08-01-2024, 03:56 PM
Hi Adam, I have done the transformers for these sets in the past if you are stuck
Cheers, Ed
Cheers, Ed
RCA 9PC41 PROJECTION TV - 1949
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08-01-2024, 03:56 PM
Hi Adam, I have done the transformers for these sets in the past if you are stuck
Cheers, Ed
09-01-2024, 01:10 AM
(07-01-2024, 12:18 AM)LENINGRAD T2 Wrote: The main power supply is heavily corroded from the top. From the bottom, the chassis looks quite good. The sockets require re-riveting. Three 5U4 rectifiers have excellent emission. I obtained two voltages: 490V /correct/ from the larger transformer and 360V /should be 265V/ from the smaller one. The smaller transformer also provides two heater voltages of 5V and 6.3V, which are actually 10% higher. Possibly when fully loaded the voltages will be closer to what is specified. Is the incoming mains voltage also within the tapping that is set on the transformers?
Cheers.
Trevor MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC.
10-01-2024, 09:06 PM
I made quick preliminary measurements and presented them. The diagram of the TV I have does not include voltage values on the transformer outputs. I read the 265V voltage from another diagram from an RCA TV from the same period. I now found another diagram with a voltage of 360V, which is the voltage I obtained. So for now I can assume that the main power supply module is functional. Voltage values will certainly decrease when the load on the power supply occurs. I'm now waiting for the valves for the audio module. There are also two transformers there. Next in line is the horizontal deflection system and high voltage with another transformer. Thank you for comments.
10-01-2024, 09:13 PM
That's great news Adam.
I'm certain when all the work is completed you will find the transformer is indeed good.
Cheers.
Trevor MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC.
03-02-2024, 02:34 AM
The audio output stage is very efficient. It has its own power supply with a tube rectifier. It was designed by RCA in 1936. It was used in pre-war televisions. The same scheme is used in my receiver. The loudspeaker is suitable for a cinema hall. He is 32 cm in diameter.
I replaced the capacitors, low-power resistors, amplifying tubes and mains plug. In addition, I designed and 3D printed a mounting base for the electrolytic capacitor. Everything works. The speaker produces a pleasant sound. Adam
03-02-2024, 06:51 AM
(This post was last modified: 03-02-2024, 06:59 AM by Mike Watterson.)
Looks like a serious amp. Maybe about 12W is possible class B? Or perhaps as much as 25W with some distortion. About 10W in class A push pull.
I wasn't familiar with the 6F6, but it seems to be a higher power version of the 6V6, but less than the 6L6. I've used 6V6 and 6L6. Edit Reading up more it seems the 6F6 is the oldest of those and in late 1930s was replaced by 6L6 and 6V6, the 6V6 being a derived lower power version (0.5A vs 0.9A heater) of 6L6. The 6L6 is still produced and the 6V6 was very popular. So I guess that's why the 6F6 was unfamiliar to me.
03-02-2024, 10:27 PM
You are right, the 6F6 was replaced by the more modern and powerful 6V6 and 6L6 tubes in the late 1930s. I came across information that after the war, military warehouses still had many 6F6s, which is why they disappeared only around 1950.
03-02-2024, 11:07 PM
The next element is a large metal box with oscillator and horizontal deflection circuits. The final stage consists of two 6BG6G tubes. There is also a high voltage source with three 1B3GT rectifiers here. The transformer looks promising.
Adam
20-02-2024, 08:15 PM
The horizontal scanning section and high voltage power supply are almost ready for test run. I am only waiting for rare resistors for the high voltage circuit, 10Mom and 1.5Mom 2W. Unfortunately, old items have a value deviation of up to 50%. Initially, I wanted to insert any resistors that met only the criteria of resistance and power. However, I came to the conclusion that it would be better if I tried to get original new AB resistors. The high-voltage system is very well thought out and, in my opinion, there is no randomness in it. The large four valves are horizontal output and dampers. The frequency of the pulses supplied to the high voltage circuit is, of course, 15750.
20-02-2024, 10:03 PM
Hi Adam.
The work you are doing looks indeed very nice. The work on the Timebase section is excellent. Certainly watching this thread as often as I can. another up and coming operation though could curtail some time and then hopefully get a proper neck diagnoses done to relieve me of constant pins and needles and pain in my right arm and hand, very debilitating. Might be able to get on with some work if it gets sorted out.
Cheers.
Trevor MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC. |
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