[skyscraper]

Thank you so much, Mondial. That makes much more sense.

Morzh - I went ahead and bought that one on eBay. Based on other sales I saw, I think $35 is a reasonable price. Thanks for the offer, I might take you up on it, depending on how well this one works. Wish you had posted just a little earlier

[morzh]

Absolutely.

BTW there is a FET (solid state) mod of this unit called 1G-102FET.

Exact same sch, with FETs instead of tubes and batteries to power it.

[Mondial]

Will, that Heathkit should work out fine for you. Just don't put too much faith in the frequency dial calibration.

You mentioned that you had a digital receiver which was fairly accurate so you can use it to confirm the generated frequencies. For example to check 260 kHz output, set the digital receiver to 780 kHz which is the third harmonic. Tune the generator around 260 until you hear the 780 signal in the receiver and then you will know you are exactly on freq.

Of course, regular AM broadcast freqs can be checked directly on the fundamental output.

[NostalgiaRadioTime]

Rather than start another new model 89 thread, I thought I'd post this here, as we're both at about the same place in our restorations. Had to rewind the primary on the RF coil and the tickler on the OSC coil, as they both were open. The set was completely recapped and all resistors replaced as well. Now I get only one station... but only if I touch the grid cap of the #36 tube with a lead from the antenna (or even with just my bare finger!). The station comes in between 650 and 750 on the dial, and can be heard faintly on the opposite end of the dial as well around 1100 or 1200. In between, the set will motorboat or squeal around 900. So far, adjusting the trimmers makes no difference. Am kind of at a loss as to why the set isn't receiving more or at louder volume. If anyone has any ideas on what to check or what could be the culprit I'd love to hear from you. Thanks.

[Warren]

I must have missed where it said it has audio modulation.. that's good. Glad someone saw it.

[skyscraper]

Mondial, my receiver tunes down to 200kc, so I won't have to mess with harmonics.

I went through everything tonight, got the local very close to 260kc, and the tuning dead on with strong voltage on the avc. It still dies below 1000kc without the jumper lead on the plate of the 36. I'm going to redo the tickler coil again, just to rule it out if nothing else.

Greg, my set did similar before I replaced the 36 tube, the original was weak. Out of curiosity, what happens if you attach a wire (12in or so) to pin 2 of that tube? Be careful, there's high voltage on it. Doing so completely fixed my radio...

[NostalgiaRadioTime]

Will try that tomorrow, Sky. Thanks. Where did you gator clip the other end of the wire to off of pin 2?

[skyscraper]

Don't connect it to anything. That's the peculiar part. It apparently creates a miniscule amount of capacitance that throws everything into balance, they don't call it the 89 from h*ll for nothing...

[Mondial]

Will, have you tried increasing the value of the .0007 uF cathode bypass cap of the 36? It seems later production increased the value to .0014 uF.

How short can you make the gimmick wire before the osc quits? If you make it really short, does it make a difference if you bring it near the other coil terminals?

There is an advantage to using harmonics when checking low freqs with your digital receiver. The receiver has a fixed bandwidth and resolution regardless of RX freq so you want to measure at the highest freq possible to minimize percentage error.

Say you can measure the RX freq to an accuracy of 5 kHz. If you can receive the third harmonic at 780 kHz to an accuracy of 5 kHz, then your accuracy of measurement of the fundamental increases to 1.66 kHz at 260 KHz, which is much better than if you measured it directly. If you used the fifth harmonic at 1300 kHz then the possible measurement error drops to only 1 kHz.

[Ron Ramirez]

The later 89 sets that use a .0014 uF cap use a 77 tube as first detector-oscillator instead of a 36.

[skyscraper]

That's what I thought, thanks.

Adding capacitance did nothing. The lead has to be at least 6 inches, and less than 20 or so. Gripping it stops oscillation, and moving the wire near any of the coils or antenna dampens it. A small cap between it and ground stops it. Moving it near the other lugs seems to dampen it, but it's a bit hard to move things around with all the high voltage.
As soon as I get a free hour I'll redo the coil.

Very interesting on the harmonics, Mondial. That makes sense. Thank you.

[NostalgiaRadioTime]

Sky, I tried your test tonight and connected a gator wire to the plate of the #36 tube (or pin 2). I was able to get several stations across the dial... though none of them local...and the squeal and motorboating mid-range on the dial disappeared as well. I clipped a second gator wire on and the length made no difference. I probably had 24 to 30" worth of wire. Now, holding the gator wire up in the air and moving it slowly would change the frequency. It was as if that wire was acting as a variable capacitor just by my moving it around! Interesting, the band switch did absolutely nothing going from broadcast to police... I got the same stations on police band too. What this all means or what it did I'd love to know

I rewound the primary of the RF coil with 32 gauge wire. Now I get .5 ohms across it. According to the schematic it should be 1.68 ohms. Wonder if that makes a major difference and how I could add more resistance if need be without rewinding?

Lastly, and this might be a good question for Ron, I have a model 89 parts chassis here I've been robbing the coils from that uses the #77 tube. The headache I'm working on uses the #36. I know the #77 tube makes the oscillator a bit more stable, but am wondering what the real advantage is to converting my #36 to a #77? Is it really worth it and what is all involved to make the conversion? Comparing the two tubes, the #36 is a 5 pin, and the #77 is a 6 pin, and it looks like the 6th pin is just an extra grid that is grounded.

Thanks for the help. It is MUCH appreciated. This is by far the most complicated radio I've ever tackled. I'm bound and determined to win the fight with it! LOL

[skyscraper]

Well, at least now I know it isn't a completely isolated problem. Did you end up rewinding the oscillator tickler coil? What size resistor is in the 36 cathode bias network? The resistance of the coil isn't a concern, your wire is thicker than the original. But as morzh said earlier, it's the turns that count

My bandswitch doesn't work either, it just needs to be cleaned. There isn't anything to hear up there, so I haven't gotten around to it yet.

If you go to all the trouble to replace the 36 tube socket, I would do the 'Super 89 Mod' here: http://www.philcoradio.com/notebook/supercnv.htm That ought to be even better.

Still holding out hope this is fixable, it seems like plenty of people have gotten it done. I hope the rf generator will shed some light (and other forms of radiation) on the problem. Do you have the means of a proper alignment?

Good luck,
Will

[NostalgiaRadioTime]

Yes, I rewound the tickler on the OSC too, using 38 gauge wire. The primary of the RF wasn't that small, but probably a little smaller than 32 gauge. More like 34 or 36. I'll have to double check the cathode bias resistor value tomorrow. Getting ready to turn in for the night soon. I have an RF signal generator here but that's it. We're going to win the war yet! LOL

[NostalgiaRadioTime]

Forgot to mention that clipping a gator wire between the grid caps of the #36 tube and the #44 tube next to it improved the signal. I get very little response from the antenna lead, yet the coil ohms out fine. It's not open.