I have ha AC-60 that had expereinced overheating in the FB (FB is about 6" x 6" x 6" and its contents are schematically shown on the AC-60 rider's schematic) and caused a lot of wax to melt into the chassis. Unit also had a distorted tuner (warped pot metal) which I have since replaced and cleaned out the wax. Repaired Unit worked perfectly for some time during limited checkouts (15 -30 minutes at atime). I then accidently left the unit on for several hours and when I came back it had a 60 cycle hum over the entire band (typical of a filter cap mot working correctly) and was leaking wax again (couldn't be much left)and hot (but not burn level) to the touch. What is most likely to generate the heat in the FB? I assume a shorted cap or filter coil or maybe just not enough wax to act as heat sink. Could it be that the components has shorted to the chassis because the wax is gone - I don't know how they are secured in the box.I can't do much diagnostics on the installed unit since ethe wax has discolored all of the wires so they look the same (don't trust the schematic since there were several versions of the AC-60 wiring on my parts chassis doesn't look anything like the almost good one. My plan is to mark the wires, remove the FB, melt out the wax and test the indvidual parts speparately. Any guess as to the cause and remedy and what kind of wax was used in these units (it looks like muddy bees wax). The tubes all test out OK so I dn't think I have a maverick tube, but then again I'm a novice.

Hi,
Chances are good that filter caps dried out enough to allow arcing between plates This explains the greater heating. Some heat is normal, but usually it is only a few degrees above ambient air temperature. Just replace the caps once removed- even if they test "ok". New caps will fit inside of the old box, even if some of the old material is left behind- Just make sure it is insulated from any electrical parts that get placed back inside.

I would also not be at all surpised if the output tubes were not also gassy now as a result. This may take more than just 5 minutes for the first signs of ionization to be visible once you have the filter repaired. Just check to make sure the coil is not burned out, or shorted before putting it into use again.

The wax is likely beeswax, and it may not have been refined, which explains the coloring. You could try to reuse the old, or use a high grade parafin sealing wax.

: I have ha AC-60 that had expereinced overheating in the FB (FB is about 6" x 6" x 6" and its contents are schematically shown on the AC-60 rider's schematic) and caused a lot of wax to melt into the chassis. Unit also had a distorted tuner (warped pot metal) which I have since replaced and cleaned out the wax. Repaired Unit worked perfectly for some time during limited checkouts (15 -30 minutes at atime). I then accidently left the unit on for several hours and when I came back it had a 60 cycle hum over the entire band (typical of a filter cap mot working correctly) and was leaking wax again (couldn't be much left)and hot (but not burn level) to the touch. What is most likely to generate the heat in the FB? I assume a shorted cap or filter coil or maybe just not enough wax to act as heat sink. Could it be that the components has shorted to the chassis because the wax is gone - I don't know how they are secured in the box.I can't do much diagnostics on the installed unit since ethe wax has discolored all of the wires so they look the same (don't trust the schematic since there were several versions of the AC-60 wiring on my parts chassis doesn't look anything like the almost good one. My plan is to mark the wires, remove the FB, melt out the wax and test the indvidual parts speparately. Any guess as to the cause and remedy and what kind of wax was used in these units (it looks like muddy bees wax). The tubes all test out OK so I dn't think I have a maverick tube, but then again I'm a novice.

Thanks, what are the perfomance indicators of a gassy output tube and will my Hickok or I-177 pick it up on the gas test?- lower gain or contribution to hum. DWG

: Hi,
: Chances are good that filter caps dried out enough to allow arcing between plates This explains the greater heating. Some heat is normal, but usually it is only a few degrees above ambient air temperature. Just replace the caps once removed- even if they test "ok". New caps will fit inside of the old box, even if some of the old material is left behind- Just make sure it is insulated from any electrical parts that get placed back inside.

: I would also not be at all surpised if the output tubes were not also gassy now as a result. This may take more than just 5 minutes for the first signs of ionization to be visible once you have the filter repaired. Just check to make sure the coil is not burned out, or shorted before putting it into use again.

: The wax is likely beeswax, and it may not have been refined, which explains the coloring. You could try to reuse the old, or use a high grade parafin sealing wax.

:
: : I have ha AC-60 that had expereinced overheating in the FB (FB is about 6" x 6" x 6" and its contents are schematically shown on the AC-60 rider's schematic) and caused a lot of wax to melt into the chassis. Unit also had a distorted tuner (warped pot metal) which I have since replaced and cleaned out the wax. Repaired Unit worked perfectly for some time during limited checkouts (15 -30 minutes at atime). I then accidently left the unit on for several hours and when I came back it had a 60 cycle hum over the entire band (typical of a filter cap mot working correctly) and was leaking wax again (couldn't be much left)and hot (but not burn level) to the touch. What is most likely to generate the heat in the FB? I assume a shorted cap or filter coil or maybe just not enough wax to act as heat sink. Could it be that the components has shorted to the chassis because the wax is gone - I don't know how they are secured in the box.I can't do much diagnostics on the installed unit since ethe wax has discolored all of the wires so they look the same (don't trust the schematic since there were several versions of the AC-60 wiring on my parts chassis doesn't look anything like the almost good one. My plan is to mark the wires, remove the FB, melt out the wax and test the indvidual parts speparately. Any guess as to the cause and remedy and what kind of wax was used in these units (it looks like muddy bees wax). The tubes all test out OK so I dn't think I have a maverick tube, but then again I'm a novice.

Hi,
Gassy tubes usually show a purple glow from the ionization. Usually the tube may also indicate an excessively high trasnconductance, or even in some cases a variable nature that can cause sporadic noise or distortion, or emission value. Current draw through the plate would also be higher than it should be in normal operation. It is rare to have the output stages survive when a filter cap goes bad in the manner yours did, but it is cheaper to replace tubes than to replace a radio, or an amp if the tubes start to draw excessive current, so testing is more for insurance against other trouble, or fire.

I actually have found a few gassy tubes by testing them with the lights in the room off. They were not working correctly, and after about 5 minutes a faint glow surrounded the space between the filament and the plate.

: Thanks, what are the perfomance indicators of a gassy output tube and will my Hickok or I-177 pick it up on the gas test?- lower gain or contribution to hum. DWG

: : Hi,
: : Chances are good that filter caps dried out enough to allow arcing between plates This explains the greater heating. Some heat is normal, but usually it is only a few degrees above ambient air temperature. Just replace the caps once removed- even if they test "ok". New caps will fit inside of the old box, even if some of the old material is left behind- Just make sure it is insulated from any electrical parts that get placed back inside.

: : I would also not be at all surpised if the output tubes were not also gassy now as a result. This may take more than just 5 minutes for the first signs of ionization to be visible once you have the filter repaired. Just check to make sure the coil is not burned out, or shorted before putting it into use again.

: : The wax is likely beeswax, and it may not have been refined, which explains the coloring. You could try to reuse the old, or use a high grade parafin sealing wax.

:
: :
: : : I have ha AC-60 that had expereinced overheating in the FB (FB is about 6" x 6" x 6" and its contents are schematically shown on the AC-60 rider's schematic) and caused a lot of wax to melt into the chassis. Unit also had a distorted tuner (warped pot metal) which I have since replaced and cleaned out the wax. Repaired Unit worked perfectly for some time during limited checkouts (15 -30 minutes at atime). I then accidently left the unit on for several hours and when I came back it had a 60 cycle hum over the entire band (typical of a filter cap mot working correctly) and was leaking wax again (couldn't be much left)and hot (but not burn level) to the touch. What is most likely to generate the heat in the FB? I assume a shorted cap or filter coil or maybe just not enough wax to act as heat sink. Could it be that the components has shorted to the chassis because the wax is gone - I don't know how they are secured in the box.I can't do much diagnostics on the installed unit since ethe wax has discolored all of the wires so they look the same (don't trust the schematic since there were several versions of the AC-60 wiring on my parts chassis doesn't look anything like the almost good one. My plan is to mark the wires, remove the FB, melt out the wax and test the indvidual parts speparately. Any guess as to the cause and remedy and what kind of wax was used in these units (it looks like muddy bees wax). The tubes all test out OK so I dn't think I have a maverick tube, but then again I'm a novice.