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 Return to top of page · Post #: 1 · Written at 10:47:33 PM on 11 February 2020.
Patrick's Gravatar
 Location: Katoomba, NSW
 Member since 11 February 2020
 Member #: 2408
 Postcount: 29

Hello all,

Please let me know if I'm the sort of member you are looking for and I wont be offended if I'm not .

To be honest although I do have a number of vintage valve radios my passion is vintage British and Australian guitar amplifiers, well any old valve amplifiers actually.

I am 68 and retired and since April last have been studying valve electronics with the aim of repairing and building valve amps for my own pleasure. So far I have built three and my son who currently lives in London is sending some old British amps over for me to have a look at and possibly repair.

I am keen to learn and would appreciate being able to access information provided by this site along with buying components. For example I would like to have a go at repairing burnt out transformers but getting the old core plates and bobbins is difficult.

So there you have it!

Cheers.


 
 Return to top of page · Post #: 2 · Written at 12:05:39 AM on 12 February 2020.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5997

Welcome to V-R. A few members here are into vintage amplifiers.


 
 Return to top of page · Post #: 3 · Written at 4:25:07 AM on 12 February 2020.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1571

If it has valves its all very cool Smile .


 
 Return to top of page · Post #: 4 · Written at 7:30:14 AM on 12 February 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 872

Hullo Patrick, yes this is the place to see every thing.
As well as radio enthusiasts you will find odd people like me who through ignorance have a go at making anything.
Have a look at the special projects section and you will find articles where I have made Bass guitars and Bass amps as well as all sorts of radios.
You will laugh at some of the follies like the last effort making a lightweight Bass guitar.
Actually plays quite well with a stock Chinese neck and strings mounted on chunks of Bunnings best wood.
In the amps I like sticking the valves up front in clear view so you can see the glowing heaters!
Enjoy and laugh because that's what its all about.
Fred.


 
 Return to top of page · Post #: 5 · Written at 9:21:20 AM on 12 February 2020.
Patrick's Gravatar
 Location: Katoomba, NSW
 Member since 11 February 2020
 Member #: 2408
 Postcount: 29

Hello Fred, Taller Carl and GTC,

Thanks Fred I'll check it out. I know what you mean about the glow of the valves. At school we had an amp which was open and I remember being totally mesmerised by that glow and it still does things to me, that's one reason why I decided to learn how to make them and fix them. It has given me such a buzz to have made them myself.

As I said in my intro I have made three amps, two Vox AC4's and a Champ. It's like painting by numbers at the moment but I'm learning slowly, its like going back to school with the maths though and I was never good at it then. I have also had a go at making a bobbin winding machine, haven't used it in anger yet but I think it should work well enough.

I like the bit about the Bunnings bass wood Ill have to go to my local store and ask for some of their best bass wood!

I'm looking forward to going for a wonder so thanks very much for the welcome.

Cheers
Pat.


 
 Return to top of page · Post #: 6 · Written at 7:54:57 PM on 12 February 2020.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6334

Pat,

Please let me know if I'm the sort of member you are looking for and I wont be offended if I'm not .

We have all sorts of members here so we all fit right in. Smile

Welcome to Vintage Radio. If we can help with anything, we will.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 7 · Written at 11:14:42 PM on 12 February 2020.
Patrick's Gravatar
 Location: Katoomba, NSW
 Member since 11 February 2020
 Member #: 2408
 Postcount: 29

Thanks Brad for your welcome and offer of assistance it is truly appreciated but you may regret it as I have so many questions. It's like opening Pandora's box and everything you find is so complicated. I'm finding the journey very rewarding however, although frustrating at times.

First question: It is my understanding that when a valve is operating current flows from the cathode/filament to the anode which picks up the grid signal on its way and it is not possible for current to flow in reverse as the cathode/filament has to be heated. If this is true why then do circuits show current flowing from the anodes to the cathode/filament in a rectifier valve?

Maybe I should have directed the question to the technical forum. I will in future.

Thanks again,
Pat


 
 Return to top of page · Post #: 8 · Written at 12:29:00 AM on 13 February 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4330

There should be some data lying around here. But there was originally confusion as to which way current actually went. & the valve was actually not fully understood in Edison's early time: Boyle did not describe the electron till around 1898.

It was never fully understood for quite a while, with a light bulb why it went black. & that's what lead to the valve.

A hot filament / heated cathode assumes a negative charge so applying AC to the plate of a diode will see negative repelled & only positive appear at the cathode, or filament. So in the globe the filament was throwing off negative charged bits & the glass albeit virtually pF, was positive so the charged particles went to it causing the metal thrown off to stick to the glass.

The control grid is like a tap, the more negative it is the more the negative charge on it, the lesser will be the current through the valve, to the point that it can shut the valve off. Variations in the grid voltage will cause considerably more, or less current to flow between Plate & grid which is the amplification.

I like the early Field Effect Transistors: So simple. You applied power to the "Source", opened the "Gate" & it all went down the "Drain".

Marc


 
 Return to top of page · Post #: 9 · Written at 7:29:27 AM on 13 February 2020.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6334

My understanding of it all is that current flows from positive to negative and electron flow is inversely proportional. That is what I was taught at tech anyway.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 10 · Written at 9:45:40 AM on 13 February 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4330

The rule of "like charges repel" also applies which is why the positive current will travel to the cathode, whilst negative will not.

Marc


 
 Return to top of page · Post #: 11 · Written at 9:47:46 AM on 13 February 2020.
Gandhn's Gravatar
 Location: Windella, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 343

I find it easier to understand how valves work, to only consider electron flow.

Picture the typical radio circuit, the regular valves cathodes are at or near earth potential, the anodes are at HT potential and are connected to the rectifier cathode or heater and the rectifier anode(s) are connected to the transformer winding at a higher voltage.

Electrons are boiled off the cathodes and because they carry a negative charge are attracted to the anodes, in both valves. So an electron is boiled off the lower valve, passes through to the anode, flows through the wire connecting to the rectifier, flows off the rectifier cathode to the anode, to the transformer winding and returns to earth and back to the lower cathode.

If you draw the simplified circuit, with just two tubes one above the other, with the transformer winding across both tubes, they are in series and it all works. As Brad mentioned, the conventional current approach is for current to flow from positive to negative and is exactly the reverse direction to electron flow.

Harold


 
 Return to top of page · Post #: 12 · Written at 2:39:32 PM on 13 February 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4330

We can explain things in wonderous ways without getting too technical. Amplification manifest where you put a wobbly set of signals of around 1V into a big triode or pentode's grid and even bigger amplitude wobbly signals appear at the cathode & plate.

Marc


 
 Return to top of page · Post #: 13 · Written at 9:51:22 AM on 14 February 2020.
Patrick's Gravatar
 Location: Katoomba, NSW
 Member since 11 February 2020
 Member #: 2408
 Postcount: 29


Thank you all for taking the time to reply. I have had no formal training in electronics so my basic understanding of the characteristics of electricity is very limited at this stage, it will take me a while to work through the answers you have provided.
I really appreciate the help.

Cheers

Pat


 
 Return to top of page · Post #: 14 · Written at 10:09:53 AM on 14 February 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4330

I am on a Farm and one got diversified very quickly. I went to a Technical School before they stuffed them up. So one did the basics of Turning & Fitting, to apprenticeship level, Wood working, Sheetmetal work as for plumbing. All of those & more like welding later.

I was repairing radios before I left Tech but circumstances let me to turn from electrical to a chemistry based career. I still have done all of those early things & one shed, actually has a lathe & the welding stuff. Motor mechanics also fits in there; Machinery on the farm breaks & needs fixing & maintaining. Last annoyance was the tractor deciding to blow the head gasket in mid fire season. Amazing what I found in the way of annoying peripheral nasties, as I had not pulled that engine down since May 1985.

Marc


 
 Return to top of page · Post #: 15 · Written at 12:33:13 PM on 14 February 2020.
Gandhn's Gravatar
 Location: Windella, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 343

Patrick, in my earlier post, I was trying to address the question you raised, regarding the different current flow in a rectifier and any other valve. I was hoping to point out that the direction is the same in both valves and is equally true if you consider conventional current flow, (positive to negative). The rectifier anode is at the highest voltage.
I was certainly not trying to baffle you with science!
Harold


 
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