I just ran across and purchased a vey nice condition Philco 531 in a consignment shop and it seems to be intact with the exception of needing a new grille cloth and a cabinet back (assuming it was made with one). I haven't removed the chassis from the mounting board and checked any components underneath as of yet, but since it looked in such decent shape I decided to hookup the unit to a variac and slowly bring it up to voltage. All the tubes have good filaments (and to my surprise the dial light works) but I hear nothing at all (even AC hum) from the cabinet speaker. As it was about 1AM, I didn't go any further.
Just wondered if any of you had any tips on this unit you could share - I'd appreciate it. I did run across an article about replacing the speaker using a PM type and audio transformer if the speaker was bad. Didn't check the coil last night but I did see "Utah" on the speaker itself if that gives a clue about some of the faulty units. Thanks in advance!
Had some time to play with the 531 today and found a bad solder joint on the ground lug of the transformer coupling the first and second AF stage. Now I get a slight buzzing in the speaker. Did a voltage check with just the rectifier tube installed and had 302VDC at point "G" on the schematic. For kicks I hooked up an iPod shuffle into the phonograph jack and the AF section is working. Still nothing from the tuner though. Eliminated the first through third RF tubes by subbing them into the first AF socket and all appear to work. Possible detector tube failure or something else to check (plate voltages, etc.) Thanks.
Sorry about the multiple posts - I feel like a kid at Christmas with a new toy with this 531
. Had more time to tinker with it. Simple oversight on my part for the lack of reception. While there was a coil of wire on the antenna lug, apparently spreading it out (or simply connecting the LOC lug to the ANTENNA lug) was that problem. Found that when I was cheking plate voltages, the meter lead made a station pop in. Now that this is resolved, I have one additional problem with the set and a recapping question.
When the unit is first powered up and a station tuned in, I get good volume output for about a minute or two and then it slowly fades to very low volume. Turning the set off and back on after less than a minute will again result in a good output until it again fades.
Question on recapping this unit. Should I just be concerned with recapping the electrolytics in main 'condenser' or in your experience should other caps be replaced. Also with the electrolytics - can I simply install new caps on the underside of the chassis and leave the existing condenser wires in place?
Thanks again!
Since the paper caps are not too terribly expensive to replace I would replace them with newer caps, why chance it when they are in most cases under a buck to buy. On the new electrolytics you can mount them underneath if you find space but cut the leads from the old one and connect them to the new one, taking the old one out of the circuit but leaving it for looks if it is an above chassis electrolytic. Or you can check out this link
http://www.philcorepairbench.com/tips/svctip46.htm to re-stuff the old cap can.
Hi Tony, and welcome!
If your 531 has a Utah speaker, then it is a replacement. The original Philco/Timmons speaker was of the magnetic type, high impedance, and has a pot metal driver which goes bad over time. A replacement speaker with matching audio output transformer will give the radio better fidelity (i.e. will sound much better), at the sacrifice of originality. But if the original speaker was bad anyway, you don't have much choice if you want your set to play...
Be careful once you reinstall the set in the cabinet. There are some bakelite washers that mount in the phonograph jack to insulate it from the brass escutcheon which it mounts on. Lose one of these, and you may lose all sound from your unit due to the jack shorting out from the missing bakelite washer(s). (This may not apply to your set since it has a wooden cabinet, but it is very much applicable to the metal cabinet 511 series sets.)
Please follow Stude's advice and replace ALL of the paper capacitors. Your set did not originally use electrolytics in the power supply circuit; instead, it uses a large, rectangular can which houses six capacitors. It's up to you if you want to replace the old filter caps with mylar or electrolytic. You can purchase 1, 2 and 4 uF mylar caps but they will be physically large (yet nowhere near as large as the originals). If you want a really compact component layout inside the filter can, use electrolytics - the 1, 2.2 and 4.7 uF electrolytics are quite small. You must watch polarity though if you use electrolytics.
You can remove the old filter can from the radio, disassemble, melt out the old components and mount the new caps on the terminal board so that they will be inside the can when reassembled and reinstalled in the radio.
A schematic may be found at
http://www.philcoradio.com/tech/images/511.jpg .
The mylar caps for stuffing the old can works well and you don't have to worry about the if you have the polarity correct. If the can on this unit is about the same as the model 95 or 96 there is enough room to install them. To get the mess out of the can what I did was get an eye screw big enouth to get the shank of a screw driver (larger one) in and screw the eye screw in (the longer the better, 2-4") and bake the can in the oven at 300-350F for at least and hour or so and then with some leather gloves on hold the can and put the screw driver shank though the eye bolt and pull the tar mess out. It's smelly and sometimes messy but it is worth it because the original look is maintained.
Stude - you mean your significant other lets you bake radio parts in your oven?
The 511 series filter can is the same physical size as the 95/96. But, of course, it uses a different pinout.
Normally I do this when she is visiting friends and doesn't know what I am cooking. You take the lower portion clipping the leads, the 95 was fun because you have quite a few caps to replace so I used some shrink wrap on the leads to keep them from shorting. Even baking that can for an hour or so does not melt it to the core but does melt most of the outer mess and the eyebolt helps pull it out of the can. If I had to do the 95 again I would solder a terminal strip in for the ground leg and attach the leads to the terminal strip and this would make some of the clutter a bit better. The 95 had 8 total caps to pack in which made it a little more difficult. I will do the same thing to my model 16X but luckily there are less to stuff in the can, only 5. That stuff does stink and get gooey so I put the can inside an empty coffee can so if any goo drips out it won't drip in the oven. I use leather gloves with holding it because cap can does get a bit hot.
Just got back from a short Halloween camping trip with the kids and thanks for the welcome and replying to my 531 questions. I think I'm going to go with electrolytics for the 1, 2 and 4 uF units in the container. I'll be sure to get my wife's permission before baking that old unit first though. Looks like three of the .1uF caps have the 100 ohm resistor wound around them. I will be leaving the caps in as not to have to replace the resistors and just cut the lead that goes to the transformers from the old unit and installing new caps alongside the old. Probably won't get to play with this again until next weekend...sigh.
The issue with the fading audio - is this possibly related to the caps as well?
Once the caps are replaced then that will make any other trouble shooting much easier. Also check the resistors for values, on older radios with the dogbone type resistors the values will shift much higher than they are rated. Normally +/-20% of the original value is ok, replace any that exceed this. Some people like to keep the look of the dogbone and I try to run the replacement resistor under the dogbone and clip the one lead and put a shrink warp around the clipped leg act as the original lead. Most people just replace them all together but that is up to you, if you want to retain the original look.
All the resistors seem to be in tolerance with the exception of the 70k unit that feeds the primary of the first AF stage. That one measures low - around 54k. I'd like to replace that when I recap the unit as well however I'm not sure what the wattage rating on that is. It's a glass cartridge type resistor (Z-129) and want to make sure I don't underrate the replacement. Thanks!
Did you measure in circuit or one lead clipped to take it out of circuit, sometimes if a cap is in the circuit it causes the resistance to be lower than expected. Normally you see most resistors creep up rather than dropping down in resistance.
I pulled this and the 2 Meg 'cartridge type' unit out and checked them on the bench out of circuit.
Both the 70K and the 2Meg resistors have cone shaped metal ends and 'snap' into the circuit. I had them out to insure the ends and 'receiver contacts' were clean and checked the resistors out of circuit. Thanks!
Just finished recapping the 531 about a half hour ago and fired the radio up slowly 'just in case' with the variac and lo and behold it appears that the fading audio issue went away. Still wondering about that low resistance value in series with the plate supply on the detector tube. What effect would too much voltage have on the set? I did read on another site in trying to find information on the resistor wattage that those units sometimes absorbed moisture into the core and that might explain the lower value.
Now that the recapping is done, I believe the set needs a good alignment as it seems the higher band stations come in much better than the lower. Have a bid on an RF signal generator and hopefully will win that one. Question on aligning and neutralizing the set. Can it be done with the bottom plate off as I will just leave it aside until I get a generator, or does the shielding of the plate make a difference in alignment?
Another question about the general operation of the set. There is a terminal for a ground connection - do these sets benefit by connecting them to earth ground? Also another thing I found strange was on the tuning scale. My first thought was that on the 0 to 100 scale, 0 would be at the low end of the tuning range, not 100 as it operates.
Again - thanks for putting up with all my posts, questions and the help! I think I'm catching the bug and hope to find another low priced set to tackle.