04-18-2021, 05:56 PM
When each tuning condenser is fully meshed, the cursor on the panel should point to 100...
So expect that the radio will not tune all of the BC band and may only reach 1350Khz and no higher.
Although the speaker clicks the diaphragm may rattle..
The type of driver in the speaker will determine if polarity of the speaker leads ar to be observed. If there are (+) and (-) markings on the driver, connect the (+) wire to the B+ and the (-) to the plate circuit of the last audio tube...
If the driver is the bi-polar pin driven diaphragm motor the polarity is not important.
Be best to find used A-K transformers for the set. The audio transformers can be rebuilt by using modern units that have a high resistance primary. Some modern make-do replacements lack the primary resistance the net result is low volume and/or distortion...
If this is your first 20's battery set, be aware that scrimping on the power sources can also introduce problems like oscillation, poor sensitivity and poor volume. An absolute must is the "A" supply of at least 6 to 6.6 volts, even though the tubes are 5 volts. The reason is the rheostats lower that voltage and the difference is part of the tube bias. The rheostats also control the volume and detector sensitivity. The "B" battery must also have a low impedance using 9 volt transistor battery's will work but the set can oscillate. There is a chassis mounted cap in a metal can the should either be "stuffed" or replaced. This cap helps prevent oscillation.
http://www.atwaterkent.info/TechData/Dra...640sch.pdf
The url will help with the tubes:
http://www.nostalgiaair.org/References/A...lash08.htm
So expect that the radio will not tune all of the BC band and may only reach 1350Khz and no higher.
Although the speaker clicks the diaphragm may rattle..
The type of driver in the speaker will determine if polarity of the speaker leads ar to be observed. If there are (+) and (-) markings on the driver, connect the (+) wire to the B+ and the (-) to the plate circuit of the last audio tube...
If the driver is the bi-polar pin driven diaphragm motor the polarity is not important.
Be best to find used A-K transformers for the set. The audio transformers can be rebuilt by using modern units that have a high resistance primary. Some modern make-do replacements lack the primary resistance the net result is low volume and/or distortion...
If this is your first 20's battery set, be aware that scrimping on the power sources can also introduce problems like oscillation, poor sensitivity and poor volume. An absolute must is the "A" supply of at least 6 to 6.6 volts, even though the tubes are 5 volts. The reason is the rheostats lower that voltage and the difference is part of the tube bias. The rheostats also control the volume and detector sensitivity. The "B" battery must also have a low impedance using 9 volt transistor battery's will work but the set can oscillate. There is a chassis mounted cap in a metal can the should either be "stuffed" or replaced. This cap helps prevent oscillation.
http://www.atwaterkent.info/TechData/Dra...640sch.pdf
The url will help with the tubes:
http://www.nostalgiaair.org/References/A...lash08.htm
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
