The PHILCO Phorum
Model 89 Cathedral - Printable Version

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RE: Model 89 Cathedral - NostalgiaRadioTime - 03-13-2014

Maybe you have to rewind the secondary under the tickler as well? Perhaps the baking process of the coil may have damaged the secondary winding somehow? It's just a thought based purely on conjecture.

RE: Model 89 Cathedral - skyscraper - 03-14-2014

Here's what I have so far. Since it sometimes works with wires touching various points of the oscillator, I'm going to assume the other five circuits are functioning correctly for now.

It occurred to me to play with the value of the cathode resistor, like I mentioned earlier. By raising the resistance closer to where it was originally (10-13k) I can get it to oscillate a few hundred kilocycles lower. But it didn't fix it, I can't receive strong stations at 560 and 620. 840 and 890 are now coming in, so some improvement.

The options I can think of now:

Change 36 cathode resistor to 10k. Seems to help.
The plastic insulator on the coil, or perhaps the clear coat lacquer, is interfering with the field
The cathode capacitor is a cheap 680pF Y5P, maybe replace with a higher quality more stable cap.
Find a NOS 36 tube, most of mine are used but supposedly tested excellent.
The (secondary?) winding under the tickler has a few small spots of green corrosion. Ohms out fine, and there is no continuity between the surface and the windings.

I think I can rule out all the variable capacitors, they seem to work fine. Does anyone have any further suggestions, or where to start?

RE: Model 89 Cathedral - Ron Ramirez - 03-14-2014

Try changing 36 cathode resistor to 8.2K.
Lacquer will not harm the coil (I've rewound literally hundreds of Philco coils using lacquer or clear nail polish over the new winding - never a problem yet, knocking wood).
Use a mica 680 or 700 pF cap for the 36 cathode.
You may have to try different 36 tubes until you find one that oscillates normally. This was a known fault with the autodyne circuit.

Those green spots on the coil will eventually corrode and fail. You know what to do (unfortunately). This takes either 30, 31 or 32 gauge wire. I have used 32 with no problems. Although...I don't think this is your (current) problem. This will become a future problem, though.

RE: Model 89 Cathedral - skyscraper - 03-14-2014

Thanks Mr. Ramirez

I disconnected the resistor and jumpered in a potentiometer, it seems to work best around 10k. I've tried all the way down to a few thousand ohms.

I just bought a couple Philco NOS 36s. I'll try to find a mica cap next, then.

RE: Model 89 Cathedral - gregb - 03-15-2014

I just finished my 89 and guess I was really lucky. All coils ohmed out real close to what was on the schematic. I recapped everything and replaced four resistors. I had a look at the coils for the green death and didn't see any sign of it. My radio had a 15k resistor on the 36 cathode so I dropped it to 8k. As for the bypass cap I went with a yellow .0015uf and happy to say the radio works perfectly. It aligned right up without issue and plays great right across the band.
So skyscraper, if you have any voltage or resistance readings you would like to compare let me know and I will take them from my radio for comparison to yours. It wont be installed in the cabinet for a little while just yet so any way I can help just let me know.

Gregb

RE: Model 89 Cathedral - NostalgiaRadioTime - 03-15-2014

Just for comparison, I went with a 7.5K resistor on the 36 cathode and a 700 pF cap. I had a .0015 mfd. in originally, but when I was having all of that trouble with getting nothing but shortwave, I found a 700 pF and changed it out. I doubt it would've made much difference.

RE: Model 89 Cathedral - Ron Ramirez - 03-15-2014

...people, the 1500 pF is only for use with 89 sets using the 77 tube...the older 89s want a 700 pF...

RE: Model 89 Cathedral - gregb - 03-15-2014

Well Ron, I didn't have a 700pf cap and being impatient I went and put in the .0015uf just for fun and what can I say. The radio works awesome and tracks perfectly. Next time I place a cap order I will get a 700pf and give a try but I really cant imagine the radio working any better than it does at the moment.

Gregb

RE: Model 89 Cathedral - Ron Ramirez - 03-15-2014

This is why I'm staying away from Philcos these days and working on Fishers. Apparently I don't know anything about Philcos anymore. Icon_rolleyes

RE: Model 89 Cathedral - gregb - 03-15-2014

I am only saying that this was the only thing I had to work with and it works. I am not saying it is right or wrong just that it works for me. I sure didn't mean anything by what I said.

Gregb

RE: Model 89 Cathedral - Ron Ramirez - 03-16-2014

Here's the thing. You have a situation where someone is receiving SW frequencies on a radio designed to receive only the AM band and low end SW of 1.5 to 3 mc. The first thing you want to confirm is that the circuit is as designed by the manufacturer. That means if Philco calls for 700 pF on the cathode of the 36 tube, then you use 700 pF. As for the cathode resistor, Philco called for a reduction from 15K to 10K to help the fussy 36 tube to oscillate properly. It is also documented (I think it's in the Radio Troubleshooter's Handbook) that it may take a reduction in the cathode resistor to 8.2K or even 7.5K to get the 36 tube to oscillate properly.

Baking the oscillator coils is a known, and an excellent, way to remove trapped moisture in the bakelite coil forms. Moisture absorption is known to prevent proper oscillation, especially in 19/89 sets. Just be sure the baking is done before any windings are rewound!

Knowing how much trouble people have with 89 and 19 sets, this is why I published the "Evolution Of" series on my website with schematics of every known variations of these (ditto for model 60). I have to admit, I have only had one 89 (so far) that really gave me fits; its story is chronicled on Chuck's site. I guess I've either been lucky...or methodical repair/replacement/troubleshooting techniques are working for me on these. I happen to really like a good, working 19 or 89 as they are very sensitive radios when properly restored and are perhaps Philco's best smaller radios (they do not have a multitude of tubes, but they just play really well).

If the set isn't working right, then you need to make sure all is as it should be, then troubleshoot to find out why it is not working properly.

If you don't have the parts you need, you will have to order and replace them.

I don't claim to know it all, but I've been puttering around with this junk for 40 years now, so I hope I've learned a little bit.

RE: Model 89 Cathedral - NostalgiaRadioTime - 03-16-2014

I agree with Ron 100% that making sure the circuit is wired right and the components are correct per the schematic is the very first thing to check when encountering a problem. And I had ordered a 700 pF but when it came time to install it, it was MIA. Couldn't find it anywhere, even after ransacking the workbench and muttering a few choice adjectives. That was my mistake, or carelessness, whichever you prefer. So I looked what I had on hand that might work, and the .0015 mfd was as close as I could find. It was only after I grabbed the manual for my RF signal generator and began paging through it did this little black thing come rolling out. How it got there, I'll never know, but that was the 700 pF I was pulling my hair out trying to find! So I immediately took out the .0015 and installed it.

When I wrote "I doubt it would've made much difference", I was referring to the SW problem. I had my doubts that that one change in value would cause me to receive the wrong band. And indeed after I installed the correct 700 pF it didn't change anything. The fact that Gregb's set is playing with the 36 tube and a .0015 mfd cap confirms my assumption. Does that mean it's right to use a wrong value cap? Of course not. But sometimes, in one's eagerness, you try using what you have on hand that's close. We've all done it at some point, I'm sure. If you would've seen this chassis when I began on it, your jaw would've dropped as mine did. There were so many components soldered in that didn't belong there (my favorite were two bullet sized wire wound resistors soldered in parallel with a wax cap soldered to them for good measure) that I had to trace out every single wire and connection on this chassis based on the schematic. And I've never had a set where I had to go to that extreme on before.

Speaking of schematics, I have to offer my deepest gratitude to Ron for assembling that Model 89 evolution page on this site. Invaluable doesn't even begin to describe how helpful that was in the detective work figuring out just where my set fell into the run. The first and most obvious clue was the #36 tube, but then seeing K-21 stamped on my speaker further narrowed it down to within 3 schematics. There were a few other clues but those were the main one's.

I had started with an 8.2K 36 cathode resistor, but when I wasn't even on the right band, taking a tip from Ron's "ANOTHER PHILCO 89 FROM H**l" document on Chuck's site, I went down to a 7.5K. It didn't change anything, as my problem all boiled down to a miswound OSC coil.

I have the greatest respect for Ron for the vast knowledge he possesses and for all he's done to aid folks restoring Philco radios for so many years. You learn a lot and gain lots of experience in 40 years, I'm sure. I'll be 42 in July, and I've only been restoring radios since high school. But most of my experience was with post war sets. This was my first experience with re-stuffing bakelite blocks AND rewinding coils. I made a lot of mistakes, and I'll be the first to admit it and to admit that I still have a LOT to learn. But I consider it a major accomplishment, despite all of the obstacles I encountered along the way, that this set plays at all. And I couldn't have imagined making that happen without this site, Ron's wonderful resources, and the generous and kind people here willing to help a newcomer along Icon_smile

RE: Model 89 Cathedral - skyscraper - 03-16-2014

Gregb, thanks for the offer. I'm going to wait for the new tube and capacitor, and maybe rewind the coil one final time, then I might have some questions.

It isn't green death that will be your problem, it's black goopy celluloid death Icon_razz Maybe the lack of problems so far is a function of Canada's climate? Even then, it will probably fail eventually.

As far as component values go, I think there are incredible tolerances in (most of) these circuits, but I would recommend highly against toying with anything in the 89 oscillator... Icon_biggrin

RE: Model 89 Cathedral - gregb - 03-16-2014

Sounds good Skyscraper, I went to a friends this morning and was able to get the correct 700pf cap and it is now installed in the radio and is working fine so we will be comparing apples to apples so to speak.

I do know about the old plastic material failure the eats up the wire and at this point in time they look ok but you are right that sooner or later it will get them.

Gregb

RE: Model 89 Cathedral - skyscraper - 03-17-2014

Got the beautiful, brand new still sealed in the box Philco 36 tube today. I cleaned and tightened its contacts, put it in, wired in the new 680pf silver mica capacitor and a 8k2 resistor.

Now it only plays above 1310kc Icon_madIcon_madIcon_mad Tried many other resistor values, no change.

At Gregb's suggestion, I may leave this alone and come back to it later. My 'skyscraper' console is calling. Maybe one last coil rewind, following Greg's suggestion of 3-hole transparencies. Other than that, I'm at a complete loss.