I'm currently recapping a Zenith 8S463 for a friend, as well as replacing wires with bad insulation. I'm more than a bit stymied by the capacitor can. I know which color wire lead to which capacitor, but my question is: is the negative side of the new capacitor supposed to be on the rectifier side or on the other side.

Also, I'm replacing the cord and plug with a polarized plug because I've read in multiple locations that this increases safety as well as preventing the radio from being damaged. Should the neutral side of the plug opposite the transformer, like I'm thinking or do I have it all wrong.

I feel a bit embarrassed to be asking this question, but it is much better to be safe than sorry. Thankfully I start school for a bachelors in EE in January so maybe I can start answering a few of these questions for noobs like myself currently.

Thanks in advanced.

:I'm currently recapping a Zenith 8S463 for a friend, as well as replacing wires with bad insulation. I'm more than a bit stymied by the capacitor can. I know which color wire lead to which capacitor, but my question is: is the negative side of the new capacitor supposed to be on the rectifier side or on the other side.
:
:Also, I'm replacing the cord and plug with a polarized plug because I've read in multiple locations that this increases safety as well as preventing the radio from being damaged. Should the neutral side of the plug opposite the transformer, like I'm thinking or do I have it all wrong.
:
:I feel a bit embarrassed to be asking this question, but it is much better to be safe than sorry. Thankfully I start school for a bachelors in EE in January so maybe I can start answering a few of these questions for noobs like myself currently.
:
:Thanks in advanced.
:
I meant to include the schematic on my original post. Here it is: http://www.nostalgiaair.org/PagesByModel/455/M0025455.pdf

::I'm currently recapping a Zenith 8S463 for a friend, as well as replacing wires with bad insulation. I'm more than a bit stymied by the capacitor can. I know which color wire lead to which capacitor, but my question is: is the negative side of the new capacitor supposed to be on the rectifier side or on the other side.
::
::Also, I'm replacing the cord and plug with a polarized plug because I've read in multiple locations that this increases safety as well as preventing the radio from being damaged. Should the neutral side of the plug opposite the transformer, like I'm thinking or do I have it all wrong.
::
::I feel a bit embarrassed to be asking this question, but it is much better to be safe than sorry. Thankfully I start school for a bachelors in EE in January so maybe I can start answering a few of these questions for noobs like myself currently.
::
::Thanks in advanced.
::
:I meant to include the schematic on my original post. Here it is: http://www.nostalgiaair.org/PagesByModel/455/M0025455.pdf
:
Ken,
E caps in a can usually have a common connection for the negative lead that will go to B-. Looks like C 22,23 are in the can. Is C24 also an E cap? Use a ohm meter to ohm out your negative lead connections either to chassis or B-, this will tell you the proper orientation of the E caps. C24 may be reversed from C22,23 for the negative connection.
Hold off on changing the power cord until you are done with the restore if it is not damaged.

SAFETY: Make ABSOLUTELY sure that you are using an isolation transformer when you power this unit up and any time it has power on it. If you have a Variac use this in combination when applying power.
Mitch

:::I'm currently recapping a Zenith 8S463 for a friend, as well as replacing wires with bad insulation. I'm more than a bit stymied by the capacitor can. I know which color wire lead to which capacitor, but my question is: is the negative side of the new capacitor supposed to be on the rectifier side or on the other side.
:::
:::Also, I'm replacing the cord and plug with a polarized plug because I've read in multiple locations that this increases safety as well as preventing the radio from being damaged. Should the neutral side of the plug opposite the transformer, like I'm thinking or do I have it all wrong.
:::
:::I feel a bit embarrassed to be asking this question, but it is much better to be safe than sorry. Thankfully I start school for a bachelors in EE in January so maybe I can start answering a few of these questions for noobs like myself currently.
:::
:::Thanks in advanced.
:::
::I meant to include the schematic on my original post. Here it is: http://www.nostalgiaair.org/PagesByModel/455/M0025455.pdf
::
:Ken,
:E caps in a can usually have a common connection for the negative lead that will go to B-. Looks like C 22,23 are in the can. Is C24 also an E cap? Use a ohm meter to ohm out your negative lead connections either to chassis or B-, this will tell you the proper orientation of the E caps. C24 may be reversed from C22,23 for the negative connection.
:Hold off on changing the power cord until you are done with the restore if it is not damaged.
:
:SAFETY: Make ABSOLUTELY sure that you are using an isolation transformer when you power this unit up and any time it has power on it. If you have a Variac use this in combination when applying power.
:Mitch
:

Mitch, thanks for the response. Yes, C23 and C22 are in one electrolytic can and C24 is an E-cap across the chassis from the first two. I will ohm it out like you suggested. And yes, I do have an Variac powered from an isolation transformer. Electricity is a great helper, but it is not our friend...

C22 and 23 have their common negative connected to the transformer center tap, which is more negative than the chassis, and each positive connects to one side of R19 in the B+ side of things. C24 has its negative connected to the junction of the 19 and 52 ohm sections of R18.

None of these capacitors has its negative connected to the chassis.

Though you can use an ohmmeter to check electrolytic orientation and even test for proper operation, a far better test is with a high voltage leakage tester and capacitor bridge. The ohmmeter cannot simulate what a capacitor is subjected to during normal operation of the radio, and erroneous results can be had both concerning condition and polarity. If a high voltage leakage tester is not available, or you want to be sure about things, it is best to simply replace the electrolytics. If you do have the proper equipment and know what you are looking for, you can re-use some old electrolytics (not that I read any implications of this here).

T.

...And regarding polarity, sometimes if a capacitor is leaky or completely dried up, it will be difficult to decipher its polarity with an ohmmeter, though usually this can be done, as when proper polarity is observed, the needle will slowly drop, and if it isn't, the needle will remain high. You can see, though, how errors could develop from a leaky or open electrolytic.

T.

:...And regarding polarity, sometimes if a capacitor is leaky or completely dried up, it will be difficult to decipher its polarity with an ohmmeter, though usually this can be done, as when proper polarity is observed, the needle will slowly drop, and if it isn't, the needle will remain high. You can see, though, how errors could develop from a leaky or open electrolytic.
:
:Make a sanity check, ohm out the locations that T gave to you, no doubt about his info. Print 2 copies of the schematic and outline the power supply and other circuits in color codes. Use one schematic to make reference notes as you make measurements and component changes, if something does not work after repair starts you have a reference to go back to check and relook at your work. Document each step of your repairs to be able to go back and verify.
Best to you in school, most on this Forum, like me are retired engineers
Mitch

::...And regarding polarity, sometimes if a capacitor is leaky or completely dried up, it will be difficult to decipher its polarity with an ohmmeter, though usually this can be done, as when proper polarity is observed, the needle will slowly drop, and if it isn't, the needle will remain high. You can see, though, how errors could develop from a leaky or open electrolytic.
::
::Make a sanity check, ohm out the locations that T gave to you, no doubt about his info. Print 2 copies of the schematic and outline the power supply and other circuits in color codes. Use one schematic to make reference notes as you make measurements and component changes, if something does not work after repair starts you have a reference to go back to check and relook at your work. Document each step of your repairs to be able to go back and verify.
:Best to you in school, most on this Forum, like me are retired engineers
:Mitch
:
:

Gentlemen,

Thank you for all your assistance. I (and I'm sure my friend) thank you.

Ken

:::...And regarding polarity, sometimes if a capacitor is leaky or completely dried up, it will be difficult to decipher its polarity with an ohmmeter, though usually this can be done, as when proper polarity is observed, the needle will slowly drop, and if it isn't, the needle will remain high. You can see, though, how errors could develop from a leaky or open electrolytic.
:::
:::Make a sanity check, ohm out the locations that T gave to you, no doubt about his info. Print 2 copies of the schematic and outline the power supply and other circuits in color codes. Use one schematic to make reference notes as you make measurements and component changes, if something does not work after repair starts you have a reference to go back to check and relook at your work. Document each step of your repairs to be able to go back and verify.
::Best to you in school, most on this Forum, like me are retired engineers
::Mitch
::
::
:
:Gentlemen,
:
:Thank you for all your assistance. I (and I'm sure my friend) thank you.
:
:Ken
:
Ken,
One more thought. When making voltage measurements, be sure to use a VTVM, my choice has been a VoltOhmyst by RCA. A DVM will not give accurate measurements due to impedance of tube circuits.
Best to you,
Mitch

An anolog volt/ohm meter with 100,000 ohms-per-volt, like the Simpson 260, will give you very good (and stable) voltage measurements for lower impedance circuits such as typical plate circuits, cathode circuits, most screen grid circuits, and typical power supply circuits. A 1000 ohm-per-volt meter, as was often used back in the day, isn't good for much of anything except power supply measurements. The most critical problems (such as capacitor leakage) would never be found with such a meter. Old schematics which show grid volts to be 0 are somewhat useless. A VTVM or DVM does a better job here, the VTVM being the best choice. Typically most radio repairmen just replace the paper capacitors with far superior modern capacitors, but it is still nice to take readings just to be sure, and if trouble still arises. A meter like the Simpson 260 would show some voltage, but would still load down grid and AVC circuits too much to get a truly accurate voltage reading.

A VTVM is extremely sensitive and is very good for control grid circuits, high impedance RF circuits, oscillator circuits, and AVC circuits.

A DVM is rather jumpy and sensitive, and, as Mitch said, can give rather erroneous readings, though is sensitive enough to usually function well where a VTVM would be used, though I prefer the VTVM.

The VTVM and DVM, due to extreme sensitivity, can give erroneous readings when an attempt is made to measure a substantial DC voltage, and small AC voltages co-inside with the DC voltage, such as measuring the voltage of the electrical system of a car. A conventional anolog meter like the Simpson 260 would show the average DC voltage, but the VTVM and DVM might pick up the spikes of the alternator or generator, since the output of both is controlled by pulse width modulation of the field coil, and a generator also contains a commutator, which introduces repetitive voltage fluctuations (as well as the voltage fluctuations due merely to the armature passing the magnetic poles (or vice versa if an alternator)). If there is concern for this problem, and the small spikes and waves might be unwanted (such as in a radio or computer, where clean DC is necessary), a good oscilloscope would be handy here to show the base voltage as well as the spikes.