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Old Electronics
Problem with Bulb Radio Amplifier.
14
hace 5 años
hace 5 años
Hi. Good night. I am an electronic technician and I am spending some time repairing bulb radios. I ask for your valuable help in getting a diagram of a Bulb Radio-amplifier Brand ELA which has the number 4615 on the chassis. It happens that I got it in the market of chacharas and the intention is to restore it. Tune to Modulated Frequency only. It carries 7 bulbs including a "magic eye" or tuning indicator. The nomenclature of the bulbs is as follows: 6AQ8 / ECC85 As amp. RF and Oscillator / Mixer. 6CB6A as an intermediate frequency two stages in total, (one bulb per stage). 6AU6A / EF94 as FM limiter. 6AL5 as FM detector. UCL82 as a previous and audio output power stage, since it is an audio triode-pentode, and to culminate the EM84 as a tuning indicator (Magic Eye). The device works in the audio frequency part, not the radio, which incorporates inductive tuning, not capacitive like many others. Although the volume is somewhat low, I am sure that it worked the first time I connected it since that way I can rule out the state of certain parts such as the power and output transformers, as well as the rectifier stage, which is of Full wave and takes two diodes to perform that function. The diagram is required because it has detached wires in the part of the "pi" filter which has a three section electrolyte capacitor. I suspect that there is no current to the tuner for that cause, hence the radio is not heard. In addition there are 2 other cables inside that are also cut. (Apparently they are filaments although all the bulbs light). Another thing I noticed weird is that the UCL82 (Audio Ampl.) Its filament is directly connected with a power resistance of approx. 1kohm / 10w in series with the 117 hp line. That is, without going through the power switch of the volume control. In no scheme of this type of radios had I seen anything similar. Hence the need to have the diagram. I enclose photos of the mentioned device hoping to have your help.
Let's continue in this exciting bulb radios restoration challenge that offers so many satisfactions !!!
Thank you very much and best regards.
ATTE. Voltioferoz
14
hace 5 años
Perhaps for that reason the two cables that I mentioned below are left over, in addition to the fact that the ECL82 is for 6v, and the pin out is the same. The UCL82 is for 50v. It also happens that, connected to the lamp in series and functioning as an amplifier of an ipod, the lamp lights up 1/4 of its intensity, is this normal? Or should I search for a short or dry capacitor or something similar? Thank you for the prompt response and for the help. Warm greetings. Volt Fierce.
10.397
hace 5 años
Of course, it measures with a tester in AC the voltage that reaches the filament, it is rare that they would have replaced that valve with a UCL82 since the original, if it were as we suppose, is easier to obtain and more economical, since it was used a lot in the Winco record players, and in audio output of some valve TVs, I must have a lot of those new ones, you could measure the cables that you have loose, and if they bring 6v there would be no doubt about the reform, greetings
10.397
hace 5 años
I tell you to search without success this circuit, it could be a project made at home or built by a student of a school as practical armed lessons, since I could not find something with that brand, in a teaching institute by mail in the 70 something similar was armed but it also had AM, and other bands of OC, greetings
14
hace 5 años
Well yes, the loose wires below are filament (give 6vca). In addition, the resistance that is in series with the UCL82 only leaves the filament 35v and not 50v as it should. (It measures 35VAC the filament and 85VAC fall through the resistance.) Maybe that's why it is under the volume of audio amplification. It could be intentional to extend the life of the UCL82. I will test (doing the calculation) another R that allows more voltage (45v-48v) to the filament Do not worry about the dear colleague circuit. Your opinions have helped me too much. Many thanks and fraternal greetings!
Volt fierce.
14
hace 5 años
Hi dear pr122 how are we? Taking up a previous comment from you about ECL82 valves, I would like to see how possible it would be for you to do me the favor of selling a couple of them and thus leave the radio circuit as close to the original as possible.
Thank you very much for everything and happy end.
14
hace 5 años
Just to greet and comment that I am very happy because I already operated the FM ELA radio which kindly gave me great help here. The solution was in the power supply. He had broken wires in the tunnel module and B + did not reach him. I opened the tunnel (it was not easy to close it) I took out a line and connected to the .B + and the matter was fixed. Now I can enjoy music with very good sound quality. I am very grateful.
Thank you so much that without the help of this forum it would not have been possible to operate the radio. See you soon and ... let's continue restoring !!
14
hace 5 años
hace 5 años
Just to greet and comment that I am very happy because I already operated the FM ELA radio which kindly gave me great help here. The solution was in the power supply. He had broken wires in the tunnel module and B + did not reach him. I opened the tunnel (it was not easy to close it) I took out a line and connected to the .B + and the matter was fixed. Now I can enjoy music with very good sound quality.
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