hello
I also have a g222 tr first generation ,that has no problem for now...(I
touch my wooden head!!)
It seems that you have an excessive dissipation of your 6146.
What is the current of plate?
Check the vfo,does if give enought power,does the small variable condenser
at its output work?
Do you have enought excitation on the grid?
What is the voltage of the G2 of the 6146?
On the first version of the transmitter it is provided by a small separate
transformer and power supply,this small power supply is used for the vfo
,the two first tubes on the modulator and the G2 of the 6146 .Also change
this rectifier (tubular one,black) I did the same modifications than you
:replaced chimical condensers and rectifiers,for the rectifiers I used small
'bridges 'with 1N4007.
I am not a specialist of those machines...it is just the first tx I knew 45
years ago at my grand father's station...
it is just some ideas.
Also a way to save your pa tubes until you find the problem would be to
decrease the hv ,so decrease the plate dissipation ,I have used a variac to
underpower the transformer,not standard but it helped me.
73 F1GQB
It is my turn to ask a question ,I also have a geloso g209 receiver that has
some problems:from times to times one of two second lo stops (the one used
on am,and usb,the one used in lsb works),it seems a thermal problem,I used
antioxidation produtcs,I reshaped the contacts,I resoldered everything,It
continues,
what can it be????



--
Alain Nierveze
www.radio-astronomie.com

a écrit dans le message de news:
...
Hi all,

I'm repairing an old Geloso G.222 TR transmitter for a friend (this is the
first version, I understand there were two issues from the schematics I've
found on the net).

First of all, this set has been modified with two relays for
transmit/receive
antenna changeover and HV switching. I don't know if this mod was common
back
in the days or not.
Repair so far consisted in using silicon rectifiers in place of original
selenium bridges (all were leaky), changing almost all electrolytics
(almost
all were too leaky and couldn't be reformed, so I also changed the only
two
ones that seemed to start reforming with voltage applied). I replaced all
resistors that had drifted more than 20% in value and replaced the
resistor
inside the 6164's plate suppressor (original 33 ohm resistor was broken,
replace with 47 ohm 2W carbon composition as I didn't happen to have
a suitable 33 ohm one), finally replaced the 6146 final tube that was dead
(getter was white despite no apparent external damage in the glass
envelope).
Replacement was a NOS W8289.

First thing I noticed (my usual experience with tube finals are more
modern
Yaesu and Kenwood hybdrids) is that the 6146 has no bias setting point, so
I'm a bit puzzled about how it is supposed to work without burning.

I found in the technical bullettin n.83 the schematic and alignment
instructions. The first thing I noticed is the G1 of 6146 is supposed
to be at -85V in CW tx. How is that possible since the only negative
supply in this transmitter is -50V? I infact measured -50V when in CW
mode,
but I didn't key the transmitter as the 8289 died before I could try.

When I started the first TX experiments, I tried on 80m band AM mode, with
50 ohm 500W bird dummy load connected at the antenna socket. I could
obtain
50W out with plate capacitor around middle position and loading capacitor
fully meshed. That was with no modulation, carrier only, so far so good.
I tried on 40m band and power was much less, and 8289 started to show
signs
of red spots on the plate. On the higher bands, problem much worse, almost
no
power and 8289 plate glowing soon after going into TX, no tuning of the
plate
capacitor seemed to help.
These tests, even if short, killed the 8289 which cracked the glass under
the
plate cap... I think it was a marginal tube, because I didn't allow the
tube
to remain in TX as soon as the plate was starting to glow red.

Relay contacts were cleaned and contact resistance checked before the
tests.
The Pi coil is rather oxidized (it is not silver plated, so copper oxide
grew
on it), I tried to clean it the best I could. Is there any way to test if
the coil is still good enough?

Grid bias of the 6146 in AM mode appear to be 0V + vfo driver (about 100V
pp),
is this correct? As I said, I've never seen a 6146 with no negative grid
bias
anywhere else. Grid bias in CW mode is -50V but I never tried keying as
the 8289 was already dead when I was checking this.
Now I'm shopping for another 6146, can the 6146B work in this
transmitters?
I have several used 6146B as they're common in Yaesu and Kenwood
transmitters,
but no plain 6146 or 6146A.

Any other hint is welcome! I'd like to hear from G.222 experts if any :-)

Best 73 and season greetings

Frank IZ8DWF