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Step by Step Restoration: GE T-106C, Let's go for it!

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Post by Bill Cahill on Wed Mar 20, 2013 10:58 pm

Looking at your picture of the transformer, I see that what happenned is clearly that. Almost every normal output transformer I see on radios have the wires the other way. GE clearly turned the wire colors around.
That's GE for you.
Great thread.
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Post by Dr. Radio on Fri Mar 22, 2013 10:04 pm

Time for some very important safety information. We'll step aside from the radio project to break-away and give some background on not only the use of the isolation transformer, but why it comes into play for radio restoration work.

If you've ever taken a good look at the outlets in your residence, you'll notice there is a difference in the prongs. Older dwellings may lack the 3rd ground connection, but they still have one blade wider then the other to accommodate "polarized" plugs on electronics and appliances. If the outlet is wired correctly the wider blade (Neutral) is theoretically at the same potential (voltage) as earth ground. The neutral wire, which is colored white connects back to the breaker or fuse panel and is eventually tied to earth ground. It is an uninterrupted path. The smaller blade on the outlet is at a large potential difference from ground. Typically 120 volts. This smaller blade (Hot) is the feed that is fused or switched by a breaker in the circuit panel. It's wire color is black. Ground connections are colored green, or use a bare copper conductor.

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If you were to measure between Neutral and Hot, you'd have 120 volts AC. If you were to measure between Hot and Ground, you'd also read 120 volts AC. If you were to take a ground rod and pound it into the actual earth's soil far enough to get a good connection with "ground", you could measure between the hot on an outlet and your ground rod and also measure 120 volts AC.

The point I'm getting at here is, you don't have to be directly across hot and neutral to measure 120 volts OR receive a shock! affraid

I've provided some cartoon-like illustrations to help with some visualization of current paths and how some paths can be overlooked and dangerous! I am not trying to make light of these situations, but hope the simplicity drives the message home.

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Obviously if you were to make contact between the hot and neutral connections (touching the outlet connections), you'd receive a nasty and potentially fatal shock. If this is not obvious to you, it's time to leave this hobby as this should be a common sense matter, not an electronics knowledge matter.

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While that should seem obvious, what may not seem obvious, or be the result of an accident is the scenario of you becoming a path between an earth ground connection and the hot connection in the power supply circuitry. The "earth" side may be an old room radiator, a water pipe, metal apart of your work bench, a cement floor, etc. Anything that would allow a current path back to earth ground.

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So what does all this have to do with working on old radios--particularly AC/DC radios that are of a "transformerless" design--a design that use direct connections to the wall outlet to feed the circuitry??

Vintage radios were built long before more stringent safety standards came into play. You will notice that your old radio's power plug is non-polarized so you can plug it into the outlet either way (rotate 180 degrees) and it still plugs in just fine, unlike modern polarized plugs.

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Here is where the problem begins. The inherent design of AC/DC radios involves one side of the incoming power line connected through a capacitor to the chassis OR directly connected to chassis. Since the power plug will insert into the outlet either way, you have a 50/50 chance of the chassis and related exposed hardware becoming "hot" connected. ....May not seem like an issue until a piece of test equipment or you become a current path between this new hot connection and a ground connection....

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So if you are going to be working on radios, touching exposed parts, connecting separate pieces of test equipment to it, etc, you need something that would "break" this potentially lethal current path between ground and hot.
This is where the all-important ISOLATION TRANSFORMER comes into play. It isolates the piece of equipment you are working on from the potential hot to earth connection. The separate windings inside the transformer provide the electrical isolation.

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No current path between ground and hot thanks to the isolation transformer. Bear in mind, you can still get shocked if you get across the output outlet of the isolation transformer, so don't think you are shock-proof if you are using one! An outlet is still an outlet and has high voltage across it!








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Post by Dr. Radio on Fri Mar 22, 2013 10:29 pm

Here's my isolation transfomer. It was marketed to tv servicers, but will work for any piece of equipment.

This style provides internal taps so when you set the incoming line voltage, you have a "high", "medium" and "low" output voltages via the different the outlets. This unit also provides direct (non-isolated) outputs. If you have a similar unit make sure you ONLY connect the equipment you are working on to the isolated side. Don't connect anything else to isolation transformer.

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I set the line-in voltage to 125 (as the bench power was a tad bit over 120). With this input set, the "high" output was around 130 volts, the "medium" output was around 117 and the "low" was about 107 volts. We'll use the medium outlet to power our radio as 117 volts is just about right for a vintage piece of equipment. The point of having different outputs is it can be a useful aid in troubleshooting. Running something at a higher voltage can "force out" any intermittents, so a set acts-up, lower voltage could be used to determine if poor performance soon results if a set is marginal at best.

So we'll be powering up our GE radio for the first time. cheers

The GE's "cheater" cord will connect between the radio chassis and the isolated side (the medium outlet) of the isolation transformer. The isolation transformer's power cord will connect to a regular outlet on the bench.


Stay tuned.... Very Happy

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Post by Dr. Radio on Fri Apr 05, 2013 10:36 pm

Well, it's time to power-up our radio for the first time!

Here's the bench set-up....

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There's enough bench space cleared so nothing can short if the chassis of the radio should lose it's balance due to an accident. The radio's "cheater cord" is connected and plugged into the isolated side of the isolation transformer. Don't forget, we don't have any speakers since those were pulled out of the cabinet as well. My bench has built in test speakers, so it was just a matter of connecting test jumpers from the output wires of the audio output transformer to the test connections above. The tubes were already plugged in (making sure they are in the correct socket).

So, with a "click" off the on/off switch.....


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Well, that's always a reassuring sign.... Very Happy Our tube heater circuit is good, we have the tubes lighting up! After a few more seconds some static and with the spin of the tuning capacitor's shaft----Picking up local radio stations clearly!
cheers

Now, especially for beginners, one might think we've successfully "restored" this radio.....NOT SO FAST! Just because it "works" doesn't mean it is working to it's full potential. Also, there could be problems just waiting to rear their ugly head. As tempting as it is to skip the next step, it is time to do some important 'health' checks of the radio's circuitry. Time to do the all-important voltage measurements.

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Post by Dr. Radio on Fri Apr 05, 2013 10:59 pm

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto73_zpsa11d998b

As noted on the schematic, our voltage measurements are taken in reference to "common", or B- on this radio. With our meter set to DC volts and the black negative probe connected to B-, we can now take the red probe of the meter and check various tube pin connections and test points and compare our readings with what is specified on the schematic.

***Important Hint***, These readings were taken with either a vacuum tube voltmeter or a low impedance multimeter back in the day. Modern equipment like my digital multimeter looks nearly "invisible" to the circuit, which means the readings will differ. It just takes some experience to get used to the differences to recognize what is clearly a wrong reading. Older equipment would tend to "load down" circuitry and you'd get lower voltage readings. Line voltages coming out of the wall outlet today are higher then they used to be.

Remember I used the "medium" outlet on the isolation transformer. You can see by my meter, it's pretty well dead-on to what the recommended input was stated at--117 volts AC input.

Don't forget to make sure your meter is correctly set to either DC or AC before you connect it into the circuitry under test.

Before reorganizing, or connecting anything, always unplug the incoming power and let electrolytic capacitors drain their charge before handling the components to avoid a shock. Keep the radio's on/off switch "ON" while you unplug it.

Here's the set-up for taking voltage measurements.....

As specified the volume control is turned-up to maximum, the tuning capacitor was "tuned" to dead air (no signal/away from any stations) and the chassis is placed downward to prevent any "spills" while checking test points. You'll notice there is black electrical tape holding down/covering our AC input connection and the B- connection. Not only does this prevent wires from creeping off the bench and pulling out, it also prevent the human error factor--bumping or rubbing against live wires! Although we are using an isolation transformer, the output of the isolation transformer only protects us from the dangerous hot-to-ground path explained earlier. It does not protect us from all-out shock--there is still high voltage leaving the isolation transformer and powering the radio chassis!

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The old "one-hand rule" comes into play. Keep one hand AWAY from the chassis, wires, test equipment etc. Only one hand holds the test probe. The idea here is so you don't become a complete circuit from hand to hand and ultimately arm-to-arm....because your heart is in this path should an electrical current hitch a ride!

Now, let's take a closer look at that "reference" I keep mentioning. If you look at the schematic, the simplest way to make a B- connection is to the power's switch's output side. A test clip is connected here. The other end of the test lead connects to our meter's negative (black) probe and is left alone after the connection is made.

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto72_zpsc60316d3
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Post by Dr. Radio on Fri Apr 05, 2013 11:28 pm

Now it's just a matter of checking our voltages against the printed voltages in the schematic. You'll notice the pin numbers are shown, as well as the expected voltages. Going through this radio, all voltages were pretty much spot-on, only differing by small values....except there was a problem when checking the grid of the output tube.... Mad

But, this why you check voltages--to find problems before they turn into bigger problems! Rolling Eyes

As you can see in the schematic, The audio coupling unit (which is a bunch of parts housed in a single component) labeled "K1"--has it's leg or pin #7 feeding the grid of the 50C5. Pin #2 and #5 of the output tube (the 50C5) are internally connected, so that's why the schematic shows this as 2-5 on this tube. Above this is the reading of 0 volts. There should be NO positive voltage on the grid of our output tube......

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Well....here's our reading on pin 2/5 of the output tube. It was easier to get a solid test connection by touching leg #7 of the audio coupling unit (again, this is directly connected to output tube per the schematic and the circuit trace on the board of the radio).

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Hmm, positive voltage on the grid. "Houston, we have a problem".... Evil or Very Mad Schematic indicates ZERO volts, we have almost +1.5 volts!

This is not good. A positive voltage on the grid of the output tube will cause it draw excessive current and will ultimately lead to destruction of the tube and possible damage to circuitry. This needs to be corrected by finding the cause!

I won't go in theory, you can research this by going online or reading, but there are (2) typical causes.

It could be electrical leakage from a coupling capacitor or a bad tube.

The other voltages were good. We can't simply unplug the output tube to take a measurement, that will kill power to whole radio...We could desolder "leg 7" of the audio coupling unit--this would kill the radio's audio as this is the audio path, but the circuits would be kept live to see if we have positive voltage. If we did have positive voltage, this would be a bummer. We'd have to replace the whole audio coupling unit due to internal problems--and guess what? They don't make them anymore so I'd have to show you how to build one from scratch with discrete components. Mad

Is it the tube? Sometimes a hot (temperature wise) output tube will suffer from "grid emissions" (do a google search on this phenomenon), but basically the fault come from the tube itself internally causing a domino effect of self-destruction.

What do we do??!!

Here's my answer to performing a quick check without even having to plug in the soldering iron....

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Post by Dr. Radio on Fri Apr 05, 2013 11:39 pm

Here's my handy-dandy "test tube" for just such an occasion..... Razz

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Notice it's marked with a blob of high temperature RTV silicone...This is so it doesn't accidentally get used other then for a specific test....and here's why.....

Check out the bottom:

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto77_zps8bc73d70
Yup, pin #2 and #5 have intentionally been removed. Now when we plug this tube into the output tube socket on the radio, we are still able to make voltage measurements--specifically leg #7 of the audio coupling unit. Since the tube is no longer linked to the audio coupling unit via pin #2 and #5, if we read ZERO volts on leg 7 of the audio coupling unit, our original tube was to blame! Simple enough eh?

Guess what? Our audio coupling unit is.....GOOD cheers

Another spare 50C5 confirmed my original suspicion--grid emissions inside the 50C5 tube that was found in this radio. After swapping a different 50C5 there is no positive voltage on the grid.

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto78_zpsa9bcbe9d

Our voltage measurements provided us some very important clues to solving the issues.




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Post by Dr. Radio on Fri Apr 05, 2013 11:45 pm

Well are we ready for the next step? Well, we have bigger issues with this radio and I couldn't be happier. (yes, you read that correctly). Even though there was no signal when taking measurements, after several minutes of operation a static filled crashing noise was soon present in the speaker. It disappeared as mysteriously as it began. Several minutes later it was back, but again short lived. There was no electrical disturbances present in the area and it was a clear day.

?????

Tapping on the chassis did nothing. No poor connections.

Ok, this should be obvious to the more seasoned restorers....do you know what is going on? This is VERY common in miniature AA5 radios, especially the inexpensively produced GE's.

HINT: Some would refer to this as "A thunderstorm on a sunny day"............


Make your guesses and stay tuned........
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Post by Bill Cahill on Sat Apr 06, 2013 1:15 am

Oh, Oh. Either a poor connection, or, a bad I F transformer.
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Post by bill57 on Sat Apr 06, 2013 10:23 pm

1 would say that sounds like SMD

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Post by NashvilleRad on Tue Apr 09, 2013 2:59 pm

Is the thunderstorm immediate, or after the set warms up for a minute or two?

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Post by Dr. Radio on Fri Apr 12, 2013 9:03 pm

For those of you thinking IF (intermediate frequency) transformers and SMD (silver mica disease), you'd be right on! A dreaded thing to have happen during a rebuild, but a great opportunity for learning here, that's why I'm actually glad it's acting up.

At first it seemed liked a normal intermittent after the set was on a while, but soon after, you hear the "storm" very soon after a cold power-up.

GE's are very prone to this issue and I will explain why when I go through rebuilding BOTH IF cans....
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Post by Dr. Radio on Wed Jan 22, 2014 8:01 pm

Okay, time to continue on with this project after a long hiatus!

Time to clear off the bench and scoot up to the computer again for this "follow-along" on restoring this simple little 1963 General Electric table radio.

Where we left off was a mysterious "thunderstorm like noise" that was beginning to rear its ugly head not longer after the chassis was powered up.  

The following was already ruled out:

-Bad solder joints
-Faulty tubes and tube sockets
-Out-of-spec voltages
-Out-of-spec components
-Mysteriously appearing thunderstorms or other electrical disturbances

I'm actually glad this radio's Intermediate Frequency Transformers are acting up! This will allow to explore this invaluable learning experience that is oh-so-common among late 40s to late 60s table radios. I'll be upfront, it's never fun, but once you grasp the concept and practice the repair techniques, you'll be more confident in repairing those All-American 5 tube radios.  rabbit 
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Post by Dr. Radio on Wed Jan 22, 2014 8:15 pm

GE's are quite notorious for IF transformer issues. I'll touch on why a bit later. First let's take a look at what we are dealing with.

The IF transformers are pretty simple to locate. They are among the largest items on the chassis. The tall, bright, shouldered aluminum "cans" aren't easily missed. The first thing I did was grab (2) permanent markers of different colors.

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Here's our schematic again. (I've purposely placed the different markers by the corresponding IF transformers).  As you can see from the schematic, the outer "cans" provide a shielded structure to enclose the coils and capacitors inside. The capacitors inside this style of transformer are the real troublemakers!  Mad 

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In order to do our repair work (or surgery as I like to call it!), we first need to be very careful we make some sort of mark or "witness" indicator so we can put everything back together properly. It's just like when we removed and replaced the electrolytics in this project--one must be very careful connection orientation is observed! Embarassed 

This is where the markers come into play. What I've done is placed a highly visible mark on one side of the can and continued that on to the actual circuit board. There will now be no question on the correlation of connections (well at least at this point!).

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This transformer in the corner was no issue, but space is at a premium where the other unit is mounted. I'll make a mark on the easy-to-get-to surfaces.

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Okay. We'll remove and rebuild only one at a time.
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Post by Dr. Radio on Wed Jan 22, 2014 8:33 pm

We'll just remove the 1st IF transformer to begin with. This is the one that was marked in blue, and the one that is indicated by the blue marker pointing at it in the schematic. This is also the easier one to remove thanks to less crowded real estate on the circuit board.

Time to get out the desoldering tools again. Before we remove the first unit, time to take an assessment of what needs to be desoldered.  There are (5) connections to the circuit board. (4) provide an electrical connection to the internal coils and capacitors in the assembly. The 5th point is the physical mounting point for the housing itself. This provides structural support, protection for the internals, and an electrical shield.

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I've circled the connections and drawn an arrow to the main mounting point. Construction of IF transformers varies, so you have to do a little bit of investigating to find out exactly how each mounts. GE produced some very cheaply made units, that's why there is only one main mounting point on these units.

You want to be very careful when desoldering. Too much heat, or too much aggressive pulling, rocking or bending can damage the fragile internal structuresShocked 

After some heat, some desolder braid, a lot of patience and holding one's breath, the "can" is free without any damage. There's that pesky mounting tab again. Rolling Eyes 

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto84_zps13c62d31
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Post by Dr. Radio on Wed Jan 22, 2014 8:51 pm

Let's take a closer look at the bottom of the unit. Like the vast majority, there is some sort of marking or legend indicating the pin layout. This unit actually has numbers molded into the plastic. That's good, but we'll be better with our handy-dandy marking scheme before we go any further. Further? Yup, like it or not, we have to actually take these apart. Something that was never anticipated when these rolled off the assembly line. Back in the golden days of servicing, the repair person would simply replace the offending transformer with a new unit. We don't have that luxury of easily obtained NEW parts in the 21st century.  You'll see the "can crimps" as I call them. These are basically indented portions of the can that "bite" into the plastic base to hold everything together.

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BUT before we think about starting to disassemble, let's take the permanent marker and "continue" the mark we already made on the outside of the can. Now we can later verify reassembly. The base's relationship to the outside can is marked so there are no questions later.

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto86_zpsb0d36783
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Post by Dr. Radio on Wed Jan 22, 2014 9:22 pm

Again, different styles and manufacturers dictate how the transformer is assembled, and ultimately how we will have to go about disassembling it.  I'll be honest, this is never "fun" or "simple". It is a sometimes necessary evil when it comes to radio restoration of models of this era.  Evil or Very Mad 

This is something you don't want to attempt if you are in a rush, have many distractions to contend with, aren't good with paying attention to small detail items or are clumsy when it comes precision parts... Embarassed 

Take your time and deep breath! Shocked 

Much like the "captive knob" we had to deal with way back in the beginning of this thread, we have another "vampire" to make lose it's bite! Very Happy 

There's not much to those darn can crimps, but they can sure make things frustrating. What I do is take a precision pair of needle-nosed pliers and carefully bend out the sides of the can. With more room to work, I then carefully take a small screwdriver and push between the plastic base and the crimps sticking out. The key word here is carefully. The inner structure is very fragile. We are talking about a coils made of very fine wire and a tube to support the coils in this design. Slip up and upset the tube's positioning and pooof--you rip the fine wire inside and/or destroy the mounting hardware.  Sad   Sad  Sad

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Once the bottom of the can has been flared out enough, the base is carefully wiggled out.

Success!

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We'll investigate more about how this unit is assembled (we have to do even more reverse-engineering!) and review what it takes rebuild the troublesome internal components with modern replacements.

AND.....it will be time to play detective once again!  The mysterious rattling I would hear when moving the chassis around appears to have been coming from this can....What is this inside?  Mysterious chunks of melted plastic?........ Shocked 

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto89_zpsbb188831

Stay Tuned.... Very Happy 
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Post by Bill Cahill on Wed Jan 22, 2014 11:31 pm

Better you than me. I have to deal with one that was on fire in my Bendix combination..... Thanks for this interesting thread............

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Post by Dr. Radio on Thu Jan 23, 2014 6:47 pm

Well, luckily Bill, this one wasn't on fire!  Shocked 

I was able to "piece together" what took place with my detective skills. It's just another interesting and important element to this restoration.
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Post by jerryhawthorne on Sun Jan 26, 2014 7:31 pm

Dr. Radio, I'm really enjoying this. Not often on this forum but this is great. I don't work on "later" radios and always worried about SMD problems. I can hardly wait for your great presentation and pictures to guide me.
Regards, Jerry

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Post by Bill Cahill on Sun Jan 26, 2014 7:50 pm

I agree. I always look forward to your projects, Dr. Radio. Want to do some surgery on a few of my radios??

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Post by Dr. Radio on Tue Jan 28, 2014 2:08 pm

Thanks for the feedback guys! More to follow.
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Post by Dr. Radio on Tue Jan 28, 2014 9:12 pm

Okay, ready to dig in?!  Shocked Embarassed 

Pushing my photographic equipment to its boundaries, I was able to get some "super zoomerific" pictures of the fine detail of the internal workins' of a typical General Electric IF transformer.

So let's take a look......

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto90_zpsea2d299b

But, I digress to shed some light on the purpose of these troublesome little "cans".  I encourage you to do a little more research and read about all the stages in a basic superheterodyne radio circuit. My goal was to focus on the repair/resto steps and not "bore" some with in-depth theory and analysis. Some would argue though, you must truly understand what is going on to truly troubleshoot and be successful.  I won't argue with them, but simply want to keep this thread straight-forward without typing several novels worth! Shocked 

In a nut-shell (or would it be an IF can shell?);

The intermediate frequency transformers provide pretty much the "heart" of the superheterodyne radio circuit. This is what gives a superhet its renowned "selectivity", or the ability to cleanly pic out a specific radio station out of the entire band.  Both IF transformers comprise of 4 tuned circuits--two in each "can". The idea is to "sharply" tune to the intermediate frequency of the radio (in our case, as with most radios, 455 kHz.).  By only allowing the intermediate frequency to pass from one stage to the next, this ultimately provides the selectivity . They (the transformers) allow coupling to the subsequent circuit stages by the transformer characteristics, but also allow "sharp tuning" or resonance at the frequency desired thanks to the L-C circuits comprised within. L, being the inductive portion (wound coil), and C being the capacitor.  Refer to the schematic drawing again...
So where are those pesky capacitors located? All you see are coils you say? We'll get to that, don't worry! Very Happy 

The original "intelligence" (what was sent out from the broadcast end) is a component of the signal being passed through the IF stages until it finally reaches it's destination--the loudspeakers and our ears. So naturally, when there are troubles abound inside the IF can(s), you can guarantee it won't be long until your radio isn't much more useful then a paperweight.

The "cans" need to contain the L-C combinations to work properly. This way the can be "tuned" to resonate at the proper intermediate frequency. This is up to the specific manufacturer on how this is done. It can be done with either making the capacitors variable or the cores of the inductive portion variable. Pre-war IF transformers were typically variable capacitor (top trimmer) styles. After World War II, with the advancement of
technology and the need for cheaper, mass-produced goods to keep manufacturing costs low, a new miniature style was developed (what we have here).  This style is set-up with the capacitor elements being fixed values and mounted in the base of the "can".  The variable part was the inductor--accomplished by moveable "slugs" (ferrite cores) that were accessible from the top and bottom of the "can". They turned on threaded tracks to allow resonance at the precise frequency--455kHz.  These cores ride inside the cardboard tube holding the coil forms in our radio.

So what's wrong with the "new" modern IF transformer design?  Cheap and easily mass produced with the capacitors being fixed...What could go wrong? Crying or Very sad Here in lies the problem. The traditional capacitors as we know them were not employed. There were no "sealed" components found in the base of these style of transformers. In fact the connections linking them was meager at best...
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Post by Dr. Radio on Tue Jan 28, 2014 9:39 pm

Back to the hands-on portion of our rebuild...in order to get ahold of those pesky capacitors (the troublemakers) in the base of the transformer, we must disassemble the unit completely!

To put things into perspective, here's what we have to work with.

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto91_zpsb75bca41

The quarter shown helps drive home the point we're in for some micro-surgery! It doesn't matter if you are a pro or a newbie. No one likes dealing with IF transformer rebuilds due to the tiny and fragile nature of them. See those little "wisps" soldered to the connection legs? Yup, its the very fine wire linking the circuit connections to the coils. We're talking like "hair" fine or finer!. Did I mention we have to successfully disconnect all this without destroying??!!!  Evil or Very Mad 

We will completely remove the coil form assembly from the base. We can't lift it off until we carefully make some notes first, then disconnect the wires from the connection points apart of the base.

The first step will be to take our permanent marker and make a line on the coil assembly tube where it meets the base. Again, we are marking everything for proper location. The mark is made so it corresponds with the mark we made previously on the bottom of the base. This way, when we go to reassemble there is no "I think it went together like this....?"....


But once again I digress....

Remember earlier the new "mystery" that popped up? (Maybe I should say rattled around?) There were mysteriously melted chunks of plastic loose inside the IF can housing discovered upon disassembly. Let's take a closer look....

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto92_zps27c61003

Ahh, the true picture is coming into view. You can see how GE assembled the base. They melted plastic "tabs" over the base's top cover to secure it down. One end obviously popped off completely! (see the opposite side for comparison). These "melts" broke free!  Evil or Very Mad  I'll let you in on a little secret...this is why this radio is starting to exhibit problems now Rolling Eyes  More on this when we actually pull the base apart!
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Post by Dr. Radio on Tue Jan 28, 2014 10:08 pm

So, with the bottom end the coil form assembly marked with a line to correspond with the line we previously made on the bottom of the IF transformer base, we can now go about verifying and recording where those fine wires go...exactly.

It's important to make sure (again!) the exact original orientation of the factory connections. Personally, I find that making my own drawings and notes works best. Which ever method you can reliably use to recreate the connections come rebuild time, is the one you should use. Wink

I don't just double, but triple-check what wire goes where. I notate what pin ultimate leads to the top coil's top-most exiting wire for example. Some IF transformers have more than 4 pins. Coils may be tapped, multiple capacitors in various arrangements crowding the base. Whatever the set-up, it's important to make good notes.

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto93_zpsdcc58b1e


With everything carefully notated, it's now time to carefully free the fine wires from the connection posts. I do this with either an exacto knife or razor blade. I simply cut the wire close to the solder connection. I do this rather than desoldering for two reasons. The first is heat and a large iron is just asking for trouble in close to proximity to such fragile parts.  The second reason is I don't want to heat up the connections any more than absolutely necessary. I don't want to risk causing further connection issues inside the base by the introduction of heat which could make things difficult come "reading time". More on "reading time" (not the book style) later.

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto94_zps21210a0a

So with surgery-like precision, all the wires get disconnected. On this IF transformer, the "tube" or coil form assembly just lifts straight out of the base. Nothing more, nothing less.

It's free!   Laughing 

Step by Step Restoration: GE T-106C, Let's go for it! - Page 3 Geresto95_zpsab1b7d53

-It's a little easier to see the ink marks now with the assembly apart.-


As stated, no need to goof-up at this point. Store that "thing" so it doesn't get trashed by tools or or misc. on the bench!  Embarassed 

Still more fun to come!  Stay tuned!  Razz
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