I replaced all the tubes, substituting them with known good ones one at a time, but the sound didn't change or get any better. I finally pulled the speaker out of my 5S119 thinking the speaker might be bad, but that didn't make any difference either.
As a side note the performance on shortwave is very low. I can hear stations on the SW bands, but the volume is very very low. Could these problems be related? I don't think so, I assume the harsh tone is due to a problem in the audio section and the lackluster performance of SW being located in the RF section. Any of you Zenith guru's have any suggestions?
Did the radio act like this before you recapped it?
:I have fully recapped a Zenith 5S127. I removed all the old caps and replaced them with new electrolytics and paper caps. The radio works, but it has a sound like the speaker is being "overdriven" even at low volume.
:
:I replaced all the tubes, substituting them with known good ones one at a time, but the sound didn't change or get any better. I finally pulled the speaker out of my 5S119 thinking the speaker might be bad, but that didn't make any difference either.
:
:As a side note the performance on shortwave is very low. I can hear stations on the SW bands, but the volume is very very low. Could these problems be related? I don't think so, I assume the harsh tone is due to a problem in the audio section and the lackluster performance of SW being located in the RF section. Any of you Zenith guru's have any suggestions?
I finally had a chance to check the tube voltages on this set. With 117 Volts on the line, I'm only getting 190 volts on the plates of the 6A8 and 6K7 when it calls for 240 volts. Additionally, on the 6F6
output tube, I'm only getting 165 volts on the plate and 190 volts on the screen when the schematic calls for 230 and 240 volts respectively.
The voltages on the other pins of these same tubes test OK. The cathode voltages on all the tubes are within 1/2 a volt and the screen voltage on the 6A8 is 156 volts when it should be 166, not really a problem. Pin 4 of the 6A8 measures 83 volts as well as pin 4 of the 6K7 and both of these should be 85 volts, again not a problem.
I'm stumped as to why I'm 50 volts low on some readings and practically dead-on on others. I measured the voltage out of the transformer and
it is 190 volts, just like I'm getting at the tube plates that are fed this voltage through the coils. I'm getting 530 volts across the rectifier plates. The transformer is original to this radio, at least
the part numbers match.
Could this be related to the electrolytics? They have been replaced, both 16uF, 450V.
David
:Hi David,
:
:First, check all your voltages shown on the schematic.
:
:Did the radio act like this before you recapped it?
:
::I have fully recapped a Zenith 5S127. I removed all the old caps and replaced them with new electrolytics and paper caps. The radio works, but it has a sound like the speaker is being "overdriven" even at low volume.
::
::I replaced all the tubes, substituting them with known good ones one at a time, but the sound didn't change or get any better. I finally pulled the speaker out of my 5S119 thinking the speaker might be bad, but that didn't make any difference either.
::
::As a side note the performance on shortwave is very low. I can hear stations on the SW bands, but the volume is very very low. Could these problems be related? I don't think so, I assume the harsh tone is due to a problem in the audio section and the lackluster performance of SW being located in the RF section. Any of you Zenith guru's have any suggestions?
Something to check. If you replaced C19 with a cap underneath the chassis, make sure you completely isolated the old cap from the circuit. Also note that this cap's minus does not connect directly to the chassis but to the centertap of the power transformer which then goes thru the speaker choke to chassis.
Radiodoc
:Hi Again,
:
:I finally had a chance to check the tube voltages on this set. With 117 Volts on the line, I'm only getting 190 volts on the plates of the 6A8 and 6K7 when it calls for 240 volts. Additionally, on the 6F6
:output tube, I'm only getting 165 volts on the plate and 190 volts on the screen when the schematic calls for 230 and 240 volts respectively.
:
:The voltages on the other pins of these same tubes test OK. The cathode voltages on all the tubes are within 1/2 a volt and the screen voltage on the 6A8 is 156 volts when it should be 166, not really a problem. Pin 4 of the 6A8 measures 83 volts as well as pin 4 of the 6K7 and both of these should be 85 volts, again not a problem.
:
:I'm stumped as to why I'm 50 volts low on some readings and practically dead-on on others. I measured the voltage out of the transformer and
:it is 190 volts, just like I'm getting at the tube plates that are fed this voltage through the coils. I'm getting 530 volts across the rectifier plates. The transformer is original to this radio, at least
:the part numbers match.
:
:Could this be related to the electrolytics? They have been replaced, both 16uF, 450V.
:
:David
:
::Hi David,
::
::First, check all your voltages shown on the schematic.
::
::Did the radio act like this before you recapped it?
::
:::I have fully recapped a Zenith 5S127. I removed all the old caps and replaced them with new electrolytics and paper caps. The radio works, but it has a sound like the speaker is being "overdriven" even at low volume.
:::
:::I replaced all the tubes, substituting them with known good ones one at a time, but the sound didn't change or get any better. I finally pulled the speaker out of my 5S119 thinking the speaker might be bad, but that didn't make any difference either.
:::
:::As a side note the performance on shortwave is very low. I can hear stations on the SW bands, but the volume is very very low. Could these problems be related? I don't think so, I assume the harsh tone is due to a problem in the audio section and the lackluster performance of SW being located in the RF section. Any of you Zenith guru's have any suggestions?
I'll double check on it tonight. This radio worked for a while, but now my voltages are off so there could be a problem with this cap having found a short to ground without going through the speaker field. Since the sound has bee affected, this could very well be the problem. Thanks!
David
:David R.,
:
:Something to check. If you replaced C19 with a cap underneath the chassis, make sure you completely isolated the old cap from the circuit. Also note that this cap's minus does not connect directly to the chassis but to the centertap of the power transformer which then goes thru the speaker choke to chassis.
:
:Radiodoc
:
:
::Hi Again,
::
::I finally had a chance to check the tube voltages on this set. With 117 Volts on the line, I'm only getting 190 volts on the plates of the 6A8 and 6K7 when it calls for 240 volts. Additionally, on the 6F6
::output tube, I'm only getting 165 volts on the plate and 190 volts on the screen when the schematic calls for 230 and 240 volts respectively.
::
::The voltages on the other pins of these same tubes test OK. The cathode voltages on all the tubes are within 1/2 a volt and the screen voltage on the 6A8 is 156 volts when it should be 166, not really a problem. Pin 4 of the 6A8 measures 83 volts as well as pin 4 of the 6K7 and both of these should be 85 volts, again not a problem.
::
::I'm stumped as to why I'm 50 volts low on some readings and practically dead-on on others. I measured the voltage out of the transformer and
::it is 190 volts, just like I'm getting at the tube plates that are fed this voltage through the coils. I'm getting 530 volts across the rectifier plates. The transformer is original to this radio, at least
::the part numbers match.
::
::Could this be related to the electrolytics? They have been replaced, both 16uF, 450V.
::
::David
::
:::Hi David,
:::
:::First, check all your voltages shown on the schematic.
:::
:::Did the radio act like this before you recapped it?
:::
::::I have fully recapped a Zenith 5S127. I removed all the old caps and replaced them with new electrolytics and paper caps. The radio works, but it has a sound like the speaker is being "overdriven" even at low volume.
::::
::::I replaced all the tubes, substituting them with known good ones one at a time, but the sound didn't change or get any better. I finally pulled the speaker out of my 5S119 thinking the speaker might be bad, but that didn't make any difference either.
::::
::::As a side note the performance on shortwave is very low. I can hear stations on the SW bands, but the volume is very very low. Could these problems be related? I don't think so, I assume the harsh tone is due to a problem in the audio section and the lackluster performance of SW being located in the RF section. Any of you Zenith guru's have any suggestions?
I always hate it when a topic just kind of dies after a solution is found, so here it is. I found the cause of the harsh tone, just as you said it was C19 being shorted directly to ground. I had rebuilt the can and thought I had isolated it from ground using the fiber washer that was part of the original electrolytic can. However, somthing must have jarred the can out of place and it was shorting against the side of the mounting hole. I used a small bushing to fix it and it is working perfectly now.
I still need to address the weak reception on the shortwave bands, but I'll have to do some more research on that as I have time. Thanks for the advice.
David R
:Doug,
:
:I'll double check on it tonight. This radio worked for a while, but now my voltages are off so there could be a problem with this cap having found a short to ground without going through the speaker field. Since the sound has bee affected, this could very well be the problem. Thanks!
:
:David
:
::David R.,
::
::Something to check. If you replaced C19 with a cap underneath the chassis, make sure you completely isolated the old cap from the circuit. Also note that this cap's minus does not connect directly to the chassis but to the centertap of the power transformer which then goes thru the speaker choke to chassis.
::
::Radiodoc
::
::
:::Hi Again,
:::
:::I finally had a chance to check the tube voltages on this set. With 117 Volts on the line, I'm only getting 190 volts on the plates of the 6A8 and 6K7 when it calls for 240 volts. Additionally, on the 6F6
:::output tube, I'm only getting 165 volts on the plate and 190 volts on the screen when the schematic calls for 230 and 240 volts respectively.
:::
:::The voltages on the other pins of these same tubes test OK. The cathode voltages on all the tubes are within 1/2 a volt and the screen voltage on the 6A8 is 156 volts when it should be 166, not really a problem. Pin 4 of the 6A8 measures 83 volts as well as pin 4 of the 6K7 and both of these should be 85 volts, again not a problem.
:::
:::I'm stumped as to why I'm 50 volts low on some readings and practically dead-on on others. I measured the voltage out of the transformer and
:::it is 190 volts, just like I'm getting at the tube plates that are fed this voltage through the coils. I'm getting 530 volts across the rectifier plates. The transformer is original to this radio, at least
:::the part numbers match.
:::
:::Could this be related to the electrolytics? They have been replaced, both 16uF, 450V.
:::
:::David
:::
::::Hi David,
::::
::::First, check all your voltages shown on the schematic.
::::
::::Did the radio act like this before you recapped it?
::::
:::::I have fully recapped a Zenith 5S127. I removed all the old caps and replaced them with new electrolytics and paper caps. The radio works, but it has a sound like the speaker is being "overdriven" even at low volume.
:::::
:::::I replaced all the tubes, substituting them with known good ones one at a time, but the sound didn't change or get any better. I finally pulled the speaker out of my 5S119 thinking the speaker might be bad, but that didn't make any difference either.
:::::
:::::As a side note the performance on shortwave is very low. I can hear stations on the SW bands, but the volume is very very low. Could these problems be related? I don't think so, I assume the harsh tone is due to a problem in the audio section and the lackluster performance of SW being located in the RF section. Any of you Zenith guru's have any suggestions?