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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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25th Jun 2020, 10:56 am | #1 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Pye PF8 Circuit
I wonder if anyone can help with this?
The PF8 was constructed using plug in modules some of which were conventional contruction while others were potted in epoxy. Of course the epoxy ones are pretty much unrepairable. As far as I can remember the PF8 schematic treated each module as a box with only the functional symbol for what it does, multiplier, PLL, AF Amp etc. Has anyone seen any more detailed info please? I want to experiment with the DC/DC converter. It used 2x 1.2V NiCads and a DC/DC to ~10V for the main supply - I have no idea why they chose to do that. The DC/DC Converter is one of the "fixable" modules so the circuit could be traced out if needs be. I would like to see if it would be safe to run it from a single 3.7V Lithium Cell or if it could be modified to do so. |
26th Jun 2020, 9:19 am | #2 |
Heptode
Join Date: Sep 2006
Location: Woodbridge, Suffolk, UK.
Posts: 643
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Re: Pye PF8 Circuit
I haven't got a circuit but referencing the late Chris Lorek's first book on pmr conversions he says "connect a suitable 2.4v supply but NEVER (his emphasis) exceed 2.7v otherwise you're likely to damage the set's circuitry" suggesting I think that some mods will need to be done to facilitate 3.7v
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Dave G1AGK. My perception is my reality! Last edited by davidw; 26th Jun 2020 at 9:22 am. Reason: addition |
26th Jun 2020, 9:26 am | #3 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Re: Pye PF8 Circuit
Interesting info. Thanks.
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26th Jun 2020, 10:01 am | #4 |
Octode
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 1,572
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Re: Pye PF8 Circuit
This page any use there is a pdf manual at the bottom.
https://sites.google.com/site/g3xbmqrp3/vuhf/pf8 Adrian |
26th Jun 2020, 3:51 pm | #5 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Re: Pye PF8 Circuit
Brilliant Adrian - thank you. There is more in the manual than I recalled.
The inverter circuit is there so it is exactly what I wanted to know. My own manual is deep down a pile in the shed - now I don't need to scan it. |
26th Jun 2020, 8:33 pm | #6 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Re: Pye PF8 Circuit
Now it gets interesting.
I have robbed a scrap set and here we find the Inductor/Transformer is AL21447 - I will be dissecting that. The main DC/DC switch transistor is X44H260. Er - wassat then?? Might be K44H260. The plug in PCB has most of the rest of the works. |
26th Jun 2020, 9:56 pm | #7 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Re: Pye PF8 Circuit
Here is the ferrite core..
Looks like a gapped core without an adjuster fitted. I have yet to look up the spec but it should not be too difficult to find. |
27th Jun 2020, 1:33 pm | #8 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Re: Pye PF8 Circuit
The transformer has been disassembled now. It revealed why the set was scrapped. A probable impact with the hard deck has caused the ferrite mass to crack the former - there were no supporting legs on the side clips. The secondary winding had a break in it.
Here is my dissection in the hope it might be of some use to others. I'm thinking to increase the 6 Turn primary to more like 9 Turns to allow for 3.7V instead of 2.4V supply. The original primary winding was 4 parallel strands of wire or ~24 turns total. I will probably cut back to 3 parallel strands for 27 turns total. I will rewind this core and try it in a lash up first. Last edited by Jon_G4MDC; 27th Jun 2020 at 1:41 pm. |
27th Jun 2020, 1:55 pm | #9 |
Guest
Posts: n/a
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Re: Pye PF8 Circuit
Why not build a buck converter to change the (rather nominal) 3.7V from the LiIon cell to a proper 2.4V. Nicads have a very flat discharge curve unlike LiIon.
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27th Jun 2020, 2:00 pm | #10 |
Nonode
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 2,015
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Re: Pye PF8 Circuit
It's a thought if this doesn't work I suppose. Not much space though!
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