*Solved Minerva Tropic Master model w117 "early"-crackle pop & no vol ****SOLVED
Posts: 184
Threads: 3
Joined: Feb 2018
City: Chesapeake VA
(06-29-2018, 09:21 PM)jcassity Wrote: I know what you mean Tom but the resistor is starting to smoke if I leave it on too long now
Guess I missed the resistor wattage.
The string consists of five 6.3v tubes totaling 31.5v, along with 75v for the two 50L6 in parallel and the 25Z5 equal 106.5v. To make up difference, one needs to drop a additional 15v. So ohm's law says set needs additional 50 ohms @ 4.5 watt. Since there is virtually no air movement, it's std practice to increase wattage approx 3x. Resistor will still run hot, has to dissipate that 4.5w. If all the set's 460ma is routed through resistor, it's going to smoke. B+ should be derived from AC line, fed from switch directly to 25Z6 plate(s) and B+ from the cathodes. This current should not be routed through above resistor.
Basically I'm saying we can't cheat ohm's law. A 40 ohm resistor @ 300ma is going to drop 12v, that was OK in the 40s/50s but with today's line voltage, ought to be increased. BTW 460 ma through 40 ohms is 8.5w. At 3X it should be at least 25 watt.
Once you have the heater string sorted out we'll figure out why it's drawing a extra 80ma. Correction of string may fix that.
Tom
(This post was last modified: 06-30-2018, 12:38 AM by 35Z5.)
Messages In This Thread
RE: Minerva Tropic Master model w117 "EARLY" - by 35Z5 - 06-30-2018, 12:34 AM
Users browsing this thread: 1 Guest(s)
|
Recent Posts
|
Need to purchase some accessories for restoration of my Old Philco Radio
|
Hi Paulo,
Welcome to the Philco Phorum.
I can see why you want to find good reproduction parts. That is a bea...MrFixr55 — 11:10 PM |
HiFi (Chifi) tube amp build - but my own design.
|
Tim,
I have some bakelite sockets in my work shop that I can dig up. I believe quite a few are NOS. I will take photo...RodB — 10:03 PM |
Philco 610B oscillator wiring
|
> The cathode as noted is wired directly to the ground side of the heater filament for that tube, not to the #17 and ...Radioroslyn — 08:12 PM |
HiFi (Chifi) tube amp build - but my own design.
|
Tim;
I noticed your post a little late, but I would take one of the junk sockets and try to break a chunk out of it wi...Arran — 08:07 PM |
Need to purchase some accessories for restoration of my Old Philco Radio
|
Here is a list of resources found in our online library that you might find useful. Mike's Gobs of Knobs email addres...klondike98 — 01:46 PM |
First Radio restoration
|
Hi Tubeman,
Welcome to the Philco Phorum. Phamily Phriendly Pfun with Phine Pholks Phull of Philco Phacts. (See a p...MrFixr55 — 12:33 PM |
First Radio restoration
|
You could post in the WANTED ADs section here on the Phorum and see if anyone has an RF generator that they want to sell...klondike98 — 11:55 AM |
Zenith H725
|
Good ideas, thank you Arrange and Rich. I have the adhesive aluminum foil already and can try that immediately.
More ...EdHolland — 10:18 AM |
Graphics for majestic 1050 dial glass.
|
Murf;
I found this thread on the ARF, the first photo has a pretty good view of the dial glass.
Regards
ArranArran — 01:12 AM |
Zenith H725
|
hello Ed,
how about that speacial tape used for ducting it's like foil or how about thin piece of
aluminum roof flash...radiorich — 12:19 AM |
Who's Online
|
There are currently 1429 online users. [Complete List] » 3 Member(s) | 1426 Guest(s)
|
|
|

|