Tuner not working on 46-420 code 121 - Printable Version
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Tuner not working on 46-420 code 121 - terrylett - 08-03-2018
Hello –
I just joined the Phorum and I wanted to see if I could get some suggestions for the issue I’m having after recapping a Philco 46-420 “Hippo” Code 121 radio.
When I got it off ebay I checked the power cord and looked under the chassis to see if looked safe to plug it in and power it up.
I powered it up and noticed that it sounded very good but somewhat weak in the volume department.
It only picked up WLW (AM 700) in Cincinnati and faintly something at the high end. I wasn’t concerned about that; my apartment is way over shielded.
King Tut gets better reception.
I knew based on everyone’s insistence that I needed to get the wax and electrolytic replaced. Did so and replaced a 7C6 tube that I had a spare of.
When I was done with the recapping and the polarized AC cord installation I was getting great volume and still clear tone sound.
Now comes the snag. I can only hear WLW all across the tuner. At 550 to 1600 the station won’t let go. It’s as though the variable cap isn’t even in the circuit anymore.
I checked all my solder points and they look good. No wires seemed crossed either.
Another point (and maybe this is more common to you then newbie me) I can touch almost any metal part of the chassis and the volume gets way loud.
Do you have any ideas about the tuner not doing its job anymore?
I appreciate your feedback – this Hippo and I could have a lasting relationship if I can just get it right.
Thanks.
Terry Lett
RE: Tuner not working on 46-420 code 121 - cparsons2391 - 08-03-2018
I hope someone with a better answer jumps in, but double check tube sockets and coils and be sure nothing is shorted to the chassis.
Also, be sure no coils are open.
Good luck!
RE: Tuner not working on 46-420 code 121 - terrylett - 08-03-2018
Thanks for your suggestions.
The tuner seemed to be working fine when I got the radio so I don't know what happened.
I looked at all the solder points to the tubes and nothing looks shorted anywhere.
To check the coils I would (it seems to me) have to try to get the aluminum enclosures off and that would take unsoldering everything it the way of those irritating screws on the underside of the chassis.
I don't at this point have any meters or scopes so I was hoping there were a few things to try that weren't too difficult.
If I have to I'll salvage my new caps and pull everything to completely rewire the radio but I certainly want to avoid that.
It just bothers me that when I got the radio the tuner worked and the volume was weak and now I've gone to strong clear volume and a useless tuner in the circuit.
Thank God there's beer in the fridge...
Terry Lett
RE: Tuner not working on 46-420 code 121 - Radioroslyn - 08-03-2018
Hi and welcome,
A couple of things to check. The loop ant inside the cabinet, that it's not open and that it's connected. Use another receiver to listen for a signal @ 455kc higher than the dial setting of the hippo. This will verify that the local oscillator is operating. Do you live next door to WLW's towers??
RE: Tuner not working on 46-420 code 121 - terrylett - 08-03-2018
Yes I live very close to the WLW tower but when I got the radio the tuner when dialed to the 550 position did not receive WLW. It did not even start to tune it in until I got near AM 700 and it tuned it out when I passed 700 so the close proximity to the station can be ruled out.
The loop antenna when reattached makes no difference at all.
RE: Tuner not working on 46-420 code 121 - Kenneth F. Besso Jr. - 08-03-2018
Did you change wires ,,(NEW),, or move wires around to a different location,,,sounds like bleeding thru something,,,,how about tube shields ,,they on ???? CHEERS
RE: Tuner not working on 46-420 code 121 - NostalgiaRadioTime - 08-03-2018
It almost sounds as if your antenna is directly grounded to the chassis and not going to the variable capacitor (tuner), based on the fact that the radio gets louder when you touch any part of the chassis.
You should try what Terry suggested. Tune the Hippo to around 700 on the dial, which is where you said WLW initially appeared before the recap. Then place another AM radio next to the hippo and tune it 455kc higher on the dial than the hippo (or, around 1155 on the dial). You should be able to hear WLW through the other radio, or at least a "whistle" as you rock the dial on the other radio around 1155. To verify, turn off the hippo and leave the other radio on. You should hear a change in the sound at 1155 on the other radio. That would indicate the OSC on the hippo is working. If the OSC isn't working you won't receive anything but the strongest station.
You could try reversing the leads on the loop antenna. Sometimes if they're hooked up backwards it can cause problems.
Have you attempted an alignment? Without a signal generator you'll have to do it by ear, but it's pretty straight forward.
RE: Tuner not working on 46-420 code 121 - terrylett - 08-03-2018
Fantastic troubleshooting ideas!
All of you.
There were no shield cans over the tubes themselves - only the IF coils.
I'm wondering if while I was tuning the coils I might have pushed down a little hard on the screw and part of the coil inside (maybe the 1st IF) is now touching the aluminum cover.
I'll also try another set next to the Hippo and try that higher frequency test.
I'll be back in touch.
Thanks to you all.
RE: Tuner not working on 46-420 code 121 - 462ron - 08-04-2018
Looking at the schematic on nostalgia air, give C14 and L1 a check. They help connect chassis to line neutral at rf frequencies. If they were open it could leave the tuning condenser floating and maybe affect the tuning. Worth a quick check!
Ron
RE: Tuner not working on 46-420 code 121 - terrylett - 08-04-2018
OK I set up an RCA 65X-1 with a known good tuner next to the Hippo.
I turned on the Hippo and got the dial as close as I could get to AM 700. I turned on the 65X-1 and turned the dial to what I thought would be 1100 (the dial string is broken in that one and the chassis is out of the case sitting next to the Hippo).
There was absolutely nothing received from the Hippo no matter where I tuned the 65X-1 and I turned off the Hippo which had no effect. The 65X-1 picks up WLW at 700 and leaves it behind when dialing past so I know its a good tuner.
So at this point it seems like the oscillator is not working in the Hippo.
One other note: I snipped out what I thought was an old wave trap wax cap when recapping. This contained C14 and L1. Think I should put that back in the circuit to see it it was the cause of all this evil?
RE: Tuner not working on 46-420 code 121 - 462ron - 08-04-2018
Wouldn't hurt. Even just try something like a .01mfd there and see if there is a change!
Ron
RE: Tuner not working on 46-420 code 121 - terrylett - 08-04-2018
Absolutely no change.
At this point I'm defeated.
Hippo 1 Terry 0.
RE: Tuner not working on 46-420 code 121 - 462ron - 08-04-2018
If you can't hear the osc in the second set, then possibly it's not working. Check continuity on the T-5 coil and check voltages on the 7A8 converter.
Ron
RE: Tuner not working on 46-420 code 121 - Radioroslyn - 08-04-2018
Ok so check the resistance across the tuning cap on the oscillator side, should read abt 5 ohms. If it measure 0 you've got a bend plate that's shorting the cap out. If there is a bent plate if you turn the cap till it's all the way open should show the 5 ohms and will drop to 0 when closed.
Measure the dc voltage on P3 of the 7A8 (from B-) should see some hv there abt 60-90dc. P4 should show a little - voltage a volt or two.
GL
RE: Tuner not working on 46-420 code 121 - terrylett - 08-04-2018
Alright thanks again.
This whole project now gets put on hold for a little while because I need to buy a meter.
I'm just starting out in this hobby and I don't have scopes or meters yet.
I'll check back in but I appreciate the input - you folks know how to pinpoint those possibilities.