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

wrote:
Replacement was a NOS W8289.

of course it is W8298 (non A).

Frank IZ8DWF

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

nierveze wrote:
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?

unfortunately I didn't pay attention to the value as I was paying attention
on the plate colour and other sign of problem, like smoke somewhere. It was
on the very first TX tests and the final tube lasted too short a time.

Check the vfo,does if give enought power,does the small variable condenser
at its output work?

yes the driver tuning condenser work, but what's "enough" output?
I can measure the RF voltage at the grid of the 6146 but how can I tell
what is supposed to be the right drive voltage?

Do you have enought excitation on the grid?

on the service information I haven't seen any indication on what's enough
excitation voltage. I'll try to realign the VFO again for maximum output on
all bands


What is the voltage of the G2 of the 6146?

it's 210V at no load
Can you check what DC voltage you have on the 6146 G1 when TX in AM mode?
Can you confirm G1 bias is -50V in CW mode?

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.

yes, I also used 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.

well yes, good suggestion. I didn't expect the tube to die so quickly. I
once repaired an old Yaesu FT-101E that had a failure in the 6JS6C grid bias
circuit and basicly it had no negative bias on control grid, so as soon as the
heather was switched on, the tubes would start drawing a large amount of
current and the plates were glowing bright red. I of course switched off
the set as soon as I saw the plates glowing but I think the owner didn't
realize wath was going on since most of the wires around the power transformer
were carbonized. It's amazing that the power transformer itself survived
and what was amazing too is that those tubes still were putting 50-60% of
their rated output power after the problem was fixed and many wires were
changed.

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????

if it has two separate xtals for USB and LSB, check the xtal socket and
the tuning of the oscillator. Try gently moving the USB xtal and see if
RX come back again.

Thanks and 73
Frank IZ8DWF

hello again Frank,
as there is no indication in the documentation of what is the normal output
power of the vfo,maybe it would be useful to use new 6cl6 and 5763,also an
indication of grid excitation is useful,on my set the excitation
potentiometer is about 1/4 turn to get the 3.5 ma required on 80M
with the driver tuning condenser correctly tuned,this can be checked in
RECEIVE position of the transmit/receive switch(but this has maybe been
modified in your set
) AND the am/vfo-beat/cw switch in vfo-beat:this powers up only the vfo,not
the
pa ,this is used to tune the tx to the rx frequency(heterodyne).In this
condition you can get an indication of the excitation,without using the
pa,you should not have hv
so no risk for the pa tube,but I am just wondering
what are exactly the modifications don on your tx...
-why not try to put it back in its original condition by removing all those
relays
Hope this helps
73 alain F1gqb
thanks for your suggestions for the rx,I already dit it :-(((


--
Alain Nierveze
www.radio-astronomie.com

a écrit dans le message de news:
...
nierveze wrote:
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?

unfortunately I didn't pay attention to the value as I was paying
attention
on the plate colour and other sign of problem, like smoke somewhere. It
was
on the very first TX tests and the final tube lasted too short a time.

Check the vfo,does if give enought power,does the small variable
condenser
at its output work?

yes the driver tuning condenser work, but what's "enough" output?
I can measure the RF voltage at the grid of the 6146 but how can I tell
what is supposed to be the right drive voltage?

Do you have enought excitation on the grid?

on the service information I haven't seen any indication on what's enough
excitation voltage. I'll try to realign the VFO again for maximum output
on
all bands


What is the voltage of the G2 of the 6146?

it's 210V at no load
Can you check what DC voltage you have on the 6146 G1 when TX in AM mode?
Can you confirm G1 bias is -50V in CW mode?

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.

yes, I also used 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.

well yes, good suggestion. I didn't expect the tube to die so quickly. I
once repaired an old Yaesu FT-101E that had a failure in the 6JS6C grid
bias
circuit and basicly it had no negative bias on control grid, so as soon as
the
heather was switched on, the tubes would start drawing a large amount of
current and the plates were glowing bright red. I of course switched off
the set as soon as I saw the plates glowing but I think the owner didn't
realize wath was going on since most of the wires around the power
transformer
were carbonized. It's amazing that the power transformer itself survived
and what was amazing too is that those tubes still were putting 50-60% of
their rated output power after the problem was fixed and many wires were
changed.

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????

if it has two separate xtals for USB and LSB, check the xtal socket and
the tuning of the oscillator. Try gently moving the USB xtal and see if
RX come back again.

Thanks and 73
Frank IZ8DWF

Edmund H. Ramm wrote:

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.

Those -50V you measured are the protective bias. When excited, the
resulting grid current will add to the protective bias.

ah that's why... It's working in C class with G1 current! I would never
expect an AM TX final amplifier to work in something else than A or B class.
Thanks for the hint. Do you know if this protective bias should be present
also when the G.222 is operated in AM position?

Tnx,
73 Frank IZ8DWF

nierveze wrote:
hello again Frank,
as there is no indication in the documentation of what is the normal
output
power of the vfo,maybe it would be useful to use new 6cl6 and 5763,also an
indication of grid excitation is useful,on my set the excitation
potentiometer is about 1/4 turn to get the 3.5 ma required on 80M
with the driver tuning condenser correctly tuned,this can be checked in
RECEIVE position of the transmit/receive switch(but this has maybe been
modified in your set

I see I have VFO output when the switch is on the VFO-BEAT position but the
output to the grid of the 6146 is smaller than that I can measure in AM
position. I need to check from the schematic if this is correct.

) AND the am/vfo-beat/cw switch in vfo-beat:this powers up only the vfo,not
the
pa ,this is used to tune the tx to the rx frequency(heterodyne).In this
condition you can get an indication of the excitation,without using the
pa,you should not have hv
so no risk for the pa tube,but I am just wondering
what are exactly the modifications don on your tx...
-why not try to put it back in its original condition by removing all those
relays

this isn't possible, the original T/R switch is missing, at its place there is
an on/off switch that just energize the two added relays. The DC for the
relays has been obtained with a doubling rectifier on the 6.3V AC heather
supply.

Hope this helps
73 alain F1gqb
thanks for your suggestions for the rx,I already dit it :-(((


Thanks
Frank IZ8DWF

Edmund H. Ramm wrote:

Those -50V you measured are the protective bias. When excited, the
resulting grid current will add to the protective bias.

ah that's why... It's working in C class with G1 current! I would never
expect an AM TX final amplifier to work in something else than A or B class.

Why, it doesn't need to be linear, unlike concepts where modulation is
applied at some earlier stage.

indeed this is correct, the modulation is applied to the final amplifier,
so it can work in class C, thanks again for explaining.


Thanks for the hint. Do you know if this protective bias should be present
also when the G.222 is operated in AM position?

Not off hand, would need to dig out the circuit diagram. It's ages
since I layed hands on a G.222TR. And I operate CW only. Maybe I'm
missing something when I see no advantage in using no protective bias
in AM mode.

here you can find the schematic:

http://www.qsl.net/i0jx/222.gif

Probably since in AM mode there's always present the VFO drive, they thought
it would be enough to just trim the drive voltage while monitoring the grid
current to remain in the safe range. If this isn't the case, there must be
a bad contact in the mode switch because indeed in AM mode I don't measure
any protective bias on 6146's G1.

Do you see any reason not to use a 6146B as final tube? I have a few of these
but no 6146/6146A left.


Thanks again and 73
Frank IZ8DWF

Edmund H. Ramm wrote:

Lots of "ifs": If the mode switch shown in the diagram only has
the three positions AM - VFO Beat - CW, and if the switch's position
shown in the diagram is the AM position, then there is no protective
bias in AM mode, indeed.

ok, that's what it seems to me too (the circuit drawing isn't also very
easy to follow sometimes), and that's what I can measure on the real
thing.


Do you know this urge to wring the designer's neck until he discloses
what drugs he was on when he designed this circuit?

Other transmitters use at least a kind of brute force circuit to pull
down the PA valve's screen grid voltage with no exitation present, in
order to keep the anode dissipation low enough.

I agree, if you don't monitor the G1 current in AM mode, the 6146 will
not survive for long time.

By the way, I ordered a new 6146, the PA has no neutralization circuit so
probably even the 6146B would work fine, but none of my used 6146B is in a
known state, so I would just add other unknowns if I'd try with them.

73
Frank IZ8DWF