Grebe AC-6 Restoration Question

1/20/2007 5:50:55 PMW8VCK

I'm starting the process of bringing a Grebe AC-6 back to life. This is my first radio from this era, and I am discovering that even though I have a schematic some of the inner workings are a mystery.

Starting with the power supply... On one side is a transformer, I know how to check that out. Next to that is the rectifier tube, okay no problem... Next to that is a substantial box with two wires coming out of the bottom that is labled as a "choke" on the diagram I have. Is this a non polarized capacitor? What value would it have?

Thanks in advance, I'll probably have more questions once I get the power supply working.

Regards

Alan

1/20/2007 6:05:25 PMDoug Criner

Alan, here's the schematic:
http://www.nostalgiaair.org/PagesByModel/319/M0039319.pdf

A choke is a coil used to help filter out out pulses on the DC. Looks kind of like a transformer, but has just two leads.

The schematic shows that the choke is there if a PM speaker is used. The choke is cut out of the ckt if a dynamic speaker is used, in which case the speaker's field winding is connected instead of the choke.

The power supply might be OK. I would try bringing it up very slowly with a variac while watching current into the xfmr and the AC + DC voltages on the secondary side.

:I'm starting the process of bringing a Grebe AC-6 back to life. This is my first radio from this era, and I am discovering that even though I have a schematic some of the inner workings are a mystery.

:
:Starting with the power supply... On one side is a transformer, I know how to check that out. Next to that is the rectifier tube, okay no problem... Next to that is a substantial box with two wires coming out of the bottom that is labled as a "choke" on the diagram I have. Is this a non polarized capacitor? What value would it have?
:
:Thanks in advance, I'll probably have more questions once I get the power supply working.
:
:Regards
:
:Alan
:
:

1/20/2007 6:53:13 PMDoug Criner

More: you can check the choke with an ohmmeter. It's typically around 1K or so. If it's not open, it's good.

If you decide to bring up the power supply on a variac, you'll need to cut in the set's choke to check the B+ - or else hook up a dynamic speaker's field coil.

:Alan, here's the schematic:
:http://www.nostalgiaair.org/PagesByModel/319/M0039319.pdf
:
:A choke is a coil used to help filter out out pulses on the DC. Looks kind of like a transformer, but has just two leads.
:
:The schematic shows that the choke is there if a PM speaker is used. The choke is cut out of the ckt if a dynamic speaker is used, in which case the speaker's field winding is connected instead of the choke.
:
:The power supply might be OK. I would try bringing it up very slowly with a variac while watching current into the xfmr and the AC + DC voltages on the secondary side.
:
:
::I'm starting the process of bringing a Grebe AC-6 back to life. This is my first radio from this era, and I am discovering that even though I have a schematic some of the inner workings are a mystery.
:
:
:
:
::
::Starting with the power supply... On one side is a transformer, I know how to check that out. Next to that is the rectifier tube, okay no problem... Next to that is a substantial box with two wires coming out of the bottom that is labled as a "choke" on the diagram I have. Is this a non polarized capacitor? What value would it have?
::
::Thanks in advance, I'll probably have more questions once I get the power supply working.
::
::Regards
::
::Alan
::
::

1/20/2007 8:12:33 PMW8VCK

Thanks Doug! I already have the schematic.

Wow that's a big choke!

I had some wiring that was in pretty bad shape that had to be replaced or covered with heat shrink, and it was pretty filthy in there, tomorrow I'll start with the variac. The variable capacitors in the tuning section will probably need to be taken apart and cleaned yet.

I'm guessing that the capacitors in the power supply are plates suspended in tar or something along those lines so they will probably last forever?

Thanks Again

Alan

:Alan, here's the schematic:
:http://www.nostalgiaair.org/PagesByModel/319/M0039319.pdf
:
:A choke is a coil used to help filter out out pulses on the DC. Looks kind of like a transformer, but has just two leads.
:
:The schematic shows that the choke is there if a PM speaker is used. The choke is cut out of the ckt if a dynamic speaker is used, in which case the speaker's field winding is connected instead of the choke.
:
:The power supply might be OK. I would try bringing it up very slowly with a variac while watching current into the xfmr and the AC + DC voltages on the secondary side.
:
:
::I'm starting the process of bringing a Grebe AC-6 back to life. This is my first radio from this era, and I am discovering that even though I have a schematic some of the inner workings are a mystery.
:
:
:
:
::
::Starting with the power supply... On one side is a transformer, I know how to check that out. Next to that is the rectifier tube, okay no problem... Next to that is a substantial box with two wires coming out of the bottom that is labled as a "choke" on the diagram I have. Is this a non polarized capacitor? What value would it have?
::
::Thanks in advance, I'll probably have more questions once I get the power supply working.
::
::Regards
::
::Alan
::
::

1/20/2007 8:57:17 PMDoug Criner

Alan: Not actually "plates suspended in tar," I suspect. Probably paper-dielectric caps, but maybe OK. I'm going by what Atwater Kent did with AC sets. (My Grebe experience is with the battery-powered MU-1.)

:
:I'm guessing that the capacitors in the power supply are plates suspended in tar or something along those lines so they will probably last forever?
:
:Thanks Again
:
:Alan
:
::Alan, here's the schematic:
::http://www.nostalgiaair.org/PagesByModel/319/M0039319.pdf
::
::A choke is a coil used to help filter out out pulses on the DC. Looks kind of like a transformer, but has just two leads.
::
::The schematic shows that the choke is there if a PM speaker is used. The choke is cut out of the ckt if a dynamic speaker is used, in which case the speaker's field winding is connected instead of the choke.
::
::The power supply might be OK. I would try bringing it up very slowly with a variac while watching current into the xfmr and the AC + DC voltages on the secondary side.
::
::
:::I'm starting the process of bringing a Grebe AC-6 back to life. This is my first radio from this era, and I am discovering that even though I have a schematic some of the inner workings are a mystery.
::
::
::
::
:::
:::Starting with the power supply... On one side is a transformer, I know how to check that out. Next to that is the rectifier tube, okay no problem... Next to that is a substantial box with two wires coming out of the bottom that is labled as a "choke" on the diagram I have. Is this a non polarized capacitor? What value would it have?
:::
:::Thanks in advance, I'll probably have more questions once I get the power supply working.
:::
:::Regards
:::
:::Alan
:::
:::

1/21/2007 4:47:41 PMMarv nuce

Alan/Doug,
I found that the power supply filter types in cans are larger paper/foil construction, and most often wrapped in thin cardboard, whether there are one or more in the can. The can is then filled with pitch/tar, and a cover with holes or terminals secured on the bottom. Interstage coupling types are smaller and of paper foil construction. Sometimes wrapped with thin cardboard, but usually the can filler is bee's wax, and a secured cover with holes or terminals. Most times the can is lined on 4 sides and top with thin cardboard, and if access can be gained to this interface, the whole assembly can be removed.

marv

:Alan: Not actually "plates suspended in tar," I suspect. Probably paper-dielectric caps, but maybe OK. I'm going by what Atwater Kent did with AC sets. (My Grebe experience is with the battery-powered MU-1.)
:
::
::I'm guessing that the capacitors in the power supply are plates suspended in tar or something along those lines so they will probably last forever?
::
::Thanks Again
::
::Alan
::
:::Alan, here's the schematic:
:::http://www.nostalgiaair.org/PagesByModel/319/M0039319.pdf
:::
:::A choke is a coil used to help filter out out pulses on the DC. Looks kind of like a transformer, but has just two leads.
:::
:::The schematic shows that the choke is there if a PM speaker is used. The choke is cut out of the ckt if a dynamic speaker is used, in which case the speaker's field winding is connected instead of the choke.
:::
:::The power supply might be OK. I would try bringing it up very slowly with a variac while watching current into the xfmr and the AC + DC voltages on the secondary side.
:::
:::
::::I'm starting the process of bringing a Grebe AC-6 back to life. This is my first radio from this era, and I am discovering that even though I have a schematic some of the inner workings are a mystery.
:::
:::
:::
:::
::::
::::Starting with the power supply... On one side is a transformer, I know how to check that out. Next to that is the rectifier tube, okay no problem... Next to that is a substantial box with two wires coming out of the bottom that is labled as a "choke" on the diagram I have. Is this a non polarized capacitor? What value would it have?
::::
::::Thanks in advance, I'll probably have more questions once I get the power supply working.
::::
::::Regards
::::
::::Alan
::::
::::