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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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Old 24th Aug 2016, 10:52 am   #1
johnny
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Default Woodsons SR-12 receiver

Has anyone got any paperwork for a woodsons SR-12 receiver with circuit diagram etc.

Thanks
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Old 24th Aug 2016, 10:53 am   #2
Jon_G4MDC
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Default Re: Woodsons receiver

I'm not sure what this is. Any more info?

First thought was a VHF RX called a Search12 which I recall from late 70s.
Anywhere close?
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Old 24th Aug 2016, 11:38 am   #3
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Default Re: Woodsons SR-12 receiver

Opposite end of the band, this is a LF receiver 1.6 to 3.8Mhz and 150Khz to 500Khz. All valves. It comes in rack with tx and rx and was probably made for fishing trawlers etc.
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Old 24th Aug 2016, 2:05 pm   #4
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Default Re: Woodsons SR-12 receiver

OK - not what I had in mind.
Good Luck.
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Old 24th Aug 2016, 3:32 pm   #5
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Default Re: Woodsons SR-12 receiver

I may need it as there is nothing on the Net about it at all, so going to be a tough one. Been running the valves in for a couple of hours and working out the wiring from the valve bases.
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Old 24th Aug 2016, 4:24 pm   #6
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Default Re: Woodsons SR-12 receiver

Hi,
Woodson's of Aberdeen who made your receiver are still in business in marine electronics in a big way, though I think they no longer manufacture equipment.
It may be worth giving them a call to see if they can help.
It may be worth posting a few pics if you can as a photo often jogs the memory..
Good Luck
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Old 25th Aug 2016, 9:14 am   #7
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Default Re: Woodsons SR-12 receiver

Thanks for that, I have just been on the phone to them, but it seems that they don't have any info on it, although they will ask their older workers if they remember anything and get back to me.
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Old 28th Aug 2016, 7:08 am   #8
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Default Re: Woodsons SR-12 receiver

Johnny,

Here's a picture of my complete set up which worked well into the vmars net many years ago when I was keen. It always reminded me of Wireless Set 18 layout. A very neat compact design capable of about 15 to 20 watts output in good carbon mike AM.

The receiver has a direction finding capability which I never used. It also has the letters PIM, the meaning of which I found out but have now completely forgotten. Anyone know?

I remember it has Denco coils soldered in.

Here also is the circuit diagram. If it's not clear enough send me your email add. by PM. I do have some more info.

Jim
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Old 28th Aug 2016, 12:06 pm   #9
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Default Re: Woodsons SR-12 receiver

Delightful little rig, Jim. Shame it's no longer used...
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Old 28th Aug 2016, 12:57 pm   #10
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Default Re: Woodsons SR-12 receiver

I know Keith. I've just lost complete interest in amateur radio. I've had 25 years or so when I was quite active in building, restoring and operating but I've got other hobbies now.

I'm gradually getting rid of almost everything.

Who knows in perhaps 10 years if I'm spared I might become interested again.

Jim
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Old 28th Aug 2016, 4:06 pm   #11
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Default Re: Woodsons SR-12 receiver

Johnny & Jim,
Please reconsider any thoughts of leaving old marine band radio telephone sets in the loft, or, dread of dreads, dumping them. Woodsons(3 sons of the original Mr Wood) of Aberdeen do still exist and supply the fishing fleet & offshore installations with comms equipment. They haven't built their own Tx/Rx equipment since the 60's. By the time I started to work for them in the late 70's, part-time, they were main agents for Sailor Radio equipment. HF AM & SSB, and VHF's. Which is what I mainly worked on. By then most of those old R/T's were obsolete.
Last I heard, they had some of the old circuit diagrams on micro-fiche, at their Goval House HQ outside Aberdeen. Ask for Mike Newman - the Boss, or his no2 - Robin. Mind you, they might have retired by now.
I just have the circuit diagram for the 120N HF(two TT22's in P - P) Tx from that era.

Regards, David
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Old 28th Aug 2016, 4:35 pm   #12
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Default Re: Woodsons SR-12 receiver

David,

No fear. I won't be dumping it after all the time I spent on it.

Thank you for the explanation of the Woodson name I didn't know that. Can you explain the meaning of PIM seen on the front of the receiver.

Jim
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Old 28th Aug 2016, 7:17 pm   #13
GW3OQK Andrew
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Default Re: Woodsons SR-12 receiver

I can't resist having a go.

I see the PIM switch switches it into a condition for DF. That's AGC off, manual gain and BFO on. The meter then indicates audio output level. Disconnect the main aerial. The loop would be turned for a sharp audible null, corresponding to minimum meter reading, and the DF bearing and ship's heading noted.

If required the 180 degree ambiguity is resolved by connecting the main aerial to the sense terminal on the front of the receiver then turning the loop +/- 90 degrees (Perpendicular) until the loop signal is in Phase with the main aerial giving max Indication on the Meter. (One side would be somewhat stronger than the other.) There would be a Pointer on the loop's rotator wheel which would show the correct direction. (Refer to manual!)

Next apply correction from the DF calibration curve, and add the ship's (corrected) heading from the compass to get true (or magnetic) bearing from the ship.

I suggest PIM means Pointer Indication Meter and wait for the correct explanation.

73, Andrew ex MN R/O and DF bearing taker.
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Old 31st Aug 2016, 8:32 pm   #14
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Default Re: Woodsons SR-12 receiver

Cant say what PIM stands for ,Woodsons-wise. But I suspect that Andrew is spot-on.
Their later range of 66TS Sailor Rx's did have a loop/sense aerial facility. My recent Loop/DF-ing experience has just been with my BEME Loop Rx's, and Coastal Radio Curlew Rx which worked "Consol".
Incidentally, back in the 50's, Woodsons lost out to Coastal Radio Ltd for supplying the RNLI with HF AM R/T's (C/R Curlew & Nimbus).

Regards, David
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Old 31st Aug 2016, 8:45 pm   #15
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Default Re: Woodsons SR-12 receiver

Thanks Jiim for the circuit. Unfortunately, I dont have the transmitter, but do have the caseing which looks as if it was mounted against a bulkhead or wall. I am now looking for a psu for it either homebrew or the original one. Yes, the pim is for df'ing. Nice little receiver.
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Old 30th Aug 2017, 2:46 pm   #16
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Default Woodsons SR-12 receiver

I fired up the filaments today for several hours, then applied just 50v ht for a few hours to see if the electrolytic caps will hold and so far so good. No speaker noise as yet, although I can hear some crackles when connecting HT. Next step is to increase HT slowly.

Thanks
J

Last edited by AC/HL; 30th Aug 2017 at 3:05 pm. Reason: Thread split
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Old 30th Aug 2017, 7:27 pm   #17
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Default Re: Woodsons SR-12 receiver

Hoping you get life out of it on the eve of the first anniversary of the last post!

Go for it
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Old 31st Aug 2017, 1:23 pm   #18
johnny
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Default Woodson's sr-12 dead

With full HT applied, there is no hiss from the receiver speaker. The speaker does crackle when low ht was applied, so this is working. Cannot find my signal tracer right now....AARRRGH I was wondering if there is a mute connection when used with its transmitter. Does anyone know ?

J
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Old 31st Aug 2017, 2:14 pm   #19
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Default Re: Woodsons SR-12 receiver

Have you tried the obvious things like checking voltages around the output valve and output transformer?

Do you get a buzz when you touch the centre tag of the volume control with an insulated screwdriver?
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Old 31st Aug 2017, 8:51 pm   #20
johnny
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Default Re: Woodsons SR-12 receiver

Will check that tomorrow. Valves all warming up ok. No smoke or bangs, so looking good. Will probe around tomorrow when my brain is in gear and fingers have returned to normal. Its a slow progress here, due to medical and other issues.
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