW THAT).
Reinstall the terminal board and mounting ring and restore the crimp around the base (I use a plastic faced hammer).
Reinstall the cardboard cover (it was not re-glued - just held on by friction). The cover hides any signs of the bottom crimp being disturbed.
I have attached a copy of the schematic, for those members who are not members of RadioMuseum.
I tried using Photobucket as recommended, but when using a width of 900 pixels, the size was about half the size when using an attachment. If anyone would like a clearer copy, send me a PM or email.
Been following your thread on this tropic. Looks like you are going all out on this one and doing great work.
I have an 53-960 tropic I hope to get to later this summer or fall.
The replacement power transformer and restuffed filter capacitors were next re-installed. As mentioned before, the mounting centers of the original and replacement transformers were exactly the same, so no modifications to the chassis were needed. All of the wiring associated with the 115/230 voltage selector switch and Hi-Med-Lo line voltage switch was removed. The switches were left in place. The power transformer primary leads were connected directly to the AC power supply terminal strip. The existing AC power switch wiring was left in place (also connects to the AC power terminal strip). There was some fraying and wear where the wiring bundles passed through holes in the bottom transformer cover. The cover was removed and shrink tubing was applied to any wiring that was frayed to prevent future shorts. Some of the lead wires were very stiff and could break if bent. I used a heat gun to soften up the old insulation prior to bending the leads. There was no room inside the transformer covers to splice on new leads, so the existing leads had to be used.
The replacement power transformer leads exited the bottom cover, just like the original. However the positions of the primary plus 6-volt filament bundle and the high voltage plus 5-volt rectifier bundle were swapped on the replacement – they were on opposite sides of the cover. This meant that some of the replacement transformer leads were too short. These leads were spliced with appropriate new wiring and the splices insulated with shrink tubing (double layers for the high voltage secondary leads).
The wax/paper capacitors that were removed in order to gain access to the filter capacitor wiring, and were subsequently restuffed, were also reinstalled. A few out of tolerance resistors in the power supply and audio amplifier sections were replaced. I do not like to have too many loose parts at one time, so before doing any further recapping or resistor replacement I wanted to reinstall everything that had been removed up to this point. Once some of the (leaky) capacitors in the audio section were removed, additional resistors were discovered to be out of tolerance. And some had likely been damaged by soldering heat. I tried to make sure that all resistors in the phase inverter circuit were within 10% tolerance, as they affect the balance of the audio output stage, and thus the fidelity.
C100 and C101 (bottom center of bottom view) were replaced with 0.0027mfd 1600v dipped film capacitors. The originals (0.003mfd 1500 volts) had been replaced with 0.003mfd 600 volt paper caps as received. Since these are connected between the high voltage secondary leads and the chassis, I did not trust using 630 volt caps here.
Attached are photos of the top and bottom views of the power transformer area of the chassis. The AC power cord has not been installed at this point.
Looks like I may have tone control trouble! When I first did my survey, the tone control pot was questionable. But at that time there were leaky capacitors and some shunting resistors that would affect a clean measurement. After disconnecting the control, I was able to get a good measurement. The control (part number 33-5508-2) was supposed to be 6megs. The control measured about 16megs across the resistance element (rather than 6 megs). But the action is really weird. If I measure from the wiper to one end of the pot, the resistance starts near zero and goes up to about 16megs at approximately ½ rotation. The resistance then stays at 16 meg for the remainder of rotation. Measuring from the wiper to the other end, the resistance starts at 16megs and stays there for about ½ rotation. It then smoothly moves down to near zero ohms! It almost appears that the resistance element is split at about the middle. Each end starts at near zero, increases to about 16megs at ½ rotation, and then does not change for the remainder of the rotation. I don’t know how they did this – it looks like a normal control inside, although there are two rotating contacts that move together on the resistance element. I have included a portion of the schematic that includes the tone control. It appears that starting from one end, as the control is rotated the bass is gradually increased or decreased. As rotation continues, treble is cut.
The control may work as is, but certainly does not match the schematic as far as value. I did clean it, but that did not change anything. I’m not sure how this control could be replaced with other than a 5 meg normal control. The original appears to be tapered on BOTH ENDS! Does anyone happen to know for sure how this circuit works? Any suggestions as to a replacement if needed?
Continuing with the recapping process, I found that capacitor C306, which couples the output of the second detector/AVC diode to the high end of the volume control, is rated at 0.01mfd and 1000 volts! I cannot see a reason for this voltage rating. There is no high voltage involved - just signal level audio. Anybody have a guess why this voltage rating would be used? The capacitor is original and has a Philco part number 30-4598. I am planning on using a 630 volt part to replace it.
The rest of the capacitors were restuffed and reinstalled. Any out of tolerance resistors not yet replaced were replaced. All of the original tubes that tested good were replaced, and any bad ones replaced. A new power cord was attached. I assumed that flat brown vinyl (likely originally rubber) is appropriate for 1946. I then carefully examined the chassis for unsoldered joints and solder blobs. I then checked once again for any B+ shorts. The speaker was plugged in, and an antenna wire attached. I pulled the rectifier tube and powered up the chassis using a Variac through a watt meter. I started at zero volts and gradually increased the line voltage while watching the watt meter. All the tubes lit up and current draw was normal.
I then reinstalled the rectifier tube and monitored B+ with my DVM. I again powered up the chassis with my Variac through a watt meter while monitoring the B+. Power was increased at about 10 volt increments, allowing time for the new filter caps to reform. The band switch was set to the broadcast band and the volume control set a maximum. At about 80 volts AC I heard some noise. I increased the AC to 115 volts. The radio actually worked on all bands. The volume control was smooth and free of noise. The tone control, which was an area of concern, seemed to work OK although I’m sure not as well as it should, since the resistance had drifted from 6meg to 16megs! At maximum CCW, bass boost or loudness compensation was reduced. As the control was rotated clockwise to about ½ rotation, bass increased. Further CW rotation reduced the treble. So for most fidelity the control should be centered. CCW rotation reduces the bass, and CW rotation reduces the treble. This seemed to agree with the schematic.
The next step is alignment of the two IF stages and 10 bands of trimmers! At this writing I have completed alignment of the IF stages and Shortwave #3 band. I was concerned about this band since my signal generator only goes up to about 12mHz with any stability. I have to use harmonics for adjusting anything above 12mHz. So to set the SW3 band to scale at 21mHz, I set the generator to 10.5mHz. I use a frequency counter to calibrate the generator. SW3 was easier than I thought it would be. Even the image frequency appeared where it should have been. All that’s left is to complete the alignment, clean the cabinet, and reassemble.
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