Converting a positive ground valve/tube car radio to negative ground ?
N_Cook
you still get right polarity for the anode supplies. Heaters presumably
happy enough powered the other way round but how to change the biasing of
the valves ?
Brenda Ann
"N_Cook" <div...@tcp.co.uk> wrote in message
news:g66s5p$lk4$1...@registered.motzarella.org...
Unless it's a synchronous vibrator, it should run equally well on either
polarity. The radio doesn't get anode voltage from the car's DC, it gets it
from the radio's DC-DC converter (vibrator, transformer, rectifier,
filtering).
N_Cook
news:0-edncDP6PrvZhvV...@giganews.com...
With positive ground you automaticly get a negative voltage for biasing but
what to do in the negative ground case ?
In this case its a synchronous mechanism but its easy enough to get inside
to rewire it for the opposite polarity, it is the biasing voltage I cannot
fathom out.
Brenda Ann
This must be an unusual radio (by old US car radio standards). No valve car
radio I have ever seen has used the car's battery supply for any voltage
other than the valve heaters. All DC voltages to run the valves come off the
output of the transformer, with bias voltages developed by raising the
cathode of the valve above B- (making the grid negative with respect to the
cathode, but not with respect to ground).
Ken
bias in a 6V pos gnd system, but it would only be -6V, not much. Easy to
get that off the xfmr center tap. Ken
N_Cook
This one also, on checking.
I had not realised that the 12V to the radio is just for the heaters and the
dial lamp and the on/off switch.
Just leaves whether there is an added RFI noise problem from the "inverter".
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
Dave Plowman (News)
No need if it's a mechanical vibrator. That produces AC...
--
*Procrastination is the art of keeping up with yesterday.
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
N_Cook
news:4fc3729...@davenoise.co.uk...
not this one - synchronous - see recent thread on Ekco CR280.
I had to rebuild the contacts to get it working. Needs smoothing yes,
because its chopped but not ac. Does not require a rectifier thermionic, Se
or Si. But feed it the wrong way and you get negative HT
John Byrns
"N_Cook" <div...@tcp.co.uk> wrote:
Why would the RFI issues change? If it is a synchronous vibrator, isn't
it simply a matter of reversing two transformer connections to convert
from positive ground to negative ground, how does this change affect RFI?
Regards,
John Byrns
--
Regards,
John Byrns
Surf my web pages at, http://fmamradios.com/
Ken
going to the vibrator. Ken
oldcoot
This was mentioned in the previous thread on
synchronous vibrators. To enable running on reverse supply polarity,
just reverse the two HV (HT) secondary leads that would normally go to
the anodes of a tube rectifier.
Bill(oc)
William Noble
few dozen), you could swap ground polarity and do nothing and it works.
Now, if you put in an SS vibrator, then it's a different story. Why are
you thinking yours is different?
"N_Cook" <div...@tcp.co.uk> wrote in message
news:g66s5p$lk4$1...@registered.motzarella.org...
** Posted from http://www.teranews.com **
Jim Mueller
sockets were symmetrical so that the vibrator could be plugged in two ways,
one for positive ground and the other for negative ground. If it isn't that
kind, then you will have to reverse the wiring as others have mentioned.
The reversible vibrators I have seen have + and - symbols on top to show
which way to install them.
--
Jim Mueller wron...@nospam.com
To get my real email address, replace wrongname with eportiz. Then replace
nospam with sacbeemail.
"N_Cook" <div...@tcp.co.uk> wrote in message
news:g66s5p$lk4$1...@registered.motzarella.org...
Dave Plowman (News)
> not this one - synchronous - see recent thread on Ekco CR280.
Can't seem to find that.
> I had to rebuild the contacts to get it working. Needs smoothing yes,
> because its chopped but not ac. Does not require a rectifier thermionic,
> Se or Si. But feed it the wrong way and you get negative HT
Right. Heard of them but never seen one.
Is this a UK market radio? It would be strange to produce a positive earth
only radio given that even in the UK not all makes went to positive earth.
--
*It's o.k. to laugh during sexŚ.Ś.just don't point!
N_Cook
news:BM6dnUMFbt-knxXV...@posted.dakotacomip...
This one has 2 polarising pins so one way round only. Changing round the 2,
12V supply leads is easier, the can is earthed but not connected internally
to the vibrator coil or contacts.
a circuit for a synchronous one ( no rectifier required) I've put on
http://www.diversed.fsnet.co.uk/vib2.gif
oldcoot
>
> This one has 2 polarising pins so one way round only. Changing round the 2,
> 12V supply leads is easier, the can is earthed but not connected internally
> to the vibrator coil or contacts.
> a circuit for a synchronous one ( no rectifier required) I've put onhttp://www.diversed.fsnet.co.uk/vib2.gif
>
synchronous-vibrator system I was referring to back in post # 11. But
exactly the same principle applies:
To enable running on reverse supply polarity, simply reverse (swap)
the two transformer secondary leads, i.e., the ones which have the
1500V buffer cap across them. Been there, done that. It works.
Bill(oc)
oldcoot
There appears to be an error in this schematic. Someone else may
confirm.
The armature should be connected to common negative. Instead, the line
from the armature is shown 'jumping over' the common negative line. As
shown, this is an open circuit with no DC return path. Make the
correction by tying the armature to common neg., and operation of the
circuit becomes self-explanatory.
John Byrns
"William Noble" <nob...@nowhere.com> wrote:
> aaah, this doesn't make sense - on every vibrator radio I ever used (only a
> few dozen), you could swap ground polarity and do nothing and it works.
> Now, if you put in an SS vibrator, then it's a different story. Why are
> you thinking yours is different?
Probably because it uses a synchronous vibrator to eliminate the need
for a rectifier tube.
nesesu
Um, it IS connected to common negative were the line comes down from
the armature terminal. From that point a line then goes to the bottom
end of the .1u input filter cap.
Neil S.
terry
> "N_Cook" <dive...@tcp.co.uk> wrote in message
>
> news:g66s5p$lk4$1...@registered.motzarella.org...
>
> > No user switchable option. I can see its possible to rewire the vibrator
> > so
> > you still get right polarity for the anode supplies. Heaters presumably
> > happy enough powered the other way round but how to change the biasing of
> > the valves ?
>
> polarity. The radio doesn't get anode voltage from the car's DC, it gets it
> from the radio's DC-DC converter (vibrator, transformer, rectifier,
> filtering).
Sounds right. But as not in this posting, do recall at least one 12
volt European car radio of the 1950s that had a polarity plug that had
to be placed in the correct position. But reading this now can't think
why that was necessary! Maybe they were synchronous vibrators or
something.
BTW not pertinent to this posting but have operate an item of 6 volt
DC w. vibrator gear by feeding in 6.3 volts AC from a radio, removing
the vibrator and strapping one half of the input winding of vibrator
transf. to the supply. So instead of alternatec pulses of DC to each
half of the CT input winding, we had 6.3v 60 hertz AC constantly to
half the winding.
Don't understand the biasing question?
oldcoot
Maybe the image I'm looking at is different than yours (if that's
possible), but mine clearly shows the line from the armature 'jumping
over' the negative DC bus, and ending at the bottom of the .1uf cap
(the bottom of this cap should also be tied to common neg., but
isn't). On my print, the 'jump over' symbol is clearly an error. John
B., Halp! :-)
Bill(oc)
Dave Plowman (News)
<2b40edef-2eae-4956...@59g2000hsb.googlegroups.com>,
terry <tsan...@nf.sympatico.ca> wrote:
> Sounds right. But as not in this posting, do recall at least one 12
> volt European car radio of the 1950s that had a polarity plug that had
> to be placed in the correct position. But reading this now can't think
> why that was necessary! Maybe they were synchronous vibrators or
> something.
Wonder when transistors started to be used? Hybrid sets were certainly
around in the early '60s.
--
*I'm pretty sure that sex is better than logic, but I can't prove it.
Jim Mueller
a strange way to draw it but it is correct.
--
Jim Mueller wron...@nospam.com
To get my real email address, replace wrongname with eportiz. Then replace
nospam with sacbeemail.
"oldcoot" <oldco...@sbcglobal.net> wrote in message
news:697813da-f93e-49fe...@v1g2000pra.googlegroups.com...
N_Cook
Probably a bit difficult getting back to the author, G A Quarrington ,
printed 58 years ago
Ken
there is a connection. I like the connection represented by a dot, but
on some hard to read prints, this dot can disappear, leaving you
wondering, which is it. Ken