Hi,
i recapped tried to align but can only tune 1 strong station at the top frequency. if i try i can make 830 AM (strongest local station) come in, it's bearly perceptible at very low volume. I wonder whether one of the coils has a break. I can't decide which because i don't measure an open coil, the ohms are 5.6, 10 or 11. Maybe my alignment is bad but i've followed the schematic at 175kc etc. I hate to rewind a coil if i don't have to. Rich
Winston
Have you measured both input AND output of every coil? (## 2,5 and 7)
If you use a generator you can see which stage is not amplifying. With using stations every stage can work as an RF amp even if the previous one does not work, there a TRF for you.
So, measure both prim and second windings of all three coils.
Mike.
Hi Rich,
Methinks Mike is looking at the wrong schematic (the one for model 50 trf set)
Unfortunately the info from Rider's doesn't show the placement of the trimmer adjustments. One thing to take note of is when you adjust any of the trimmers is there a peak in the signal when adjusting the rf and IF? Does oscillator frequency change when adjusting oscillator trimmers? If not this is a clue as to which coil may be bad.
Prime canadets are the cathode winding on the 24 mixer tube and the antenna coil. An ohm meter is your friend to find the bad one. All good coil will show a low resistance like 10 ohms or less
thanks guys. Yes, i measure 10 ohms or less and when i adust the trimmers i do notice the changes but at the lower frequency it's a high pitch squeel like from the signal generator, not the actual radio signal. I can't help but feel it's something in my alignment and not the coil but the fact i can't tune a lower (830AM) station that is REAL strong makes me feel it's in the coil. I just can't prove it. Rich
The 51/52 is at the bottom. It's the one that is the superhet w/ 175kc IF. The 50 is the TRF set on the top. You gotta quit standing on your head!
I know. The last numbers are from that bottom sch.
This has always bothered me, where do i go to know the correct ohms readings per coil, to quote " I'd still measure ## 2,5,6,12 and 15 continuity." Mine read within that range but i don't know which "one" matches the 3 coils.
Also, does this measure correctly in circuit or like resistors, can the only true measure occur when removed from the radio?
thanks for the help,
Rich
(08-06-2016, 11:19 PM)winston763 Wrote: [ -> ]This has always bothered me, where do i go to know the correct ohms readings per coil, to quote " I'd still measure ## 2,5,6,12 and 15 continuity." Mine read within that range but i don't know which "one" matches the 3 coils.
Also, does this measure correctly in circuit or like resistors, can the only true measure occur when removed from the radio?
thanks for the help,
Rich
Hi Rich,
>This has always bothered me, where do i go to know the correct ohms readings per coil.
We are not necessarily looking for an exact resistance per say but continuity. Does the winding have a much higher resistance that it should? Physics tells us the the lower the frequency the more turns of wire you'll need on a coil. Your IF transformer coils @ 175kc are going to have more resistance than your antenna coil @550-1700kc. In rough numbers this equals about 5 ohms or so for the antenna secondary and the primary much less because it's a non resonate winding it's used to couple the rf signal from the antenna to the secondary and is much smaller. It's going to be just an ohm or two. IF coils are going to be around 15-40 ohms again depending on the frequency. The resistance specifications are nice to have but not a necessity. A bad coil will measure a high resistance like 1000 ohms or high like open
>
Also, does this measure correctly in circuit or like resistors, can the only true measure occur when removed from the radio?
Well this depends. When you have two components in parallel they will have some sort of interaction. For instants let's look at #1 and 2 on your 52. What you have is the volume control and the primary of the antenna coil. Can you measure the coil with the volume control connected to it? As long as the volume control is not turned full up (shorting the coil) since the coil has a much lower resistance than the control what your ohm meter will see is the lower resistance. A little different story with resistor and caps in parallel. There you have a resistance and a device that stores electricity. Your ohm meter applies a small voltage to what you are measuring in this case, the cap will try the store the applied voltage and the resistor will try to discharge the volt confusing your ohm meter. So best to separate them for an accurate reading. You don't have to remove the part just disconnect one end and your good. Generally parts in series don't have much of an interaction so you don't have to disconnect them. Rule of thumb is if it measure way out in circuit disconnect one end and remeasure.
Second what Terry says; in short we need continuity. Typical resistances of these coils are from units to a posdibly hundred of Ohms. If these are, it is likely you are ok. Should not be in kiloohms and up range.
4,10,50,100 Ohms are reasonable to expect.
Thank you for sharing your insights. Now i understand. Yes, i have continuity within the exact ohm ranges you listed. From 1 to 10, depending upon the coil.
So i believe my issue is not in the coils. However i can still only tune to higher frequencies and best at 1 strong station, 1280 to be exact. Comes in screaming loud to the neglect of any other station.
I did replace the oscillation winding on the Osc/detector coil. is this a symptom of winding it backwards/wrong direction? I think i tried both directions with the same result (did this a few months ago).
Anyway it's a good radio but plays only 1 station and nothing in the lower frequencies except squeels. I followed the alignment starting at 175kc - but the 600kc low frequency alignment, again, is not loud but perceptible.
My guess is, you know exactly where this points to but I've been struggling with it for weeks/months off/on.
>I did replace the oscillation winding on the Osc/detector coil. is this a symptom of winding it backwards/wrong direction? I think i tried both directions with the same result (did this a few months ago).
Now I'm assuming that you mean feedback winding or tickler (that would be the small winding at the bottom of the coil). If that is backward the oscillator won't work. Simple test, try listening for the osc in another set. You can use a small transistor job. hold it near the #24 tube nearest the ant post. Since the IF frequency is 175kc your osc is going to be running at 175kc above the dial reading of your 52. For instants if the dial on the 52 is set to 600kc the osc signal should be heard @ 775kc (600+175=775) or at 1500kc the osc should be heard @ 1675kc.
The osc signal will quite the transistor set when it's on the proper frequency. It's not uncommon for the osc to be a bit off frequency so tune around a bit if you don't hear it right where it's suppose to be.
OR
You can use your generator as the LO by connecting the unmodulated output to the cathode of the 24 tube, tune it to the frequency of a known station + 175kc. Set the radio dial for the station's frequency. With an antenna connected to the set you should be able to tune in that station. Basically you are using the radio's tuning to tune the RF side of things and the generator to tune (or act as) the osc tuning but both have to match, radio dial to the incoming frequency and the generator at 175kc above the incoming frequency.
"You can use your generator as the LO by connecting the unmodulated output to the cathode of the 24 tube, tune it to the frequency of a known station + 175kc. Set the radio dial for the station's frequency. With an antenna connected to the set you should be able to tune in that station. Basically you are using the radio's tuning to tune the RF side of things and the generator to tune (or act as) the osc tuning but both have to match, radio dial to the incoming frequency and the generator at 175kc above the incoming frequency."
#1 - yes, it was the tickler coil at the bottom of the det/osc coil that i rewound. I can align 1 very strong station (don't even need an antenna connected) at 1280 and hear it as loud as i want.
#2 - couldn't get the transistor radio tuning to work so i use the signal generator as i quoted you. Now i could get 830AM our local strong station by having the radio at approximately 830 and the signal generator at around 1000+ so it is around +175kc.
i couldn't get other weaker stations at 900 or 980 but they're very weak at night.
Does this conclude that i wound the coil in the wrong direction? I thought i tried winding it the other way too and it didn't align at all but i could be mistaken. I've been at this problem off and on for months.
I thank you so much for your help.
Since you can't hear the the osc it's a safe bet that it's not working. If the tickler is wound in the wrong direction you don't have to rewind it. What you can do is just reverse the components soldered to the two lugs on thr coil. Do you recall how many turns you wound on it? Wound think that it should be about 30T, maybe a bit more. 24 tube isn't overrun with gain. Plate, cathode, and screen voltages seem reasonable?
I reversed the tickler connections and i couldn't align to anything.
So at 110 volts using my variac, (should have measured at 115) i read the following:
24 osc/1st det 182/67/5.5
35 IF 182/68/2.5
24 2nd det. 108/60/4.83
the 24 2nd det. is high but i kept checking and i don't know why this is or the impact.