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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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13th Apr 2022, 10:45 pm | #1 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,853
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Heater Wiring on PCB designs using valves?
Hi!
I was looking at the Assembly Book for the Heathkit S–99 Amplifier I'll be doing in the summer, and I noticed that instead of attempting to run heater wiring along copper tracks, two short pads lead off pins 4 & 5 of each valve and ordinary lengths of 1/0.6 solid–core wire run as a twisted–pair are used, run along the topside of the PCB and connected to the pads for pins 4 and 5 of each valve – is this the most effective way of running heater wiring rather than trying to route it along the copper itself? I've looked at countless valved TV PCBs over many years and the designers have always been able to run the heater circuit as part of the copper pattern, which is a bit easier when heaters are in series, as is almost always the case! Are thermionic valve circuits generally easier to design on a PCB as a rule than "old–school" wired layouts? Chris Williams
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13th Apr 2022, 11:25 pm | #2 |
Heptode
Join Date: Dec 2020
Location: Swaffham, Norfolk, UK.
Posts: 582
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Re: Heater Wiring on PCB designs using valves?
Yes Chris. Far superior, it's to keep hum to a minimum. You can't do twisted pair on a copper foil pattern on the PCB very easily.
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14th Apr 2022, 7:19 am | #3 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,288
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Re: Heater Wiring on PCB designs using valves?
Its also more flexible, if you run into hum problems you can experiment with the heater wire layout, not as easy with a pcb.
Peter |
14th Apr 2022, 7:59 am | #4 |
Banned
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
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Re: Heater Wiring on PCB designs using valves?
I spent many years as a teenager resoldering heater wiring on PCB,s way back. They were ALWAYS 6.3 volts parallel heaters, involving SOME amps of current.
MY opinion, and its mine only so far, is PCB heaters are the tackiest, nastiest, cheapest method to make short lived junk. Series heaters ?? MAYBE in old blighty, not here in Australia, I continue to say, " I have NEVER seen a transformerless TV, Radio, tape recorder or ANY other device. I can always rearrange my heater wiring to reduce hum and noise. When I fold up a PCB it gets all nasty, bitter and twisted. Chris, you have specifically asked about amplifiers, I am only answering my experiences. Short as my 68 years may be. Forgive my rant, but if you want NICE amps, DONT wire the heaters onto the PCB. In fact I wont use PCB's at all with audio. Best regards Joe |
14th Apr 2022, 5:27 pm | #5 | |
Heptode
Join Date: Dec 2020
Location: Swaffham, Norfolk, UK.
Posts: 582
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Re: Heater Wiring on PCB designs using valves?
Quote:
To answer the second question...the reason for PCB assembly of such eqipment initially was to ease assembly by unskilled labour, and reduce production costs. Or, to put it another way maximize profit by cheap manufacturing. Who hasn't seen valve equipment in its later life that was built on SRBP PCB's that has started to carbonize and develop bad solder joints on the valve holders. Metal chassis any day over PCB, at least with the fire tubes |
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14th Apr 2022, 6:58 pm | #6 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: Heater Wiring on PCB designs using valves?
I infer from that that Australian manufacturers have never had to allow for DC mains.
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14th Apr 2022, 7:16 pm | #7 |
Heptode
Join Date: Dec 2020
Location: Swaffham, Norfolk, UK.
Posts: 582
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Re: Heater Wiring on PCB designs using valves?
You can perhaps also infer, that although AC/DC chassis were sold there in small numbers, (mostly imports), and were not actually banned, safety prevailed over profit in most Aussie designs.
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14th Apr 2022, 11:10 pm | #8 |
Banned
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
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Re: Heater Wiring on PCB designs using valves?
There used to be 240 volt DC many years ago in Sydney. MANY years before I was hatched. BUT, I think there was also AC available. Origionally for trams I seem to remember. Only reason I know that, is I read an article in some magazine that was "going back " in time sort of thing. There was even a photograph of a massive battery bank.
Joe |
14th Apr 2022, 11:44 pm | #9 | |
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,060
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Re: Heater Wiring on PCB designs using valves?
This sums it up for me:
Quote:
Though, many a TV of late 1960's and early 1970's used heaters tracked on the PCB, successfully. They were series heaters so current wasn't huge. And I have a Pye attaché-case 4-valve battery radio with circuitry built up on a PCB, again, the filaments are tracked-in. But this if course is DC so there's no hum. |
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15th Apr 2022, 4:40 am | #10 | |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
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Re: Heater Wiring on PCB designs using valves?
Quote:
The HP9810 calculator uses a normal twisted pair of wires for this. |
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15th Apr 2022, 7:50 am | #11 | |
Hexode
Join Date: Mar 2019
Location: Edinburgh, Scotland, UK.
Posts: 340
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Re: Heater Wiring on PCB designs using valves?
Quote:
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15th Apr 2022, 8:31 am | #12 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,288
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Re: Heater Wiring on PCB designs using valves?
Personally, I like the Radford approach, pcb to take the bulk of the components. Tagged valve bases with the heaters run by twisted wires, grid stoppers wired direct to the valve bases, PSU electolytics bolted to the chassis.
Best of both worlds. Peter |