[SET Man]

Hey!

    A sad day for me yesterday. After 25 years, my Audio Note M1 Phono preamp just stop working in the middle of listening yesterday afternoon. The sound just got cut off. The fuse blown out, I opened it up and noticed some smell but no smoke. Also the power transformer was very hot, I also saw some melted potting insulator.

   I'm very bummed out about this. If the transformer is burn out than getting an exact replacement can be hard. Even if I can get one I'll have to find out the cause of why this happened before I put a new transformer in.

   So, any of you with more knowledge than me can help me where to start looking?

Buddy 

[FullRangeMan]

It is a tube pre-amp?
If you have the schematic it will be easy.
Most parts will have to be checked.

[timind]

Hope you have a spare pre to keep the music flowing. As a seasoned tube guy, I'm sure your're prepared for this eventuality.

[avahifi]

There is an old Audio Note thread here on AC that has lots of info about your phono preamp.

Search on AC for Audio Note M1.  Lots of useful info.

Frank Van Alstine

[SET Man]

It is a tube pre-amp?
If you have the schematic it will be easy.
Most parts will have to be checked.

Hey!

  Yes, a tubed pre. To start with, I'm planning to replace all caps.

Hope you have a spare pre to keep the music flowing. As a seasoned tube guy, I'm sure your're prepared for this eventuality.

    Strangely enough, I have 2 CDP, 2, turntables, 2 SET amps but I only have one pre amp. Luckily my local audio friends here in NYC have extra preamps that they could loan me.

There is an old Audio Note thread here on AC that has lots of info about your phono preamp.

Search on AC for Audio Note M1.  Lots of useful info.

Frank Van Alstine

    I think I remembered that post. But it was pretty things that I already know about this preamp.


   Anyway, I contacted Audio Note UK on Wednesday. They got back to me the next day. I sent them more info and they said they will check for me. I'm still waiting.

    Meanwhile, I looked around and found power transformer on eBay that might work in my preamp. But I want to run this over you guys here with more experience first. The original power transformer have 3 voltage outputs 290V, 6.3V and 13.6V all 2 legs. The one on eBay the high voltage is center tapped 290V-0-290V. But they can custom wind one for me with 2 legs out 0-290V.

    So, if I have them wind one with 0-290V for me will that work? And looking at the high voltage amperage, is that enough to power six 12AX7/12AU7 tubes?

https://www.ebay.com/itm/325186374236?mkevt=1&mkpid=0&emsid=e11051.m43.l1123&mkcid=26&ch=osgood&euid=78ad8e32ca984daaa965b8b5a5715d34&bu=43191157078&osub=-1%7E1&crd=20220804202242&segname=11051

   Any help will be appreciated.

Buddy

[FullRangeMan]

The original power transformer have 3 voltage outputs 290V, 6.3V and 13.6V all 2 legs. The one on eBay the high voltage is center tapped 290V-0-290V. But they can custom wind one for me with 2 legs out 0-290V.

Nice the factory replied to you.
This transformer have various windings.
Better do what the factory tells.
Do you mean say 13.6V or 12.6V?

[SET Man]

Nice the factory replied to you.
This transformer have various windings.
Better do what the factory tells.
Do you mean say 13.6V or 12.6V?

Hey!

      Yes, 13.6V output. There is V regulator IC for the 12V heater in this preamp, so that would explained the 1V more.

     Anyway, I measured the transformer with no load and 6.3V and 13.6V still measured fine but the high V is not anywhere near 290V. And the transformer got hot quick! So, the transformer is shot for sure

Buddy

[FullRangeMan]

And the transformer got hot quick! So, the transformer is shot for sure
Too bad, the insulating varnish may have worn.

[SET Man]

And the transformer got hot quick! So, the transformer is shot for sure
Too bad, the insulating varnish may have worn.

Hey!

   Yup, that could be the case. I don't see any burnt resistor or leaking caps anywhere.
   
   Since you know more about transformer. Do you think this transformer have enough high voltage amperage to drive six 12AX7 and 12AU7 tubes? I'll have it custom wind to 290V 2 legs output.



https://www.ebay.com/itm/325186374236?_trkparms=amclksrc%3DITM%26aid%3D777008%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D20201018205123%26meid%3D9f23f33e50e84c20a9b9bb23054371e9%26pid%3D101286%26rk%3D1%26rkt%3D1%26mehot%3Dnone%26itm%3D325186374236%26pmt%3D1%26noa%3D1%26pg%3D2380057%26algv%3DWatchlistVariantWithMLR&_trksid=p2380057.c101286.m47999&_trkparms=pageci%3A12c05f9d-1652-11ed-88b3-327b1cb4d001%7Cparentrq%3A786c1d3a1820aaf27897b658fffc4df0%7Ciid%3A1

Buddy

[FullRangeMan]

Bro Iam not expert in any way but as an audiophile by the little I know my personal opinion is not. The core in this Ebay link is too small, it say only 65VA or about 70W what STM are suited to one or two 12ax7.
65VA R-core Transformer 115V/230V To 300V-0-300V +6.3V +13.6V For Tube Preamp
Further down they say amperage are only 0.03A
What is 3 hundredths of 1 ampere.
The price are according the transformer size.
Primary：0-115V   0-115V    (it can connect as 115V or 230V input)

Secondary:  300V- 0-300V (0.03A)         0-6.3V(2A)       0-13.6V(2.5A) 

Transformer Power: 65VA

[FullRangeMan]

Is your damaged transformer encapsulated?
If it is not encapsulated you can use the original core
(which must be of high quality steel, M6 or higher grade)
and have it rewound, I mean say redoing the transformer
with the original core.