11-06-2019, 09:00 PM
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c- c+ on old battery radios
 
11-07-2019, 11:46 AM
Fortunately C battery voltages are not high, so I just make my own using modern batteries. I solder the terminals together. Some liquid flux made from powdered violin rosin and rubbing alcohol helps with this. Make a suitable box from white cardboard, and there you are. The drain is so low that a series of C cells hooked up will last for years. You can also tap them off to get -3, -4.5, .-6, -9 volts, or whatever you need.
11-07-2019, 02:40 PM
You will need to know exactly what model Freshman you have. Some are with "C" battery, some without.
"Most" schematics for the Freshmen can be found online. Download and review if it is correct for your radio. The schematic will identify the "C" voltage required. Sometimes a radio will use two "C" voltage, usually because of the last audio tube type. Generally, if all the tubes are '01a then the "B" voltage will be 67-1/2 for no "C" battery. For "B" voltage of 90 volts a "C" battery will be 4-1/2 volts. You will need to know what tube is used for the last audio stage to get it correct... A 112 or a 171a will need both a higher "C" and "B" voltage. If you are using '99 tubes and socket adapters the "A" voltage will be 4-1/2 volts. Without any "C" battery connected the radio may play for a moment and stop. If the "C-" is connected to A+B- connection essentially jumping out the "C" circuit, the radio will play with a maximum of 67-1/2 "B", no more. The purpose of the "C" battery is to provide negative potential for the grid(s) of the tubes. If the grid in the tube is not negative enough it will draw excessive plate current and soon exhaust the thorium on the filament. The tube becomes "paralyzed" and will have to be rejuvenated. The tube can only be rejuvenated a few times then all the thorium is gone. The emission of electrons goes to zero. Yes a radio will play loud and distorted without "C". A "C" battery does not provide current, just potential so most any cell(s) can be used. But, your power supply does have a "C" output... Also, set the power supply "A" voltage that lights the filaments if you are using '01as to 6 to 6.6 volts. Do not set it for 5 volts, the rheostats provide not only volume, but lower the voltage and provide a small amount of bias as well. Do not use 1 amp 01 tubes in this radio, they may cause the filament rheostat to burn up and may overload your power supply... GL Chas Pliny the younger “nihil novum nihil varium nihil quod non semel spectasse sufficiat”
11-07-2019, 05:59 PM
Um, Your pictures are so revealing
 Missing knobs, no cabinet, missing battery nuts both on your power supply and on the radio. The power supply looks like an early Gary Schneider model, good unit... Not many around... That said where are your tubes and some good advice: Check the DC resistanc of the intestage audio transformers, Freshmans are "notoriously" open... Any connection to power must always follow a protocol to keep from blowing out the filaments of the radio. Never try to cheat with clip leads, these often will not pass the filament current and may short at the clip, that could be a disaster... Always connect the filament first and preset the power supply filament voltage. For '01as set for 6-6.6 volts do not get fooled because the tubes are 5 volts. The rheostats drop the voltage and provide bias as well as regulation o tube emission (volume). Then look at the "B" voltages, be very careful in setting these up and always have the tubes out until the connections have been checked and voltages confirmed. You can fabricate you own battery cable. choose at least #16 to #14 for the filament circuit. The other wires can be 20 ga. All voltage drop for the "A" circuit should be in the rheostats not the wiring... GL Chas Pliny the younger “nihil novum nihil varium nihil quod non semel spectasse sufficiat”
11-07-2019, 07:36 PM
i have the cabinet,o1a tubes,112 tube the knobs and yes open wires on the transformers.does anyone know where i can get new ones or someone who could rebuild these transformers.
11-07-2019, 08:38 PM
I'm sorry to hear that the transformers are open.
There are some options depending on costs, authenticity and originality. - Have the transformer re-wound. This can be done by Heyboar. Estimated some $40 each. They will appear as original FWIR the transformers are below the "deck". FWIK the transformers have 3:1 ratio, but there is a chance the 1st AF could have a higher ratio from 4 to 9:1. Only someone who has one original and willing to measure the ratio could help. The winding resistance is good in this replacement. - A solid-state replacement, recently designed, more info from Robert Lozier of ARF relatively in expensive. Old transformer stays in place. Postage stamp size circuit board nearby. Can be covered with black heat shrink to look like vintage paper capacitor. - Replace just the winding bobbin with one from ARBE, Yes the power supply maker has made transformers bobbins of 3:1 ratio in three sizes of cores. Go to ARBE-III... Winding resistance is also good - Hold off, take good sharp images of the transformers and measurements and post ads in the Phorum and ARF classifieds for originals. It will take time... - Use the A-53 transformer from AES or the Hammond bobbin for Radiola III if the core size fits.. The A-53 is a late model transformer with a saddle strap mount, modern looking. very low resistance tone does suffer. The Radiola replacement has good DC resistance. - Use R/C coupling, it will work but volume will considerably lower even if "pushing" the tubes. Tone will be good, alas, volume not so... The 112a tube will use the 135 volts B+ and at least 9 volts "C" bias. See: http://www.nmr.mgh.harvard.edu/~reese/RC10/RC10-25.GIF The plate resistance is a good match for an AA5 audio output transformer so a modern speaker could be used... Good Luck! Chas Pliny the younger “nihil novum nihil varium nihil quod non semel spectasse sufficiat”
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