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Old 5th Aug 2022, 3:05 pm   #61
Whaam68
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Join Date: Feb 2007
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Default Re: Leak Stereo 30 Plus

I once fixed a Leak Stereo 70 which is very similar and the diodes connected to the output transistors needed replacing on the dead channel but so did the output transistors on mine. The equivalent replacement parts were fairly cheap and the horse shoe style pre set pots are definitely mechanically suspect due to age. It looks like you’ve done some of the caps on the faulty board so if it were me AND you are totally happy the output transistors are ok, I’d consider shot gun replacement of all the pre set pots, the small signal transistors on the faulty channels board and probably those diodes. There aren’t that many to replace. The resistors if carbon film and not obviously physically damaged are probably fine but worth checking values against the circuit diagram values anyway. Do them all on the duff channel board though before powering up on a lamp limiter. Also re clean the edge connectors and check for bent pins and any solder bridges (I’ve been caught out there before). I also used a dab of conductive grease on the edge connector pads but that was probably overkill. If you aren’t that savvy (like me) it may in the end be quicker than trying to find the fault by elimination. At least the removable cards make this era of Leak easy to work on. I usually get to the stage of losing the will to live then suddenly figuring it out. Good luck.
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Old 5th Aug 2022, 11:29 pm   #62
Pcspike
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Default Re: Leak Stereo 30 Plus

Quote:
Originally Posted by Whaam68 View Post
I once fixed a Leak Stereo 70 which is very similar and the diodes connected to the output transistors needed replacing on the dead channel but so did the output transistors on mine. The equivalent replacement parts were fairly cheap and the horse shoe style pre set pots are definitely mechanically suspect due to age. It looks like you’ve done some of the caps on the faulty board so if it were me AND you are totally happy the output transistors are ok, I’d consider shot gun replacement of all the pre set pots, the small signal transistors on the faulty channels board and probably those diodes. There aren’t that many to replace. The resistors if carbon film and not obviously physically damaged are probably fine but worth checking values against the circuit diagram values anyway. Do them all on the duff channel board though before powering up on a lamp limiter. Also re clean the edge connectors and check for bent pins and any solder bridges (I’ve been caught out there before). I also used a dab of conductive grease on the edge connector pads but that was probably overkill. If you aren’t that savvy (like me) it may in the end be quicker than trying to find the fault by elimination. At least the removable cards make this era of Leak easy to work on. I usually get to the stage of losing the will to live then suddenly figuring it out. Good luck.
Hi there and thanks for your input and advice, it's appreciated. I would very much like to change those pre-set pots but, where to get suitable replacements that will physically fit is the question. No doubt there will be something out there but as yet I am yet to find them. I've purchased a set of resistors and intend changing them even though the existing ones seem ok (elimination at work).
Regarding a lamp limiter, I've just made one and it seems to work ok. I tried it out on the faulty board earlier today and the bulb glowed....very dimly. What that means compared to glowing very brightly, I'm not too sure

Last edited by Pcspike; 5th Aug 2022 at 11:30 pm. Reason: Typo
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Old 5th Aug 2022, 11:46 pm   #63
Silicon
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Default Re: Leak Stereo 30 Plus

I was looking for suitable pre-set potentiometers to replace the carbon film 'skeleton' potentiometers used in the Leak amplifiers.

I would avoid carbon types and look for Cermet track types like the Bourns 3296, 3386 or 3006 pre-sets.
Most of them are very small, the leads are short and won't line up with the holes in the PCB.

I might glue the new pre-sets to a small piece of PCB or matrix board fitted with stiff wires to fit the holes in the Leak PCB.
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Old 6th Aug 2022, 8:37 am   #64
Pcspike
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Default Re: Leak Stereo 30 Plus

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Originally Posted by Silicon View Post
I was looking for suitable pre-set potentiometers to replace the carbon film 'skeleton' potentiometers used in the Leak amplifiers.

I would avoid carbon types and look for Cermet track types like the Bourns 3296, 3386 or 3006 pre-sets.
Most of them are very small, the leads are short and won't line up with the holes in the PCB.

I might glue the new pre-sets to a small piece of PCB or matrix board fitted with stiff wires to fit the holes in the Leak PCB.
Thanks, will look into that option
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Old 6th Aug 2022, 1:27 pm   #65
Pcspike
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Default Re: Leak Stereo 30 Plus

Great news, it is now fixed, turned out to be a transistor T8. Checking all the transistors was the first thing that I did, and today decided to check them again. T8 showed up as faulty but when I checked it again it said it was OK and based on this I decided to change it. I'm assuming it was as Silicon suggested, that components may test OK on a digital multimeter but then break down when subjected to the full working voltage in the amplifier. In the end it turned out that there were two faults P5 and T8.

I would like to thank everyone who offered help in this matter, I'm really grateful. I've certainly learnt a great deal by going through this process, especially the introduction to the dim bulb tester.
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Old 6th Aug 2022, 2:18 pm   #66
Whaam68
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Default Re: Leak Stereo 30 Plus

That’s great news. Re the lamp limiter if the bulb glows brightly on switch on and stays bright don’t take the lamp out of circuit. Just switch the amp off as there is a fault ….the lamp is glowing brightly as the amp is drawing too much current. If the lamp glows a bit on start up then dims right down you should be good to go to switch the lamp out. Re the pots you just need to see what you can find on eBay or wherever. From memory I bought some larger modern plastic horseshoe types from Dada electronics in the Netherlands. Sometimes you’ll have to bodge it a bit soldering short pieces of solid core insulated wire into the board to make the “legs” long enough. Adapting things is part of the fun unless you are a purist.
Best
Mike
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Old 6th Aug 2022, 2:38 pm   #67
Pcspike
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Default Re: Leak Stereo 30 Plus

Quote:
Originally Posted by Whaam68 View Post
That’s great news. Re the lamp limiter if the bulb glows brightly on switch on and stays bright don’t take the lamp out of circuit. Just switch the amp off as there is a fault ….the lamp is glowing brightly as the amp is drawing too much current. If the lamp glows a bit on start up then dims right down you should be good to go to switch the lamp out. Re the pots you just need to see what you can find on eBay or wherever. From memory I bought some larger modern plastic horseshoe types from Dada electronics in the Netherlands. Sometimes you’ll have to bodge it a bit soldering short pieces of solid core insulated wire into the board to make the “legs” long enough. Adapting things is part of the fun unless you are a purist.


Best
Mike
Thanks Mike
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Old 6th Aug 2022, 3:48 pm   #68
Sideband
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Default Re: Leak Stereo 30 Plus

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Originally Posted by Pcspike View Post
Great news, it is now fixed, turned out to be a transistor T8.
I would like to thank everyone who offered help in this matter, I'm really grateful. I've certainly learnt a great deal by going through this process, especially the introduction to the dim bulb tester.
That is brilliant news! Well done for persevering. I suggest you now carefully set up the quiescent current....you do this with no input and volume at zero. No point in guessing about the setting of P5. You got this far, you may as well make sure that it's adjusted correctly and hopefully it will give many years of service. Just follow the instruction in the manual....five minutes is all it takes.
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Old 6th Aug 2022, 8:29 pm   #69
Pcspike
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Default Re: Leak Stereo 30 Plus

Quote:
Originally Posted by Sideband View Post
Quote:
Originally Posted by Pcspike View Post
Great news, it is now fixed, turned out to be a transistor T8.
I would like to thank everyone who offered help in this matter, I'm really grateful. I've certainly learnt a great deal by going through this process, especially the introduction to the dim bulb tester.
That is brilliant news! Well done for persevering. I suggest you now carefully set up the quiescent current....you do this with no input and volume at zero. No point in guessing about the setting of P5. You got this far, you may as well make sure that it's adjusted correctly and hopefully it will give many years of service. Just follow the instruction in the manual....five minutes is all it takes.
Yes, as you say just a quick job, did it without any problems. Thank for your help....look out for my next project
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