Radio Newbie in need of some guidance for an 84
Posts: 34
Threads: 2
Joined: Jan 2015
City: Fleming Island, Florida
Hello, this is my first radio and what a radio I chose to start with. I recapped the entire thing and put in new resistors where needed. I also replaced the wiring as it was in bad shape. I followed a precise wiring map that I create before starting and know it is wired correctly.
When I turn on the radio, the pilot lamp does not light, the Rectifier tube warms but the other tubes are silent. I checked my transformer 3 times, filament leads go to the right pins on the 42 tube and yet nothing.
I do get a slight hum from the speaker but have not left it on long enough to see if it gets louder. Any rudimentary things I can check to see why the pilot lamp is not lighting ?
Posts: 1,475
Threads: 69
Joined: Nov 2012
City: Kansas city, MO.
Hello. Did you take a voltage reading of the filament pins on each tube? Should be about 6.3volts ac. I belive the dial lamp is also on the filament circuit.
(This post was last modified: 01-07-2015, 10:22 PM by KCMike.
Edit Reason: add
)
Posts: 1,106
Threads: 88
Joined: Jun 2011
City: Tacoma
State, Province, Country: Washington
Make sure there is not an inadvertent short in the filament wiring. It only takes one short to chassis to kill the filaments.
Posts: 15,307
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
Have you checked the tubes?
Posts: 34
Threads: 2
Joined: Jan 2015
City: Fleming Island, Florida
As is very common, I have had to replace the Electrolytic Cap on the Philco 84. This model has a 4uf and 8uf , which I have replaced with a 4.7uf and 10uf at 630v.
I have asked around and am not sure the right place to tie the Negative ends of the new caps. The radio as I received it had a make shift wire soldered to the ring washer on the bad Cap Can which went the center tap as shown below.
My instinct is telling me to simply attach the negative leads to the metal clamp that holds the can in place( after its restuffed.)
What is the proper way to attach the two negative leads of the new caps ????
thank you
[Image: https://pbs.twimg.com/media/B7BWolBCMAEiNDG.jpg]
Posts: 7,212
Threads: 266
Joined: Dec 2009
City: Roslyn Pa
Connect the two negatives together and connect that to the center tap of the power transformer. Just like the diagram. If you connect the negatives to the chassis you will short out the bias voltage for the output tube.
Terry
Posts: 34
Threads: 2
Joined: Jan 2015
City: Fleming Island, Florida
Posts: 1,562
Threads: 56
Joined: Nov 2008
City: Sedona, AZ/Placentia/CA
I suspect that if the original cap that had a clamp to hold it to the chassis also had a cardboard sleeve over the area that was clamped? That was to isolate the cap can (negative) from the chassis which as indicated above is required. A tab off a washer under the attaching nut on the bottom of the cap would be isolated from the chassis and a fine place to pick up the isolated ground and route it to the C/T of the power transformer which as indicated is where it needs to go. Not the chassis. Now, to get the negative leads out of the restuffed cap, you will need to drill a small hole in the cap plastic base and feed a wire out to attach to the lug. Hope that make sense.
Good luck, Jerry
A friend in need is a pest! Bill Slee ca 1970.
Posts: 34
Threads: 2
Joined: Jan 2015
City: Fleming Island, Florida
I have an interesting problem here. When connected in the prescribed way, the 8uf Electrolytic pops when powered up.... bulge and puff of white smoke kinda stuff. I have the 8uf side connected correctly..... (+) side to to the Rectifier Tube(pin1) and GreenWhite Speaker wire, Negative side to the CenterTap.
I am using a 450v 8uf Cap.... Given the amount of voltage that can come thru here on power, I am wondering if I have to go with a 600V cap instead. Has anyone seen this before? Perhaps a bad (80) Rectifier Tube ?
(This post was last modified: 01-11-2015, 09:46 AM by rciancia.)
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
The old capacitors should no longer be connected to the power supply circuit (if they are still physically present in the radio for cosmetic purposes. Use a terminal strip for mounting replacements if you choose not to gut and restuff old components.
Posts: 34
Threads: 2
Joined: Jan 2015
City: Fleming Island, Florida
The old E.C. are not in the radio any longer. The new 8uf cap is the one that is blowing.
I see the plate voltage of the rectifier tube should be 340v, so will measure that. That is what should be flowing thru the 8uf cap...the one blowing is rated at 450v so I don't see why it would pop it... yet...
Posts: 34
Threads: 2
Joined: Jan 2015
City: Fleming Island, Florida
Chose this radio as it is as simple as it gets.
Just finished a complete rewire, recap and resistor replacement for a Philco 84. Unit powers up, but no audio.
I also had to repair some coils, but all ohm out ok now so I know they are good. Used 20AWG, solder joints are clean and checked. Continuity checked connections around and all are good.
Transformer is 199 on one side, 215 on the other and 425 in the center
5v and 6v on the filament sides.
First power on started with a bad rectifier tube, which promptly blew out the 10f Electrolytic (Nice puff of white smoke) , but put in a new 80 and that problem has stopped.
What could be the common cause of No Audio ?
I truly appreciate everyones help here.
Posts: 15,307
Threads: 532
Joined: Oct 2011
City: Jackson, NJ
Anything.
You obviously have not checked the tubes. Checking them after piwer-up as something blows up is not the way.
Check all tubes.
Check the speaker.
Measure voltages.
And...84 is not simple, it is a regenerative superhet and is a finicky little thing.
Posts: 34
Threads: 2
Joined: Jan 2015
City: Fleming Island, Florida
Guilty as charged. How would I go about testing the tubes without a tube tester ?
Posts: 2,569
Threads: 336
Joined: Jun 2013
City: lawrenceville nj
moved to same thread
the Phorum Rules:
Quote: Wrote:II. Multiple threads on the same subject not allowed.
When you start a thread, please keep the discussion within the same thread.
Example: "Philco 90 broken"
After you've started that thread, please do not start another thread on "Philco 90 bad resistor" if it is the same Philco 90 being discussed in the original thread. Give others a chance to respond to your questions rather than asking them again in a new thread - please be patient.
These sort of threads will be immediately deleted, to keep clutter to a minimum.
Please cooperate with me in keeping one thread in the same place rather than scattering it around.
sam
Some day, and that day may never come, I will call upon you to do a service for me. But until that day, accept this justice as a gift
mafiamen2
Users browsing this thread: 1 Guest(s)
|
