I just acquired a Mars Thunderbird Mobile Tansmitter that uses a pari of
6AQ5 tubes and a 12AU7. The 12AU7 is the oscillator/Amp and one of the
6AQ5's is the PA. The other 6AQ5 is the AM modulator. This is a very nice
Japanese made radio from the early 60's designed for mobile use.

It looks like it is all there but I need a schematic to get in on the air
again after all these years, especially the pin out of the connector on the
back for the power supply and control.

If you happen to have one of these nice little radios I sure could use some
information from you.

Steve NU0P

Hi,
The Mars Thunderbird was reviewed in March 1960 QST.

73,
Ed Knobloch

Steve NU0P wrote:
I just acquired a Mars Thunderbird Mobile Tansmitter that uses a pari of
6AQ5 tubes and a 12AU7. The 12AU7 is the oscillator/Amp and one of the
6AQ5's is the PA. The other 6AQ5 is the AM modulator. This is a very nice
Japanese made radio from the early 60's designed for mobile use.

Ed

Thanks for the information but unfortunately my library of QST goes back to
1990 only, will have to ask around to see if anyone has that but as I recall
QST did not publish any schematics usually.

Steve


"Edward Knobloch" wrote in message
news:OMtcf.23445$w_6.17319@trndny09...
Hi,
The Mars Thunderbird was reviewed in March 1960 QST.

73,
Ed Knobloch

Steve NU0P wrote:
I just acquired a Mars Thunderbird Mobile Tansmitter that uses a pari of
6AQ5 tubes and a 12AU7. The 12AU7 is the oscillator/Amp and one of the
6AQ5's is the PA. The other 6AQ5 is the AM modulator. This is a very
nice Japanese made radio from the early 60's designed for mobile use.

"Steve NU0P" ) writes:
Ed

Thanks for the information but unfortunately my library of QST goes back to
1990 only, will have to ask around to see if anyone has that but as I recall
QST did not publish any schematics usually.

Steve

It depends. If the rig was simple enough, they might. And it was
pretty normal for them to show snippets of the schematic, because there
was something different about that bit of the circuit, and they wanted to
talk about it. It's only in recent years that they dropped the any schematics
from the reviews.

Given the description, I can't imagine the rig being particularly unusual.
Look in old handbooks to find rigs with that tube arrangement, and you've
got something close, which can be used to visualize the rig and use
as a start for tracing the schematic or troubleshooting.

Michael VE2BVW


"Edward Knobloch" wrote in message
news:OMtcf.23445$w_6.17319@trndny09...
Hi,
The Mars Thunderbird was reviewed in March 1960 QST.

73,
Ed Knobloch

Steve NU0P wrote:
I just acquired a Mars Thunderbird Mobile Tansmitter that uses a pari of
6AQ5 tubes and a 12AU7. The 12AU7 is the oscillator/Amp and one of the
6AQ5's is the PA. The other 6AQ5 is the AM modulator. This is a very
nice Japanese made radio from the early 60's designed for mobile use.

Hi, Steve

You're right, the QST article has no schematic.
I just thought the review would be interesting reading for you.

The rig requires 6 or 12V for the heaters,
and 250VDC for the plate supply.
The 6AQ5 modulator is designed for a carbon mic.

Ed

Steve NU0P wrote:
Ed

Thanks for the information but unfortunately my library of QST goes back to
1990 only, will have to ask around to see if anyone has that but as I recall
QST did not publish any schematics usually.

Steve


"Edward Knobloch" wrote in message
news:OMtcf.23445$w_6.17319@trndny09...

Hi,
The Mars Thunderbird was reviewed in March 1960 QST.

73,
Ed Knobloch

Thanks Ed for letting me know the plate voltage. I have been using it with
a Heath PS23 and using the low voltage feed and as it turns out it is 250vdc
but it is good to veryify that was the designed B+.

I have looked through a quite a few handbooks and a Google search but no
luck finding anything like this yet. So will keep pluging.

It does have a few problems......1.) The tuned output from the buffer does
not respond on 80 meters like it should. I can not get the coil to resonate
like it should on 80 but it works fine on 40......2.) The antenna loading
tuning capacitor has no effect at all...just like it is not there or
something but it is wired in and not shorted...So this has me stumped...The
plate loading cap works but when rotating it I get a peak in the power
output but no dip in the plate current...How can this be???

I did find a bad tube socket in the oscillator (12AU7) and have replaced
that now and it doesn't get intermmitant any more so there is some progress.
Any ideas from anyone as to why the Antenna Load Control has no effect and
how I can get a peak in power output with a dip in the plate current??

Steve NU0P


"Edward Knobloch" wrote in message
news:FxKcf.8566$SV1.1636@trndny01...
Hi, Steve

You're right, the QST article has no schematic.
I just thought the review would be interesting reading for you.

The rig requires 6 or 12V for the heaters,
and 250VDC for the plate supply.
The 6AQ5 modulator is designed for a carbon mic.

Ed

Steve NU0P wrote:
Ed

Thanks for the information but unfortunately my library of QST goes back
to 1990 only, will have to ask around to see if anyone has that but as I
recall QST did not publish any schematics usually.

Steve


"Edward Knobloch" wrote in message
news:OMtcf.23445$w_6.17319@trndny09...

Hi,
The Mars Thunderbird was reviewed in March 1960 QST.

73,
Ed Knobloch

Hi

If you're getting output without a good plate dip,
it may be that the rig is taking off at a parasitic frequency.
(outside the range of the grid or plate tank circuits).
Is the "peak" in power output kind of "twitchy"?
(Meaning that a slight change in plate tuning makes for a big
change in rf output, which shouldn't be the case on 80 or 40m).
This could be another sign of a spur,
like the final either oscillates or doesn't oscillate
depending on the setting of the tuning capacitor.

I doubt that the simple rig has a neutralization circuit,
so the final depends on getting drive at the correct frequency
to avoid taking off.

Have you a grid dipper to check the tank circuits?

Another thing to check is on the tuning/loading capacitors -
there is a spring metal wiper that is fixed to the frame
of the variable capacitor and touches the shaft of the rotor.
The wiper may need a drop of electronics cleaner
to break loose some debris and make a good contact
with the shaft.

Regards,
Ed

Steve NU0P wrote:
Thanks Ed for letting me know the plate voltage. I have been using it with
a Heath PS23 and using the low voltage feed and as it turns out it is 250vdc
but it is good to veryify that was the designed B+.

I have looked through a quite a few handbooks and a Google search but no
luck finding anything like this yet. So will keep pluging.

It does have a few problems......1.) The tuned output from the buffer does
not respond on 80 meters like it should. I can not get the coil to resonate
like it should on 80 but it works fine on 40......2.) The antenna loading
tuning capacitor has no effect at all...just like it is not there or
something but it is wired in and not shorted...So this has me stumped...The
plate loading cap works but when rotating it I get a peak in the power
output but no dip in the plate current...How can this be???

I did find a bad tube socket in the oscillator (12AU7) and have replaced
that now and it doesn't get intermmitant any more so there is some progress.
Any ideas from anyone as to why the Antenna Load Control has no effect and
how I can get a peak in power output with a dip in the plate current??

Steve NU0P


"Edward Knobloch" wrote in message
news:FxKcf.8566$SV1.1636@trndny01...

Hi, Steve

You're right, the QST article has no schematic.
I just thought the review would be interesting reading for you.

The rig requires 6 or 12V for the heaters,
and 250VDC for the plate supply.
The 6AQ5 modulator is designed for a carbon mic.

Ed