[Bruce B]

This is my first post to this forum.  I am here to see if I can find help bringing a Philco 89 121  back to life.  I know we're supposed to talk about radio repair here but first I want to say I studied electronics in the early 60s and used to work on old pre-war radios but it's been 50 years now since I did anything with old radios.  Now I want to get back in and I'm not sure if I remember much.  Not like riding a bicycle.
  So I have been playing with this radio for about a week now.  The radio is not dead it has audio and produces a loud buzz when an antenna is provided and it is quiet without an antenna attached and volume up.  There is no detection of a station signal, just buzz and static.  I got a signal generator and set the coil trimers to 260 KC.  I can here a modulated 1150 KC signal from my signal generator but not anything from a strong station at the same frequency using an antenna,just buzz.   The buzz stops when a signal from the generator is applied.
  What I have done so far is to replace the capacitors involved from the antenna circuit up to the 44 IF.  Nothing has changed yet in the radios performance.
  Other investigation was to ohm out all of the coils from antenna to the 44 IF tube.  All are ohming out to the specs I have.  I got an oscilloscope and am able to see a 260 KC signal on the scope when I place the probe close the the 36 mixer tube so I know it's dancing ok.  So this is about what I have done.  I will continue to replace caps till I have done  them all.  It has been quite tedious but interesting to figure out how to replace capacitors inside those bakelite boxes.
  One thing that would make my life easier is to have a schematic and parts list that works for the radio I have.  I have a schematic that so far fits the radio I am looking at but the drawing calls one value of capacitor and when I trace it down I find a PN on a block and when I look the blocks specs up the value might be different.  I replace with the value I find in place, not the value in the drawing.  I have also been taken down a rabbit hole over a capacitor bank (drawing part 4) showing .09 uf of part 4 going to a location but whenbthat location is traced out I end up with a potted capacitor that did have a .09 uf value.  I haven't looked yet as to where the capacitor bank is really wired?  I'll get there.  My radio is a model 89 code 121 and uses a 36 mixer tube.  The Riders manual I am using shows a 77 mixer. So I am confused ? but I am proceeding with it for now.  If anyone knows where I can locate a drawing and parts list for my 36 tube it radio it would be nice.  Also I looked around for a drawing that would have suggested voltages at the tubes, I don't know if such exists but it would be nice ? 
  So I hope I didn't get to wordy.  I hope I have explained what I am doing and for some patient Pearson to make suggestions about how to approach what I have gotten into.
Bruce B

[GarySP]

Welcome to the Phorum, Bruce! I haven't had an 89 on my bench (yet), but I'm sure many other members will be happy to help you through. Take care and BE HEALTHY! Gary

[morzh]

Do you have any strong interference source nearby?
Have you performed full alignment?
If you have not finished recap, finish it first.

89 is not that different from 19, and I have done one 19LZX. Nothing special.

[DaleHCook]

We have factory documentation for most models, indexed here:

https://docs.google.com/spreadsheets/d/1...sp=sharing

That spreadsheet has many columns, so be sure to scroll to the right to see them all.

[462ron]

Hi Bruce, here is original Philco factory service info on your set from the Philco Radio Library at the bottom of this page!
https://philcoradio.com/library/download...l.%201.pdf

Ron

[Bruce B]

Gee! That is a great help, I can now see what I am looking for and it's crisp and clear and matches exactly the radio I am working on.
  Next week I get a package of more capacitors so I can continue with recapping.
  The thing I am curious about is that all but one of capacitor blocks was untouched with original soldering on there terminals.  The one that had obviously been charged was in the RF section.  I have replaced all caps involving tuning of the coils then did an alignment.
  The radio looks an molested throughout the whole radio section but around the power supply and audio is a different story.  For one thing there are at least 4 electrolytic caps at values from 10 to 30uf the original pair or 8uf caps are still there but have been clipped.  Underneath is a  home made resistance bridge of 4 dog bone resisters that are just suspended through creative, artistic soldering.   It's a mess but for now I am leaving it alone because there is quality DC and the audio is quiet strong.  I have two 8uf cans coming and then will make a project of putting the power supply back to the way it used to be.
  Do you know what voltage is expected at the grip cap of 36 mixer? I have about -1v seems low?
Thanks again for the cool factory data, Bruce

[NostalgiaRadioTime]

Fingers crossed you'll get lucky and won't have to, but chances are you're going to have to rewind at least one, possibly all three of the coils (ANT, OSC and RF). The model 89's are notorious for having open primary windings on their coils. Here's the notes from when I did mine many years ago: https://philcoradio.com/phorum/showthread.php?tid=8753

[Arran]

I don't know if this would help but there is a page about the model 89s, and the changes they made over the years they were in production.
https://philcoradio.com/library/index.ph...-model-89/
Regards
Arran

[Radioroslyn]

Hi Bruce and welcome,

Not to inundate you with more schematic info but https://philcoradio.com/library/download...%20146.pdf This has it all except the parts values on the diagram.

If all seems well up to the mixer (36 tube) connect the generator to the grid cap w/a 260kc signal that is modulated. If all is working you should be able to align the IF stage #'s 15, 19, 22, 26.

The next step I would do is measure the resistance from the cathode pin of the 36 to the junction of #'s 8 & 10 and the osc coil. Should be around 5 ohms. Anything much higher makes the osc coil feedback winding suspect. Pop it out and inspect it, the small winding near the bottom of the form. It may have hazy appearance but a little heat from a heat gun will clear it up it's wax. What you are looking for are green dots. This is rot in the copper wire caused by a chemical reaction. If so it's time to rewind.

>end up with a potted capacitor that did have a .09 uf value<.
You've probably already figured this out that some values are not available anymore. .09 is a .1 as is a .05 is a .047. There are many of resistor values that are discontinued. On these old sets the spec is 20% so there's a fair amount of latitude in value to find a modern replacement. It's tough on servicing tube type TV's.

[radiorich]

Hello Bruce,
Welcome to the Philco Forum !
I too have that same radio in my collection .

Sincerely Richard

[462ron]

Bruce, I don’t have an 89 myself but have seen many posts on here like Greg’s and others and understand the 89 can be a finicky set to get working properly.

Ron

[Bruce B]

I have to thank all of you for these nice posts that have given me good information and documents that will help me on this radio project.
One of the first things I did before a power up was to look for shorts and to own out all of the coils. They all checked out ok. I replaced all the caps from the antenna to the 2nd detector. When I powered on I got plenty of sound, no stations though. I then did an alignment that seemed to go well but still no stations, just tunable noise. The noise gets quiet when a modulated single is applied to the antenna.
I have used an oscilloscope and and can see a 260 KC wave form when placing the prob close to the ocilator. So I think the coils are still good for now,?
I am waiting till next week to hopefully resume playing with my radio. A couple of things have developed, one I ran out of capacitors and and am waiting on an order of more caps.
The other thing is Morzh ask about nearby by interference. Well I got curious and got an old battery powered radio, turned off the main breaker at our power pool and WOW! I still had loud noises coming out of the battery powered radio. I live on a farm and my closest neighbor is a mile away. There is nothing nearby that can be making interference. I realized that this noise is coming onto our property via the power line. Standing in my front yard this interference was preventing a known working radio from receiving stations. By turning the dial I learned that it peaked out at 2 KC intervals from 16 KC to 8 KC. I got into my car and went for a drive discovering that this interference is present half a mile away when I park under the power lines. Tomorrow I will call my power provider and hope that the conversation goes well ?. They have an arc going on somewhere like cracked, dirty insulators or trees ? touching
Well I will sign off before I use up too much text and will report back when I have more capacitors and no harmonics floating around in my house.
Bruce B

[Radioroslyn]

< I have used an oscilloscope and and can see a 260 KC wave form when placing the probe close to the oscillator. So I think the coils are still good for now,? >

I'd be happier to see a waveform from the oscillator tuning from 810kc (@ 550kc) to 1760kc (1500kc) as you tune the dial.

You might enjoy this video: https://www.youtube.com/watch?v=hz_mMLhUinw

[MrFixr55]

Hi Bruce, and welcome to the Phorum. I have experienced only one 89 and hope to never experience one again.

So far, I have done 2 Philco 80s, which also use a '36 as an "autodyne" mixer. In the beginning, superhets had a separate local oscillator and a mixer circuit that produced the beat frequency IF signal. Later, the "pentagrid convertor" was developed (2A7, 6A7, 6A8, 6SA7, etc.). In between, the "autodyne" circuit was in use. The issue is getting them to oscillate with stability. The 80 and 89 both use the autodyne circuit, but there are differences between the two, with the 80 being more stable in my limited experience.

Use your signal generator to determine if the mixer is oscillating correctly. In theory, with direct injection into the antenna terminal, you should be able to tune any frequency generated by the signal generator in only one place on the dial, that being the frequency (or close to the frequency) selected on the generator.

Definitely follow the advice given by Terry (Radio Roslyn) and Greg (Nostalgia Radio Time). Almost all coils from early 1930s Philco sets have the primary wound over the secondary with a cellulose insulator between them. Apparently, the cellulose breaks down into a component that is corrosive to copper, corroding the primary till it opens. This is exacerbated by the fact that the primary carries the tubes' plate current in the RF and IF coils. However, in the case of the mixer (1st detector) coil, it is the "tickler" (oscillator feedback) coil that opens. This coil carries all the tube current because it is in the cathode circuit.

If you find the tickler to be open, remove it, remove the celluloid band and inspect the winding underneath it. Ensure that the enamel has not come off the winding below the tickler. Repair if so. Bake the coil in an oven at a low temperature (200 Deg) for a minimum of 30 minutes. Apply a layer of mylar tape that is equivalent to the thickness of the celluloid material previously removed. Wind 25 turns of #39 wire in the same direction as the layer that you removed. Shellac the complete assembly to prevent moisture absorption. More detailed instructions on repairing these coils is found in the Philco Library.

The resistor and capacitor that is in series between this coil and ground should be changed. Replace the 15K Ohm resistor with a value between 8.5K and 10K Ohm. Replace the 700pF cap with a 680 - 700 pF mica or npo ceramic disk cap.

Hopefully this helps. Good luck, keep us posted on your progress and don't hesitate to ask for help!

[MrFixr55]

Hi Bruce,

Don't worry about being wordy, I am also wordy.

Sorry, I forgot to recommend a test with a good radio. If the "test radio" was a portable transistor type with a ferrite core antenna and you could not receive stations, then yes, you really, really have interference. Between the self-reporting what-hour meters in use now, all the computer, switching power supplies, LED and CFL bulbs, etc., AM is now a total nightmare. This is one reason why the big 3 Auto makers want to stop putting AM reception on their radios, especially in hybrid and electric cars.