Model 89 Cathedral - Printable Version
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RE: Model 89 Cathedral - Mondial - 03-04-2014
Greg, it appears that your problem is in the RF stage. If you can hear stations when you connect the antenna to the grid cap of the 36 tube that means the osc and converter is working properly. The 44 RF stage should amplify the signal from the antenna and transfer it to the grid of the 36 converter. This seems to not be happening.
Do you hear stations if you connect the antenna to the grid cap of the 44 RF stage? Have you tried another 44 tube? Are the tube voltages correct?
Something else you can try is to disconnect the grid cap wires from both the 44 RF and 36 osc/converter. Then connect the grid cap wire that went to the 44 to the 36 instead, leaving the 36 cap wire disconnected. You will have to extend the lead to the cap with a wire to make it reach. What you will be doing is bypassing the 44 RF stage entirely, feeding the signal from the ant coil directly into the 36 converter. If the radio now receives normally, then you have confirmed the problem is in the 44 stage or its associated interstage RF coil.
RE: Model 89 Cathedral - NostalgiaRadioTime - 03-04-2014
Thanks, Mondial. I will try those things tonight. Just got home from work and have a few other chores to take care of before I get down to the workshop.
When I take a gator wire from the antenna clip to the grid cap on the 36 tube I get one station, between 600 and 700 on the dial. The rest of the dial has a buzz that gradually gets louder until you get to 1000, with squeal and motorboating around 900. Then it drops off and around 1100 I get the same station again that I do at 600, albeit more faintly. Funny thing is it's a religious station out of Atlanta, GA! A far cry from just north of Milwaukee. We have a powerful station in town located at 1470 that I normally can pick up on my radios even with the volume all the way down! I can't get it on this 89.
The only thing that makes the dial more functional is when I hook the gator wire to the plate of the 36 tube. It almost acts like an antenna.
What would be really helpful is if someone with a working set that took a picture of the bottom of the chassis before they put it back in the cabinet could post it here. It would at least give me something to compare connections on.
Thanks again for your help. Will let you know what I find.
What I'm thinking is the primary I rewound on the RF coil may be causing a problem. Possibly there is a tiny gap between the windings. I would imagine the windings have to be as close together as possible for it to work properly.
RE: Model 89 Cathedral - Mondial - 03-04-2014
It sounds like the RF stage might be in oscillation itself at around 900 kHz, which is why you get the squeal at that freq and noise when tuning above and below. You could try removing the 44 RF tube completely and feed the ant into the 36 to see what you receive then.
RE: Model 89 Cathedral - NostalgiaRadioTime - 03-04-2014
OK... I have determined I'm receiving short wave on the broadcast band instead of regular broadcast stations! An Asian station, a Latino station, Religious station... everything but local stations. One said they were at 5985 on the dial. I get still get stations on both ends of the dial... from 600 to about 800, and then 1100 to 1400, with squeal & motorboating in between 900 to 1100.
To backtrack... Sky, I'm using an 8200 ohm resistor in the 36 cathode bias network.
Mondial: When I take the grid cap off of the 44 RF tube and put it on the 36 tube, I received a few more stations. But again, they are shortwave not local stations. Dead in the middle of the dial...just the squawking.
With the #44 RF tube out completely, and the grid cap from the 36 tube on the 36 tube where it belongs (meaning the 44 tube is out, and its grid cap unused), I get nothing but buzzing on the dial. Even with a gator wife from the antenna terminal to the grid cap of the 36.
Now as I said, I used 32 gauge wire for rewinding the primary on the RF coil, as I didn't have 34 gauge here. But the number of turns and direction is correct. Does that small difference in wire gauge make a big difference? Should I get some 34 gauge and redo it?
Here is a pic of the bottom of my chassis. It was a total mess when I got it... there was hardly anything connected where it should be and so many extra components added I had to literally go wire by wire on the schematic to trace it out. The schematic I'm going off of is also below. I'm at a loss as to how to get rid of the shortwave and get local stations on the dial. If there was a pulling one's hair out icon I'd post it here!
RE: Model 89 Cathedral - Mondial - 03-04-2014
How about trying with the 44 RF tube out and its grid connection to the 36? This would eliminate any interaction with the RF stage and focus on how the 36 converter is working.
Receiving SW is really unusual unless you have the osc coil windings miswired. The only way you can receive 5.9 MHz is if the osc is also operating in that range and that could seemingly only occur if the wrong winding is connected to the tuning cap. Are you sure you rewired all the coil connections correctly?
Do you have a signal generator to inject a signal and determine what freqs the radio can actually receive?
Can you take a close up photo of the wiring to the osc coil under the chassis? Maybe I can compare it to how the coil in my 89 is wired.
RE: Model 89 Cathedral - NostalgiaRadioTime - 03-04-2014
Thanks, Mondial. Let me sleep on it. Will take a close up pic after work tomorrow. You don't by any chance have your notes on rewinding the osc tickler do you? That's the only thing I rewound on it. BUT... this coil came off my parts chassis which uses the #77 tube instead of the #36. I wonder if that might be the problem... that the coil used for the model with the #77 tube is wound differently from the coil for the #36 tube model?
RE: Model 89 Cathedral - NostalgiaRadioTime - 03-05-2014
Mondial, Fresh from the toils of work, I came home and snapped a couple of close up pics of the RF and OSC coils showing the wiring. Not sure you can make out where they're going, but I'm certainly grateful for all of your help and would very much enjoy hearing your thoughts on what may be causing the short wave signal instead of hearing local stations. I suspect one or the other or both coils is either wired incorrectly, or wound incorrectly. Could there be a difference between these two coils in the early models with the 36 tube to the later versions with the 77 tube? Or the fact that I used 32 guage wire instead of 34? Thanks!
RE: Model 89 Cathedral - Mondial - 03-06-2014
Ok Greg, I took a look at the photos and my 89. Its really hard to tell, but I don't notice anything obviously wrong with the osc coil wiring. I did trace out the wires to my coil so you can compare with what you have. I am starting from the lower left of the coil referenced to your photo and counting clockwise from there.
Term 1 - to pin 4 of 36 tube
Term 2 - to resistor 10 and cap 8
Term 3 - to LF osc compensator 16 and one side Ist IF comp 15
Term 4 - to IF primary and other side of 1st IF comp 15
Term 5 - to tuning cap
extra wire from coil center - to pin 2 of 36 tube
I also tried a test with my 89. I pulled out the 44 RF tube and jumped antenna to the cap of the 36 ( leaving cap wire connected). Doing this I got great reception, almost as good as normal. So if your 36 stage is working properly you should hear broadcast stations with the 44 tube removed. Otherwise there is a problem with the 36 circuit and that's where you need to look first.
RE: Model 89 Cathedral - NostalgiaRadioTime - 03-06-2014
Wow! Thanks so much, Mondial, for taking the time to do that for me. It will be a great help. I will compare your terminals to mine tonight. I did rewind the RF coil primary that came out of this set tonight. 12 turns of 38 gauge wire. I used a micrometer to measure the diameter of the old coil wire and the 38 gauge is only .0015 smaller in diameter, where as the 32 gauge I used on the coil from my parts set is about .0025 bigger in diameter. I think the 38 gauge is pretty darn close. A piece of paper is .003 thick, so we are talking miniscule amounts of difference. The thing that makes me most nervous is did it get the wire wound tight enough. If there's a teeny tiny gap between one of the windings is that going to throw everything off or not? I guess time will tell once this coil is installed. I'm hoping that is what is causing me to receive short wave. I did notice the RF coils have different part numbers between the early set with the #36 tube and the later sets with the #77 tube, while the OSC coils share the same part number for both versions.
If this still gives me problems I may call on your kindness once more to trace the wires for your RF coil for comparison.
Again, my most grateful thanks for your help. That's what's great about this Phorum... everyone is united in a common bond to get these long dormant radios playing again. And there is compassion for those whose skill levels and knowledge may not be up to par with some of the more seasoned radio restoring veterans rather than ridicule.
RE: Model 89 Cathedral - skyscraper - 03-08-2014
I received the Heathkit rf generator, it seems to work well. I'm assuming it needs to be recapped, at least the electrolytics, but I took my chances.
I performed what I think is a solid alignment on the radio, the dial is almost perfect now and the IF was very carefully peaked. I used the audio out instead of the AVC this time, just in case it changes anything, based on the instructions on the schematic. Still won't oscillate on the bottom 2/3rds. But the audio is significantly better, and I was immediately able to hear 1510 WLAC loud and clear from Nashville. Steps in the right direction.
I've exhausted my options, time to rewind the coil again.
Greg, how is yours going?
RE: Model 89 Cathedral - Radioroslyn - 03-08-2014
If you rewound the osc coil I would add few more turns to that winding. Sound like you don't have enough feedback. Should have 25t or so.
GL
Terry
RE: Model 89 Cathedral - skyscraper - 03-08-2014
I think it has 27, I'll add one or two more.
Thanks for the suggestion Terry
RE: Model 89 Cathedral - Radioroslyn - 03-08-2014
27 sounds pretty healthy. Try switching the coil connection around just in case it's wound backwards.
Terry
RE: Model 89 Cathedral - NostalgiaRadioTime - 03-08-2014
I'm glad I picked one of the easier Philco's to restore!
I still am getting short wave on the broadcast band. And the weird thing is, changing the off/on switch from broadcast to police does not kill the broadcast band. It stays playing on the same station, pretty much the only one I get in loud and clear around 750 on the dial... WWCR in Nashville... a short wave religious station that has "four 100,000 Watt, state of the art, transmitters which serve the world on 10 different broadcasting channels", as their website touts. And I live 35 miles north of Milwaukee, WI.
But I only get the station with the #44 RF tube disconnected, and the grid cap from that tube on the #36 tube. I clip a gator wire from my external antenna to the antenna coil grid cap wire now on the #36 tube and the station comes in strong. Basically bypassing the RF coil (and the #44 tube) by connecting the grid cap wire from the antenna coil direct to the #36 tube.
I am totally at a loss as to why I'm getting shortwave where the broadcast band should be. Like I said we have a strong local station at 1470 on the dial only about 5 miles from my home that I should have no problem receiving.
Mondial: I checked out the terminal connections on my OSC coil based on the connections on your set and it was right where they should be. Would you happen to have the same info. for the RF coil, as that section seems to not be working correctly on my set?
I did notice a white colored wax like substance that (at some point, long before I got the set) had oozed out of the bottom of the 1st IF can, but not sure what's in there?
Also, I used two 250 pF's in the #26 bakelite block instead of the 110 pF's called for, because that's all I had here. I wouldn't think that little bit of difference should be causing the wrong frequency. I'm using the 700 pF along with the .09 mfd cap in the #8 bakelite block as the schematic calls for.
Any ideas for a balding guy who doesn't have more than 3 more strands of hair left to pull out on how to coax some local stations out of this "Philco that refuses to be repaired"?
RE: Model 89 Cathedral - Mondial - 03-09-2014
Greg, It still seems you have a problem with the oscillator coil. The only way that you can receive a 6 Mhz signal is if your oscillator (or one of its harmonics) is running 260 kHz lower or higher than than the received SW signal.
I would take out the coil and re-examine it. Perhaps you mixed up the terminals of the winding or wound in the wrong direction. It has to rewound exactly as per the original or it won't work.
Nothing else you mentioned can cause you to receive SW. By removing the 44 and connecting the antenna to the 36 grid cap you are bypassing both the ant and RF coils so these are not the problem.
The 89 uses the same osc freq for both the broadcast and police bands. That's why your reception does not change when switched. The difference is that the ant and RF coils are tuned to the police band freqs and the second harmonic of the osc is used for conversion. The osc always runs at the same freq for both bands and is not switched in any way.