GE 516F - static and intermittent reception after playing for 10-15 minutes

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GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Fri Jul 15, 2011 11:14 am

Restoring a GE 516f clock radio. Tubes all test good. Fully recapped. It plays great and has good sensitivity for about 10 to 15 minutes. Then, the signal weakens/fades and is sometimes accompanied by loud static (sometimes the static is very soft). The volume controls the loudness of the static. Tapping tubes doesn't affect operation.

The radio has a built in loop antenna. If the reception has faded, often i can get some reception back by putting my hand on the antenna. The sound is somewhat distorted. If I don't touch/disturb the radio, static comes and goes as does reception. Sometimes returning fully to normal from time to time.

Turning the radio off for 15 minutes then turning it on has the same results as noted above except it takes less time to act up. So, obviously heat is a factor.

The schematic is good and gives details on voltages so I'll be checking those today. There is a ceramic resistor, 1000ohms (R16) ......it gets very hot....about 130 degrees F. It tests just at 1046ohms.

It plays better/longer without issue in normal operating position than it does on it's side (where I can get to the underside of the chassis and check parts while it's playing.

So.....in my newbie status and this being only my 4th restoration (2 successes and 2 under construction), I seek your collective wisdom on this GE.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Fri Jul 15, 2011 1:17 pm

I suspect one of your I F transformers has gotten leaky. Caused by silver mica disease. The pop rivet corodes, causing leakage between primary, and, secondary mica caps in transformer. There are two good ways to repair this.
Either replace the internal built in mica caps with correct value caps., or, replace entire transformer.
Voltage testing will tell which one is the culprit.
If you get any positive voltage on the secondary, that transformer is the culprit.
Good luck.
Bill Cahill

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Fri Jul 15, 2011 2:58 pm

Thanks Bill. I'm checking pin voltages with the B- post on the chassis as the reference. Is that also where I check the IF cans? If so, then T1 is the culprit. I show 1VDC postive on the secondary pins, with 90VDC on the primary side, the 90VDC is right in spec. The ground pin of 12AV6 has -.55VDC, the ground pin of 50C3 has +.5 VDC, the specs show 0 VDC on those pins. Those pins are connected with that interesting 4 part ceramic cap. I stand corrected on my earlier remark....I didn't replace ALL the caps....that one is still original. Earlier, it played for 4 minutes before losing signal and going to static. As I was checking voltages, it came back and played for over 20 minutes with no issues. Thanks.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Fri Jul 15, 2011 6:38 pm

Is it still playing correctly?
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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Fri Jul 15, 2011 6:46 pm

No. During that time it played correctly more than not, but it lost signal and went to static 5 or 6 times during a 30 minute period. I saw no change in voltage readings whether it was playing correctly or not.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Fri Jul 15, 2011 7:02 pm

Try tapping, and, wiggling tubes. If that isn't it, check voltages on I F's again.
If you still have a positive voltage, then, that's your culprit.
The positive voltage on audio out. grid wouldn't cause a reception problem, but, you'd totally lose audio in time, and, dammage the tube, and, other components.
All paper caps need to be replaced, or dammage can be done.
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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Fri Jul 15, 2011 7:12 pm

Tapped and wiggled. Nothing. I'll check again for positive voltage and I'll replace that 4 part ceramic cap unit with individual pieces. I may be chasing 2 issues....something in that ceramic cap and a bad IF.

If it all went smoothly....I wouldn't learn anything!

Back to the workshop! Thanks for the help.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Fri Jul 15, 2011 7:26 pm

I wouldn't replace that cuplate just yet.
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If you are getting reception problems, you are looking in the wrong place.
The cuplate isn't likely to do that.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by repairtech on Fri Jul 15, 2011 9:00 pm

Best to stock up on those little cute brown 100pf silver mica caps.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Fri Jul 15, 2011 10:26 pm

Let it play without touching a thing. Played for well over 20 minutes, no issue. So I moved the tuner and lost signals got just a little light static. Turned up the volume and the signal returned clearly. Ultimately through trial and error found that just touching the lead of the silver mica on the converter tube with a non conductive probe could lose the signal or bring it back. After about 45 minutes of operation, lost the signal completely but no static. I'm guessing due to heat. Also after 45 minutes, the voltage on 2 of the pins on the converter tube that should have been 90VDC and was such earlier, had moved up to 112VDC. So....I'm guessing that little silver mica has failed.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by sprman on Sun Jul 17, 2011 12:48 pm

If that does not fix it check your tube sockets, had one do same thing to me years ago..Sprman : )

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Fri Jul 22, 2011 12:08 pm

I'll be back on this one today, have a 50c3 and new micas ready to install. Thanks for the help....I'll post results after replacing parts.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Resistance is Futile on Fri Jul 22, 2011 1:53 pm

Have you checked the tuning condenser itself?
Look and make sure none of the plates are touching, as even a little vibration could cause them to short if there to close to one another.

Another clue is if the insulation on the varible cap has a conductive trace has developed from moisture. Its like a path that develops from high voltage, dust and moisture. Another thing would be some variable caps have a brass finger that touches the tuning shaft to ground it to the cap frame. They need cleaning and be causing intermittent reception.
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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Tue Jul 26, 2011 9:36 am

Replaced a couple of suspect tubes. Also, obtained a signal tracer from my father in law and took some voltage readings.
When the audio goes out and I hear static from the radio speaker, there is still a strong signal out of the 1st IF. The second IF has the sound I hear from the speaker.

When cold, the voltages are 98 into the IF's (90 is the spec). The 1st IF has +.5 volts on both the "out" pins. The 2nd IF has -.3 out of both pins. When the audio drops and the static sound starts, the 1st IF goes to +1 volts out and the 2nd IF goes to +2 volts out. The audio came in and out while I was checking voltage and I noted that when the sound returned, the 2nd IF went back to -.1 volts.

So, to this newbie, looks like the 2nd IF is really the issue, although given that the 1st IF also shows positive voltage, it's got issues too. I may try to tackle the repair, but where can one find suitable 455 IF's for this radio?

Thanks for the help gang!

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Tue Jul 26, 2011 8:29 pm

Are they miniature, or, standard size?
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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Tue Jul 26, 2011 8:42 pm

The IF's are 3/4 inch.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Wed Jul 27, 2011 10:07 pm

Another note. Tonight I replaced the 47mmf mica on the oscillator. Might have been my imagination, but the signal strength and quality seemed a bit better. However, after 10 minutes or so, back to the lightning storm. And as before, signal tracer found a strong signal off the 12BA6 into the second IF, but a very weak signal and lightning out of the 2nd IF. And, about 1 vdc out of the 2nd IF when the static was occurring.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Wed Jul 27, 2011 10:57 pm

Personally, this is not something that I would do, but, to get it temporarily working, I have a friend who has done this with success. I make no claims here.
Take a little household oil. Not detergent, not heavy weight.
Turn chassis upside down.
Purt a fairly liberal amount of oil around the terminls on bottom of can, and, around pop rivent in center. Then, turn radio right side up, and, put more oil though top hole. Let sit over night. It should be better in morning.
The problem is that the pop rivet corodes around the mica insulators, and, causes corosion between the capacitors mounted in base of can. This is a common problem.
If that doesn't work, something else can be done, but, it's more extreme, and, alot of work.
Do you have a schematic on this set, and, if so, do they show capacitor values for the primary, and, secondary windings on I F cans?
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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Wed Jul 27, 2011 11:43 pm

I've been reading online about servicing the IF caps. I have a schematic and it shows the specs. I also found some 455 IF's at Talon Electronics. None are listed as a direct replacement for RTL117, which is the part number for the IF's installed in the radio. Would any 3/4 inch, chassis mount 455 designed for use with tubes be compatible?

Bill, I'm having a blast restoring and learning a lot. I really appreciate your help and help from members of this forum.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Thu Jul 28, 2011 12:54 am

It would depend on the wiring of the replacements. If both the ones in your radio, and, replacements are four prong replacements, they should work fine.
The green dot is on secondary.
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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Thu Jul 28, 2011 4:48 pm

Thanks for the help. Found one online today...got it coming. The second IF, the one that has the static on the output side thru the tracer, will get replaced first while I search for another. Then, I might try a repair on the old IF.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Thu Jul 28, 2011 7:21 pm

Remember, in most cases the second I F is called just that, and, you would not want to replace that one with one that is intended to be the first I F.
Good luck on the set. You should get it working, again. What brand I F did you purchhase, and, from who, if I may ask. Some of the new old replacements were made just as poorly, others better.
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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Thu Jul 28, 2011 10:35 pm

This GE has the same part number for the 1st and 2nd if's. I bought a Meissner part from Talon Electronics.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by foxcovert on Mon Aug 01, 2011 10:14 pm

That was it. The IF came today, installed it and the radio played for well over an hour while I tuned the dial around and aligned it. No loss of signal, no lightning, it sounded great. My voltages are correct and steady. I would still like to find a replacement for the 1st IF given the output side runs about +.5 volts. Now I can finish the small repair on the case and it can take up residence on my nightstand. Thanks all for your help.

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Re: GE 516F - static and intermittent reception after playing for 10-15 minutes

Post by Bill Cahill on Mon Aug 01, 2011 11:47 pm

You are most welcome!
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