10-19-2008, 03:31 AM
Im restoring a customers 1936 model Kadette mod 66X. It is one of the "cheapie" orig design chassis! The schemat is in Riders vol #7 pgs #1 & 2 ( International Radio Corp). It has the 4-pin socket for ballast-tube( tapped for dial lamp GE #47 lamp also) voltage hard-to-find voltage regulator tube, 1-side in line with AC cord filament-string set.
This set uses the 0.3 fil-amp type tubes of: 25Z5 rectifier,2-6D6,1-6C6,& 43 pwr amp pentode. My preferences are to "rid-completely" the ballast-tube altogether, and bypass it, since regulator tubes are hard to find. I found one (only-1) still avail in Fla tube-supplier if he still has it.
I have 2-options on this as I see it? After doing some quick-math,purchase his tube,or, I can use some of my nichrome-wire wrapped around a new ceramic bare coil-form, or, use a couple new wirewound- pwr resistors to get proper cntr-tap for the diallamp and help regulate power consumption in place of the orig broken ballast-tube.
My "quick-math" equations seems the 5-tube set utilizing the orig tubes equates at :
5 tubes total fil-amps= 1.8 amperes ( added dial lamp .015 amperes 6-8 volt GE # 47) at ballast-socket pins.
5 tubes total fil-volts= 75.2 volts ac all in 1-side of fil-string ( not including inrush for cold filaments).
Therefore, I need to supplement approx 50 volts AC tube filament resistance,approx 50 ohms?.. ( on todays modern AC line current) @ approx 15 watts consumption?, to rid the old ballast tube? But then again, Im not sure exactly where to "tap" for the dial-lamp, using 2 different modern-type resistors, except play around with my ohms/volts meter if I build one with nichrome wire.
Since I have a variac, I can play-around slowly-upping & testing until I get it right if needed. Seems using a couple low uf ( 5-10 ufs) type ratings "non-polarized" type electrolytics Solens types might also work without any resistance- heat at all also? Have you guys had any luck previous doing this conversion?
Was wondering if any techs here may have any orig printed- data on the "pin-outs" of the old ballast tubes to share? This particular glass (broken)ballast tube is number 165R4. I want to get rid of it (ballast) altogether to restore this set so it wont be a "hard to find" ballast replacement item in the future.The GE tube manual only shows 1-other tube I could "sub" in place of the ballast that has 50 V filament @ 0.3 fil amp. It could be subbed to take up "slack" in fil voltage, but it is a old 12-pin socket type behemoth and costs $8. and I would have to buy a tube-socket also to fit it in with no CT for dial lamp, but then I could pick-off 6 volts diallamp elsewhere under chassis. My concern is really "inrush"limit on this conversion without also having to purchase a separate inrush limiter.
Any help & your thoughts appreciated!Randal
This set uses the 0.3 fil-amp type tubes of: 25Z5 rectifier,2-6D6,1-6C6,& 43 pwr amp pentode. My preferences are to "rid-completely" the ballast-tube altogether, and bypass it, since regulator tubes are hard to find. I found one (only-1) still avail in Fla tube-supplier if he still has it.
I have 2-options on this as I see it? After doing some quick-math,purchase his tube,or, I can use some of my nichrome-wire wrapped around a new ceramic bare coil-form, or, use a couple new wirewound- pwr resistors to get proper cntr-tap for the diallamp and help regulate power consumption in place of the orig broken ballast-tube.
My "quick-math" equations seems the 5-tube set utilizing the orig tubes equates at :
5 tubes total fil-amps= 1.8 amperes ( added dial lamp .015 amperes 6-8 volt GE # 47) at ballast-socket pins.
5 tubes total fil-volts= 75.2 volts ac all in 1-side of fil-string ( not including inrush for cold filaments).
Therefore, I need to supplement approx 50 volts AC tube filament resistance,approx 50 ohms?.. ( on todays modern AC line current) @ approx 15 watts consumption?, to rid the old ballast tube? But then again, Im not sure exactly where to "tap" for the dial-lamp, using 2 different modern-type resistors, except play around with my ohms/volts meter if I build one with nichrome wire.
Since I have a variac, I can play-around slowly-upping & testing until I get it right if needed. Seems using a couple low uf ( 5-10 ufs) type ratings "non-polarized" type electrolytics Solens types might also work without any resistance- heat at all also? Have you guys had any luck previous doing this conversion?
Was wondering if any techs here may have any orig printed- data on the "pin-outs" of the old ballast tubes to share? This particular glass (broken)ballast tube is number 165R4. I want to get rid of it (ballast) altogether to restore this set so it wont be a "hard to find" ballast replacement item in the future.The GE tube manual only shows 1-other tube I could "sub" in place of the ballast that has 50 V filament @ 0.3 fil amp. It could be subbed to take up "slack" in fil voltage, but it is a old 12-pin socket type behemoth and costs $8. and I would have to buy a tube-socket also to fit it in with no CT for dial lamp, but then I could pick-off 6 volts diallamp elsewhere under chassis. My concern is really "inrush"limit on this conversion without also having to purchase a separate inrush limiter.
Any help & your thoughts appreciated!Randal
