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 Project Ideas and advice wanted!
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 Return to top of page · Post #: 1 · Written at 7:37:26 PM on 21 May 2010.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

I am thinking of building my own valve radio. I have plenty of old chassis that are beyond repair and am thinking since I have power, O/P and I/F transformers and a large stock of valves (From Old Octal to modern Miniatures) what would be good design out there to build.

Some of the things and options I am considering are:
At least AM(BC) band, Even maybe FM and SW as well if I can find the correct IF coils?
Magic tuning eye?
Aux I/P for connecting up CD player or MP3 player.
Stereo?
Around 5W of audio OP?

For the power supply I may even go for a solid state supply (I do have a few different types of rect valves but want something reliable.

I have a large chassis from someone else that was their project with a 3 gang tuner from and old AWA radio gram with the original dial glass. Their cct was parted out to fix other radios by them.

Does anyone have any other ideas and where to find a nice CCT that could do some or all of the things listed?

I have just got the RT&H DVD from Silicon Chip but as yet haven’t got a good read of it yet to see if there is something in there.

I was thinking of a modified little general or something similar. I am not looking to make something and pass it off as an old valve radio. I want it to be a something I can have in my workshop and say “I built that!” and use daily.
Smile Smoke


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 2 · Written at 10:47:56 PM on 21 May 2010.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

Valve rectifiers are not particularly, unreliable unless you use a 6X5.

Marc


 
 Return to top of page · Post #: 3 · Written at 11:16:08 PM on 21 May 2010.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Ok I will keep that in mind. Do you know of any good cct that I could use?


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 4 · Written at 1:05:05 AM on 22 May 2010.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

I tend to like HMV circuits, but it depends on what era and what valves you have?

Eg if you want to make a set with FM, it is preferable to use TV valves, as TV audio was FM

Do not have much in the way of circuits with FM

Marc


 
 Return to top of page · Post #: 5 · Written at 1:39:06 AM on 22 May 2010.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Ok. I have a box of old TV valves. I havent had time to go through them yet. I dont mind if I have to use a MIX of valves from different ERAs but.

I have plenty of stuff from a workshop that I use to work in as a kid after school.

So with plenty of stuff I figure I should be able to put together something respectable and its just for fun!


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 6 · Written at 8:35:44 AM on 22 May 2010.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6174

I haven't checked my R&H magazines as yet but there may be some discussion about FM radio around 1947 as there were government-sponsored test transmissions around this time. They were later abandoned in favour of rolling out television. As Marc said, the sound was on FM. The picture, in good old AM, though obviously with a greater bandwidth allowance than they gave to radio broadcasters.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 7 · Written at 10:00:42 AM on 22 May 2010.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

Do not overlook circuits from the Europe & US. I have had a few German sets pass through with FM.

Remember Australia seemed to stay many years behind the times (and in certain quarters that still applies).

FM was discovered by the same Anderson that created the Super Hetrodyne in 1911....... when did we get them.....?

America & Europe had TV, albeit crude in the 30's. (Audio AM I think, back then)

Marc


 
 Return to top of page · Post #: 8 · Written at 3:33:07 PM on 22 May 2010.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Ok thanks guys. I might drop the idea of FM then. I dont have any FM coils to play with so I might just stick to BC and maybe SW. I still havent had time to go through my valves yet but they are mostly common types used in radios.

I had the chance to get more of them at the time but couldn't fit them in my boot along with all my Kids stuff. I just wish that I had got themSad

I have a pair of old KT66's plus transformers on an old chassis. I think they were High powered O/P valves? Since I have this chassis complete I might make this my starting point. How would I test these Valves???

Any ideas?


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 9 · Written at 4:22:07 PM on 22 May 2010.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6174

Yep, KT66's are power amps. I have a couple of these made by GEC that were salvaged from the hall (later demolished by our penniless state government) at the old Gladesville Hospital. Like all old halls this one had facilities for showing movies, two big projectors with cinemascope lenses, mercury-arc rectifier for the arc lamps, big mono speaker system, the whole shebang.

One thing you could try is to get an old TV chassis, ditch the driver circuit for the tripler, and the tripler itself for safety reasons, and then modify the sound part of the circuit to receive FM. The FM band lies in the lower part of the VHF TV spectrum, namely channels 3, 4, 5 and 5A.

I couldn't say how to go about this apart from using extreme caution - all televisions have circuitry that generate very high voltages to run the picture tube. I still remember the time I was handling a picture tube which wasn't even hooked up, yet still had enough static electricity stored in it to belt me through the chest. I was lucky that when I got the jolt that the picture tube wasn't far off the ground and there was no damage to it or me.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 10 · Written at 8:32:02 PM on 22 May 2010.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

I have had a little training with TV (modern ones about 10 Years ago) when I was doing my initial tech training. I may decide to put in FM later on.

I will trace out the cct of the power amp module that I have. I think it might be my starting point and then build a radio with an Aux I/P and feed it to this amp.

(Assuming the amp can be made to work and the valves are working!)

So all I need now is a decent receiver set-up.


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 11 · Written at 10:40:18 PM on 22 May 2010.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

The old B&W TV's normally had a wide tuner with different coils for sound etc. as long as you bring the mixer signal to the IF frequency of the TV, it would go through whatever is there.

If you leave out the Horizontal Valves the thing will not generate EHT. some even had a "service" switch to kill it.

Marc


 
 Return to top of page · Post #: 12 · Written at 10:17:33 AM on 23 May 2010.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Hmmmmm,,,,,,

Well this sounds like something to Play withSmile
I dont know of any stuffed B/W valve sets. All the stuff I played with was digital (Analog tuner!) TVs. The only B/W TV set I had was a little 10cm (4") transistor and IC set to use when my family went camping to watch the footy on! Guess I am showing my age here but!

So with a little bit more time I have checked out the power Amp chassis I have. Its a home built setup with the largest power transformer I have seen! its got a choke and a large centre tapped O/P Transformer to run the KT66's in push pull. It looks like it supplied voltage to the tuner Chassis that I plan to build My radio on. At the moment I think I will forget about Stereo and build myself a descent Mono set-up. What RMS roughly could I expect to get from the KT66's in push pull?

I think I like the look of the little General Cct in RT&H magazine. Does anyone know out there if they made a better Cct in this magazine. I am not after just a simple set. I would like to build something from the Best of the Valve era without duplicating an expensive LEEK or other type of amplifier and receiver.

Thanks
Daniel


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 13 · Written at 2:38:05 PM on 23 May 2010.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

I have just sent Brad a copy of the photos and my hand drawn cct for the amp.

Any comments and suggestions on it are appreciated.

Note I don't have any info for V1, I removed it along time ago.

The valves I have sitting from the 2 chassis I have are:
6SN7GT
6SJ7GT
Unknown rubbed off!

Could any of these be my missing Valve????

I am tipping its a 6SN7GT but looking at its pin out and the Chassis wiring it doesn't make sense to me!Sad

any thoughts???


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 14 · Written at 8:42:27 PM on 23 May 2010.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4178

The transformer will be several hundred mA the KT66's will need around 85mA each.

6SN7 does not follow convention. heaters are pins 7& 8 not the normal 2&7 like the KT66.

Its a double triode, therefore liable to be the phase splitter for the KT66's.

6SN7 1, G'; 2, A"; 3 K"; 4, G"; 5 A'; 6, K'

KT66 3, A; 4, g2; 5, g1; 8, K &g3, 6, NC

Marc


 
 Return to top of page · Post #: 15 · Written at 9:01:16 PM on 23 May 2010.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Marc

I sent you an email with the details of what I have.


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Valve radios, They just don't make them like they used to

 
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