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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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17th May 2023, 12:44 pm | #1 |
Octode
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PYE PT.501 Marker Oscillator
Hi,
I have picked up a PYE PT.501 10.7MHz Marker Oscillator, manufactured originally by Labgear Ltd. An interesting little box, very simply with an on/off switch and a banana socket for the output. It contains an OC170 transistor and a crystal. Does anyone know anything about these? I would love to try it out, but have no idea what battery it would have originally used, and cannot seem to find any information about it. Thanks. Last edited by agardiner; 17th May 2023 at 12:52 pm. Reason: Added pictures |
17th May 2023, 1:15 pm | #2 |
Nonode
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Re: PYE PT.501 Marker Oscillator
I believe the OC170 is susceptible to tin whisker syndrome.
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17th May 2023, 1:23 pm | #3 |
Nonode
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Location: Spalding, Peterborough, Cambridgeshire, UK.
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Re: PYE PT.501 Marker Oscillator
I think they take the 15v avo battery? I can't see a crystal in your picture. Is it there? Original was hc6/u type.
These were made for 455KHz, 2MHz and10.7MHz. Used to zero beat the rx to carrier frequency. I will look later to see if I have any circuit information. Rob
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17th May 2023, 1:31 pm | #4 | |
Octode
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Re: PYE PT.501 Marker Oscillator
Yes, I did wonder that.
Quote:
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17th May 2023, 4:28 pm | #5 |
Moderator
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Re: PYE PT.501 Marker Oscillator
Could be intended as a centre marker for use when wobbulating.
David
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17th May 2023, 4:43 pm | #6 |
Dekatron
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Re: PYE PT.501 Marker Oscillator
They were used for 'zero beating' the RX crystals to the base-station transmitter in AM Pye PMR radios.
I've probably got one or two of these in the attic somewhere along with a low-band AM Westminster or three.
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17th May 2023, 4:45 pm | #7 |
Octode
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Location: Ross-on-Wye, Herefordshire, UK.
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Re: PYE PT.501 Marker Oscillator
Virtually every engineer who had been at Pye Telecom a while had one of these in his desk drawer. They were given out well before my time (1977) so I had to make my own, I recall. As I never had one, I never saw what batteries were used....
They were principally used to adjust receiver local oscillators precisely on to frequency, with the aid of a calibrated sig gen to produce a known RF input frequency - typically a HP8640B. Richard |
17th May 2023, 4:48 pm | #8 |
Octode
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Re: PYE PT.501 Marker Oscillator
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17th May 2023, 5:47 pm | #9 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
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Re: PYE PT.501 Marker Oscillator
OK, tried powering it up with 10V from my bench supply and hooked up to my scope. Nothing initially, but a sharp tap on the OC170 brought up a nice, stable 10.7MHz waveform. So it works, and the frequency is bang on. Yes, I think this will make a good marker.
Need to sort out the tin whiskers now, plus source a suitable battery. |
17th May 2023, 5:54 pm | #10 |
Dekatron
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Re: PYE PT.501 Marker Oscillator
If it were mine, I would replace the obviously-whiskered OC170 with any modern general-porpoise P-N-P silicon transistor, and use a PP3 battery.
[You _may_ need to tweak the biasing but chances are you won't.)
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17th May 2023, 5:57 pm | #11 |
Nonode
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Re: PYE PT.501 Marker Oscillator
Yours is the first model, dating back to valve days, that's why some were 2MHz.
I only have the later version details, service sheet attached. There was a series after these as well, built in a blue diecast box, about 75mm x 30mm x 30mm. 10.7/11MHz, 21.4 MHz and 23.455KHz. Rob
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17th May 2023, 7:59 pm | #12 | ||
Octode
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Re: PYE PT.501 Marker Oscillator
Quote:
Quote:
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17th May 2023, 8:39 pm | #13 |
Dekatron
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Re: PYE PT.501 Marker Oscillator
If you can't wangle a PP3 in there, then perhaps a few stacked CR2032 coin-cells in series could be fitted? They probably contain more Coulombs/amp-hours of usable charge than the originally-specified zinc-carbon Leclanche cells would have managed.
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17th May 2023, 8:45 pm | #14 |
Octode
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Re: PYE PT.501 Marker Oscillator
I was thinking of buying the correct battery as there are 15V AVO batteries on ebay for around £6. Cheaper than a stack of coin cells and the unit only draws about 2mA.
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22nd May 2023, 8:24 pm | #15 | |
Octode
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Re: PYE PT.501 Marker Oscillator
Quote:
Richard |
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22nd May 2023, 8:45 pm | #16 |
Nonode
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Re: PYE PT.501 Marker Oscillator
That handbook is maybe 15 to 20 years newer model than the one Adrian has.
A pp3 will not fit width ways inside the older case, but the 15V AVO type will, just! Rob
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22nd May 2023, 10:26 pm | #17 |
Octode
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Re: PYE PT.501 Marker Oscillator
Yes. After I measured the space, I concluded that the 15V AVO battery was probably correct and ordered one. Besides the circuit is simple enough and probably quite tolerant of a wide voltage range. It is also interesting that the on / off switch, although a slide switch type, has an internal spring so that it has to be held in the on position.
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23rd May 2023, 4:54 pm | #18 |
Pentode
Join Date: Feb 2021
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Re: PYE PT.501 Marker Oscillator
Love these little gadgets, I'd use any single rechargeable that will fit in there with a mini step up converter for stable voltage and maybe even fit a mini screw on charging port.
I normally have a bunch of various size batteries though from all sort of discarded devices. |