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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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10th Feb 2019, 3:28 am | #1 |
Pentode
Join Date: Jul 2014
Location: Bangalore, India
Posts: 132
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Drake TR-4C - PTO problem
In the process of troubleshooting a faulty Drake TR-4C, years ago, the root cause was traced to a non-working PTO.
A visual examination of the mint-condition PCB revealed nothing. Component checks with a multimeter also showed nothing amiss. Then 'Eureka'! A continuity test showed that the PTO coil was isolated from ground. A closer examination of the PCB, with a magnifying glass, revealed a dry-solder connection at the ground end of the PTO coil. Just one solder touch-up and the old workhorse was back in business! Regards, Nandu.
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10th Feb 2019, 12:24 pm | #2 |
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Location: Ipswich, Suffolk, IP4, UK.
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Re: Drake TR-4C - PTO problem
Excuse me for asking, but what's a PTO coil?
To me PTO denotes Power Take Off as used by tractors.
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10th Feb 2019, 12:42 pm | #3 |
Heptode
Join Date: Jan 2008
Location: Birchington Kent, UK.
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Re: Drake TR-4C - PTO problem
Permeability tuned oscillator. AFAIK all the '4' series Drake rigs used this tuning method.
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10th Feb 2019, 12:51 pm | #4 |
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Re: Drake TR-4C - PTO problem
Thanks Pete.
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10th Feb 2019, 1:08 pm | #5 |
Pentode
Join Date: Jul 2014
Location: Bangalore, India
Posts: 132
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Re: Drake TR-4C - PTO problem
Hi Graham,
Yes, as Pete says, PTO refers to 'permeability tuned oscillator'. Thanks, Pete! Permeability tuning is variable-inductance tuning effected by the movement of a ferrite slug in the coil. Linear tuning is achieved with a variable-pitch coil. All Drake rigs use a PTO as VFO. Regards, Nandu.
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10th Feb 2019, 1:53 pm | #6 |
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Re: Drake TR-4C - PTO problem
Yes. I'm familiar with permeability tuning as it was often used in car radios having mechanical pre-set tuning. I just hadn't heard the term PTO used in this context before.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
10th Feb 2019, 2:10 pm | #7 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Re: Drake TR-4C - PTO problem
Thanks for the enlightenment about variable pitch inductor winding to linearise the tuning.
I have some Swan rigs that use these and I always wondered how they got it so good. I have never taken one apart - maybe I should now |
10th Feb 2019, 2:26 pm | #8 | |
Pentode
Join Date: Jul 2014
Location: Bangalore, India
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Re: Drake TR-4C - PTO problem
Quote:
Regards, Nandu.
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10th Feb 2019, 5:00 pm | #9 | |
Pentode
Join Date: Jul 2014
Location: Bangalore, India
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Re: Drake TR-4C - PTO problem
Quote:
Real great rigs were the Collins, Drake & Swan! Regards, Nandu.
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10th Feb 2019, 5:13 pm | #10 |
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Re: Drake TR-4C - PTO problem
Drake used a permeability tuned oscillator, the Ten Tec Corsair sports one, but the famous user was Collins i a lot of their professional and amateur classics.
In lieu of a gearbox, a screw thread gave lots of reduction. Artful variation of the spacing of the turns along the former could give a nice linear tuning scale. Wear of the screw can be a problem David
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11th Feb 2019, 12:13 am | #11 |
Heptode
Join Date: Apr 2009
Location: Scratby, Norfolk, UK.
Posts: 649
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Re: Drake TR-4C - PTO problem
Hi,
I have a Drake SPR-4 receiver with a PTO, Unfortunately there is wear on the threads, and tuning can be a bit of a lottery! Kind regards Dave |