Alron Mosfet 1000 Project (Made in NZ)
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- Cdog
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Alron Mosfet 1000 Project (Made in NZ)
Picked this NZ made beauty for my daughter as a project we can work on together. I'd repaired a much smaller one of the same brand a couple of years ago, a neat sounding amp. This is much bigger however... and ridiculously heavy. I'm hoping it'll sound nice for both her bass and guitar. Has a reverb tank! Be interested to hear your thoughts about these, especially from any tex who've poked around in their guts before.
Speaker is blown, with no discernible markings so first port of call is getting a new 15".
Sucky because it had a speaker fuse, but someone had used a 13A instead of a 4A fuse... Fuse choice makes me think there was a problem before the speaker blew. Not much info online about these, so thought I'd see if anyone here has had experience with them... need to see what power handling my replacement speaker needs.
It has two pair of K135/J50 Mosfets in the poweramp as pictured... so that might put the output at up-to 300-400W? Which seems high, except the sticker says 300W, but methinks that's supply related. 4A (speaker fuse) for 16Ohms (assumed load) could be a clue... P=i^2R = 256W? 128W if 8Ohm. Speaker's coil has gone open circuit, so not sure.
I suppose I could just put a big-ass 8 ohm resistor and some 1kHz through it to see 'watts' going across the load.
Speaker is blown, with no discernible markings so first port of call is getting a new 15".
Sucky because it had a speaker fuse, but someone had used a 13A instead of a 4A fuse... Fuse choice makes me think there was a problem before the speaker blew. Not much info online about these, so thought I'd see if anyone here has had experience with them... need to see what power handling my replacement speaker needs.
It has two pair of K135/J50 Mosfets in the poweramp as pictured... so that might put the output at up-to 300-400W? Which seems high, except the sticker says 300W, but methinks that's supply related. 4A (speaker fuse) for 16Ohms (assumed load) could be a clue... P=i^2R = 256W? 128W if 8Ohm. Speaker's coil has gone open circuit, so not sure.
I suppose I could just put a big-ass 8 ohm resistor and some 1kHz through it to see 'watts' going across the load.
- sizzlingbadger
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Re: Alron Mosfet 1000 Project (Made in NZ)
The wattage will be higher at lower impedance, due to more current flowing. Solid state usually have a minimum impedance rating which is usually the maximum power rating. Example 200W into 4 ohms which would be 100W into 8 etc.
I have 15” speaker in the shed, it’s old and I have no idea if it’s suitable, I’ll check it out tomorrow.
I have 15” speaker in the shed, it’s old and I have no idea if it’s suitable, I’ll check it out tomorrow.
Tube amp and guitar tones straight from 1958… amazing how believable the sounds were back then, even without the modellers...
- RectifiedAmps
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Re: Alron Mosfet 1000 Project (Made in NZ)
If the speaker is blown and the speaker fuse rating was boosted, then be very suspicious of the output transistors. If any are shorted, they’ll dump the whole power supply’s-worth of DC voltage onto the speaker, hence the open voice coil. Do NOT fire it up again with a new speaker connected before you check the output for DC offset. If you need new K135s (or whatever their complement is - cant read it), I may have some spares in my stash.
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Re: Alron Mosfet 1000 Project (Made in NZ)
Ah...cool, thanks for the reply... that makes sense. And, keen if the speaker is suitable! Cheerssizzlingbadger wrote: ↑Sun Sep 05, 2021 9:42 pm The wattage will be higher at lower impedance, due to more current flowing. Solid state usually have a minimum impedance rating which is usually the maximum power rating. Example 200W into 4 ohms which would be 100W into 8 etc.
I have 15” speaker in the shed, it’s old and I have no idea if it’s suitable, I’ll check it out tomorrow.
Thanks for the reply... great to hear what the fault condition might be. I have a big 8Ohm resistor, I' ll fire it up with that connected and do some probulating to see whats goin on . Appreciate the offer of trannies too, will post when I've had another chance to look at itRectifiedAmps wrote: ↑Sun Sep 05, 2021 10:14 pm If the speaker is blown and the speaker fuse rating was boosted, then be very suspicious of the output transistors. If any are shorted, they’ll dump the whole power supply’s-worth of DC voltage onto the speaker, hence the open voice coil. Do NOT fire it up again with a new speaker connected before you check the output for DC offset. If you need new K135s (or whatever their complement is - cant read it), I may have some spares in my stash.
- RectifiedAmps
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Re: Alron Mosfet 1000 Project (Made in NZ)
It doesn’t need a load connected at all- there’s no output transformer and transistors don’t care. You can fire it up without a load and measure for DC across the speaker wires without causing any damage. Note that if a transistor is shorted and you see DC offset, you should switch it off as soon as possible or it’ll strain the power transformer and the shorted transistor(s) will start to smoke! If you have a light-bulb limiter, this is the perfect situation to use it.Cdog wrote: ↑Mon Sep 06, 2021 7:47 am Thanks for the reply... great to hear what the fault condition might be. I have a big 8Ohm resistor, I' ll fire it up with that connected and do some probulating to see whats goin on . Appreciate the offer of trannies too, will post when I've had another chance to look at it
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Re: Alron Mosfet 1000 Project (Made in NZ)
Here it is, I just checked and its 16ohms, bit dusty too
The box is 44x44x24cm and its 8KG, you can have it for free, just arrange the postage if you want it. PM for my address.
The box is 44x44x24cm and its 8KG, you can have it for free, just arrange the postage if you want it. PM for my address.
Tube amp and guitar tones straight from 1958… amazing how believable the sounds were back then, even without the modellers...
- RectifiedAmps
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Re: Alron Mosfet 1000 Project (Made in NZ)
What do they mean by ‘70 watt USA’? Is that to account for americans being louder than the rest of us?
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Re: Alron Mosfet 1000 Project (Made in NZ)
American watts are only half as powerful as everyone elses?RectifiedAmps wrote: ↑Mon Sep 06, 2021 11:59 am What do they mean by ‘70 watt USA’? Is that to account for americans being louder than the rest of us?
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.
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Re: Alron Mosfet 1000 Project (Made in NZ)
I think years ago USA used to quote "Music Power" instead of RMS, its was roughly double.RectifiedAmps wrote: ↑Mon Sep 06, 2021 11:59 am What do they mean by ‘70 watt USA’? Is that to account for americans being louder than the rest of us?
Tube amp and guitar tones straight from 1958… amazing how believable the sounds were back then, even without the modellers...
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Re: Alron Mosfet 1000 Project (Made in NZ)
That's a mighty generous offer sir... Thank-you! PM incomingsizzlingbadger wrote: ↑Mon Sep 06, 2021 10:53 am Here it is, I just checked and its 16ohms, bit dusty too
The box is 44x44x24cm and its 8KG, you can have it for free, just arrange the postage if you want it. PM for my address.
IMG_4411.jpeg
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Re: Alron Mosfet 1000 Project (Made in NZ)
Quick update as we had a half hour to work on the amp this weekend. First time power on with Lightbulb in series... And no DC on the speaker wires... Win! Young miss and I did some ohms law equations to set a safety fuse to protect the new speaker from sizzlingbadger. Other than a few crackly pots, it actually sounds pretty good. Haven't tried the spring reverb yet. I'll give it a proper overhaul before we put it back together. Looks like its been worked on at some stage, I'm hoping the filter caps have plenty of life left.
And a bit of hunting has this as a mid to late seventies build. Google search yielded a recently serviced one that looks identical... And only down the road in Rangiora too!
https://m.facebook.com/story.php?story_ ... 3415580131
And a bit of hunting has this as a mid to late seventies build. Google search yielded a recently serviced one that looks identical... And only down the road in Rangiora too!
https://m.facebook.com/story.php?story_ ... 3415580131
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Re: Alron Mosfet 1000 Project (Made in NZ)
That's a cool project to do together. Makes me wish I was a bit more receptive to my father when he suggested projects.
Curious, though. Why do the speakers need protecting from Mr Badger. What does he do to them?
- Cdog
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Re: Alron Mosfet 1000 Project (Made in NZ)
I know right... Me too tbh. It's pretty fun working on something like this together.
Ahh my england. Well I hope the fuse will help that too
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Re: Alron Mosfet 1000 Project (Made in NZ)
Rob Magnus! There's a name. Great guitarist, fine bloke. Old neighbour I haven't seen for far too long.Cdog wrote: ↑Sun Oct 03, 2021 6:29 pm Quick update as we had a half hour to work on the amp this weekend. First time power on with Lightbulb in series... And no DC on the speaker wires... Win! Young miss and I did some ohms law equations to set a safety fuse to protect the new speaker from sizzlingbadger. Other than a few crackly pots, it actually sounds pretty good. Haven't tried the spring reverb yet. I'll give it a proper overhaul before we put it back together. Looks like its been worked on at some stage, I'm hoping the filter caps have plenty of life left.
And a bit of hunting has this as a mid to late seventies build. Google search yielded a recently serviced one that looks identical... And only down the road in Rangiora too!
https://m.facebook.com/story.php?story_ ... 3415580131
Screenshot_20211003-193601.png
Beyond a critical point within a finite space, freedom diminishes as numbers increase. This is as true of humans as it is of gas molecules in a sealed flask. The human question is not how many can possibly survive within the system, but what kind of existence is possible for those who so survive.