Hi All,

More noob questions.

Just wondering if anyone knows of a good resource on the Net of Valves types and cross reference to each other for their functional use & differences.

Like for Example * 6A8G 6J8G can be subbed... but... and what are the" Buts" the differences or changes you;'d have to make to accommodate a similar but different Valve type
( I know to some extent that would depend on the circuit)

EG like a 6D8G has a heater current demand of 150mA
fine as a sub in a parallel heater arrangement but in a series string the Voltage drop would throw it all out.

Inter electrode Capacitances differences, how they come in to play and I guess for that were getting into knowing from more so a design level how the circuits works.

I find lots of posts in different forums with info but just wondering if anyone ever gathered that knowledge in one place.. for Converter, IF Det Amp, Rec and Audio valve types.

I guess its really the knowledge you accumulate over time but be nice if it was in one place..anyway if any resources like that does exist it would be handy to know...

Thanks All

(* thought similar these are not the same and so not necessarily can be called direct replacement or substitute for each other)

What you need is one of the AWA or Philips valve data books. They come up occasionally on Ebay. I once pondered on reproducing my Philips one here but it'd involve a lot of data entry and thus a lot of time as there's hundreds of types that were available in the day.

From that valve data it is possible to work out what can and cannot be substituted. It was also the case that there were valves with identical innards but with different bases - the four pin 80 and eight pin (octal) 5Y3G being one of many examples.

Having some knowledge of valve geneology helps. For instance, the 1930's 75 valve can be substituted with a base change to a 6B6G and a miniature 7 pin 6AV6. I wouldn't say that 6J8G & 6A8G are a direct substitute, although you are right that it does depend on the circuit. A 6J8G can be subbed with a ECH35, and with a base change, a 6AN7 or 6AJ8. A 6A8G can be substituted with a miniature 6BE6.

If you find yourself with a old Healing that uses a EBL1 output valve, which are as rare as hens teeth, you can always use a 6BV7 which are electrically very similar. And just in case a good EBL1 turns up one day, you can always make up an adaptor socket for the 6BV7. But even 6BV7's are getting harder to find and they have a reputation for being unreliable. No problem - a brand new Sovtek EL84 and a couple of germanium general purpose signal diodes will do the trick. EL84's can also replace 6M5's, EL3's, EL3NG's and EL33's. You can even get a radio that uses a 42 or 6F6 to limp along with the pentode section of a 6BM8.

Years ago there was a great quarterly magazine from San Francisco called "Vacuum Tube Valley". There was a segment called "Uncle Erics Dumpster" by Eric Barbour. This segment had articles about uses (mainly audio) for unwanted cheap ex military, oddball and TV valves. Unfortunately the editor Charlie Kittleson passed away some years ago and the magazine is no longer.

But getting back to valve subs. With a good valve manual you can compare the characteristics of different valves and see how newer valves are often based on earlier ones.

I don't know of any one site that accommodates your wishes. As others have said, it usually boils down to comparing one set of specs against another.

This site gives general substitution data. Can't vouch for its accuracy:

http://www.worldtubecompany.com/mm5/merchant.mvc?Screen=TSL.

... and Franks Electron Tube Pages is a good source of data sheets for individual valves:

http://frank.pocnet.net/.

Thanks Guys

Yes I was I guess thinking of a simplified site of cross references with the "reasons as to why and
how" Valve Geneologly was what I was thinking too, I believe there is a book out there on that

yes I should correct that as 6A8G & 6J8G aren't per say direct replacements but you find them being interchanged a lot... cant recall what the difference is now but I think the 6A8G was the predecessor and the 6J8G was an evolution of the 6A8G

That being the trouble the is just so so many different types out there and I was reading really there needs to be as the idea of a "universal valve" was a bad Idea..a tailored Valve was really the needed item for the job (optimized for a purpose in one way or another)

Still there seems to be a more finite base of well used Valves for radio sets and thats were I was going with this

Brad, yes I think it would be an idea to pick up a Valve subs book you see the milliwatt ones come up from time to time...thank you Will do at some point soon

Monochrome Thanks for that info
Quote
"But getting back to valve subs. With a good valve manual you can compare the characteristics of different valves and see how newer valves are often based on earlier ones."

I have been finding that out (as Brad said too on that with regard to the 5Y3 and 80 types)
I must track down more info on the Gemology book..

Thank you GTC I was aware of Franks site and it is a great resource but didnt know of the other

Anyway Guys appreciate the feedback on this, more food for thought here
Cheers

Have great Father day

Here's an article by Rodney Champness. Depending on how many modifications you're prepared to make and how original you want to keep the radio there's an awful lot you can do.

http://archive.siliconchip.com.au/cms/A_101781/article.html.

6A8 is a Pentagrid 6J8 is a Triode Heptode with the Triode as a separate oscillator exciter directly coupled to the Heptode.

Because of the Triode the 6J8 superseded the 6A8 in SW sets. They will work in each others place but with sets like Astor JJ 6J8 will throw the band spread out by compressing it.

The one to watch in early Pentagrids is 6SA7, it works a whole lot differently than all of the others and is built very differently.

Several early valves only got a heater change & base change 6A7 is 6A8 with a different base, 6D6/ 6U7: 80/ 5Y3; 75/ 6SQ7 same deal.... and so it goes on.

Marc

Thanks Scraps much appreciated

Yes that the kind of thing I ment just wondering if someone had done a bigger more comprehensive version of it

Side point
-----
You know actually I did find that idea of using Didoes interesting but I found some site which I should find again as I was going to post it up for comment

The Idea is to actually use two silicon diodes in series with a rectifier valve so that if a Valve ever does short you have the safety net of the Silicon Doide taking overt the rectifying action fully...

The down side is of course the voltage B+ climbs due to the silicon diode but at lest the transformer wont be killed I think is the idea or a fire Start since most all radio seems to be un-fused...Thought I think the idea originally come from doing it to guitar amps were the hi abuse is probably very likely to kill a rectifier Valve

Must find the reference links...
OK found one forum link, I think it was RG's comments that lead me on the chase for more info on this as a protection measure

http://music-electronics-forum.com/t1938/.

(Edit additional, just on that.. dont think it will help if you have an indirectly headed Cathode and you end up with HK leakage or short ..it still going to end badly I think as far as earthed heaters in a radio)

I really should do this as a separate thread thought
cause if it can possibly be a safe guard for a lovely refurb radio that you dont what to do an SS rectifier on its probably worth a couple of diodes in series for protection

Thought how do you tell if your rec tubes gone belly up short.
-------

I 've been looking for that article for you but just haven't found were the 2K+ issues are yet..I dont have complete years but I do have a lot of SC EA AEM and ETI...but occasionally Id miss months and I did stop buying SC and was using online version for a few years..later 2K+

Oh and I think that book I've been reading the odd comment here and there about is

Saga of the Vacuum Tube By by Gerald F. J. Tyne

http://www.amazon.com/Saga-Vacuum-Tube-Gerald-Tyne/dp/0672214709.

(Hardback copies can get very expensive)

Seems it deals with the physical construction history of design from the beginning to about 1930
So not quite what I was looking for but defiantly it seems well worth getting your hands on if you want to know the who's who of early valves and their construction...bootlegging was a very common practice
No electronic version exist as far as I know which is a bit of ashame so you cant buy it in that form
still I prefer books really...anyway seems a good tomb to get your hands on if you can at the right price

There is an excerpt in this doc out lining what it goes through
http://ieeexplore.ieee.org/stamp/stamp.jsp?reload=true&arnumber=1090014.
(the link fell out of google so hope its ok Brad)

$20 back in the day lol 1977

Anyway

Thanks Marc didn't see your post there

Yes that what I am after and Thanks for the info on the 6A8 6J8 Differences I guess really it all there but you have to go through the pdf docs for the differences ...but the Genealogy of them is something that not so well known these days thought back in the day as each appeared you probably got the flow and the changes and improvements

Oddly I do have 6SQ7GT here I would have thought it was a newer tube design but seems it has history...

Again thank you all

6SQ7 has history it was cloned from a 75. As a point, with the exception of some 6X5 the only common short is turning a 5Y3 sideways. Often they blow apart internally with a decent short.

Albeit that is was not for that purpose you often found around 100 Ohms in the plate circuit of 6X5 of low wattage & it would burn when the tube shorted, hopefully before the transformer.

Marc

That's interesting, how do you perform an alignment on a set with a 5Y3? Very gently? I did notice the 5Y3 on the AWA 617 got physically noisy whilst I was aligning it. It took me a while to track down the noise. I wondered about it going boom but with no bench supply the only way to align it is with the chassis on end.

Scaps wrote

"That's interesting, how do you perform an alignment on a set with a 5Y3?"

Yes actually I was aware of not mounting them in a horizontal plane....for the reason of destruction
not sure if there is a window of time you get but it definably dont sound like a good Idea even for servicing...there is some info out there about this.... mounting rectifiers valve and possibly a point to watch...as it seems TV are (were) liable to mount them in strange ways

Still I suppose for the safety's sake maybe a suitable PSU is the go or perhaps a silicon purpose built sub rectifier is an Idea

Thought no experience here.... at all
(PS Scraps, I cant find those SC issues.. stuffed if I know were they are... sorry about that)

Yes Marc I've read of 100 ohms being used and forgotten why but yes a fusible aka sacrificial resistor
is an idea....*seems Type 47 Lamps were recommend as the "fix" for US sets that liked to kill Transformers but theres like many threads and opinions on that one with over worked 6X5
So I wont bother saying more...(*the above comment with a 6X5 is due to HK failure I think from memory)

I suppose the bigger Question is "how liable a rectifier valve is to go short in a radio circuit"
(as I said , can understand in a guitar circuit..were they get heavily used and abused)

Anyway was side point

Cheers

PS atm having Net woes so not sure when I'll be logging back on.

I wonder if it is possible to build an ADSL modem with valves...

They built computers with them.

At then end of the Day it just a bunch of modulated frequencies..(or was) thought geez getting the phase and time relationships right would be fun...and high speed switching of valve digital WOW what fun.

You could get higher speed I suppose and reduce the size with lots of Nuvistors & maybe compactrons.
https://en.wikipedia.org/wiki/Nuvistor.
https://en.wikipedia.org/wiki/Compactron.
(links for general ref)

But I dont think I'd want to pay the power bill to run it ;)
(even with nuvistors & compactrons)

And yes I am joking but well its not to say its impossible either.

There is but one position that a 5Y3 can be run horizontally, and that can be found in its data sheets "Franks electron tube pages". If the filament sags, which they do, fireworks if you get it wrong. The Russian Sovtek is built more like a 6X4 etc and appears to have a cathode sleeve. It is a slow heater, because of the sleeve. & does not generate the same surge.

Filament is more like a heater, but huge and is not like a towel on a clothes line, mounted in an air conditioner duct.

What sort of IF's & trimmers have you got? In what? Top trimmers can be done from the top with something that won't short them. 5Y3 & the rest work upside down. You need to know where everything is before generalizing, as they put them all over the place.

Marc

I wonder if it is possible to build an ADSL modem with valves...

Sounds like a project for Art.