Leak TL/12 Plus / Point One Plus

[Darmok]

The valve sockets on all Leak valve amps are relatively cheap and not that good imv.

The Leak TL50+ had better ceramic octal valve sockets fitted because of failures especially with the GZ34 original valve socket.

Changing to ceramic sockets on the TL12+ makes for a better more reliable amplifier but looses out on originality!

 

[TonyScarlett]

Really enjoying this thread, would love to take on a project like this sometime.
I wouldn't feel bad that the amp didn't work 1st time Tony, you've probably learned more about fixing & troubleshooting these amps in the last 24 hours than the previous 24 years!
TS

 

[snowman_al]

That is excellent news Tony, you must be pleased.
Any further dropping out, then I would suggest you very Very gently re-tension the valve holder forks. A strong needle is ideal (after the amp has been switched off for half an hour or so...) Might be they are just not grippy enough to bite through the skin that forms on the valve pins. And those Russian valves sometimes have very slightly thinner pins.
If a fork goes really loose, I have spares and it is relatively easy to replace one or two if needed.

Will be interesting to know how you get on with a stereo pair. You might encounter a little ground loop hum depending on the set up there. There is a fix if you do. Alan

 

[Darmok]

Really enjoying this thread.

^^ +1

 

[Raoul Duke]

Glad you seem to have come right Tony! unsoldering everything to get the board out is a bit of a PITA, especially after all the neat and careful work you've already done.

 

[John_73]

Fab news Tony, pleased for you!

"...apologies for wasting your time with such a dumb noob mistake which I really should have known."

No time wasted, in fact it's a very helpful outcome, as it adds to the list of things to check for after a rebuild. I hadn't considered cleaning the pins on my original set of '67 Mullards, which I shall now do before testing the amp. Something else to add to the memory banks!

You going to set them up together now and have a proper listening sesh?

P.S. Can highly recommend Piksters interdental brushes for cleaning valve sockets.

 

[lordsummit]

Great news!! Which speakers are they going to play with first?

 

[Tony L]

You going to set them up together now and have a proper listening sesh?

Absolutely! I’ll give them a good test tonight. I’ve got them ready with a set of gold-pin Russian military 6p14p-ER thinking they won’t be tarnished. I’ve got some nice early Mullard EF86 and ECC81 of the type they’d have originally shipped with, I’ve just done some pin-cleaning. If either doesn’t boot up right I’ll look again at the bases.

The test set of valves were what came from Hi-Fi Hanger, a late-50s Mullard EF86, a Mazda ECC81 (I’ve not date checked it as I haven’t a pair) a pair of ‘foreign’ Mullard EL84s (nice valves, sadly I don’t have another pair to match), the Tungsram GZ34 (which is actually a Blackburn Mullard of a design I have two others).

Great news!! Which speakers are they going to play with first?

They are upstairs with the LS3/5As. The good thing with valve amps is it is very hard to hurt speakers with them. They can blow up, burn the house down, but nothing bad can get out of the output transformer as I understand it! They are also the easiest to fix speakers I have to hand, all drivers are available from Falcon!

 

[Darmok]

Great news!! Which speakers are they going to play with first?

Big Tannoys hopefully, able to check the bottom end performance of the TL12+s.

 

[lordsummit]

They are upstairs with the LS3/5As. The good thing with valve amps is it is very hard to hurt speakers with them. They can blow up, burn the house down, but nothing bad can get out of the output transformer as I understand it! They are also the easiest to fix speakers I have to hand, all drivers are available from Falcon!

Excellent! I’d be really surprised if they didn’t give the 303 a run for its money downstairs. Could open up a wormhole of pre-amp and phono stage swaps though...

 

[Tony L]

Still not out of the woods I’m afraid, I couldn’t get it to boot up properly, but I think I know the issue now. The pin gripper fork of pin 4 of the ECC81 tube socket just fell apart as soon as I touched it with a pin to try and tension it. These sockets really are utter crap!

I’ve found some similar McMurdo sockets on eBay here (I’ll not deplete Snowman Al’s collection despite the very kind offer!). I bought two, so I’ve 18 spare pin-forks. The logical thing would be to swap the lot for better modern sockets, but it is a stupid amount of work and would almost certainly devalue the amp! I’ll just replace obviously crap pins. Annoyingly this one is right under my nice neat bent resistor.

So, how do you get the forks out of the socket? I’m assuming thoroughly desolder it, unbend the back tag bit so it is straight, and then it will come out the top?

PS Whilst this is annoying I’m really happy I’ve heard the amp work once, that proves the transformer is good and also indicates I didn’t screw up the rebuild (e.g. overheat anything) - I went nowhere near this particular pin!

 

[Yank]

Excellent!

I suppose with two stages of the amp not drawing current, the B+ would rise.

 

[Tony L]

Just on a ‘trying to learn stuff’ thing any idea why I’m not reading anything on pins 4 & 4 of any of the valves? The schematic implies that’s the 6.3V. Is it a voltage across 4 & 5, or AC or something? I’d have expected to read something other than zero.

 

[Tw99]

From the circuit diagram, the 6.3v comes straight out of the transformer, so it’s AC.

 

[Tony L]

Thanks, that makes sense.

 

[snowman_al]

Just on a ‘trying to learn stuff’ thing any idea why I’m not reading anything on pins 4 & 4 of any of the valves? The schematic implies that’s the 6.3V. Is it a voltage across 4 & 5, or AC or something? I’d have expected to read something other than zero.

The heaters are as stated 6.3 volts AC. You need to check from pins 4 to 5 of the EL84s and EF86. The ECC81 is different, measure from pin 9 to 4 and 5. (4 and 5 are soldered together in the TL12+.)
If you look at your amplifier the heater wires are the doubled green and blue wires. (As the heater winding is centre tapped to the chassis, you will measure 3.15 volts AC from the chassis / ground to either of the heater pins.)

... The pin gripper fork of pin 4 of the ECC81 tube socket just fell apart as soon as I touched it with a pin to try and tension it. These sockets really are utter crap!

So, how do you get the forks out of the socket? I’m assuming thoroughly desolder it, unbend the back tag bit so it is straight, and then it will come out the top?
...

Pin 4 failure of the ECC81 does exactly account for your initial faulty voltage readings. It would mean that the heater in the first half of the valve would not come on, so that half would not operate / draw any HT current.

Actually pin 4 is one of the easier ones to get to. Just remove R10 before you start and put it back after.
You remove and replace them just as you say. Remove all the old solder, straighten the pin so it is vertical and in line with the slot in the holder and push it through from the wiring side. Make sure you get all of the old fork out before you fit the new one.
Push the new one in then bend it carefully to match the original shape. Give the tag part a good clean before you try to solder it.
You will find pins 4 and 5 soldered together on the ECC81 which might make it a little more difficult to unsolder them.
Personally I would replace both pins here. If you decide to do that you can cut the pins off with side cutters, carefully just below the wires, and push the remains out with a pin or jeweller's screwdriver. Then it is much easier to unsolder the bits of the tag from the wires. 'In free space'.

When you have replaced the pins, before you solder the wires back on put an old valve in the socket first. That will align the pins in the socket correctly and keep stress to a minimum.

If you want to practice / mend the amp before you get the new sockets, both the EL84 sockets have 'spare' pins on 6 and 8...

 

[Tony L]

Many thanks. Great to know that pin failure explains the situation. I’ll definitely do the pair of pins and using side-cutters is a great idea and would save putting a lot of heat and stress on the plastic base. I’ll do exactly that.

It had occurred to me that I could steal the non-connected pins from the 84s, but I’ll just wait for the spares to arrive. I can wait. The stressful bit was when I wasn’t sure about the transformers and didn’t know if I was throwing good money at a non-fixable amp, but now I know it is solid I’ll just take my time and get it exactly right. I spent an hour or so getting as much flux and crud off the board as I can. A lot actually being the original stuff from the 1950s. I can understand why folk desolder and remove the board, it would make a lot of sense to chuck them in an ultrasonic cleaner full of isopropyl or whatever for five minutes. They really were filthy, and I have no idea what grubby mess exists on the top of the board. The good thing is Leak did use very decent wiring, I’m surprised just how solid and robust the plastic coating is given so much vintage electronics needs total rewiring.

PS Another thing to document for completeness is as expected a 1A fuse seems fine in the transformer fuse-holder. They are a now obsolete size, but you can get a 15mm fuse in there.

 

[Yank]

Unless the sockets are riveted to the chassis, I can't see any reason to try to replace pins if you have whole, matching replacement sockets.

 

[John_73]

Unless the sockets are riveted to the chassis, I can't see any reason to try to replace pins if you have whole, matching replacement sockets.

I’d go this route too and replace the whole socket. Might be more pins that are on their last legs for that particular socket.

 

[Tony L]

The sockets I have on order (link), which are the only NOS ones I could find, are the same make and socket type, but a different mounting, so it would not be practical to replace whole sockets. The pins certainly look the same, though obviously I’ll only know for sure when I have fitted one.

I have a Stereo 20 and two TL12 Plus amps, the youngest being 60 years old. To the best of my knowledge only one pin across all these (13x) B9A sockets has failed! Statistically that is one pin out of 117, i.e. less than one percent! I really don’t see the logic of replacing all sockets (a crazy amount of work), or even just the one whole unit (still a PITA!), though it certainly makes sense to have a good stash of spares available should any more fail.

PS Obviously if they do start to fail I’ll reconsider. I have done a heck of a lot of tube rolling on the Stereo 20 and they are still hanging on in there. For all I know something bad may have happened to the failed pin in a past life, e.g. some one jammed a bent valve pin into it, I just can’t know, but hopefully it is an exception rather than an indication of future mass failure.