I have reviewed some of the posts here on low-volume problems and hope you can offer some advice based on a specific symtom.
I recapped a Crosley E20 MN but volume is very low. The alignment is per specs. All electrolytic caps are installed properly. If I connect the external antenna screw with wire to a water pipe ground volume returns to completely normal. Do you have any suggestions?
Thank you in advance for any advice.
Randy
Check all capacitors for any leakage at all, even in the millions of ohms. If you didn't replace the mica capacitors, check these. People assume that these never short, and are made of mica. They do occasionally short or have leakage, and sometimes they are paper, not mica. Usually they are fine. Make sure you connected all wires where they should go, and even if you didn't touch the wiring of the set, perhaps someone else did. Make sure it is all correct. Make sure that the large secondary of the loop is what's connected to the radio, and not the small primary, which should be the coil you use to make external antenna and ground connections. Make sure that the tuning capacitor is connected properly. Usually, if one section is smaller than the other, the smaller section will go to the oscillator, and the larger to the antenna circuit. Make sure that all IF transformers are connected properly. Did someone reverse the primary and secondary? Usually the primary wires will be red and blue, and the secondary ones will be green and black. If you do not believe that the transformers were ever disconnected, then they are likely connected properly. Make absolutely sure that the AVC resistor has not drifted in value. It must be 2.2 meg or around that value. It cannot be lower than 2 meg or higher than 3 meg. Make absolutely sure that the AVC buffering capacitor has no leakage and that it is not open. If you replaced it, then it should be fine. Try jumpering a wire from AVC to B-. If this increases volume, then you may have trouble here. Do this only when operating the radio from the loop alone. When you achieve normal operation by using an external antenna, strong local stations will cause the AVC to automatically reduce the volume. If you have the radio tuned into a strong local station, and have full volume using the external antenna, the volume WILL increase if you short out the AVC, and this is normal operation. This does not in any way mean that your AVC circuit is faulty. When the radio is operating poorly with just the loop as it is now, or when you are tuned into very distant stations with the radio operating properly, the AVC should not reduce the volume much. If it does, then you likely have a drifted AVC resistor or other faulty component.
Now, after you've checked all of this, how new is your signal generator? How many times have you used it successfully before? If you cannot find any trouble, try adjusting the IF transformers to increase the volume of the set. Do this simply by listening to the set, and not with the signal generator. Also try adjusting the antenna trimmer in the same manner. If you are able to increase the volume of the set by doing this, then your signal generator is not callibrating the set properly, and it needs some work. (Good luck trying to get a radio repairman to retune it for you...sometimes you can callibrate some of the scales by tuning them in on a known good radio.) Either that, or you accidently looked at the wrong part of the scale. A sure sign that the radio is not aligned properly is that the stations do not line up with their designated markings on the dial. It is normal for some stations to be slightly off on many radios. Perfect alignment with a mass produced set is very difficult to achieve. For all of the stations to be off, especially if they're drastically off, or one side of the dial is off, means that the radio has not been aligned properly.
Also, a mistake I recently made was reading modern capacitor values improperly. For some reason manufacturers don't just put the value in MFD or MMFD anymore. They have to put it in a code. You can find this code (and several others that are used) on the internet, but basically the code is three digits and a letter. The little yellow "metalized film" capacitors use this code. First two digits are the value. Third digit is the multiplier. Multiply the number you get by one millionth, or .000001 to get the the MFD value. If you wish the value to be in MMFD (or PF as they now call it), simply leave the number alone. The letter at the end is the tolerance. The only one I remember is the letter K, which I think stands for +/- 10%. There are other letters from A to Z. An example would be 473K. This is 47 with 3 zeros, or 47000 MMFD. To get the MFD rating, multiply by .000001. This gives you .047 MFD. With a K at the end, you'll have a value +/- 10%. A 473K capacitor would be a fine replacement for the conventional .05 MFD capacitor.
Thomas
Many thanks for the comprehensive answer. I am relatively new to radio tinkering though I have long experience with anything from antique British bike electrics (guarenteed to drive you over the hill) to jet aircraft electrics. Anyway I am learning and this forum is very instructive.
To answer the series of questions you posed; the radio was found in a junk store about a month ago. Close visual inspection and scematic leads me to believe the radio is completely factory original and un-repaired. It was not working though the tag on it said it hums loudly.
The visual inspection revealed that the rectifier tube 35W4 was blown...probably from someone letting it hum too long. A new tube bought the power and loud hum of bad caps back for the few seconds I plugged it in for. I replaced all the caps with orange dips one at a time. All the electrolytics were also replaced to the correct value, voltage and polarity. I also have a cap value conversion chart at hand and completely understand the coding and conversions of sizes. I triple checked all the caps for value before install. For anyone interested a code guide can be found at; http://www.elexp.com/t_capaci.htm
The Riders parts list and more so the schematic I pulled off the internet leave alot to be desired as far as definition of the small numbers and letters on the schematic as they relate to the parts list. Even magnified and the schematic blown up some of the letters and numbers are nearly impossible to read which leaves me guessing and tracing the circuit from a different direction to discern some of the components.
One capacitor looking device coated with the same brown wax has me puzzled bit. It is shaped like a tubular cap but has a coller in the center that protrudes from the surface all around. The entire component has the wax covering though the wax at one end is distinctively bright red. Two leads go to common out one end an the two at the red end are across the 12BES tube with one lead via a resistor and also connected to anther resistor and on to the tuner.
Not being satisfied with the reliability of my new old signal generator I also ran the alignment sequence by ear using the strongest station at the upper end without any noticable changes. The radio volume will blare when connected to the external ground. The radio is also equipped with an external phono switch.
I will initiate the checks you suggested. I guess given the symtom of working perfectly with the external ground I was hoping for a something simple. Like Lucas electrics its rarely simple..aye?
Thank you again for the information. If you have anything else to add from this reply it will be appreciated.
Randy
:Well, since you are able to get normal volume with an external antenna, your audio section should be alright. You are able to blare the radio, correct? Did the radio work before you replaced the capacitors? Did you replace all capacitors or just the electrolytics or just the electrolytics and the paper ones? Make sure that all of the electrolytics are of the proper voltage rating and are installed with proper polarity (I know you said you installed them properly, but just double check). If they are too low a voltage rating (less than 150), or are installed backwards, then the voltages will be low in the set. Check all voltages in the set against the voltages that the manufacturer has listed. For control grid circuits, it is difficult to get an accurate reading unless you have a very good meter, but for screen grid, cathode, and plate circuits, voltage measurements should be fairly easily taken.
:
:Check all capacitors for any leakage at all, even in the millions of ohms. If you didn't replace the mica capacitors, check these. People assume that these never short, and are made of mica. They do occasionally short or have leakage, and sometimes they are paper, not mica. Usually they are fine. Make sure you connected all wires where they should go, and even if you didn't touch the wiring of the set, perhaps someone else did. Make sure it is all correct. Make sure that the large secondary of the loop is what's connected to the radio, and not the small primary, which should be the coil you use to make external antenna and ground connections. Make sure that the tuning capacitor is connected properly. Usually, if one section is smaller than the other, the smaller section will go to the oscillator, and the larger to the antenna circuit. Make sure that all IF transformers are connected properly. Did someone reverse the primary and secondary? Usually the primary wires will be red and blue, and the secondary ones will be green and black. If you do not believe that the transformers were ever disconnected, then they are likely connected properly. Make absolutely sure that the AVC resistor has not drifted in value. It must be 2.2 meg or around that value. It cannot be lower than 2 meg or higher than 3 meg. Make absolutely sure that the AVC buffering capacitor has no leakage and that it is not open. If you replaced it, then it should be fine. Try jumpering a wire from AVC to B-. If this increases volume, then you may have trouble here. Do this only when operating the radio from the loop alone. When you achieve normal operation by using an external antenna, strong local stations will cause the AVC to automatically reduce the volume. If you have the radio tuned into a strong local station, and have full volume using the external antenna, the volume WILL increase if you short out the AVC, and this is normal operation. This does not in any way mean that your AVC circuit is faulty. When the radio is operating poorly with just the loop as it is now, or when you are tuned into very distant stations with the radio operating properly, the AVC should not reduce the volume much. If it does, then you likely have a drifted AVC resistor or other faulty component.
:
:Now, after you've checked all of this, how new is your signal generator? How many times have you used it successfully before? If you cannot find any trouble, try adjusting the IF transformers to increase the volume of the set. Do this simply by listening to the set, and not with the signal generator. Also try adjusting the antenna trimmer in the same manner. If you are able to increase the volume of the set by doing this, then your signal generator is not callibrating the set properly, and it needs some work. (Good luck trying to get a radio repairman to retune it for you...sometimes you can callibrate some of the scales by tuning them in on a known good radio.) Either that, or you accidently looked at the wrong part of the scale. A sure sign that the radio is not aligned properly is that the stations do not line up with their designated markings on the dial. It is normal for some stations to be slightly off on many radios. Perfect alignment with a mass produced set is very difficult to achieve. For all of the stations to be off, especially if they're drastically off, or one side of the dial is off, means that the radio has not been aligned properly.
:
:Also, a mistake I recently made was reading modern capacitor values improperly. For some reason manufacturers don't just put the value in MFD or MMFD anymore. They have to put it in a code. You can find this code (and several others that are used) on the internet, but basically the code is three digits and a letter. The little yellow "metalized film" capacitors use this code. First two digits are the value. Third digit is the multiplier. Multiply the number you get by one millionth, or .000001 to get the the MFD value. If you wish the value to be in MMFD (or PF as they now call it), simply leave the number alone. The letter at the end is the tolerance. The only one I remember is the letter K, which I think stands for +/- 10%. There are other letters from A to Z. An example would be 473K. This is 47 with 3 zeros, or 47000 MMFD. To get the MFD rating, multiply by .000001. This gives you .047 MFD. With a K at the end, you'll have a value +/- 10%. A 473K capacitor would be a fine replacement for the conventional .05 MFD capacitor.
:
:Thomas
The page above is fairly clear. Don't know if that's what you looked at before, but I can tell what most of the components are on that page. It has the values listed right on the schematic.
The device you are talking about that connects to the 12BE6 tube, and looks like a condenser with a collar, is the oscillator coil. You will find it on the schematic, below the 12BE6 tube. The central part is probably wood or a paper tube. The collar is the coil itself.
On the diagram, in the audio section (12AV6), you will see components related to the volume control that are enclosed in a dotted line box. If you look in your radio, you may find a long epoxy coated thing with several wires coming out of it that connects to the volume control and its related components. This epoxy coated thing contains all of those components that show up in the dotted line box. If your radio has discrete components connecting to the volume control, and you do not see this epoxy coated device with many leads, then Crosley likely didn't use it in your set. This was a new thing used in the 1950s. It's kind of like an early integrated circuit chip.
In your diagram, if two wires cross, unless there's a dot where they meet, then they are not connected. I just wanted to make that clear, as there's a .002 MFD condenser that runs from the 12AV6 resistor to the 35W4 tube, and it looks like it also connects to the volume control, but in reality it does not. If it did, you'd see some very interesting things happen.
I really cannot think of what could be wrong with your set at this time, though. If you are able to receive full strength stations, both near and distant, by connecting the radio to ground, then your circuits are likely aligned. They wouldn't pass loud stations if they weren't. The only two things I can think of are checking the wiring of the loop. Were the wires broken off when you purchased the set? They often do when the loop is attached to the back cover. Make sure you reconnected them properly if they did break off. Make sure that someone else didn't connect them improperly. The other thing I have thought of is checking the tuning condenser for shorted plates. Perhaps the plates on the antenna circuit have shorted. In order to test this properly, you must disconnect the lead going to the antenna side of the condenser (this is usually the part with more plates of larger size). You do not need to disconnect the frame.
It is possible that you have a weak 12BE6 tube or 12BA6 tube. Check all resistor values. You must disconnect them to check them. Make absolutely sure that the 2.2K AVC resistor has not drifted or opened up. What happens when you connect a wire from the condenser frame to B-? B- is the side of the line cord that is switched. If volume improves (radio not grounded), then this resistor may be open or drifted.
Be absolutely sure that the part of the oscillator coil that connects to pin 2 of the 12BE6 gets connected to B- (other side of coil). Check all the power resistors. What are the voltages at the tube pins? The proper voltages are listed on the web page above.
Thomas