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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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29th Mar 2023, 9:27 am | #21 |
Dekatron
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Re: Leak Delta 30 getting hot.
Yes, thank you David. I think I will try this as it may well come in useful for other amps.
Regarding the coil wound round the resistor would thinnish hook up wire be ok? It's about the only thing I can think of that I already have
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29th Mar 2023, 10:16 am | #22 |
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Re: Leak Delta 30 getting hot.
Looking at it again today it already has a 10uH inductor and 100R resistor in parallel in the output so maybe just the shunt part?
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29th Mar 2023, 11:18 am | #23 |
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Re: Leak Delta 30 getting hot.
Success. The shunt cured it. I increased the resistor a bit as the low frequency response seemed to be affected. I was going to go for 100R but I had quite a few 82R and as they seemed to be a less popular value I chose that.
I have only done one channel at the moment pending receipt of some more capacitors but the solution seems to have worked. Many thanks for all the suggestions.
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29th Mar 2023, 5:07 pm | #24 |
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Re: Leak Delta 30 getting hot.
In terms of replacement transistors the MJ15015G would be suitable see the attached data sheet referencing it and the 2N3055.
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29th Mar 2023, 8:23 pm | #25 | |
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Re: Leak Delta 30 getting hot.
Quote:
David
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29th Mar 2023, 8:42 pm | #26 |
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Re: Leak Delta 30 getting hot.
Thanks for all the information everyone. I found another 0.1uf and it has been running with the B&Ws for several hours very cool.
Lots of possibilities for future amps with duff output transistors.
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29th Mar 2023, 9:23 pm | #27 |
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Re: Leak Delta 30 getting hot.
I have to say it is quite a revelation to hear how good it sounds through the B&Ws
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30th Mar 2023, 10:44 am | #28 | |
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Re: Leak Delta 30 getting hot.
Quote:
Enjoy!
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30th Mar 2023, 10:50 am | #29 |
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Re: Leak Delta 30 getting hot.
I bought a Delta tuner to go with it, and that sounds good as well.
The Leak solid state stuff is less well regarded than the valve, but I think it is good on the basis of this Delta 30.
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30th Mar 2023, 11:06 am | #30 |
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Re: Leak Delta 30 getting hot.
I had to change a couple of caps in mine.....on the driver PCB's I think there were a couple of 10uF caps (might have been 1uF.....it was a long time ago), that were basically open circuit giving very low volume. Changed those and set up the quiescent current and it's been fine for over 5 years. It's due for a once-over soon as one switch has developed a crackle when operated.
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30th Mar 2023, 11:13 am | #31 |
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Re: Leak Delta 30 getting hot.
I tested a couple on the driver boards and found them to have a high ESR so I changed them all. Fortunately very easy on the removable boards.
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15th Aug 2023, 12:45 pm | #32 |
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Re: Leak Delta 30 getting hot.
A few points arising here. A Zobel network is the series combination of resistor and capacitor and does not include any other components. For the given application, values of around 0.1uF and 10R are typical. It absolutely should not have any effect on bass response under any circumstances! 0.1uF has a reactance of 32K at 50Hz... Increasing the resistance to 100R or more would often make it ineffectual. I can't recall ever seeing more than about 15R used as the resistive part.
The parallel coil and resistor is not a Zobel network (see above) although it is often mistakenly described as such. In recent years the name "Thiele network" has often been applied to it, probably after Neville Thiele, but I have only seen it called this in the past 20 years or so and it has been around for much longer. |
15th Aug 2023, 1:46 pm | #33 |
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Re: Leak Delta 30 getting hot.
Thanks Jez. I have an Armstrong amp with similar problems and will try the modification when it next takes its turn
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15th Aug 2023, 4:52 pm | #34 |
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Re: Leak Delta 30 getting hot.
I also have an Armstrong in the round tuit pile..a 625 receiver. Always loved the styling and they can work very well to boot. A mate bought a S/H one around '85 ish and we fixed a few minor issues (bimetallic strip switch as switch on surge protector is the usual culprit if it won't fire up. Bypass it every time!) after which it worked well and sounded good for the next ten years or more... could still be going for all I know as I haven't seen the bloke in many years now.
Hence when I had the opportunity to buy one for £30 a couple of years ago I went for it. Strange things in as much as the electronic design is generally very good (Ted Rule was the designer) but the mechanical side was pretty bodgy verging on dodgy! |
15th Aug 2023, 7:04 pm | #35 |
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Re: Leak Delta 30 getting hot.
The bimetallic switch can be dismantled to clean the points. I did this with mine and it has worked fine ever since.
I agree that the build is a bit flimsy and I have had several solder joints parting company. There are silly things like unscreened leads from the pre to the main amp. They are ok as long as they are carefully dressed as per the factory but get them wrong and they introduce hum. At least the power transistors are mounted on the back of the case. I haven't looked at mine for a while but I seem to remember it has some small cooling fins. By contrast they are right inside the Leak with no vents near them and a cardboard inner cover over them. It's almost as if it was designed to keep itself warm!
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15th Aug 2023, 10:09 pm | #36 | |
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Re: Leak Delta 30 getting hot.
Quote:
"At least the power transistors are mounted on the back of the case." yeah with plastic fasteners IIRC! |
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