Hi all, just aquired a leak st20 that has been overhauled about a year ago by classique sounds and after ahving a look over amp, noticed the input fuse at rear is a 10A, not a 2A as shown on the original circuit diagram?
The amp is apparently being run in triode mode, can anyone confirm if this fue should be changed back to a 2A?
thanks
tom.
The amp is apparently being run in triode mode, can anyone confirm if this fue should be changed back to a 2A?
thanks
tom.
Hi Tom..
A 10 amp fuse does seem very high. Why not give classique a call or email and ask what fuse they recommend. Could always replace with a 2 amp and see if it holds out.
Regards Mark
A 10 amp fuse does seem very high. Why not give classique a call or email and ask what fuse they recommend. Could always replace with a 2 amp and see if it holds out.
Regards Mark
Hi, thanks for reply, yes will call them as it does seen much higher than original spec? I can see no reason for this much higher rated fuse?
Thanks,
Tom
Thanks,
Tom
Possibly, tried classique sounds earlier but no answer, not firing up amp till next week when my passive pre is ready, so got some time to sort correct fuse. Does the fuse protect the transformers? Any ideas as I'm a newbie to this amp and tubes in general?
Thanks again
Thanks again
A fuse protects the things near it in the circuit, especially things just upstream from problems just downstream. A fuse in the mains input may protect the cable from a transformer or switch short. In the UK the plug fuse will do the same, and also protect the cable itself from cable shorts. The right fuse may give some limited protection to the transformer from wiring shorts in the secondary circuit.
A 10A fuse may stop a switch short from completely frying the cable, but that is about all it will do.
A 10A fuse may stop a switch short from completely frying the cable, but that is about all it will do.
Why not replace with a 2A fuse, then power it all up? There are ONLY 2 outcomes! It works, or it blows.
If it blows, you have research to do.
If it works, you're good to go, and you can keep moving forward.
Other than protect from sustained (and transient) over-current use, fuses do nothing else (ideally) to the sound of the system. Though... it is amusing to see people buy cryogenically cured single-crystal oxygen-free (99.99995%) power cables to hook their house wiring (all crap) and power socket (more crap) to their uber-high-end audio system ... which for all that, has a nice little 1/10th ohm fuse made of (crap) low-melting point, medium-conductance alloy in series with the power line. LOL.
GoatGuy
If it blows, you have research to do.
If it works, you're good to go, and you can keep moving forward.
Other than protect from sustained (and transient) over-current use, fuses do nothing else (ideally) to the sound of the system. Though... it is amusing to see people buy cryogenically cured single-crystal oxygen-free (99.99995%) power cables to hook their house wiring (all crap) and power socket (more crap) to their uber-high-end audio system ... which for all that, has a nice little 1/10th ohm fuse made of (crap) low-melting point, medium-conductance alloy in series with the power line. LOL.
GoatGuy
Hi, I would have thought the plug fuse protects the cable, and this 10A fuse protects the circuits inside the amp, without a schematic to hand I'm unsure to be truthful?
Thanks
Thanks
Hi, yes your right goatguy, although its not a standard British fuse as found in uk type plugs, it looks slightly longer and narrower, I'll try Rs or maplins to see what they've got.
The current drawn by a Leak st20 should be less than an amp of mains so a 2amp should be more than adequate. 10amps would need a surge of at least 20amp to blow - by which time your power transformer will be smoke.
Shoog
Shoog
2A is more than enough for this amp, I have three of them, and the mains transformers run hot and are close to the limit. If you live in a hot climate, they do fail. With a 10A fuse in there you have a potential fire risk in the event of a failure. I think its a standard old style 1inch fuse.
Another "improvement" that inexperienced so-called over haulers make is to change the resistor in the B+ line to a modern ceramic one as the old ones often look a bit burnt. These resistors are designed to run very hot, and they are actually fitted so as to unsolder themselves and break the circuit if the amp overheats.
This may help:
Leak Stereo 20 Valve Amplifier
Also: change it back to how the designers intended. It's a sweet sounding amp the way it was originally made. Additionally, it will be worth more money put back to original condition rather than "messed" around with.
Another "improvement" that inexperienced so-called over haulers make is to change the resistor in the B+ line to a modern ceramic one as the old ones often look a bit burnt. These resistors are designed to run very hot, and they are actually fitted so as to unsolder themselves and break the circuit if the amp overheats.
This may help:
Leak Stereo 20 Valve Amplifier
Also: change it back to how the designers intended. It's a sweet sounding amp the way it was originally made. Additionally, it will be worth more money put back to original condition rather than "messed" around with.
Being the owner of an ST20 I'd absolutely suggest the 2a fuse and I wonder if the previous owner replaced it because it was blowing. These amps are pretty notorious for having the filter caps go out and if that happens, they draw a lot of current. Maybe someone didn't recognize the root cause of the problem and tried to "fix" it through brute force. At any rate, good chance the PS caps need to be replaced. Hope the power transformer is okay! There is also a 100 ohm (IIRC) resistor in the PS which, as I understand it, is supposed to drop off the tag board if it over heats, which shuts down everything down stream of the rectifier. Check to see if it is there, and if it is chared. I think it is a 1W or 2W part.
Not sure what "these" you're referring to. But if you mean the caps, yes. Get caps that have two 32uf sections at 500v caps. Same diameter. Easy to replace.
This schematic shows a 1 amp fuse for the British market or a 2 amp for the US.
http://www.oocities.org/stereo20/dwnloads/stereo20.gif
http://www.oocities.org/stereo20/dwnloads/stereo20.gif
Hi guys, I'll check with a few local sellers of these amps today to see what fuse size should be anyone in the uk with one of the stereo 20's can you check for me?
Cheers.
Cheers.
leak 20
hi, maybe it has been misread, i'll check the fuse again to see if it is a 1A?
I got some 1.6A from maplins,as a Jeff Kramer at servicesound in East Sussex,has suggested he uses, he's had significant experience in these amps and seems very knowledgeble and helpful.
My amp, as mentioned,has been overhauled by classique sounds and all components have been changed,so I assume are all in tolerance,the green resistor has been replaced by a white oblong 3W version and all valve have been run for about 200hrs.
I'd also like to add that my 20 is being run in Triode mode, the chap at servicesound has suggested this is a bad move and suggested it be put back to ultralinear, is this a diy job?
The previous owner has said its reasonably straight forward anyone any help on whether this is feasible for a newbie?
thanks,
tom.
hi, maybe it has been misread, i'll check the fuse again to see if it is a 1A?
I got some 1.6A from maplins,as a Jeff Kramer at servicesound in East Sussex,has suggested he uses, he's had significant experience in these amps and seems very knowledgeble and helpful.
My amp, as mentioned,has been overhauled by classique sounds and all components have been changed,so I assume are all in tolerance,the green resistor has been replaced by a white oblong 3W version and all valve have been run for about 200hrs.
I'd also like to add that my 20 is being run in Triode mode, the chap at servicesound has suggested this is a bad move and suggested it be put back to ultralinear, is this a diy job?
The previous owner has said its reasonably straight forward anyone any help on whether this is feasible for a newbie?
thanks,
tom.
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