Leak TL12+ - UK Vintage Radio Repair and Restoration Discussion Forum

ROLO1946 · 20th Jun 2008, 6:46 pm

Hi folks

My first attempt at valve amp restoration..
A TL12+ from 1972 (30.08)
Its in good nick with all valves and xformers
Hasn't been used for years
No blown caps or leaky caps
No shorts
No oil or bad burn marks
Im thinking of giving a gentle 110vac whilst loading the op with an old speaker
Any helpful comments?

Roger

Sean Williams · 20th Jun 2008, 6:59 pm

It will almost certainly have leaky caps (electrically), I would be worried about cathode bypass components on the output bottles.

As for 110v....

Why? - to poison the cathodes of the valves perhaps - if it wont take full mains at switch on, then there is a fault that needs to be fixed

So, power it up without any valves in it.

measure the voltages at the anodes of the rectifier, and check heater volts.

Plug the rectifier in.

Check HT volts at rectifier cathode (it will be higher than specified due to no load).

Leave running for a few minutes and check for hot/stressed components.

Plug preamp and driver valves in, check voltages/components again.

Finally, connect known speaker to amp, install output bottles, then power up, and listen for odd noises, look for signs of overheating components, or glowing anodes, then measure grid voltage on output valves.

positive volts on the grid? Switch off, and change those leaky caps (told you there would be some)

Power up again, measure cathode volts on output bottles, compare to spec - all OK? - good, connect signal source to amplifier, and run up for a while.....

Anything more than this is down to personal choice.

Cheers
Sean

ppppenguin · 20th Jun 2008, 7:04 pm

Sean's advice is all good. If you're nervous about it, put a 100W lamp in series with the mains to limit any possible damage.

I would go a little further and change the output stage grid coupling and cathode decoupling caps before applying any power. They're likely to be less than perfect and a failure here can destroy an ouput transformer.

Don't know the circuit of the TL12+ but if there's a cap across the mains change that too before applying power. Use an X or X2 rated component which is designed for the job.

Trevor · 20th Jun 2008, 8:56 pm

The coupling capacitors to the grids of the output valves must be replaced by now if they are the origional units this was always a week point on them
regards trev

phase_splitter · 20th Jun 2008, 10:12 pm

Lovely!
Beautiful little EL84 PP monoblocs.

All previous advice should be heeded.
I would be inclined to re-cap them entirely; except possible the 'lytics in the CRC filters. Some people like to change this arrangement to a CLC pi filter, but I think best left as Harold intended.
In a vintage amp it's not (IMHO) worth risking damage to iron and valves due to leaky caps.
Check critical resistors such as cathodes, and also anode loads of the phase splitter.
Be warned, replacement valves are getting expensive (EF86, ECC81, EL84 and GZ34)
Well worth joining the Leak yahoo group, manuals, etc. can be found there.
http://tech.groups.yahoo.com/group/hjleak

Good luck and have fun!

ROLO1946 · 20th Jun 2008, 10:42 pm

Ta folks
I am a complete novice
Thanks
Roger

ROLO1946 · 21st Jun 2008, 9:52 am

Where do the illuminati advise for components?

Roger

'LIVEWIRE?' · 21st Jun 2008, 10:02 am

I mainly use Cricklewood Electronicshttp://www.cricklewoodelectronics.comwho have a good range of capacitors, resistors and valves. Savoy Hill Publications stock, amongst other things, dual electrolytic capacitors(contact details not to hand, but a Google Search will find them)
Other sources can be found on the 'Suppliers, repairers and Links' page of this site

phase_splitter · 21st Jun 2008, 11:32 am

I don't know about the illuminati, but I use RS!

yestertech · 21st Jun 2008, 1:11 pm

I agree with all the other comments - these are great amps and nice to look at too !
Definitely CHANGE the 2 x 0.25 TCC metalpack caps feed the EL84s, if they havent been done already ! Also check the 270 ohm cathode resistors as they will have changed in value.
Before powering up, check the DC resistances of all the Mains xformer secondaries and also the centre tap to anode and screen grid resistances of the OP xformer, as amps which have been neglected can burn out the transformers quite easily.
If youre lucky, the electrolytics will reform OK. Leak used TCC caps almost exclusively and they seem to have a good lifespan.
When you first hear it , it's guaranteed to bring a smile to your face !!

Andy

Valleyjinker · 24th Jun 2008, 4:21 pm

I rate the TL12+ amps very highly. Tried them against many other vintage types (including a pair of Stereo 20s, Quad 11s and Radford) and always go back to them.

I've heard more than one enthusiast say that if you change all the components for modern types - particularly the metal 0.22 driver caps - then you don't get the real character of the amp. Same bloke managed to find some NOS ones - which were leakier than the ones on his amp!

Two choices:

Leave everything as standard as you can, watch it carefully and hope it doesn't go bang,

or change everything that might cause a problem.

If you do the latter could it be argued that you will be listening to a modern Chinese valve amp?

20th Jun 2008, 6:46 pm	#1
ROLO1946 Retired Dormant Member Join Date: Nov 2007 Location: Cotswolds, Stroud, Glos Posts: 8	Leak TL12+ Hi folks My first attempt at valve amp restoration.. A TL12+ from 1972 (30.08) Its in good nick with all valves and xformers Hasn't been used for years No blown caps or leaky caps No shorts No oil or bad burn marks Im thinking of giving a gentle 110vac whilst loading the op with an old speaker Any helpful comments? Roger

20th Jun 2008, 6:59 pm	#2
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,518	Re: Leak TL12+ It will almost certainly have leaky caps (electrically), I would be worried about cathode bypass components on the output bottles. As for 110v.... Why? - to poison the cathodes of the valves perhaps - if it wont take full mains at switch on, then there is a fault that needs to be fixed So, power it up without any valves in it. measure the voltages at the anodes of the rectifier, and check heater volts. Plug the rectifier in. Check HT volts at rectifier cathode (it will be higher than specified due to no load). Leave running for a few minutes and check for hot/stressed components. Plug preamp and driver valves in, check voltages/components again. Finally, connect known speaker to amp, install output bottles, then power up, and listen for odd noises, look for signs of overheating components, or glowing anodes, then measure grid voltage on output valves. positive volts on the grid? Switch off, and change those leaky caps (told you there would be some) Power up again, measure cathode volts on output bottles, compare to spec - all OK? - good, connect signal source to amplifier, and run up for a while..... Anything more than this is down to personal choice. Cheers Sean __________________ Engineers make things work and have spare bits when finished

20th Jun 2008, 7:04 pm	#3
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: Leak TL12+ Sean's advice is all good. If you're nervous about it, put a 100W lamp in series with the mains to limit any possible damage. I would go a little further and change the output stage grid coupling and cathode decoupling caps before applying any power. They're likely to be less than perfect and a failure here can destroy an ouput transformer. Don't know the circuit of the TL12+ but if there's a cap across the mains change that too before applying power. Use an X or X2 rated component which is designed for the job.

20th Jun 2008, 8:56 pm	#4
Trevor Octode Join Date: Aug 2006 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 1,082	Re: Leak TL12+ The coupling capacitors to the grids of the output valves must be replaced by now if they are the origional units this was always a week point on them regards trev

20th Jun 2008, 10:12 pm	#5
phase_splitter Retired Dormant Member Join Date: Jun 2008 Location: East Sussex Posts: 25	Re: Leak TL12+ Lovely! Beautiful little EL84 PP monoblocs. All previous advice should be heeded. I would be inclined to re-cap them entirely; except possible the 'lytics in the CRC filters. Some people like to change this arrangement to a CLC pi filter, but I think best left as Harold intended. In a vintage amp it's not (IMHO) worth risking damage to iron and valves due to leaky caps. Check critical resistors such as cathodes, and also anode loads of the phase splitter. Be warned, replacement valves are getting expensive (EF86, ECC81, EL84 and GZ34) Well worth joining the Leak yahoo group, manuals, etc. can be found there. http://tech.groups.yahoo.com/group/hjleak Good luck and have fun!

20th Jun 2008, 10:42 pm	#6
ROLO1946 Retired Dormant Member Join Date: Nov 2007 Location: Cotswolds, Stroud, Glos Posts: 8	Re: Leak TL12+ Ta folks I am a complete novice Thanks Roger

21st Jun 2008, 9:52 am	#7
ROLO1946 Retired Dormant Member Join Date: Nov 2007 Location: Cotswolds, Stroud, Glos Posts: 8	Re: Leak TL12+ Where do the illuminati advise for components? Roger

21st Jun 2008, 10:02 am	#8
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Leak TL12+ I mainly use Cricklewood Electronicshttp://www.cricklewoodelectronics.comwho have a good range of capacitors, resistors and valves. Savoy Hill Publications stock, amongst other things, dual electrolytic capacitors(contact details not to hand, but a Google Search will find them) Other sources can be found on the 'Suppliers, repairers and Links' page of this site

21st Jun 2008, 11:32 am	#9
phase_splitter Retired Dormant Member Join Date: Jun 2008 Location: East Sussex Posts: 25	Re: Leak TL12+ I don't know about the illuminati, but I use RS!

21st Jun 2008, 1:11 pm	#10
yestertech Nonode Join Date: Dec 2002 Location: Coulsdon, Surrey, UK. Posts: 2,135	Re: Leak TL12+ I agree with all the other comments - these are great amps and nice to look at too ! Definitely CHANGE the 2 x 0.25 TCC metalpack caps feed the EL84s, if they havent been done already ! Also check the 270 ohm cathode resistors as they will have changed in value. Before powering up, check the DC resistances of all the Mains xformer secondaries and also the centre tap to anode and screen grid resistances of the OP xformer, as amps which have been neglected can burn out the transformers quite easily. If youre lucky, the electrolytics will reform OK. Leak used TCC caps almost exclusively and they seem to have a good lifespan. When you first hear it , it's guaranteed to bring a smile to your face !! Andy

24th Jun 2008, 4:21 pm	#11
Valleyjinker Retired Dormant Member Join Date: Oct 2006 Location: Nottingham Posts: 35	Re: Leak TL12+ I rate the TL12+ amps very highly. Tried them against many other vintage types (including a pair of Stereo 20s, Quad 11s and Radford) and always go back to them. I've heard more than one enthusiast say that if you change all the components for modern types - particularly the metal 0.22 driver caps - then you don't get the real character of the amp. Same bloke managed to find some NOS ones - which were leakier than the ones on his amp! Two choices: Leave everything as standard as you can, watch it carefully and hope it doesn't go bang, or change everything that might cause a problem. If you do the latter could it be argued that you will be listening to a modern Chinese valve amp?