With the Hammarlund HQ120 that I recently purchased, If been having a great time DXing on all the bands and learning the in's and out's of this particular Vintage radio operation. However, yesterday I lost my OD3 tube. While working, I noticed that it put off a what appeared to be... ultraviolet or bluish colored light, and about mid-day the radio quit working. Wondering what might have went out, I let the radio return to room temp and later turned it back on with the top lid opened a couple inches to view the bulbs in operation. From what I could see, they all lit except the OD3 tube which I initally noticed because of the color, so I asume that is the cause of inoperability. I got online and bought a tube kit which included a complete HQ120 tube-set. I have no idea of course as to the lifespan of the old 'original' ....OD3 tube and if it's 'is' original or has been replaced sometime in the life of this radio.

Back to the title of this post.... should one operate the HQ with the lid opened for cooling or add additional fan cooling from an outside source? Also I was operating this in an enclosed cabinet with sides, top and back, with about 8-10" of open space all around the radio? The inside temp of the room was probably 60 or so degrees, so it was typical cool fall weather. SHOULD I also cool and have the hood open? and should it be in a more open environment? Thanks......... Plotus AKA Richard...

On 11/26/2010 9:48 AM, Plotus wrote:
snip However, yesterday I lost my
OD3 tube. While working, I noticed that it put off a what appeared to
be... ultraviolet or bluish colored light, and about mid-day the radio
quit working. Wondering what might have went out, I let the radio return
to room temp and later turned it back on with the top lid opened a
couple inches to view the bulbs in operation. From what I could see,
they all lit except the OD3 tube which I initally noticed because of the
color, so I asume that is the cause of inoperability. snip

Hi,
An 0D3 tube normally glows blue or pink when operating.
It is a gas-filled voltage regulator,
and operates like a 150V Zener diode.
The fact that the 0D3 is now dark and your radio has stopped working
indicates that you have lost the dc supply in your HQ-120.
I'd look carefully at the electrolytics in your power supply,
one may have developed a short.

73,
Ed Knobloch

On Nov 26, 9:31*am, Edward Knobloch wrote:
On 11/26/2010 9:48 AM, Plotus wrote:

snip *However, yesterday I lost my
OD3 tube. While working, I noticed that it put off a what appeared to
be... ultraviolet or bluish colored light, and about mid-day the radio
quit working. Wondering what might have went out, I let the radio return
to room temp and later turned it back on with the top lid opened a
couple inches to view the bulbs in operation. From what I could see,
they all lit except the OD3 tube which I initally noticed because of the
color, so I asume that is the cause of inoperability. snip

Hi,
An 0D3 tube normally glows blue or pink when operating.
It is a gas-filled voltage regulator,
and operates like a 150V Zener diode.
The fact that the 0D3 is now dark and your radio has stopped working
indicates that you have lost the dc supply in your HQ-120.
I'd look carefully at the electrolytics in your power supply,
one may have developed a short.

73,
Ed Knobloch

My guess would be the the dropping resistor in series with the 0D3.
The 0D3 probably supplies the oscillator and possible the bfo tubes.
So, they won't work and you won't receive anything. However, you
should be able to still get some sound from the audio stages.

The other possibility is the rectifier died and then you will not have
any audio output and the 0D3 will not light. Look for the heater in
the rectifier, 5Y3?, should be glowing.

If you detect a bad smell, then it is more serious!

Paul, KD7HB

I did have a distinct acrid odd smell, no smoke was discernable and the radio still powers up but will not tune in any band. The on/off/audio gain switch turns on the radio of course and the ever present low decible hum is present. Thanks for the tips and info guys.

I have found a semi-local (75 miles away) restoration/repair shop David De Betta in Pineville NC. I'll be contacting him this morning hopefully to schedule a repair. At this juncture of my novice knowledge, I believe it would be prudent................lol 'GW bush' lol, again thanks.

Plotus wrote:

With the Hammarlund HQ120 that I recently purchased, If been having a
great time DXing on all the bands and learning the in's and out's of
this particular Vintage radio operation. However, yesterday I lost my
OD3 tube. While working, I noticed that it put off a what appeared to
be... ultraviolet or bluish colored light, and about mid-day the radio
quit working.

The OD3 is a cold-cathode regulator tube. It's supposed to be glowing
with a blue light, that is how you know it is working. You can tell it
is a cold-cathode tube since the first number is a zero, indicating it
has no filament.

Wondering what might have went out, I let the radio return
to room temp and later turned it back on with the top lid opened a
couple inches to view the bulbs in operation. From what I could see,
they all lit except the OD3 tube which I initally noticed because of the
color, so I asume that is the cause of inoperability.

No, it's a symptom that you have no high voltage going into the OD3,
either because it's not coming out of the transformer or because there
is a rectifier or droppin resistor gone bad.

I got online and
bought a tube kit which included a complete HQ120 tube-set. I have no
idea of course as to the lifespan of the old 'original' ....OD3 tube and
if it's 'is' original or has been replaced sometime in the life of this
radio.

It's fine, there's probably nothing wrong with and there's probably nothing
wrong with any of the other tubes either. Heat the thing up, pull the
bottom of the case, and get out the meter. Work back from the OD3 plate
pin to the plug and see where the voltage drops.

Back to the title of this post.... should one operate the HQ with the
lid opened for cooling or add additional fan cooling from an outside
source? Also I was operating this in an enclosed cabinet with sides, top
and back, with about 8-10" of open space all around the radio? The
inside temp of the room was probably 60 or so degrees, so it was typical
cool fall weather. SHOULD I also cool and have the hood open? and should
it be in a more open environment? Thanks.........

It won't hurt to keep it cooler and it might last longer, but if you run
it with the lid open, the RF performance will be degraded since you will
have defeated much of the shielding.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:


No, it's a symptom that you have no high voltage going into the OD3,
either because it's not coming out of the transformer or because there
is a rectifier or droppin resistor gone bad.

Another possibility would be something on the load side is pulling down
the B+. Short/partial short, etc.

-B.

The info on sheilding is good to know, I'll start with a replacement OD3, (I have two coming from an ebay supplier) and go from there since I have no test equiptment. If that fails, I'll look into the power supply issue. And probably contact the fella I spoke of above who works on tube radios.

Plotus wrote:
-B. The info on sheilding is good to know, I'll start with a replacement
OD3, (I have two coming from an ebay supplier) and go from there since I
have no test equiptment. If that fails, I'll look into the power supply
issue. And probably contact the fella I spoke of above who works on tube
radios.

There's nothing wrong with the OD3. Go buy a good multimeter..
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Fri, 26 Nov 2010 14:48:16 +0000, Plotus did
make me awaken from my chaotic existentialism when they didst announce:

snipped

My bet is you've got a shorted capacitor or another problem in the DC circuit.
After several mystery ailments, I re-capped my HQ-120X and all was well after a
re-alignment, never a problem since.

73


--
OldbieOne -
The guy who tells it like it is!

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