First, a little background. I picked up this GE 515 for $5 at a thrift store. I checked the tubes and replaced a couple. When I went to bring up the variac there was a bad hum and the amp meter started to spike. That problem was two tubes in the wrong sockets. Switched those and replaced the filters. Turned it on and it played so I put it on display. Turned it on the other day and heard some crackling, but it still tuned stations. I finally got it on the bench and things have gone from bad to worse. The crackling is worse and it no longer tunes stations.

It has these stupid solder posts around the tube socket. I've unsoldered all the wires, cleaned the posts and socket holes, reconnected and resoldered the wires, replaced the tube, removed and checked both the osc and IF coils and replaced the 47pf cap. I didn't replace the 22K or 110 resistors because I didn't have any, and no way to get to the 'Shack. My signal tracer has the noise on the plate leading into the 1st IF. I didn't remove that lead and do a buzz test through the rest of the set, nor did I inject a local IF freq. I did check both resistors and they checked within tolerance. I've spent hours on this set, and seem to be getting further from the problem. I decided to set it aside and get a little distance, and thought I'd put it on the forum to see if anybody has any ideas. It's obvious the osc. is no longer working, and it's not a bad solder connection. My suspicion is a leaky cathode to screen resistor, but I don't want to tear the whole socket apart again without a little more input.
So-any ideas guys?
Thanks, terry

:First, a little background. I picked up this GE 515 for $5 at a thrift store. I checked the tubes and replaced a couple. When I went to bring up the variac there was a bad hum and the amp meter started to spike. That problem was two tubes in the wrong sockets. Switched those and replaced the filters. Turned it on and it played so I put it on display. Turned it on the other day and heard some crackling, but it still tuned stations. I finally got it on the bench and things have gone from bad to worse. The crackling is worse and it no longer tunes stations.
:
:It has these stupid solder posts around the tube socket. I've unsoldered all the wires, cleaned the posts and socket holes, reconnected and resoldered the wires, replaced the tube, removed and checked both the osc and IF coils and replaced the 47pf cap. I didn't replace the 22K or 110 resistors because I didn't have any, and no way to get to the 'Shack. My signal tracer has the noise on the plate leading into the 1st IF. I didn't remove that lead and do a buzz test through the rest of the set, nor did I inject a local IF freq. I did check both resistors and they checked within tolerance. I've spent hours on this set, and seem to be getting further from the problem. I decided to set it aside and get a little distance, and thought I'd put it on the forum to see if anybody has any ideas. It's obvious the osc. is no longer working, and it's not a bad solder connection. My suspicion is a leaky cathode to screen resistor, but I don't want to tear the whole socket apart again without a little more input.
:So-any ideas guys?
:Thanks, terry
:

::First, a little background. I picked up this GE 515 for $5 at a thrift store. I checked the tubes and replaced a couple. When I went to bring up the variac there was a bad hum and the amp meter started to spike. That problem was two tubes in the wrong sockets. Switched those and replaced the filters. Turned it on and it played so I put it on display. Turned it on the other day and heard some crackling, but it still tuned stations. I finally got it on the bench and things have gone from bad to worse. The crackling is worse and it no longer tunes stations.
::
::It has these stupid solder posts around the tube socket. I've unsoldered all the wires, cleaned the posts and socket holes, reconnected and resoldered the wires, replaced the tube, removed and checked both the osc and IF coils and replaced the 47pf cap. I didn't replace the 22K or 110 resistors because I didn't have any, and no way to get to the 'Shack. My signal tracer has the noise on the plate leading into the 1st IF. I didn't remove that lead and do a buzz test through the rest of the set, nor did I inject a local IF freq. I did check both resistors and they checked within tolerance. I've spent hours on this set, and seem to be getting further from the problem. I decided to set it aside and get a little distance, and thought I'd put it on the forum to see if anybody has any ideas. It's obvious the osc. is no longer working, and it's not a bad solder connection. My suspicion is a leaky cathode to screen resistor, but I don't want to tear the whole socket apart again without a little more input.
::So-any ideas guys?
::Thanks, terry
::
:
:Sorry for the double post-accidently hit the send .
:
Terry, My suspicion, if you have replaced all the paper capacitors, is one of the IF transformers. Remove the lead on the B+ side of them, one at a time, and see if the crackling stops. My money is on the IFs! You may be able to remove them from the chassis, disassemble them and find your problem is with the capacitor portion. Perhaps some type of migration of the silver causing a short.

:::First, a little background. I picked up this GE 515 for $5 at a thrift store. I checked the tubes and replaced a couple. When I went to bring up the variac there was a bad hum and the amp meter started to spike. That problem was two tubes in the wrong sockets. Switched those and replaced the filters. Turned it on and it played so I put it on display. Turned it on the other day and heard some crackling, but it still tuned stations. I finally got it on the bench and things have gone from bad to worse. The crackling is worse and it no longer tunes stations.
:::
:::It has these stupid solder posts around the tube socket. I've unsoldered all the wires, cleaned the posts and socket holes, reconnected and resoldered the wires, replaced the tube, removed and checked both the osc and IF coils and replaced the 47pf cap. I didn't replace the 22K or 110 resistors because I didn't have any, and no way to get to the 'Shack. My signal tracer has the noise on the plate leading into the 1st IF. I didn't remove that lead and do a buzz test through the rest of the set, nor did I inject a local IF freq. I did check both resistors and they checked within tolerance. I've spent hours on this set, and seem to be getting further from the problem. I decided to set it aside and get a little distance, and thought I'd put it on the forum to see if anybody has any ideas. It's obvious the osc. is no longer working, and it's not a bad solder connection. My suspicion is a leaky cathode to screen resistor, but I don't want to tear the whole socket apart again without a little more input.
:::So-any ideas guys?
:::Thanks, terry
:::
::
::Sorry for the double post-accidently hit the send .
::
:
:
:Terry, My suspicion, if you have replaced all the paper capacitors, is one of the IF transformers. Remove the lead on the B+ side of them, one at a time, and see if the crackling stops. My money is on the IFs! You may be able to remove them from the chassis, disassemble them and find your problem is with the capacitor portion. Perhaps some type of migration of the silver causing a short.
:
Here's a photo with the osc coil, resistors and cap removed while I resoldered the leads going up into the socket lugs.

Thanks again,
Terry

I used to have this chassis. Had the same problem. The crackling you are observing is most likely caused by arcing between the primary and secondary capacitors of one or both of the IF transformers. The capacitors are built into the base. You can check between the primary and secondary windings for continuity, but you probably won't find any leakage because it is occurring at high voltage only. Connect your volt meter to the plate circuit of each IF transformer and watch for voltage fluctuation at the plate, or connect your meter to the grid circuit of each transformer and watch for positive voltage spikes at the grid. If this occurrs, then the capacitors need to be removed and replaced. Disassemble the defective transformer. Unsolder the coils (clipping the leads can be easier--reconnect by splicing on some more wire....avoid overheating the plastic base). Remove the brass rivet by bending in the crimp with a needle nose pliers. Disassemble base. Remove mica sheet. Either clip the contact extensions shorter so that they do not touch (but still offer support), or place a thin piece of plastic where the mica was to keep them from shorting. You can either buy some brass tubing from your hardware store and make new rivets, or just glue the base back together with super glue or epoxy. Reconnect the coil wires appropriately. Reinstall the transformer. Solder capacitors across each coil, usually from 50 to 150pf. Don't adjust the coils until you find capacitances that make the coils come close to resonance without adjustment (that they pass 455KC well). Once the closest to original capacitance has been found, retouch the IF adjustments. Slugs should be peaked from the outside in. Do not start from the center out.

If you have a capacitor analyzer, this can help greatly in finding leakage and in possibly determining the appropriate capacitance. Sometimes different capacitances are used for the primary and secondary coils, and if the original mica capacitors are oxidized badly or shorted, measuring their capacitances will be difficult if not impossible. When measuring these small capacitances, you cannot use the leads supplied with the analyzer. For accurate results you must connect the IF transformer directly to the analyzer. Coils must be disconnected so that you are measuring capacitance only. You can check for leakage across each capacitor and between the two of them.

Some final IF transformers have additional RF blocking capacitors for use in the detector circuit. If your final IF transformer has only 4 leads, then most likely there are only two capacitors present within the transformer. You will be sure of this when you disassemble the transformer and remove the mica sheet.

T.

Here is a link showing that Silver Mica problem. Has some pictures showing what to do. About the middle of the page.

http://www.wa2ise.com/radios/repair.htm#if

:Here is a link showing that Silver Mica problem. Has some pictures showing what to do. About the middle of the page.
:
:http://www.wa2ise.com/radios/repair.htm#if
:
That transformer looks just like mine-

I can see I've got my work cut out. Here's the 2nd IF

It looks ok.

More later-
Thanks again.
Terry

If the picture you are showing is of YOUR 2nd IF, then you probably don't have to worry about it. The red objects are external capacitors, so it can't have silver mica disease. However, if your 1st IF looks like the other picture where the base is clear plastic, and it appears that a thin sheet of mica is sandwiched inside, along with contacts that are pressed against the silvered portions of it, then this is probably where your trouble lies.

The capacitors on a silvered mica sheet can oxidize and open up, causing a reduction in sensitivity and selectivity, and can cause random operation, or a short can develop between the two capacitors, allowing B+ into the grid circuit of the following stage. This, more often than not, is what causes the crackling sound.

I do not know what the long term effects will be, but I do believe that a good save for properly functioning transformers of this design is to inject dielectric silicon grease into the capacitor cavity. This has not caused any malfunctions for me, and if the grease protects properly, it will prevent future corrosion, poor contact, and possible arc trails.

T.

T.

:If the picture you are showing is of YOUR 2nd IF, then you probably don't have to worry about it. The red objects are external capacitors, so it can't have silver mica disease. However, if your 1st IF looks like the other picture where the base is clear plastic, and it appears that a thin sheet of mica is sandwiched inside, along with contacts that are pressed against the silvered portions of it, then this is probably where your trouble lies.
:
:The capacitors on a silvered mica sheet can oxidize and open up, causing a reduction in sensitivity and selectivity, and can cause random operation, or a short can develop between the two capacitors, allowing B+ into the grid circuit of the following stage. This, more often than not, is what causes the crackling sound.
:
:I do not know what the long term effects will be, but I do believe that a good save for properly functioning transformers of this design is to inject dielectric silicon grease into the capacitor cavity. This has not caused any malfunctions for me, and if the grease protects properly, it will prevent future corrosion, poor contact, and possible arc trails.
:
:T.
:
:T.
:
In the link I was sent, it recommended opening that cap up and shunting it with a 100pf cap. Think that'll work?
Also, by dielectric do you mean the white grease used for heat sinks?
Thanks.
I appreciate all of this information.
I NEVER would have known where to look, and probably have wound up eating it for parts. And that would be a shame because it's a great looking radio-

Yes, you want to open up the base and remove the capacitor sheet, and bend or cut the contacts so that they don't touch. Another method some use is to just leave everything together and drill through the contacts. Depending on your technique, this may or may not work, and may cause damage elsewhere. Technically it can work well.

100pf caps may do the trick. Definitely a good starting point. I would use a capacitor value that allows the slugs to be adjusted as closely to their original positions as possible. This maximizes the original designed efficency of the transformers, if they were in fact designed as such. Though just about any capacitance and inductance combination can be selected to resonate at a certain frequency, there are preferred values. At values other than these, either the capacitor or the inductor will be shunting the circuit excessively, thereby reducing efficiency.

T.

Dielectric grease is that you'll find at automotive stores for use on spark plugs. In the case of your IF transformers, I wouldn't bother with the grease. The silvered mica capacitors are faulty, and should not be salvaged.

T.

:Yes, you want to open up the base and remove the capacitor sheet, and bend or cut the contacts so that they don't touch. Another method some use is to just leave everything together and drill through the contacts. Depending on your technique, this may or may not work, and may cause damage elsewhere. Technically it can work well.
:
:100pf caps may do the trick. Definitely a good starting point. I would use a capacitor value that allows the slugs to be adjusted as closely to their original positions as possible. This maximizes the original designed efficency of the transformers, if they were in fact designed as such. Though just about any capacitance and inductance combination can be selected to resonate at a certain frequency, there are preferred values. At values other than these, either the capacitor or the inductor will be shunting the circuit excessively, thereby reducing efficiency.
:
:T.
:
Once again this shows the value of this forum.
Thanks again,
Terry

::Yes, you want to open up the base and remove the capacitor sheet, and bend or cut the contacts so that they don't touch. Another method some use is to just leave everything together and drill through the contacts. Depending on your technique, this may or may not work, and may cause damage elsewhere. Technically it can work well.
::
::100pf caps may do the trick. Definitely a good starting point. I would use a capacitor value that allows the slugs to be adjusted as closely to their original positions as possible. This maximizes the original designed efficency of the transformers, if they were in fact designed as such. Though just about any capacitance and inductance combination can be selected to resonate at a certain frequency, there are preferred values. At values other than these, either the capacitor or the inductor will be shunting the circuit excessively, thereby reducing efficiency.
::
::T.
::
:
:First of all-THANKS for bringing this to my attention. Do you think I should replace the caps on the 2nd IF too? Now, I don't have an endless supply of mica caps, and frankly my plan WAS to disassemble the transformer and clean it up, which I might still try. Since this is not for resale or repair, at a certain point it becomes a problem of diminishing returns. I'm going back to the link and print that info. I would like to get it working because it is a nice radio, and I HATE being frustrated. Plus, I've already invested in a speaker and caps. We'll see.
:Once again this shows the value of this forum.
:Thanks again,
:Terry
:
More- I found this AMAZING step by step tutorial for repairing the IF .
http://radiomuseum.org/forum/if_transformer_repair.html
You might want to bookmark it.
It would be nice to have a good cap meter. I have the Heathkit IT-11, which is only good for checking leaky electrolytics. I found a couple of 160pf. Maybe they'll work.
More later-
t.

You aren't going to spend much money replacing the capacitors. It's more a matter of time and patience. If the 2nd IF transformer has capacitors built into the base, replace them. If they are discrete units soldered in, no short can form between them, and they are probably otherwise fine, anyway, considering what the kind that was probably used (tubular ceramic or mica).

As far as capacitor analyzers go, I like the Solar model CB. It will test most capacitor sizes, electrolytic and non, and performs leakage tests at voltages up to 500 volts. The only thing it can't do is test the leakage of capacitors rated at less than 25WVDC. If you purchase this unit, you should replace the paper and electrolytic capacitors inside. They are of standard values. The analyzer is reasonably accurate, and if in good condition, is very attractive. The case can be refinished easily by stripping with acetone on a rag, and then coating with clear lacquer. The leather handle can be cut and sewn from new leather, and the red and black cloth test lead wire and brown cloth AC cord are readily available.

Peter and some others can recommend some fine modern digital capacitor and inductor analyzers. The added bonus of the inductor analyzer is that you can determine the inductance of the coils in your IF transformer as tuned from the factory, and by using proper calculation, determine the exact capacitance necessary for replacement. The only drawback of these modern testers is the lack of a high voltage leakage test. However, the crackling you hear is enough of a sign on its own, and you can further determine whether the silvered mica capacitors are arcing over by using your voltmeter to measure the voltage of the control grid (or diode plate) of each tube fed by an IF transformer.

T.

:As far as capacitor analyzers go, I like the Solar model CB. It will test most capacitor sizes, electrolytic and non, and performs leakage tests at voltages up to 500 volts. The only thing it can't do is test the leakage of capacitors rated at less than 25WVDC. If you purchase this unit, you should replace the paper and electrolytic capacitors inside. They are of standard values. The analyzer is reasonably accurate, and if in good condition, is very attractive. The case can be refinished easily by stripping with acetone on a rag, and then coating with clear lacquer. The leather handle can be cut and sewn from new leather, and the red and black cloth test lead wire and brown cloth AC cord are readily available.
:
:Peter and some others can recommend some fine modern digital capacitor and inductor analyzers. The added bonus of the inductor analyzer is that you can determine the inductance of the coils in your IF transformer as tuned from the factory, and by using proper calculation, determine the exact capacitance necessary for replacement. The only drawback of these modern testers is the lack of a high voltage leakage test. However, the crackling you hear is enough of a sign on its own, and you can further determine whether the silvered mica capacitors are arcing over by using your voltmeter to measure the voltage of the control grid (or diode plate) of each tube fed by an IF transformer.
:
:T.
:
SO- I drilled out the rivet, and the mica looks like a carbon resistor. I've cut out the clips, glued the retainer back in place and found some mica caps. I have a pair of 150pf @500VDC. Looks like a good place to start. I've cleaned up some other bad wiring and replaced the 2nd IF can, which I think should be ok. I'm going to take a break and walk the dog. After that I'll put in the transformer and warm up the ol' Heathkit IG-102.
Actually, this has been a lot of fun-
Wish me luck.
(Or, like Billy Crystal said about storming the castle in Princess Bride-
"It'll take a miracle"!

:As far as capacitor analyzers go, I like the Solar model CB. It will test most capacitor sizes, electrolytic and non, and performs leakage tests at voltages up to 500 volts. The only thing it can't do is test the leakage of capacitors rated at less than 25WVDC. If you purchase this unit, you should replace the paper and electrolytic capacitors inside. They are of standard values. The analyzer is reasonably accurate, and if in good condition, is very attractive. The case can be refinished easily by stripping with acetone on a rag, and then coating with clear lacquer. The leather handle can be cut and sewn from new leather, and the red and black cloth test lead wire and brown cloth AC cord are readily available.
:
:Peter and some others can recommend some fine modern digital capacitor and inductor analyzers. The added bonus of the inductor analyzer is that you can determine the inductance of the coils in your IF transformer as tuned from the factory, and by using proper calculation, determine the exact capacitance necessary for replacement. The only drawback of these modern testers is the lack of a high voltage leakage test. However, the crackling you hear is enough of a sign on its own, and you can further determine whether the silvered mica capacitors are arcing over by using your voltmeter to measure the voltage of the control grid (or diode plate) of each tube fed by an IF transformer.
:
:T.
:

::As far as capacitor analyzers go, I like the Solar model CB. It will test most capacitor sizes, electrolytic and non, and performs leakage tests at voltages up to 500 volts. The only thing it can't do is test the leakage of capacitors rated at less than 25WVDC. If you purchase this unit, you should replace the paper and electrolytic capacitors inside. They are of standard values. The analyzer is reasonably accurate, and if in good condition, is very attractive. The case can be refinished easily by stripping with acetone on a rag, and then coating with clear lacquer. The leather handle can be cut and sewn from new leather, and the red and black cloth test lead wire and brown cloth AC cord are readily available.
::
::Peter and some others can recommend some fine modern digital capacitor and inductor analyzers. The added bonus of the inductor analyzer is that you can determine the inductance of the coils in your IF transformer as tuned from the factory, and by using proper calculation, determine the exact capacitance necessary for replacement. The only drawback of these modern testers is the lack of a high voltage leakage test. However, the crackling you hear is enough of a sign on its own, and you can further determine whether the silvered mica capacitors are arcing over by using your voltmeter to measure the voltage of the control grid (or diode plate) of each tube fed by an IF transformer.
::
::T.
::
:
:So, I got it back together and I'm able to get a strong 455KC signal from my generator, but no stations. I had to crank the top slug all the way out. B+ voltages look correct. What am I missing?
:
More- I found that the correct value for the caps were 75pf, and I have some in stock. At least there's no crackling, so that must have been the problem. Thanks. My guess is that the osc isn't working. More Tue.
t.

Here the L/C meter I use:

http://www.aade.com/lcmeter.htm

Here's the L/C meter I use:

http://www.aade.com/lcmeter.htm

You say that you 'replaced' the 2nd IF can. Does that mean that you put a different one in, or that you put the original one back in?

Be sure that you connected it properly. Check both transformers for continuity to be sure that no wires were broken. Be sure to check the adjustment of both transformers, too, with your signal generator.

You can check the oscillator by measuring its grid voltage (grid 1 of the 12BE6). Should be a negative voltage in the neighborhood of 5 to 7 volts.

T.

:You say that you 'replaced' the 2nd IF can. Does that mean that you put a different one in, or that you put the original one back in?
:
:Be sure that you connected it properly. Check both transformers for continuity to be sure that no wires were broken. Be sure to check the adjustment of both transformers, too, with your signal generator.
:
:You can check the oscillator by measuring its grid voltage (grid 1 of the 12BE6). Should be a negative voltage in the neighborhood of 5 to 7 volts.
:
:T.
:
Great Peter-I'll check out that meter.
Thanks Thomas-yes, I put the old one back in. It has regular mica's and tests good I'm sure everything is correctly oriented because I take EXTRA care to mark, document and photograph everything I do. It was late last night when I finished, so when I get back into it today I'll have a fresh attitude. I found the 75pf caps, so I'll replace those, check the voltages, and then run the generator through it again. The main thing is that the crackling sound is GONE, AND-I've learned a very valuable lesson that I would never have with out your help.
I LOVE THIS FORUM!!
Thanks,
terry

:You say that you 'replaced' the 2nd IF can. Does that mean that you put a different one in, or that you put the original one back in?
:
:Be sure that you connected it properly. Check both transformers for continuity to be sure that no wires were broken. Be sure to check the adjustment of both transformers, too, with your signal generator.
:
:You can check the oscillator by measuring its grid voltage (grid 1 of the 12BE6). Should be a negative voltage in the neighborhood of 5 to 7 volts.
:
:T.
:
I know it's been a few days, but I hope someone is still watching this-
OK-
I did the repair of the caps in the IF can, successfully I think. I subbed the caps with 75pf mica, which is the value in the schematic.
I realise this is going to mess with the alignment, but right now that's not my problem.
I can inject a strong signal with my RF gen. from the antenna thru the set all across the dial. However, it is only at 430kc. (The can says 456, and of course my old gen may be off). I have 80 volts at the screen and plate of the 12BE6, but apparently none at the cathode, (pin 1).
So- I'm assuming that with all of my work I've interrupted the voltage to the osc section of the 12BE6.
My plan is to check all of the connections on those stupid standup tie points around the tube socket, test the resistors, etc. I'm pretty sure my only problem now is lack of oscillation.
Any other ideas?
Thomas-you were RIGHT ON about those caps.
I can't receive any stations, but I don't have ANY crackling noise.
Thanks-
t.

Hi Terry,
By screen, I assume that you mean pin 6 of the 12BE6.
Your writing indicates you are on the right trail.

Best Regards,

Bill Grimm

To see if the oscillator is functioning properly, check G1 of the 12BE6 (pin 1) with reference to B-. There should be negative voltage here.

If the radio WAS working before you repaired the IF transformers, I suspect that you upset something regarding them, though the oscillator may in fact have failed.

T.

:To see if the oscillator is functioning properly, check G1 of the 12BE6 (pin 1) with reference to B-. There should be negative voltage here.
:
:If the radio WAS working before you repaired the IF transformers, I suspect that you upset something regarding them, though the oscillator may in fact have failed.
:
:T.
:
Yeah, I don't have any voltage on pin 1. I'm pretty sure it's just a bad connection in one of the terminal posts. The fact that the signal from the generator goes all the way through the set is a good sign. I set it aside today to work on the 6LE8 transmitter kit I got from Bill at ARF. Fri. is going to be another rainy day here in Lou., so I'll probably get it fixed then.
Thanks again for the great info.
t.