Thanks,
Larry
You can never have a transformer with too high a current rating. The problem with high current, transformers gets large, heavy and expensive.
Mentioning 5 volts and 375 on the rectifier filaments isn't a mistake. The rectifier has 5 volts across the filaments of the tube, 5T4. At the same time the B+ voltage of 375 comes from the rectifier and will be measured to the chassis.
Your 6.3 volt filament winding needs more like 4.3 amps plus pilot lamps after adding up the current.
2-6F6 = 1.4 amps
1-6N7 = .8 amps
7@.3 amp ea = 2.1 amps
Pilot lamps?
You may want to consider going down in voltage to 325 each side of CT? They do have some with 6.3 @ 5 amps. Doug reminded me you need a 20-24 volt winding if you want motor tune to work. You could always add another small transformer.
Norm
: This is actually a follow-up question to one I posted earlier. I'm seeking a replacement power transformer for an RCA 811K. My combined current is 3.5A for my 6.3V filaments and 300mA for my rectifier filament. Doug Houston suggested a 700V (350-0-350) replacement, but the only one I can find in the Antique Electronic Supply catalog with a 3.5A filament winding is a 360-0-360V, 90mA job.
: My quest is further complicated by the fact that the voltage diagram in the service manual shows 360V to the rectifier plates and both 5V and 375V going to the recifier filaments! A typo, perhaps? I've considered the 375-0-375V, 175mA transformer, but it has a 6A 6.3V filament winding. Is this too much for an 11-tube radio?
: I'm new to this hobby, so I'm a little unsure of what's going on, particularly when it comes to those high-voltage plate windings. I don't want to buy something too small, but I don't want to cook all of my hard work, either. I'd appreciate any input or advice on this.
: Thanks,
: Larry
Thanks for correcting me on the filament voltages. Now to get the total power rating straight. My manual says this set is rated at 145 watts. I looked at the AES catalog and found part # P-T273CZ. Using P=E*I I added the wattages thus:
325V * 2 = 650V
650V * 0.15A = 97.50W
5.0V * 3.00A = 15.00W
6.3V * 5.00A = 31.50W
Total Wattage: 144.00W
This is just under the 145W figure given in the manual. Have I done my math right? The filament windings are 6.3VCT, so does this mean 6.3-0-6.3 or 3.15-0-3.15? Please let me know if I have overlooked something. I know the tuning motor draws some power, but is it figured into that 145W total? It appears this one will do the job if that motor was figured into that original number. Please let me know what you think.
Thanks Again,
Larry
You did great, even figuring wattage. That's right but wattage but will never come out exactly right. It's hard to figure in the inefficiencies of transformers. The actual wattage of the transformer will be determined by the load and losses rather than the rating. The same transformer, only connected to the AC line, will draw a few watts.
6.3VCT means 3.15-0-3.15. Since your radio doesn't require a center tap, tape the wire and leave it disconnected. Do not cut off the center tap wire.
Norm
: Norm,
: Thanks for correcting me on the filament voltages. Now to get the total power rating straight. My manual says this set is rated at 145 watts. I looked at the AES catalog and found part # P-T273CZ. Using P=E*I I added the wattages thus:
: 325V * 2 = 650V
: 650V * 0.15A = 97.50W
: 5.0V * 3.00A = 15.00W
: 6.3V * 5.00A = 31.50W
: Total Wattage: 144.00W
: This is just under the 145W figure given in the manual. Have I done my math right? The filament windings are 6.3VCT, so does this mean 6.3-0-6.3 or 3.15-0-3.15? Please let me know if I have overlooked something. I know the tuning motor draws some power, but is it figured into that 145W total? It appears this one will do the job if that motor was figured into that original number. Please let me know what you think.
: Thanks Again,
: Larry
:
:
: You can never have a transformer with too high a current rating. The problem with high current, transformers gets large, heavy and expensive.
: Mentioning 5 volts and 375 on the rectifier filaments isn't a mistake. The rectifier has 5 volts across the filaments of the tube, 5T4. At the same time the B+ voltage of 375 comes from the rectifier and will be measured to the chassis.
: Your 6.3 volt filament winding needs more like 4.3 amps plus pilot lamps after adding up the current.
: 2-6F6 = 1.4 amps
: 1-6N7 = .8 amps
: 7@.3 amp ea = 2.1 amps
: Pilot lamps?
: You may want to consider going down in voltage to 325 each side of CT? They do have some with 6.3 @ 5 amps. Doug reminded me you need a 20-24 volt winding if you want motor tune to work. You could always add another small transformer.
: Norm
:
: : This is actually a follow-up question to one I posted earlier. I'm seeking a replacement power transformer for an RCA 811K. My combined current is 3.5A for my 6.3V filaments and 300mA for my rectifier filament. Doug Houston suggested a 700V (350-0-350) replacement, but the only one I can find in the Antique Electronic Supply catalog with a 3.5A filament winding is a 360-0-360V, 90mA job.
: : My quest is further complicated by the fact that the voltage diagram in the service manual shows 360V to the rectifier plates and both 5V and 375V going to the recifier filaments! A typo, perhaps? I've considered the 375-0-375V, 175mA transformer, but it has a 6A 6.3V filament winding. Is this too much for an 11-tube radio?
: : I'm new to this hobby, so I'm a little unsure of what's going on, particularly when it comes to those high-voltage plate windings. I don't want to buy something too small, but I don't want to cook all of my hard work, either. I'd appreciate any input or advice on this.
: : Thanks,
: : Larry
: I would like to know all the various ways that a power transformer can be connected
: : Thanks,
: : Cemmats