01-10-2007, 05:28 AM
Hello,
hope you can undestand my english
I've recently bought a Philco Moel 20 on ebay. it was in vey bad condition. lot of rust, CV iout of order because of the rust, the main power transformer was burned...
I've rewind the main transformer for the voltage in France so the primary is made for 230V AC. I've renew all the bakelite caps and main block condenser.
The model 20 works good.
I've got a question about the plate voltage of the push of 71A.
If you look at the schematic, you see the point labelled "D". At this point are directly connected the plate of the 24A, le center taps of the primary windind of the output transformer and the coil of the speaker. The service manual say thaht the plate voltage of the 24 is 250VDC. So i suppose there's 250V at the point "D" and also at the center taps of the primary of the output transformer. The manual says that we do have 215V on the plate of the 71A.
I do not understand how is it possible. The resistance of the primayr of the output ttransformer is know enough high to explain the difference of 35V.
And if you look at the datasheet of the 71A, the maximum is 180V on the plate. My question is, why philco have made de decision to put 215V on the plate because it's a little bit high ?
After the rewinding of the main transformer, I've got 330V AC on each HV winding. After the first filter and the first choke, I have 240V DC, (it's not 250V but it's OK, the radio work) What is this mystery ? I don't understand. All the other voltage are OK.
many thank's for the reading (oh.. if you understand one word of course
).
I will made an page on my web site to explain all the works on this model 20 and I will give all the details of the rewinding of the main transformer, because I've count the number of turns of each winding and the diameter of the wires I've used.
I'm very happy to hear it working again.
best regards
Frederic ABGINOLI
hope you can undestand my english
I've recently bought a Philco Moel 20 on ebay. it was in vey bad condition. lot of rust, CV iout of order because of the rust, the main power transformer was burned...
I've rewind the main transformer for the voltage in France so the primary is made for 230V AC. I've renew all the bakelite caps and main block condenser.
The model 20 works good.
I've got a question about the plate voltage of the push of 71A.
If you look at the schematic, you see the point labelled "D". At this point are directly connected the plate of the 24A, le center taps of the primary windind of the output transformer and the coil of the speaker. The service manual say thaht the plate voltage of the 24 is 250VDC. So i suppose there's 250V at the point "D" and also at the center taps of the primary of the output transformer. The manual says that we do have 215V on the plate of the 71A.
I do not understand how is it possible. The resistance of the primayr of the output ttransformer is know enough high to explain the difference of 35V.
And if you look at the datasheet of the 71A, the maximum is 180V on the plate. My question is, why philco have made de decision to put 215V on the plate because it's a little bit high ?
After the rewinding of the main transformer, I've got 330V AC on each HV winding. After the first filter and the first choke, I have 240V DC, (it's not 250V but it's OK, the radio work) What is this mystery ? I don't understand. All the other voltage are OK.
many thank's for the reading (oh.. if you understand one word of course
).I will made an page on my web site to explain all the works on this model 20 and I will give all the details of the rewinding of the main transformer, because I've count the number of turns of each winding and the diameter of the wires I've used.
I'm very happy to hear it working again.
best regards
Frederic ABGINOLI
