Hello All...

I am starting on my first mechanical restoration. It is an Emerson Model 811. Using my dim bulb tester with a 15 watt bulb, the bulb lights up brightly then dims as the radio emits a loud humm. I only left it on for about 15 seconds.

This is the first time I've attempted to repair any electrics in a tube radio. All of my other radios were aquired in working condition, so my experience is in cleaning/restoring cabinets, cleaning chassis, switches, and replacing any tubes that either didn't light up or glowed purple.

I've got a multitester but have not used it yet. Would like to replace the capacitors in this 811, but wonder if the symptom I've described may be related to power supply/transformer. Forgive me if this is an obvious problem.

Tube lineup: 35W4, 12BE6, 12BA6, 12AV6, 5OC5
All tubes are Emerson. I do not believe that any work has ever been done on this radio.

Thanks for any help or info.

Chas

Chas: when you first turn on the radio, the filaments are cold, and there is a current surge. This could cause the brief brightness of the dim bulb.

The hum is likely caused by bad filter caps between the rectifier and the B+ supplies. Replacement of the electrolytic caps should be standard procedure.

Yours is an AC/DC set, without a power transformer. The primary purpose of using a dim-bulb tester is to check for shorts that could blow the transformer, which you don't have.

Doug-

Thanks for the reply. I can get replacement caps and a schematic from "JustRadios" so I will proceed with that.
As I said, this is my first attempt at recapping, and I know to be careful of the hot chassis in the AC/DC set.
When I looked at the chassis I wasn't sure if it had a transformer as it has a part mounted by the speaker, with wires going in the speaker that looks like a transformer.
I had better wait until I get the schematic to do much else.
The case cleaned up beautifully-was able to restore the dial numbers and "EMERSON" lettering with gold paint. Got out all the stains and scuffs, and the tuning knob and on/off-volume knob cleaned up nicely as well.

Thanks Again-
Chas

The xfmr near the speaker is the audio output transformer. It matches the impedance of the audio tube's output to the speaker. Not to be confused with an AC power xfmr, which your set doesn't have. Your set has all the filaments in series to equal the line voltage. The high voltage B+ plate supply is just rectified 120-V AC. This will produce a B+ of about 150V DC - less than an AC set but still quite enough to hurt.

For shock protection on an AC/DC set, it's best to use an isolation transformer to power the set while on the bench. This will protect against 120-V line-to-ground shocks, but not against getting across 120-V line to line or B+.

:Doug-
:
:Thanks for the reply. I can get replacement caps and a schematic from "JustRadios" so I will proceed with that.
:As I said, this is my first attempt at recapping, and I know to be careful of the hot chassis in the AC/DC set.
:When I looked at the chassis I wasn't sure if it had a transformer as it has a part mounted by the speaker, with wires going in the speaker that looks like a transformer.
:I had better wait until I get the schematic to do much else.
:The case cleaned up beautifully-was able to restore the dial numbers and "EMERSON" lettering with gold paint. Got out all the stains and scuffs, and the tuning knob and on/off-volume knob cleaned up nicely as well.
:
:Thanks Again-
:Chas

Hi Chas,

There is a schematic for an Emerson 811B at http://techpreservation.dyndns.org/schematics/Emerson.htm The file is in djvu format.

Radiodoc

Radiodoc:

Thanks for the link. Sadly I don't have the software to view djvu files-I checked the manufacturer of that program and they don't have anything for Mac OS9 users.
Good news-I can order the schematic when I order the caps. I've given the chassis a good cleaning and was surprised to see the underside is more like a printed circuit board. Instead of wires there are solder(?) bead lines. The capacitors go through the chassis board and are soldered to the "beads". Is there a special solder I should use for this, or any special technique to use when replacing the caps? This is my first attempt at cap replacement and I was hoping this little Emerson would be a good model for a beginner.

Thanks Much,

Chas

Chas: a printed ckt board is not particularly good news. A PCB is more difficult to work with than point-to-point wiring.

I would replace the electrolytic filter caps, and then see how the radio plays. If you're satisfied, I'd go no further.

Removing film caps from a printed ckt board will require use of desoldering braid (available at RadioShack?). Suck up as much solder as you can, and then melt the joint, and try wiggling out the cap by pulling with needle-nose pliers.

Another approach is to snip the cap off the PCB, and try to splice a replacement cap onto the original leads or solder pad.

A risk is damaging the traces on the printed ckt board. It's best to use a relatively low-wattage soldering iron, say 25W.

With older solder you may want to keep the iron wattage up around 30 or 40 watts. Old style solder is often a different mixture of tin and lead, and has a higher melting point.

Don't be frightened with the printed circuit board. Since most modern equipment uses this wiring technique, most modern components including those made for old radios (high voltage electrolytics) are circuit board friendly. You should have no trouble soldering new electrolytics to that board. They're usually more compact than old components, making it easier to find a way to make them fit correctly.

Thomas

:With older solder you may want to keep the iron wattage up around 30 or 40 watts. Old style solder is often a different mixture of tin and lead, and has a higher melting point.
:
:Don't be frightened with the printed circuit board. Since most modern equipment uses this wiring technique, most modern components including those made for old radios (high voltage electrolytics) are circuit board friendly. You should have no trouble soldering new electrolytics to that board. They're usually more compact than old components, making it easier to find a way to make them fit correctly.
:
:Thomas

Thomas, Doug, Radiodoc-

Thank you for the encouragement.

Chas

Hi Chas,
Post an email address and I'll send the SAMS Set 274 Folder 8. And to anyone else who wants it to help you. From the date (1955) I'm surprised the board isn't cooked and cracked already. The slightest work on them or at least for me ends in a broken mess a lot. Material very brittle.

Bill VA

Hello All...
:
:I am starting on my first mechanical restoration. It is an Emerson Model 811. Using my dim bulb tester with a 15 watt bulb, the bulb lights up brightly then dims as the radio emits a loud humm. I only left it on for about 15 seconds.
:
:This is the first time I've attempted to repair any electrics in a tube radio. All of my other radios were aquired in working condition, so my experience is in cleaning/restoring cabinets, cleaning chassis, switches, and replacing any tubes that either didn't light up or glowed purple.
:
:I've got a multitester but have not used it yet. Would like to replace the capacitors in this 811, but wonder if the symptom I've described may be related to power supply/transformer. Forgive me if this is an obvious problem.
:
:Tube lineup: 35W4, 12BE6, 12BA6, 12AV6, 5OC5
:All tubes are Emerson. I do not believe that any work has ever been done on this radio.
:
:Thanks for any help or info.
:
:Chas

:Hi Chas,
:Post an email address and I'll send the SAMS Set 274 Folder 8. And to anyone else who wants it to help you. From the date (1955) I'm surprised the board isn't cooked and cracked already. The slightest work on them or at least for me ends in a broken mess a lot. Material very brittle.
:
:Bill VA
:
Bill:

My email is chas054@earthlink.net. Thanks very much for the info. I'll be careful!

Chas

SAMS Data sent.
Bill VA

::Hi Chas,
::Post an email address and I'll send the SAMS Set 274 Folder 8. And to anyone else who wants it to help you. From the date (1955) I'm surprised the board isn't cooked and cracked already. The slightest work on them or at least for me ends in a broken mess a lot. Material very brittle.
::
::Bill VA
::
:Bill:
:
:My email is chas054@earthlink.net. Thanks very much for the info. I'll be careful!
:
:Chas