Re: [Harp-L] Power Transformer

[MARK BURNESS <markwjburness@xxxxxxxxxxxxxx>]

Oops! Meant to type...
 
Heater winding AC current rating: "6.3VAC @ ?A" and...
 
Rectifier winding: "5VAC @ 2/3A"  
 
...as the heater winding may be in excess of 3A, but the rectifier winding will be rated at 2A or 3A. 



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From: MARK BURNESS <markwjburness@xxxxxxxxxxxxxx>
To: John S <m3training@xxxxxxxxx>; "harp-l@xxxxxxxxxx" <harp-l@xxxxxxxxxx> 
Sent: Thursday, 6 June 2013, 16:59
Subject: Re: [Harp-L] Power Transformer


Hi John,
 
Firstly, it is worth shooting an e-mail to Marble to see if the power transformer that is in the amp now has alternative AC taps for 115/120VAC use. If so, these might be rewired quicker & cheaper than a new PT.
 
If not, the easiest & cheapest route would be to buy a 120VAC to 240VAC (or 115VAC to 230VAC - same thing, you just want to see double the voltage come out amp side, as compared to going in wall side) stand alone ,step -down transformer (NOT an "auto transformer)", 250-300VA rating should do you.
 
If you change the power transformer, then you'll need the same specs and Marble are your best bet for a replacement, or to supply you with specs for :
 
B+ winding in VAC & mA dc: "???VAC, centre -tapped @ ???mA dc", may also be descrbed as "???VAC-0-???VAC @ ???mA dc".
 
Heater winding AC current rating: "6.3VAC @ 2/3A" and...
 
Rectifier winding: "5VAC @ ?A"  
 
If a new power transformer has the same voltage & current ratings then you won't hear a big difference in the amp's tone (either in EU or the US, wall voltage fluctuates with location & time of day...so amp voltages vary a little anyway).


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From: John S <m3training@xxxxxxxxx>
To: "harp-l@xxxxxxxxxx" <harp-l@xxxxxxxxxx> 
Sent: Thursday, 6 June 2013, 15:36
Subject: [Harp-L] Power Transformer


Hello!

I am moving from Europe to the U.S. and will bring a Marble Harpwood set up for 220v. I will need to have the power transformer changed and am wondering what to consider. Is there qualitative differences in this part of the amp. I have read contrary opinions on this. Excuse my ignorance on this tech  issue. Thanks a great deal.



John S