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 20 restoration state: need the voltage chart
#9

morzh Wrote:Arran

Thanks,

yes those are carbon resistors, and I ordered everything from Mouser yesterday. All 5 of them.
Plus, what bugs me (I am sure it does not matter) - the mica cap bypassing the detector's (24) anode, which is supposed to be 250pF, when disconnected and measured, was 400pF.

I thought mica caps were long-term stable. I am sure this does not matter much in this case, but ordered another mica cap for the 250pF just in case.

I want to have all resistors right, so to compare the DC voltage values with the chart first, otherwise it becomes a guessing game. My non-tube troubleshooting experience tells me "get all values right, then troubleshoot". Usually makes all that much easier.

The last thing I will check is those potted caps and the two caps in metal boxes (so far I measured two of the potted caps I could easily unsolder, and their values were right where they are supposed to be). Hopefully the rest is like this also.

Those potted caps would be the first thing I would change, even if they test good now it's like playing a game of Russian Roulette, I would say that at least 75% of the problems in old radios are caused by leaky, shorted, and open, paper caps, the black Bakelite block condensers especially. The ones in the steel can sometimes work and sometimes they don't, some old timers will tell you that they don't need replacing and will last forever but these caps are 80 years old now and are not to be trusted. As for the micas those don't increase in value, sometimes they leak, sometimes they go open or short, if there is a 400 mmf mica in there and it looks factory it could be a factory revision, there are early and late model 20s so they may have decided to increses the value from a 250 to a 400 or reduce the value from a 400 to a 250 for some reason.
Regards
Arran


Messages In This Thread
Re: Philco 20 restoration state: need the voltage chart - by Arran - 10-28-2011, 07:17 PM



Users browsing this thread: 10 Guest(s)
[-]
Recent Posts
91H Code 126 Restore
Well I'm making good progress. All the bakelite blocks have been recapped.  I found that using a heat gun and skinny ...RealRider — 02:35 PM
Philco model 60
>>and found that the field coil is bad. Should be 1140 ohms, tests at 1.1k ohms. You have one stringent crit...morzh — 02:07 PM
Philco model 60
Yes I was there. I got some real bargains there. Plus a Zenith 7G605 clipper that I have been trying to find for a fair ...Radios1340 — 01:46 PM
A Marconi model 86
I have a Stromberg, one of the early ones, seems early 30s. This is what I call a back breaker. None of the early Philc...morzh — 08:28 PM
A Marconi model 86
A backbreaker.....PaulPaul Philco322 — 08:12 PM
A Marconi model 86
>>What a behemoth! A Juggernaut.morzh — 07:47 PM
Philco 70 antenna lead
I am not sure I understood about the coils and the mush. I looked an more than one coil in 20, 70, 90, 60, Zeniths and ...morzh — 07:46 PM
A Marconi model 86
:e_biggrin: What a behemoth!  I hope the final result is as much a quality sounding example!  Keep us posted on your pro...GarySP — 07:32 PM
A Marconi model 86
I should add that the double conversion may only be used on the shortwave bands, but I haven't looked at the schematic t...Arran — 07:27 PM
Philco 70 antenna lead
Yes, that wire will not pick up much interference as routed - the RF at that level won't be affected, and if you have st...radio1 — 07:26 PM

[-]
Who's Online
There are currently no members online.

>