[OldRestorer]

As for the grill cloth see this topic for the general consensus, I may just order it anyway..

"philco 84 restoration grill cloth question" In cabinet resto topic

Kirk

[skyscraper]

In spite of some delays and missing parts, the 89 is moving along rather well. Nine of the ten potted caps have been restuffed, I just finished the two 6uf electrolytic cans, fixed the volume control, replaced a couple resistors and found some perfect rubber grommets for the tuning cap. I'm waiting on some cloth wire, 680pf caps, and resistors.

Moving on to the broken oscillator coil. I was planning on cooking it in a toaster oven for a while, as per many online suggestions, but the form looks to be made of some sort of plastic. It is hard and semi see-through, I was expecting wax covered cardboard. Does it still need to be baked before rewinding? I'm not sure how plastic absorbs moisture.. The primary and secondary are fine, it's that hideous tickler winding. Here a picture:

[Image: https://lh6.googleusercontent.com/-Jm12L...C_7975.JPG]

Will

[morzh]

Try to take it off to see if there is damage below it. If not, should be an easy rewind.

[klondike98]

Will, some coil rewind info here: http://www.philcorepairbench.com/tips/svctip36.htm and a video link here: http://philcoradio.com/phorum/showthread...3#pid58553

[skyscraper]

Thanks for the links.

The winding and decaying plastic came off with a little help from the heat gun. I carefully made a diagram, noted the coil turns and direction, but somehow completely forgot to see which pin goes to the top or bottom I think lug 1 (from the bottom clockwise) goes to the bottom, and lug 2 to the top. Can anyone confirm?

The windings underneath seem to be in decent enough shape, but there is a bit of green corrosion in some places. I can't tell whether it's from the messed up coil, or the intact primary itself. Resistance matches the schematic, and looks like well over 100 turns. I'm going to clean the green stuff with rubbing alcohol and lacquer it unless anyone says not to. I can post a pic if it would help.

A couple resistor questions. There is a 51k resistor in the avc circuitry, the closest I had was 57k. That's a bit over 10% off, is that acceptable?
Also, the volume pot is listed in all schematics as 350k. Mine reads 230k, which I think is a rather substantial difference. I bought the closest pot I could find, that I'd rather not use, at 250k. Any thoughts?


Thanks!

Will

[Mondial]

The resistor in the detector/AVC circuit is not critical so you can use anything close. Remember the original resistors had a 20% tolerance, so anything from 40K to 60K should be fine.

Is the volume control in your radio original? If it is I would be surprised as they usually go high in value. The one in my 89 reads about 800K but still works fine. If you are concerned about the value, you can add a 100K in series with the high side of the present control to apply the correct load to the detector. This radio has plenty of audio gain so you will not notice the slight loss from the voltage divider created.

[skyscraper]

Perfect, thanks!

Yes it is. I don't remember the part number, but it matches the one on the 'evolution of model 89' page here. Those schematics all show the .35M part. I was surprised as well. I'll put in the 100k.

As always, thanks for all the invaluable help!

[skyscraper]

I'm still trying to figure out the orientation of the tickler winding. Is there any chance is corresponds to the picture in the schematic? The other two on this form do.


There is a bit of a mistake on the schematic that messed me up. It's nearly impossible to explain, but looking at the schematic: http://www.philcoradio.com/tech/images/89v3.jpg
Coming off the screen of the first 44, part 8 and 8A are wired in parallel to ground. They are two different parts. One of the blocks also has the .0007 for the 36 cathode bias. The condenser list on that schematic lists the .09 with the .0007, but it's the other way around in the radio. I put them in the wrong blocks, is that a problem? I would redo it, but I used all my spares. The only difference is the 36 bias has a .1 next to it rather than a .05 like it had before.

Last question, for that .0007 bias cap I bought 680pf ceramic caps: http://www.ebay.com/itm/370879275301?ssP...1439.l2649
I've read that ceramics are a bad idea because their values swing under heat. These have a temp coefficient of Y5P, which is 10% tolerance up to 185˚. Is that alright? I can't imagine things are getting that hot under the chassis, but thought it was worth asking.

I hope to rewind the coils tomorrow, that should be everything electronically. Very much looking forward to finally hearing her play.

Thanks,
Will

[morzh]

Depends where used. if used in resonant tanks like IF filter, I would certainly not use anything other than mica or NPO/C0G if possible.

Y5P while not a bad cap overall, has the temp range up to 85C while mica operates up to 150C.
Mica is typically 50-70ppm per degree C which makes it roughly 0.3% over temp range in a radio whereas a Y5P over the same range will change up to 10%.

But if used in an RF filter, like in a plate detector, sure - why not.

[skyscraper]

What temperature does a chassis reach under normal operation? I wouldn't think anywhere near 180˚. It's also insulated in a bakelite block, and away from the power resistors.

I'm not trying to cut corners, but at some point I need to stop spending so much money on one set

One last try. Is there any way to figure out/anyone to ask about the winding? I'd really rather not have to swap connections later, it isn't easy to get to.

[Ron Ramirez]

There is a bit of a mistake on the schematic that messed me up. It's nearly impossible to explain, but looking at the schematic: http://www.philcoradio.com/tech/images/89v3.jpg
Coming off the screen of the first 44, part 8 and 8A are wired in parallel to ground.

The error is that you misread the schematic. ( 8 ) and (8A) connect to the plate (not the screen grid) of the 44 RF tube through the primary of RF coil (6).

[skyscraper]

I apologize, I misspoke about the connection. Nevertheless, I think what I said is still true. There are still three part 8s, which doesn't make sense. The condenser list also shows the wrong two together, the .05 and the .0007 should be together, not the .09 and .0007 as printed. The .09 should be a different part number.

From the list of bakelite blocks http://www.philcorepairbench.com/bblokcap.htm I can't find anything that matches a .09 and .0007. It isn't a huge deal, but it does cause you to wire it wrong. Not electrically wrong, but the wrong caps in those two blocks.

I don't think I'm missing anything, am I?

[Ron Ramirez]

Sigh...I'll have to look tonight and see.

[skyscraper]

I really don't mean to cause any trouble or waste any time, your schematics have been the only reason I have been able to restore this radio. Thank you so much for all the work you've put into them, and all the rest of the resources.

Again, I'm not very knowledgeable about any of this, and the only schematics I'm used to are digital. This just threw me off a little.

Hope you're feeling better,

Will

[skyscraper]

Alright, a bit of an update. I rewound both of the coils today, baked the forms and coated with lacquer. Everything is reinstalled and wired back, and after a quick run through of my connections, I powered it up with a 25 watt bulb and the 80, 75 and 42 tubes, which yields about 80ish volts. I immediately got a hum out of the speaker, and a 20ma draw on B+ into the field coil. Touching the cap of the 75 created pops and buzzes, so the audio section appears to be working fine. I'm taking that as a great victory; at least I haven't wired anything on the high voltage side egregiously wrong. And half the tubes are good so far.

After an unfortunate homework break tonight, I'll put the rest together and try to pick up a real signal. Thanks again for everyone's help!

Will