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Little Dot Mark II tube headphone amp blowing fuse, help needed please
- Thread starter Califmike33
- Start date
Califmike33
Well-Known Member
ok thanks.
Califmike33
Well-Known Member
Well thanks to Lavane, for showing me where the BR was, i was testing the wrong thing, BR is fine and test fine.
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Califmike33
Well-Known Member
. EDIT, i cut the HV wire and it still blows fuses it's the Transformer for sure and this project is officially dead, thanks for all your help, until the next project. I did learn a lot from this. I wont be buying a transformer for this, i will gut it for parts.
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No they are supposed to connect. They are the two 180R resistors in the B+ line.
Okay, if you want to test the PT. Pull any cover off the top of the transformer. Now, find the two screws that are holding the transformer to the chassis. Lift the PT off the chassis. The wiring diagram should be on the transformer, somewhere. Follow the diagram, to test for shorts in the primary side. Secondary side. And heater lines.
Good you found it. Be interesting to remove the PT and dissect it, to find the short. It could be one of the leads.
Califmike33
Well-Known Member
It was free so no big deal.
Interesting. You take that PT apart? Maybe, it's an easy fix?
I agree, don't buy another PT. Perhaps, someone will give you one for free?
Califmike33
Well-Known Member
You know it really would all depend on how much the Transformer would cost me I'm not going to put $100 into a transformer into $150 amplifier.
Are there any Little Dot MkII "for parts," on eBay?
Usually, I'd say that transformers are the last things I'd suspect on relatively new units. However, how these things are made today, maybe that's not a good assumption.
Lavane
Lunatic Member
Carefully check the wires going into the transformer first before tossing it.
Maybe there are a couple wires touching? A tab where the wires connect got bent and is touching another?. Some of these transformers with tabs have the wires soldered to them. Or the thin wires coming from the windings to the tabs are touching maybe. If it's an R-core transformer, they tend to be pretty cheap. Maybe around $20.
Maybe there are a couple wires touching? A tab where the wires connect got bent and is touching another?. Some of these transformers with tabs have the wires soldered to them. Or the thin wires coming from the windings to the tabs are touching maybe. If it's an R-core transformer, they tend to be pretty cheap. Maybe around $20.
Califmike33
Well-Known Member
Okay I'll check the I'll check the Transformer I'll check all the wires in the winding I'll take a picture of it that way you can give me some kind of idea what it may cost like I said in the beginning if it's not very expensive I'd be willing to replace it.
I'm thinking one wire maybe pinched up against the transformer's chassis --- when the factory tighten it down.
Califmike33
Well-Known Member
Was not the tubes and it's not the bridge rectifier so the only thing left according to what people said is a Transformer or a capacitor. I'll check the Transformer and the lemonade that nothing I want more for it to be just a capacitor.
But further back in this thread the guy said if I cut one of the high voltage wires and turned it on and it still blows the fuse the Transformers dead that's what he said I don't know if that's true or not because I don't know enough about this I'm just going off of what he said.
I will tell you when I picked it up from the guy there was a rattling inside found out the Transformer was loose the screws were halfway out of it I did tighten the screws back down to stop the thing from rattling. I mean I don't know if this guy was on the up and up or not he tells me to come pick it up as I'm about to pull up to his house he tells me yeah I decided to plug it in just to make sure everything was good and it blew a fuse.
I arrive at his house I arrive at his house and it's dead and the Transformers rattling at that point I'm reluctant to even buy it but he did tell me if it didn't work he would refund my money and he seemed like a stand-up guy so I bought it. He did refund my money and was going to take the amplifier back but then he told me just keep it I'm not going to fix it and that's where we're at today.
But further back in this thread the guy said if I cut one of the high voltage wires and turned it on and it still blows the fuse the Transformers dead that's what he said I don't know if that's true or not because I don't know enough about this I'm just going off of what he said.
I will tell you when I picked it up from the guy there was a rattling inside found out the Transformer was loose the screws were halfway out of it I did tighten the screws back down to stop the thing from rattling. I mean I don't know if this guy was on the up and up or not he tells me to come pick it up as I'm about to pull up to his house he tells me yeah I decided to plug it in just to make sure everything was good and it blew a fuse.
I arrive at his house I arrive at his house and it's dead and the Transformers rattling at that point I'm reluctant to even buy it but he did tell me if it didn't work he would refund my money and he seemed like a stand-up guy so I bought it. He did refund my money and was going to take the amplifier back but then he told me just keep it I'm not going to fix it and that's where we're at today.
I'm hoping you can fix it. If it's the internal windings (shorted to ground) --- use the transformer as a paperweight.
Yes, that is the proper method to test the PT.
One other thing. I don't think the caps are bad. I see no bulging or leaking goo, in your photos. You can check for continuity and shorts.
Califmike33
Well-Known Member
Califmike33
Well-Known Member
The Transformer doesn't look or feel like a $25 Transformer any idea what this Transformer would cost?
Califmike33
Well-Known Member
Let me ask you guys one last question now I did test the wrong area for the bridge rectifier which I later fixed looking at this power transformer which wire is it typically that I would cut for the high voltage test to see if the Transformers dead when I plug it in? I may have cut the wrong wire.
