Help Identifying plugs

surfguy13

Hi guys

I have just bought an old Linear valve amp, probably from the 60s.  It has a small split shaft plug which looks pretty much like a mini banana plug.  I need to buy a couple of pairs of these to make up a pair of leads but I'm not sure if they're called 'banana plugs' or what they're called.  This is making it really difficult to find them online.

I will add an image below but the dimensions of the plugs are:

Full shaft length: 15.0 mm
Shaft length from plug (when screwed in) to tip: 12.8 mm
Diameter when the split shafts are closed: 3.0mm
Diameter when the shafts are open: 3.5mm

Here's a photo:

http://img9.imageshack.us/img9/2438/o86f.jpg


Anybody got any ideas?

ecc83

They are called "Wander Plugs". 

Used in radio kit for just about everything. Headphones (very early) but most often for aerial and earth connections and sometime "gram" inputs.

I have probably got a few about somewhere but under piles of old ***t so don't hold yer breath! Meantime look for Vintage Radio sites.

Mind you I doubt (ICBM?) if an old Linear |(Concord?) amp will ever be valuable so why not change them for the ever popular 4mm "bananna" sockets? Or if there is room jacks.

And from the dredges of the memory. The EL34s in those amps had a had life because they overan the screen grid volts. If they are over 400volts put in a dropper R. Have modded dozens of them, standard bingo callers fare in WMCs!

Dave.

surfguy13

Hi Dave

Magic!  Thanks for that, really helpful.  I'll have a look around and see if I can't find some but......if I draw a blank can I get back to you to see if you've got any in the depths of your parts box?

You mentioned converting to 4mm banana plugs....is that simple?  I can wield a soldering iron but that's about it!!  It's a Linear L45A so a VERY small amp but a particularly nice sounding one.  It's got a single EL84. Photos here if that helps in terms of working out if or how the Wander plugs can be changed to 4mm banana:

http://img6.imageshack.us/img6/3807/jx1m.jpg

http://img59.imageshack.us/img59/6404/jvsi.jpg

More photos here:  http://imageshack.us/g/1/10383589/

Cheers

Guy

ecc83 said:

They are called "Wander Plugs". 

Used in radio kit for just about everything. Headphones (very early) but most often for aerial and earth connections and sometime "gram" inputs.

I have probably got a few about somewhere but under piles of old ***t so don't hold yer breath! Meantime look for Vintage Radio sites.

Mind you I doubt (ICBM?) if an old Linear |(Concord?) amp will ever be valuable so why not change them for the ever popular 4mm "bananna" sockets? Or if there is room jacks.

And from the dredges of the memory. The EL34s in those amps had a had life because they overan the screen grid volts. If they are over 400volts put in a dropper R. Have modded dozens of them, standard bingo callers fare in WMCs!

Dave.

surfguy13

Just tried a standard phono plug (3.25 diameter) in the socket and it fits like a glove.  Is there any reason I can't use these...........?

ICBM

surfguy13 said:

Just tried a standard phono plug (3.25 diameter) in the socket and it fits like a glove.  Is there any reason I can't use these...........?

It's fine if it fits tightly enough to guarantee a good contact - if not, squeeze the tubes slightly on the inside.

But if you want a couple of pairs of genuine original Radiospares Wander plugs, PM me and you can have them!

Dave is also right about the screen voltages in these old amps - they were usually run from the same power supply node as the OT feed, with the result that the plate is at a lower voltage than the screen, due to the resistance of the OT primary. This is bad for the valve because the screen tries to operate as a plate, and draws a lot of current. You can fix it either by moving the OT feed one node further up the chain (usually there is an unused one directly after the rectifier - doing this will also increase power output slightly, but at the expense of more hum), or by adding a screen resistor, or probably both.

Misterg

Farnell sell 3mm banana plugs which would probably work (I think the originals would have been 1/8") - bloomin expensive, though (over a fiver each!)

http://uk.farnell.com/productimages/farnell/standard/42463374.jpg

http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=317100&MER=bn-me-pd-r3-cust-all-2

surfguy13

Just tried a standard phono plug (3.25 diameter) in the socket and it fits like a glove.  Is there any reason I can't use these...........?

It's fine if it fits tightly enough to guarantee a good contact - if not, squeeze the tubes slightly on the inside.

But if you want a couple of pairs of genuine original Radiospares Wander plugs, PM me and you can have them!

Dave is also right about the screen voltages in these old amps - they were usually run from the same power supply node as the OT feed, with the result that the plate is at a lower voltage than the screen, due to the resistance of the OT primary. This is bad for the valve because the screen tries to operate as a plate, and draws a lot of current. You can fix it either by moving the OT feed one node further up the chain (usually there is an unused one directly after the rectifier - doing this will also increase power output slightly, but at the expense of more hum), or by adding a screen resistor, or probably both.

You did mention this issue of screen voltages I think in one of my earlier posts.....if moving the OT feed will help, and potentially increase volume a little (which wouldn't be a bad thing!!!) then it sounds like a plan.  How easy/difficult would this be to do?  Is it something I'd have to get done by the guy who carries out work on my amps or potentially could I do it?  As I said before, comfortable with a soldering iron but have no test equipment other than a basic meter. 

Great re the phono plugs, I can't see any obvious reason why they shouldn't work. After I'd read Dave's comments I had a look online and couldn't find any Wander plugs but an old thread on another forum mentioned it might be possible to make a Wander plug using a standard 3.2 mm cotter pin and that got me thinking.  I was pretty sure that phonos were around 3.2 and when I tried one it was a really snug fit, no movement at all.  I'll try hooking one up and see how it goes.

surfguy13

Misterg said:

Farnell sell 3mm banana plugs which would probably work (I think the originals would have been 1/8") - bloomin expensive, though (over a fiver each!)

http://uk.farnell.com/productimages/farnell/standard/42463374.jpg

http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=317100&MER=bn-me-pd-r3-cust-all-2

Thanks for that, excellent to have those in reserve.......but, like you say, bleedin' expensive for a very basic plug!!!!!! 

ecc83

Hi ICBM. If the OP takes up your offer of plugs I will replenish your stock when I can (its the LOFT you know! Can't face it at the mo!) . 

The screen volts problem I mentioned was for the 50W (?! wasn't!) EL34 jobbie, I have never seen that wee one (looks in nice trim, be  a shame to butcher it for 4mm sockets  but if you were careful you could drill out those pop rivets and make up another plate and keep the original for possible re sale?)

Bet that is red/black/green mains wire and the amp really should be PATT'ed.

Had another look and I might not know that amp but I sure as H know those resistors! The two 2k7s are an "end cap" type and the cap is known to get loose over the years making the resistors go high, open circuit or noisy. The 220k carbon comp is infamous for going high (old Philips radiograms!) but the 27k  should be fine. 

'Twere me I would drill out that rivet just above the Rs and fit another tag strip and make a more secure job of that whole CR assemby. On the good side! The caps in there hardly ever gave problems.

Dave.

ecc83

http://www.chambonino.com/carlsbro/linear-l45aoriginal.jpg

Map.

martinw

I'd be inclined to create another HT node on that and move the screens to B+2. Change R12 to 1k/1W, add another 1k/1W and something like a 22uF/250V cap for B+3. I'd fit a smallish screen grid resistor, say 220R/1W.

You could probably remove C9 then. Also try increasing R8 for a bit less NFB, or even disconnect it altogether.

On the other hand, if you like the sound as is, I wouldn't bother doing anything. With a max HT of 180V, you're unlikely to have any issues with the valve.

surfguy13

ecc83 said:

Hi ICBM. If the OP takes up your offer of plugs I will replenish your stock when I can (its the LOFT you know! Can't face it at the mo!) . 

The screen volts problem I mentioned was for the 50W (?! wasn't!) EL34 jobbie, I have never seen that wee one (looks in nice trim, be  a shame to butcher it for 4mm sockets  but if you were careful you could drill out those pop rivets and make up another plate and keep the original for possible re sale?)

Bet that is red/black/green mains wire and the amp really should be PATT'ed.

Had another look and I might not know that amp but I sure as H know those resistors! The two 2k7s are an "end cap" type and the cap is known to get loose over the years making the resistors go high, open circuit or noisy. The 220k carbon comp is infamous for going high (old Philips radiograms!) but the 27k  should be fine. 

'Twere me I would drill out that rivet just above the Rs and fit another tag strip and make a more secure job of that whole CR assemby. On the good side! The caps in there hardly ever gave problems.

Dave.

Hi Dave

Once again, thanks so much for all the information!

Yes, the amp is in remarkably good condition for it's age.  And that's a bloody good idea re drilling out the rivets and making up a plate with 4mm plugs.....dead easy to do, even for me!!     Mind you, the amp is worth very little in terms of hard cash but it really is a VERY sweet sounding little amp.  I tend to just use it at full volume and control volume via the guitar. 

Interestingly the amp is incredibly quiet, no noise whatsoever, even flat out.  The pots function as would a new high quality pot and the EQ is very responsive and nicely graduated. 

I'm afraid the technical info in your post goes WAY over my head but I genuinely appreciate it and if I do decide to get anything done I can pass this onto Andy who does any work on my amps.

surfguy13

martinw said:

I'd be inclined to create another HT node on that and move the screens to B+2. Change R12 to 1k/1W, add another 1k/1W and something like a 22uF/250V cap for B+3. I'd fit a smallish screen grid resistor, say 220R/1W.

You could probably remove C9 then. Also try increasing R8 for a bit less NFB, or even disconnect it altogether.

On the other hand, if you like the sound as is, I wouldn't bother doing anything. With a max HT of 180V, you're unlikely to have any issues with the valve.

Hi Martin

As with Dave's post, thanks a million for your thoughts but sadly I just don't understand it!!    I wish I did but I don't.  However, the point you made about leaving well alone if I'm happy with it is a good one.....the amp runs superbly well, no noise, no issues at all and I love the sound so maybe you're right and I should just enjoy it!

Cheers

Guy