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Old 17th Sep 2017, 5:28 pm   #1
Damo666
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Default Common Pye PF1 RX deafness problem

Eventually, I've managed to get my hands on 4 x Pye PF1 Mk1 Pocketfones, 2 of which are deaf compared to the remaining 2. I've also experienced these exhibiting this same deafness when I had some years ago suggesting this is a common issue.

I've been testing the sensitivity of my PF1s by doing a range test by means of using an handheld rig set to 1W terminated into a dummy load. The receivers that are working well are picking up the signal with the HT a good 15 metres away, whereas the deaf units are only picking up the signal from 5 > 6 feet away at best.

I don't have a service manual or schematic for these, but have tuned them all up for best sensitivity as per a scan of a PF1 conversion covered in a book by Chris Lorek.

Are there any ex Pye engineers out there that have dealt with this common problem and know a possible fix?
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Old 17th Sep 2017, 5:37 pm   #2
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Default Re: Common Pye PF1 RX deafness problem

Sound like the front end transistor may be defunct. Could be worth comparing voltages with a good set around the front end. It's a very long time since I looked at one. You may need some decent test gear to track the fault down. Maybe the faulty ones are slightly off frequency, or have been dropped in the past, fracturing PCB tracks and that sort of thing.
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Old 17th Sep 2017, 5:38 pm   #3
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Default Re: Common Pye PF1 RX deafness problem

What frequency are you running them on?

In times-past I remember to put these on 70cm we sometimes had to play games fudging the local-oscillator to be on the 'wrong' side of the IF.

There were also 2 versions of Pocketfone: some had an 'active' front-end with RF-amplifier transistors, others were 'passive' - basically a couple of tuned-circuits then straight into the mixer. Some of the 'passive' versions lacked enough tuning-range on the front-end-filters to get them to peak properly on 70cm, leading to deafness.

Also, check the supply-voltage! if you're using aged battery-packs you may not be getting enough.
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Old 18th Sep 2017, 12:38 am   #4
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Default Re: Common Pye PF1 RX deafness problem

I've modified these by fitting a PP3 connector to operate off a 9V battery, and all these are active front end as there's a Transistor soldered to a screen in very close proximity to the antenna input.

I could really do with a schematic or service manual as the markings on many of these Transistors are difficult to make out, particularly the first RF amplifier transistor as mentioned.

By the way, they're all still using the crystals that were in use when they were in service - around 453 Mhz, so they've not yet been converted. When I have them working as they should, they'll be adapted for monitoring 70CM.

Last edited by Damo666; 18th Sep 2017 at 12:48 am.
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Old 18th Sep 2017, 10:20 am   #5
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Default Re: Common Pye PF1 RX deafness problem

The connection to the perforated metal plate across the speaker, which was used as the antenna, used to develop a hairline crack, so it's worth resoldering those both ends. Later sets used the speaker frame itself as the antenna, if I remember correctly...? It was much rarer to have an issue with that version.
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Old 18th Sep 2017, 11:03 am   #6
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Default Re: Common Pye PF1 RX deafness problem

I used to set these things up years ago on 70cm, and came across both PF1A (the one with the plate aerial and crystal transducer speaker), and PF1B (the one using the cone speaker frame as an aerial)

I have a schematic with alignment instructions somewhere around. As I recall, the standard front end was a BF180, which keen types would replace with a BFY90, as this had better characteristics at UHF.

The accompanying transmitter was supposed to give a nominal 100mW output on UHF when tuned correctly - I found these used to generate all sorts of harmonics, and could happily wipe out TV reception in the vicinity they were used. Happy days.
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Old 18th Sep 2017, 11:06 am   #7
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Default Re: Common Pye PF1 RX deafness problem

All PF1s had an RF amplifier AFIK.
I think the passive post might be confusing the UHF variant of PF2 which had RF amp optional and which made only a very small difference to sensitivity.

BF180s for PF1RX are easily found from telly tuners of the same vintage. I also recall a BFY90 did rather better, anything much hotter made an oscillator.

Crystals normally used were 84-85MHz 5th overtone.
84.5 * 5 = 422.5MHz +10.7=433.2MHz RX.

Watch for linked out 10.7 MHz crystal filters - some liked to wideband the RX as a monitor for certain freqs.
Without the 10.7 Filter they would receive about 0.5MHz tolerably well producing whatever signal was loudest inside the range.
Useful when you only had one crystal...

Last edited by Jon_G4MDC; 18th Sep 2017 at 11:21 am.
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Old 18th Sep 2017, 2:14 pm   #8
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Default Re: Common Pye PF1 RX deafness problem

Thank you all for your input.

I've resoldered the plate antennas, and also redone the associated wire into the 1st RF amplifier stage but there's no increase in sensitivity with the deaf receivers - so I'm going to purchase a couple of BF180 and BFY90 Transistor's and swap them out hoping for the best.

One of the units that's working fine with good sensitivity tends to go into oscillating (motorboating) if the volume is turned above a certain threshold, but vanishes when turned low - but I'm not too bothered about this just now.

John, if you manage to find that alignment/service information, I'd be happy to cover any costs for a copy.
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Old 18th Sep 2017, 2:51 pm   #9
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Default Re: Common Pye PF1 RX deafness problem

If I can find it, I'll scan it and email it to you. It's not a large publication...
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Old 18th Sep 2017, 3:00 pm   #10
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Default Re: Common Pye PF1 RX deafness problem

One of the things I used to do as well, was to change the value of the fixed value resistor that determined the squelch threshold. This made them much more useable. Otherwise, a signal anything less than S9+40dB at the aerial would be muted hard. I forget which resistor it was - once I see the diagram again, I'll probably remember.

Pretty sure I still have a couple of these around as well, plus piles of other PYE kit..
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Old 18th Sep 2017, 6:21 pm   #11
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Default Re: Common Pye PF1 RX deafness problem

I'd be very interested to know where the squelch threshold resistor is located, as this may well be the issue with these 2 deaf units.

Re' a scan of the publication, it would be great if you manage to find it. The Chris Lorek conversion information I obtained isn't particularly in depth.
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Old 18th Sep 2017, 7:15 pm   #12
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Default Re: Common Pye PF1 RX deafness problem

The circuit for the PF1C - Pye Compact - A TX and RX in the same box, with a changeover switch as the PTT, is on Mods.dk
The RX and TX boards are 99% the same as I recall.

I have been looking at the Demod and squelch. Two things I can't recall now. Which was the squelch set resistor..? And what was my modification that turned the endless economiser pfft-pfft-pfft (most annoying but apparently a comfort factor that it was still working - just not for me) into very near silence with just a quiet tick.

A 33k resistor definitely figured in that but Oh too long ago!

If this continues I will have to head for the shed where that history resides. Along with my PF1RX converted to a GB3PI monitor receiver.
BF981 front end + 19" telescopic whip ... it's in there somewhere.

Last edited by Jon_G4MDC; 18th Sep 2017 at 7:29 pm.
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Old 18th Sep 2017, 9:46 pm   #13
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Default Re: Common Pye PF1 RX deafness problem

My newly discovered schematics suggest R49 is the resistor to be changed to alter the squelch setting.

The PF1C was indeed just the two units shoved in one plastic box. I have only ever seen one or two of those.

I have sent you a pm, Damian.
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Old 18th Sep 2017, 11:35 pm   #14
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Default Re: Common Pye PF1 RX deafness problem

PM received and replied to, John. Cheers.

Many thanks all for your good advice & assistance upto now.
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Old 19th Sep 2017, 5:52 pm   #15
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Default Re: Common Pye PF1 RX deafness problem

Quote:
Originally Posted by Jon_G4MDC View Post
All PF1s had an RF amplifier AFIK.
I think the passive post might be confusing the UHF variant of PF2 which had RF amp optional and which made only a very small difference to sensitivity.
Apologies, yes you're right. PF1 had a RF amp, PF2s came in passive and active-front-end versions.

[It's 3 decades since I last worked on either, and in the intervening years bit-rot has set in on my brain]
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Old 19th Sep 2017, 8:37 pm   #16
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Default Re: Common Pye PF1 RX deafness problem

I remember the Burndept BE470 UHF handportable used to develop a fault known as "supertick" when the economiser made a loud click instead of it's normally fairly quiet sound.
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Old 19th Sep 2017, 9:23 pm   #17
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Default Re: Common Pye PF1 RX deafness problem

Supertick - that sounds interesting!!

I have never had a BE470, red or yellow PTT button version, but I counter with the ITT Starphone SF1! I don't think I have one now though...or maybe?? It's worth a look - there were thousands at the Stock Exchange back in the day.

Actually this thread got me thinking how amazing the PF1RX was for such an early and simple design. I never did work out the economiser section but I was very well versed in the rest of it. Nobody else at North London Service would touch them. I was the visiting Student Engineer so I did along with the big pile of defunct MF5AM Motafones (yuck).

Today I decided to tackle the PF1 economiser in LT Spice. It oscillates all right with about the right timing. The PNP switch transistor in Germanium gave me some fun - a poorly modelled transistor (or is it?) shows quite nasty sag in the switched output.

I decided to ditch it in favour of a PMOS fet - ahhh but they didn't exist in 1964/5.

I like what I see. This has to be tried for real!

Last edited by Jon_G4MDC; 19th Sep 2017 at 9:30 pm.
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Old 28th Sep 2017, 7:38 pm   #18
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Default Re: Common Pye PF1 RX deafness problem

This thread has been quiet for a bit, meanwhile I have been trying to reverse engineer my own mod to stop the pfft-pfft-pfft. Turned out really painful...

The answer lies in my box of paper circuits and scribbles buried deep in the shack archive which may well be unreadable now.

So far I can't find another example in my stock pile-so modified, therefore I can't work out what it was. Stumped! Most annoying.

Help? If anyone wants to start a thread about PF1s "per se" -in the right place - the accumulated knowledge & I have have lots to post - will only come back very slowly...others are probably the same.

It's a classic and IMHO it deserves it. 1964 - 450 MHz portable - respect is due....

Last edited by Jon_G4MDC; 28th Sep 2017 at 7:46 pm.
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Old 28th Sep 2017, 8:08 pm   #19
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Default Re: Common Pye PF1 RX deafness problem

I must have looked at hundreds of BE470 sets but the PF1 was a bit before my time. There was also a BE600 a bit later on which was in a much more robust diecast? case instead of that blue plastic. They were both modular construction types but to be honest we mostly first lined them and tweaked them back on frequency with the famous crystal calibrator to zero beat them back on channel, except you could get it 25KHz off if you weren't careful as the range of the trimmer was quite a bit. Deviation, current draw, supertick and Rx sensitivity were also checked. The real tricky faults went off to the MU down at Kippax. I trained up on them there for a week.
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Old 28th Sep 2017, 8:43 pm   #20
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Default Re: Common Pye PF1 RX deafness problem

hehe - you kick off another memory.

Netting in the depot was to<excuse spelling> Schömandel.
A sort of advanced BC221 affair where you set the frequency on dials and tweak for zero beat....

Remember them? It sat on a shelf and the orders were no touchy- except for wanted frequency to tweak up your set!
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