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Old 10th Feb 2021, 12:47 pm   #21
Cobaltblue
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Default Re: Pye M78F questions

Hi Steve.

If you look at the bottom of the page linked it discusses the value of R4 you probably won't need to make it lower for the reduced voltage the object is to get the input to the regulator circuit to be around 6V on load.

A lot of people like to run these valve closer to 1.2V to increase their life when being used from a mains supply.

Michael Watterson, (Golborne) has written extensively on this subject (Neon Indicator).

Cheers

Mike T
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Old 10th Feb 2021, 1:16 pm   #22
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Default Re: Pye M78F questions

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Originally Posted by ajs37 View Post
I have 2 of these radios - and they are among my favourites for their appearance. They were not cheap - one from Ebay and the other from an RWB auction (one does have an original black handle - see photos). As Mike says - not great performers - I have tried them on batteries and using an eliminator and I can see why they were withdrawn from circulation (besides the Rising Sun controversy)!
They sit in a glass cabinet, in my study - away from the little fingers of my grandchildren (there are enough robust radios on open display for them to play with).
I don't plan on 'restoring' the two I have, which is unusual for me, as I normally like my radios to work! As can be seen in the photos, one has a replacement baseplate - quite well done as well!
Good luck with yours Steve!
Cheers
Andy
Lovely looking sets Andy. I don't blame you for leaving them unrestored in many ways. As you say, their performance does not set the world alight, and some form of power supply has to be used, plus at the end of the day, they're totally original; no new caps etc. The one on the left is what I call in my first post, pale cyan/white. I've seen another photo of a similar colour that looks more pale green but I'm not sure if it's just the colour of the photos?
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Old 10th Feb 2021, 1:37 pm   #23
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Default Re: Pye M78F questions

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Originally Posted by Cobaltblue View Post
Hi Steve.

If you look at the bottom of the page linked it discusses the value of R4 you probably won't need to make it lower for the reduced voltage the object is to get the input to the regulator circuit to be around 6V on load.

A lot of people like to run these valve closer to 1.2V to increase their life when being used from a mains supply.

Michael Watterson, (Golborne) has written extensively on this subject (Neon Indicator).

Cheers

Mike T
Thanks Mike.
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Old 10th Feb 2021, 2:37 pm   #24
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Default Re: Pye M78F questions

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Originally Posted by stevehertz View Post
Quote:
Originally Posted by ajs37 View Post
I have 2 of these radios - and they are among my favourites for their appearance. They were not cheap - one from Ebay and the other from an RWB auction (one does have an original black handle - see photos). As Mike says - not great performers - I have tried them on batteries and using an eliminator and I can see why they were withdrawn from circulation (besides the Rising Sun controversy)!
They sit in a glass cabinet, in my study - away from the little fingers of my grandchildren (there are enough robust radios on open display for them to play with).
I don't plan on 'restoring' the two I have, which is unusual for me, as I normally like my radios to work! As can be seen in the photos, one has a replacement baseplate - quite well done as well!
Good luck with yours Steve!
Cheers
Andy
Lovely looking sets Andy. I don't blame you for leaving them unrestored in many ways. As you say, their performance does not set the world alight, and some form of power supply has to be used, plus at the end of the day, they're totally original; no new caps etc. The one on the left is what I call in my first post, pale cyan/white. I've seen another photo of a similar colour that looks more pale green but I'm not sure if it's just the colour of the photos?
I would say pale green Steve - perhaps pastel green?
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Old 10th Feb 2021, 3:58 pm   #25
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Default Re: Pye M78F questions

Ok, there's probably only one ' pale green/pale cyan' set then. It's just that these two photos made me think that there were a couple of colour variations of the 'green' set. I suppose the giveaway is the distinct 'yellow' colour of the sides of the 'green' set, suggesting an inaccurate (warm) overall colour rendition of that particular photo:
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Old 10th Feb 2021, 4:52 pm   #26
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Default Re: Pye M78F questions

maybe the second radio has been out in the sun too long?
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Old 10th Feb 2021, 5:59 pm   #27
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Default Re: Pye M78F questions

Could just be a difference in white balance between cameras, or colour of lighting. I have an old Raleigh Electronics radio that was black and green, some sort of plastic material, the outside of the case has faded to an almost white colour, I wonder if the same happens to these? What is the case made of?

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Old 10th Feb 2021, 7:07 pm   #28
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Could just be a difference in white balance between cameras, or colour of lighting. I have an old Raleigh Electronics radio that was black and green, some sort of plastic material, the outside of the case has faded to an almost white colour, I wonder if the same happens to these? What is the case made of?

Regards
Lloyd
I've read that it's Perspex, but not Catalin (phenolic). Personally I doubt it's pure Perspex 'as we know it' due to the amount of these that are cracked, and my understanding is that modern Perspex is quite robust and does not crack easily. Mine doesn't seem to have faded at all when you look at inside vs outside, under handle clasps etc. I don't think they fade.
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Old 10th Feb 2021, 8:01 pm   #29
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Default Re: Pye M78F questions

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Quote:
Originally Posted by ajs37 View Post
Quote:
Originally Posted by stevehertz View Post

Lovely looking sets Andy. I don't blame you for leaving them unrestored in many ways. As you say, their performance does not set the world alight, and some form of power supply has to be used, plus at the end of the day, they're totally original; no new caps etc. The one on the left is what I call in my first post, pale cyan/white. I've seen another photo of a similar colour that looks more pale green but I'm not sure if it's just the colour of the photos?
I would say pale green Steve - perhaps pastel green?
Ok, there's probably only one ' pale green/pale cyan' set then. It's just that these two photos made me think that there were a couple of colour variations of the 'green' set. I suppose the giveaway is the distinct 'yellow' colour of the sides of the 'green' set, suggesting an inaccurate (warm) overall colour rendition of that particular photo:
The one on the left is true to life colour , it's mine Mick.
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Old 11th Feb 2021, 2:28 pm   #30
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Default Re: Pye M78F questions

Having bought a dual output 0-12, 0-12 12VA mains transformer off eBay I've decided to make the power supply. I've already got a suitable box, I guess I'll have most of the C's and R's, and I've just ordered the regulator for a couple of quid for two. Regarding the diodes, there's two different types called for, 1N4001 and 1N4004, surely 1N4004 would do for all of them?

Also, looking at the construction details, the tag strip needs to be 24 tags per side, I can't find any this long?
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Old 11th Feb 2021, 6:14 pm   #31
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Default Re: Pye M78F questions

1N4004 will of course do just fine as would 1N4003, 1N4005, 1N4006 and 1N4007.
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Old 12th Feb 2021, 1:07 pm   #32
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Default Re: Pye M78F questions

For 24/48 way double tag board you can simply buy two of the common 18/36 way ones and mount 6/12 ways cut off the second board alongside the first board.

Or any variation on the theme using odd offcuts of single or double row tags trip to get 24/24.

Looking at the layout pics, quite a few tags are unused anyway- with a bit of ingenuity and some split level component mounting a common 18/36 way double tag board could be used on its own.
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Old 12th Feb 2021, 3:39 pm   #33
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Default Re: Pye M78F questions

Does anyone make/sell a pcb for this power supply?
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Old 14th Feb 2021, 6:26 pm   #34
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Default Re: Pye M78F questions

The construction info for the power supply mentions a 'TO220 Insulating Kit for U1'. If I mount the device on tag strip with a 'free standing' heatsink, then if it's not touching anything else then why would it need to be insulated? I assume it's only required in the instance of a metal housing being used as a heatsink? Am I correct? Mine is a plastic housing. Will a strip of thin ali sheet be a good enough heat sink?
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Old 14th Feb 2021, 7:43 pm   #35
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Default Re: Pye M78F questions

Hi Steve should be ok the bigger the better , It all depends on the input volts to output volts , what would be the input voltage . Mick.
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Old 14th Feb 2021, 8:17 pm   #36
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Hi Steve should be ok the bigger the better , It all depends on the input volts to output volts , what would be the input voltage . Mick.
Gotcha. Well, as I don't need the full 90v HT output level, my transformer has 2 X 12v outputs, and not 2 X 15v as specified, with the added advantage of requiring less 'drop' on the LT side. So should be less power dissipation.
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Old 14th Feb 2021, 9:03 pm   #37
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Default Re: Pye M78F questions

A TO220 regulator can handle about a watt with no heatsink, A fairly small 10C/W heatsink will up this to about 7-8 Watts. If the heatsink is floating, no insulating kit is required though a smear of heat sink compound or silicone grease is worth adding.
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Old 14th Feb 2021, 11:25 pm   #38
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Default Re: Pye M78F questions

Free standing things with heatsinks don't need insulation if nothing is touching them, but sticking-up things, especially with added mass from heatsinks are fair game for vibration-induced failures. The legs all being in a line, and even worse - flat sections in the same plane, lets TO220 devices 'hinge' until the legs work-harden and fatigue.

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Old 15th Feb 2021, 9:07 am   #39
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Default Re: Pye M78F questions

Point taken David. I mean, this isn't going to get much day to day use, it's just basically to enable me to restore the Pye and subsequently given it a run out. But maybe I will tether the heatsink to the plastic case somehow - a spacer and a bolt.
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Old 20th Feb 2021, 7:33 pm   #40
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Default Re: Pye M78F questions

A quick update, I'm about halfway through building the power supply. I'll post some pics soon.
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