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Philco 84B Power Transformer - Printable Version

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RE: Philco 84B Power Transformer - bdi1976 - 04-21-2014

I have not considered that. I think something is going on with the antenna though. Tonight, whenever I touched the third adjustment with a driver (wrapped in black tape so it wouldn't ground out), I could hear a channel coming in close to the middle of the driver. This connects to the first 77. Also, when I touched the cap of the 1st 77, which connects to the antenna coil, the reception got better. Even so, I am getting a lot of buzzing which comes and goes erratically. When I do not contact either point, I get no reception. I went through and checked all voltages end to end to make sure there were no bad connections and all look good. Also, the antenna coils shows no voltage on either prong..is this correct since the coils ground out? Thanks Fellas-
bdi

RE: Philco 84B Power Transformer - bdi1976 - 04-22-2014

...I meant middle of the tuner (not driver)

RE: Philco 84B Power Transformer - vinzer - 04-22-2014

Sounds like close to getting this radio to work from what you said it sounds like a bad ant. coil or volume control or a short in that part of the circuit.

RE: Philco 84B Power Transformer - morzh - 04-22-2014

If the radio is aligned properly (read here the alignment procedure)
http://www.nostalgiaair.org/PagesByModel/875/M0013875.pdf

Proceed to reading this
http://www.nostalgiaair.org/PagesByModel/843/M0013843.pdf
On the page 5 the note called "Philco 80 whistles".

80 and 84 are largely the same.

RE: Philco 84B Power Transformer - bdi1976 - 04-24-2014

A forum expert and I tried aligning the 84 last night. The I.F. signal aligned properly to 460KC but we picked up no stations after completion. I was picking up 7 faint channels just before we began with quite a bit of background noise (not buzzing, but sounds like it's raining on the speaker). After attempting to align, the volume was much louder, but we realized that the first trimmer (17) adjustment seemed to do nothing. I switched the 77s and got one faint channel back. At this point, I am doubting the integrity of one of the 77s so I ordered another today. If I assume that the trimmer does work, would this indicate that part of the IF circuit is open and therefore it's unresponsive?....or could it just be a bad 77? Could this be possible when we were able to tune to 460KC properly? The second trimmer (15) did seem to impact the alignment, which I assume means that portion of the circuit is closed. Any thoughts guys? Thanks

RE: Philco 84B Power Transformer - morzh - 04-24-2014

Have you buzzed your coils yet? You should do this before starting swapping trimmers. If you do not know if your coils are open or not, you are not going in the right direction starting ordering other parts.

It is an 80 (OK 84), it is very simple, and has very few coils, won't take long to buzz, so do it first.

RE: Philco 84B Power Transformer - bdi1976 - 04-24-2014

I did check continuity on all coils that were accessible. I should have checked the second coil in the IF when I was replacing the 4 Meg resistor with the 2 Meg. Guess I have to take the IF back out since there is no way to test it without a resistor in the circuit. However, I just noticed a wiring discrepancy - The second IF coil shows a center tap connecting to the trimmer (15). My trimmer only connects to the IF at one spot (not two) and the bottom connector of the trimmer is grounded, but no second wire. Any idea why it's missing?

RE: Philco 84B Power Transformer - vinzer - 04-24-2014

both the trimmer and coil goto ground if the tap on the coil isn't grounded it should be. it could be grounded some place other than the where trimmer is.

RE: Philco 84B Power Transformer - Radioroslyn - 04-24-2014

You can measure the resistance from the grid cap to gnd to get the value of the 2M resistor. The portion of the IF transformer will be very small compared the the two meg.
Replace the 77 tubes and I'll bet you it will work fine.
Terry

RE: Philco 84B Power Transformer - bdi1976 - 04-25-2014

Morzh, you were correct sir. I pulled the IF out and the wire to coil connecton was open. I resoldered a new wire, put it back in and got 5 clear and loud channels! However, still some buzzing and no channels on the first half of the dial. The first trimmer seems to still not work. 70 V DC on the bottom lug and no voltage on the top lug even with adjustment. Not sure what that means, but I have a new 77 on the way so I'll see if that helps any.

Vinzer, for some reason, there is no wire from coil to ground, so don't know what to make of that. Thanks guys-

RE: Philco 84B Power Transformer - vinzer - 04-25-2014

the secondary should have 3 wires one goes to the resistor and to trimmer 15 one to trimmer 17 witch is the regen trimmer and one to ground.

witch trimmer number on schematic is the first trimmer?

if the 70 v dc is on trimmer 17 thats right no voltage on the other lug is right to the trimmer blocks the voltage on the other side .

RE: Philco 84B Power Transformer - bdi1976 - 04-26-2014

You guys are awesome! - After the IF repair, which helped the most, the reception was further boosted by a replacement 77 (thanks Terry) and I'm getting clear stations across the dial, after I realigned again today. The IF aligned well, but the final regeneration adjustment was a bit confusing. I could barely hear a squeal and it was across all settings, so I never really knew when to back off. I'm not sure if at this point it really matters since I'm getting about 12 clear channels. I also added a 40 ft antenna which helped further boost the signal. The only thing that suks is the one channel my daughter listens to is completely mixed with another channel and starts to squeal when I put it on...of course the only channel with music. Luckily, we can hear the gospel on 2 or 3 channels...LOL. Thanks again guys for all of your support. I will now set off on my next adventure which is restoring a gorgeous 90 I found. I'm sure you'll be hearing from me again soon-