[mikethedruid]

Your misalignment problem on FM may be caused by the IF frequency for FM being off. AM IF is 455KHZ, FM is 9.1MHZ. Use the chart on pages 19-83,84 of the Riders Manual for the set. Follow the directions EXACTLY. This should help with this problem. I own a 48-482, which has very similar circuitry.

[criageek]

Thanks mikethedruid - I did align it at 455kHz for AM and 9.1MHz for FM, so I don't think that's the problem.  I've gotten quite good at installing and uninstalling the chassis from the cabinet, so perhaps I'll do it one more time just to be sure.  Actually I think the problem may be steps 7, 8, and 9 of the FM alignment procedure, since they are performed at the lower end of the band.
   
   

I don't have Philco #56-6100 so I don't know how to do these steps.  I did fiddle with the oscillator coil a bit when I was troubleshooting so perhaps it is off, but I don't know how to do these steps without the proper tool.

Thanks!

Rich

[criageek]

Another great day for the 47-1230! I decided to yank the chassis and speaker out of the cabinet and throw it back on the bench to see if I could fix the FM tracking problem. It turns out that I had expanded the loops in the oscillator coil (L406 on the Philco schematic) when I was fiddling with it. Since the dial face is mounted in the cabinet I took some measurements and put marks on the backing plate at the frequencies I was interested in and started a long, iterative process of compressing the coil so a station at the low end of the dial (94.1) was in the right place on the dial, then going to a station at the high end (104.5) and adjusting the oscillator trimmer (C405C on the Philco schematic) to set that station to the right place on the dial. I had to do this maybe 12 - 14 times but I finally got it dialed in. When I put it back in the cabinet it's very nearly spot on. It's accurate at 104.5 and at the low end it's less that 1/2 the width of the needle low...close enough for me.

Now the only remaining issue is that there are several stations that are supposed to be at the low end of the band (88 - 91) that I receive at the high end. For instance, I receive 90.9 at 90.9 as I should, but also at 108. I really don't have any idea how to fix this so my plan is to leave it as is and live with it. But if someone can give me any ideas what I could try I may pull it back out and see if I can fix that. Otherwise, I'm planning to take it to my Mom's place on the 31st and call this job complete!

Rich

[amptramp]

It sounds like you are getting an image.  90.9 + 9.1 + 9.1 = 109.1 so if the signal peaks there, it is definitely an image.  But there are other intermodulation products of the form 2 * f1 - f2 that may be happening here.

[Marsupial]

Anyone still working on their 47-1230?

I'm back at planning some workon mine, after about a decade.

[criageek]

Hi Mars - I'm not working on one now, but have done two of them.  The one for which this thread was started was my Mom's and she's still enjoying playing it.  Then I found one in Chicago and I did that one for myself and love playing it.  But to the point, I found another one in Minneapolis and picked that up as well.  I gave that to my brother to restore  and he has just done some preliminary documentation.  When we have a chance I will run over there and point out a few things I want him to be aware of, but otherwise he will do that one.

One thing I'll point out here is that the power transformer gets very hot in both that I did, so in both cases I installed an external bucking transformer with a switch on it to switch between full power, full power minus 8v, and full power minus 16v.  I've got both set to minus 14v (106v in my case) and they play fine and the transformer doesn't get quite as hot.  I printed the case for it using my 3D printer and found a way to mount it that didn't require any drilling.  I'd be glad to pint one up for you if you want to do that.  I wired both of mine so that the bucking transformer gets it's power from the radio's power switch so the wiring is a bit clumsy.    

ThatTubeSound did a video series on restoring a 47-1230 that was somewhat helpful:  https://www.youtube.com/watch?v=5vcvh0f4Dac

I have tons of pictures and documentation so let me know if you need anything.  You might find this thread interesting:  https://philcoradio.com/phorum/showthread.php?tid=19577

Good luck!

Rich

[Marsupial]

Hey Rich, I'm interested in that bucking transformer of yours. 
On mine, after about half an hour you feel the top of the cabinet being warmer than it should...
What transformer did you use? It's a great idea. 

On my radio, I had previously done the power and AM stages recap. I added a fuse, but really should install the Y safety caps... 


I recently acquired a 1953 voice of music changer to replace the stock changer that I had given to another phorum member several years ago (it was shut, stucked, missing the stylus and partly rusted)
I know it isn't original, but a likely aftermarket upgrade, and I use it quite much at 33/45 as I don't own any 78s.

On mine, the FM and phono are faint. I need to crank up volume to the max. 
I assume you don't have that issue?

[criageek]

In other bucking transformers I've built I used a 12.6v center tapped 1A transformer, but in these for the 47-1230 I'm pretty sure I used this 2A transformer, since the set draws a little over 0.75A:  https://www.digikey.com/en/products/deta...4X/5032174

and this is the switch I used:  https://www.digikey.com/en/products/deta...ZQ/3751935

I did struggle with the FM in both sets but have both working well now.  I don't remember all the details for the fixes, but I know in one case it was a matter of finding the right 7F8 tube.  Also, based on my findings in this thread:  https://antiqueradios.com/forums/viewtop...lit=philco  I think the value of the 15k resistor is important in order to provide the correct voltage to the FM section.

I'm not too smart when it comes to phono problems but I would bet your problem is some sort of impedance matching issue between the cartridge and the radio.

Let me know if you want me to print a case for a bucking transformer.  If so, I'll get started on it.  I use PETG filament for those because it has a higher temperature tolerance than the PLA I use most of the time.  I have PETG in black and gun metal grey (dark grey) so let me know which you would want.  All I want for it is the price of shipping  ;)

Rich

[Marsupial]

How does the connections go?

I currently have a modern 3 prong power cord on the radio...


I'll look about the 15k resistor for FM, but what bothers me most right now is phono.

I have connected a preamp between the changer and radio, and if I crank the volume too much I start getting distortion. I am pretty sure that's the 7AF7 being overdriven.
I'll look at voltages around the 7AF7 and 7X7 to see if something is off, and work the caps around them.

[Marsupial]

Rich, I've passed trough that antique radio thread you posted. 

Do you have any way other that wiring the power switch to the bucking transformer to prevent it from heating when idle? 


Now, 15K resistor... I first fought it was one in the tuning sub assembly (which I try to avoid working on if at all possible and you know why...) I but then realised it is R100...

I wondered if I changed it, browsed trough pictures, and no, I didn't. I'll see if I can replace it. 

However, when I have FM reception, it is faint. Maybe half volume compared to AM. So I'm thinking something else is wrong. 

Don't both the FM and Phono use the 7X7 tube? They are both faint... (phono moreso than FM)

[criageek]

Hi Mars - Now that I give it more thought I realize the design of my bucking transformer is pretty specialized for my needs and probably wouldn't work as-is for someone else.  That being said, if we can zero in on your requirements and parts to be used I can easily modify the design for your needs.  For the 3 prong power cord I could design in an opening for one of these:
   

As for ideas to keep the transformer from warming when idle, I could only think of two other ideas:

1)  Unplug the radio when not in use.
2)  Install a switch in the bucking transformer case and use it as the power switch for the radio.

I didn't like either of these ideas so I went the route of going through the radio's power switch.  But it would be easy enough to include a switch in the bucking transformer if you wanted to go that way.

I love doing this kind of thing so don't hesitate if you want me to get one designed and printed.  Here's one I built to use as a stand-alone unit.  Some radios don't have room for either a bucking transformer or a voltage dropping resistor, so I can plug them into this (there is an outlet on the back) when I want to play them.
   

Rich

[Marsupial]

Rich, That external transformer looks pretty cool.

I think if I am to add a bucking transformer, I'd too want it to be used only when the radio is on. I don't know where I'd put a switch on the transformer that would still be handy...

So... How did you do? You have two wires from the switch going to the enclosure, then the power cable going into the radio? Like, you completely bypass the original power cable?

Using this standardized connector would be a great addition IMHO.

[criageek]

I agree...adding a power switch to the bucking transformer would be easy enough, but you'd have to reach around and into the back of the cabinet to use it.  Not too handy.

I attached a drawing of my wiring.  I know it will be hard to follow so I'll try to explain it.  The AC line comes into the bucking transformer (BT) (I'll use the term "bucking transformer" or "BT" to refer to the case containing the actual transformer, switch, fuse, and terminal strip).  The hot lead goes through a fuse then out of the BT , through a connector (I installed a connector so I could remove the BT and the radio chassis separately...just easier to manage) and into the radio.  It terminates at the center terminal of the bakelite capacitor.  The other end of this terminal has a wire going to the power switch.  The other wire on the switch originally went to pin 7 of the 5Y3 rectifier.  I moved it to pin 3 of the 5Y3 which was unused.  Then I added a wire to pin 3 of the 5Y3 that runs back out of the radio, back through the connector, and into the BT to provide switched power to the BT.  Then the reduced voltage (both hot and neutral) from the BT is fed back out of the BT, through the connector and into the radio.  The hot lead connects to pin 7 of the 5Y3 (which also has a wire to the power transformer on it), and the neutral lead goes to the other cap in the bakelite block.

If you wanted to use a 3 wire power cord, you'd have to run the 3rd wire (ground) from the BT and into the radio as well.  So would have a total of 5 wires running between the BT and the radio.  I printed the grommet for the wires going into the back of the radio chassis.  It's sized for the particular wire I used so would have to be adjusted for not only the wire you use, but also for the 5th wire.

Make sense?  Let me know if you have questions  ;)

Rich

[Marsupial]

When you talk about the terminal strip of the bake lite capacitors, you're talking about C100 and C101?

Did you change those?

I got safety capacitors years ago but never did the change. It is deamed much safer and up to code to use that instead of 1940s line filter caps...
I really should get to it.



I was reading my notes on the transformer from when I worked on the radio years ago (the threads are still on the phorums) and after a 8h radio session it was warm to the touch, not hot to the touch and far from burning.

On this topic at that time it was mentionned that some bad tubes or caps could draw enough to get the transformer warmer but the situation wasn't worrying. It was mentionned that variacs or bucking transformers was the way to reduce voltage if we tought it was needed.

As far as I understand, electricity in late 1940 was at 117V compared to the 125V I currently have here near Montreal. maybe the issue isn't as big as what you have. I wonder if electricity was the same back then north and south of the border, and if Philco Canada had different values to account for that?

I'll do more monitoring on mine soon with heat in mind.

[criageek]

Yep, C100 and C101...I restuffed the bakelite block with safety caps:

   
   

It's always been my understanding that all 47-1230's suffered from hot power transformers, but apparently not.  I don't know why the difference.  Perhaps whatever is causing your FM/phono volume problem is related?  All caps and all resistors have been replaced in mine.  Initially I installed an 18 ohm, 50w on the back of the chassis to drop the AC line voltage, but it became excessively hot and caused the chassis itself to be hot.  So that's when I went the bucking transformer direction.

Rich