Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Philco 90 Help Needed
#6

First, I want to thank those who have responded to my question about the unknown cap. Now I want to delve further into my inquiry about the bad output trans. and , hopefully solicit some responses on this.
I have been pondering this problem for several days and have come up with the following questions and observations:

1. The philco sch. says the plate current on each 45 tube is 30ma at no signal. From this value, I conclude that the radio is "fixed bias" and the max. signal plate current is approx. 138ma. This thinking comes from the 45 tube info. Is this correct?

2. Looking at the Hammond 125 series of output tr.'s, it looks like an impedance match could be made using the .7ohm speaker imp. to the input imp. necessary to drive the speaker. The tube info says 3200ohms(fixed bias, 5200ohms self bias) but the philco tech section info. on this site says 6700ohms output trans. imp. Which is correct? I realize that at max. volume that the plate current would overload the Hammond 125 series but wonder if volume levels are kept at normal listening levels if this would work? According to chart, the Philco output tr. has a pri. res. of 500ohms. I have measured a Hammond 125c at 275 ohms. Would this raise the plate voltage to an unacceptable level?

3. Surely some one has faced the bad output tr. problem before. What solutions are there?

Scott


Messages In This Thread
Philco 90 Help Needed - by Scott Fletcher - 08-17-2013, 04:54 PM
RE: Philco 90 Help Needed - by morzh - 08-17-2013, 10:29 PM
RE: Philco 90 Help Needed - by Ron Ramirez - 08-18-2013, 09:13 AM
RE: Philco 90 Help Needed - by Chuck Schwark - 08-20-2013, 09:56 AM
RE: Philco 90 Help Needed - by morzh - 08-20-2013, 02:59 PM
RE: Philco 90 Help Needed - by Scott Fletcher - 08-20-2013, 04:26 PM
RE: Philco 90 Help Needed - by morzh - 08-20-2013, 09:40 PM
RE: Philco 90 Help Needed - by marty - 08-20-2013, 09:54 PM
RE: Philco 90 Help Needed - by Mondial - 08-20-2013, 11:27 PM
RE: Philco 90 Help Needed - by Scott Fletcher - 08-21-2013, 04:30 PM
RE: Philco 90 Help Needed - by Mondial - 08-21-2013, 08:33 PM
RE: Philco 90 Help Needed - by Scott Fletcher - 08-24-2013, 05:08 PM
RE: Philco 90 Help Needed - by Scott Fletcher - 09-06-2013, 04:33 PM
RE: Philco 90 Help Needed - by BrendaAnnD - 09-06-2013, 04:42 PM



Users browsing this thread: 7 Guest(s)
[-]
Recent Posts
New member
Good picture, When was it taken? You don't look in it like a guy who has a teenage son :)morzh — 06:13 PM
New member
Love the pic! I'm southern IL, so wouldn't be much help and Bob Anderson is very good on those, but lives in Chicago are...TV MAN — 05:25 PM
Philco 40-120C Filament Wiring
:thumbup:klondike98 — 04:56 PM
Philco 40-120C Filament Wiring
With these values I think you are OK; the Cmax for this tube is 40uF. Your Vbb could rise a bit, but probably not too mu...morzh — 04:53 PM
Philco 40-120C Filament Wiring
BTW, someone had replaced the original 20uF/20uF filter cap with a 47uF/33uF cap. Do you think these values are safe on ...bluecap — 04:33 PM
Philco 40-120C Filament Wiring
You're correct. I was misinterpreting the key position. I now know where it is, and things are making sense. I appreciat...bluecap — 04:29 PM
Philco 40-120C Filament Wiring
I think Morzh has a good thought. Check the key position. The under chassis diagram in the Philco info shows an “H” for ...klondike98 — 04:25 PM
Philco 630csx power cord
Yes, the third wire goes to the stud on the side and is separate from the other two. I've usually used cloth covered ...Tynwald — 03:09 PM
New member
Have you tried Alabama Historical Radio Society? They possibly could recommend someone. I remember a name of Dee Hanes...morzh — 03:08 PM
Philco 46-480 Electronic Restoration
Nope, he can’t tell me the dimensions. Looks like I won’t be buying it.jrblasde — 02:38 PM

[-]
Who's Online
There are currently 4108 online users. [Complete List]
» 1 Member(s) | 4107 Guest(s)
Avatar

>