The PHILCO Phorum
89B cannot tune lower (550-1300) stations. - Printable Version

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89B cannot tune lower (550-1300) stations. - akrgg - 08-15-2021

My 89B developed a problem.  Only recieves stations 1300 and up.   (No fun, all my locals are between 550-1110).  Using an end-fed antenna that checks good with other radios.  Tuning capacitor looks clean.  The high stations that are recieved (only at night, 600-2000 miles away), 1310-1460, show up correctly on the dial.   Before attempting to re-align this animal, are there other things I should be checking on? (Novice, but usually learn after the first or second shock)

RE: 89B cannot tune lower (550-1300) stations. - Radioroslyn - 08-15-2021

Hi and welcome,
 
There was several different versions of the 89 chassis https://philcoradio.com/library/index.php/shop-talk/model-notes/evolution-of-philco-model-89/

I would have a look at the osc and see if the tuning the whole range. It's not uncommon for the osc coil to need a feedback
winding rewound. Use a pickup wire near the osc tube and another receiver to listen for it at the 89's dial frequency + the IF frequency.

RE: 89B cannot tune lower (550-1300) stations. - akrgg - 08-15-2021

Thanks, will work on that suggestion. When tuning I basically get nothing at all, not even static, until I hit 1290 or higher, then it all seems fine(expected static/statoon)... Will try to see what I find with a pickup wire.
Believe my 89b (123) is at least after run 7.. still uses the 36 tube, has a K-21 speaker. Some other work must have been done in the past as the rectifyer had been changed from orig #80 with a 5y3w.

RE: 89B cannot tune lower (550-1300) stations. - akrgg - 08-16-2021

Thanks for the pointer.  Just finished the osc test with another radio.  Was able to track the signal, staring at the top (1500), going down to 1260; 1250 was faded in/out; then nothing detectable farther down the dial.  Think my 89B code 123 is at least Run 7 with  det-osc  #36 and speaker K-21.  Believe there was also some work in the past (before it adopted me) due to having a 5Y3W rectifyer vice an #80.

RE: 89B cannot tune lower (550-1300) stations. - John Bartley - 08-16-2021

My first thought was ....

If the set was working properly and the problem just showed up one day, then the last thing I would do is fiddle with the alignment. Alignment doesn't just change for no reason, so fiddling with it before doing the actual repair might only make the repair more difficult.

I would start the same way as the post above mine .... look for oscillator function with a second radio.

RE: 89B cannot tune lower (550-1300) stations. - Steve Davis - 08-16-2021

Hi, welcome to the Phorum!

This is a common problem with the Philco radios that use the autodyne converter. The most likely cause is the oscillator coil has drawn moisture. The fix, remove the coil and bake it at 250 degrees for about 20 minutes. Afterward, it would be a good idea to seal the coil with lacquer or clear acrylic enamel spray. I agree, don't mess with the alignment.

Steve

RE: 89B cannot tune lower (550-1300) stations. - Steve Davis - 08-16-2021

I should add, while the coil is out of the radio, it may be a good idea to go ahead and rewind the feedback winding (the outer winding), as Terry mentioned in post two above. Philco used cotton covered wire for this winding, quite often this wire corrodes and goes open. It may test good now but, could fail at any time. The larger winding is enamel coated wire and should be OK.

Steve

RE: 89B cannot tune lower (550-1300) stations. - akrgg - 08-16-2021

Thanks everyone!   Will focus on the coil as time permits over the next few days and report back.  Much appreciated.

RE: 89B cannot tune lower (550-1300) stations. - Steve Davis - 08-16-2021

Another thing, try lowering the value of the cathode resistor, item 10 I believe, from 15K to 10K or even 7500 ohm.

Steve

RE: 89B cannot tune lower (550-1300) stations. - akrgg - 09-03-2021

Thanks all for the pointers, put me in the right direction. After finally having both some time and space to pull the chassis on my radio, found the problem - one of the wires to the osc coil came loose (guessing a result of some recent earthquakes). A little solder and now back in operation. Amazing amount of knowledge in this forumn, so much to learn from.