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SAE Mark XXX Preamp Power Transformer Needed!

RanDibble

RanDibble

Member
Help ! SAE Mark XXX 30 Preamp Power Transformer Needed!

The power transformer melted down on me. Can anyone point me in the right direction for a replacement or the spec's of the transformer ?
 
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Of course, you should first figure out why the transformer melted down...It could have been an internal shorted turn, or it could have been an external load problem. After that , you want a transformer that will put out about (42+75)/2=58 volts DC. This is just a reasonable guess...it could probably be as low as 50, and as high as 65 volts DC...the service manual doesn't show the unregulated voltage, only the regulated voltage, which is 42.4 volts. That means you need enough voltage to run the regulator. The actual current that it must deliver isn't much, ...The 28 Volt pilot light probably takes more current than the preamp does. Preamp probably draws about (1.44/220+4/1000+1.3/270)*2=30 mA.

So, you wouldn't need a big transformer. One possibility might be a transformer out of a Dynaco PAT-4 (just don't bother with the center tap).

If someone knew the unregulated voltage, we could get a bit closer.
 
See if you can find the MK 1B or 1M schematic on line, if not PM me with your email and I'll send it you. The 1B/M has a very similar power supply but probably has a little bit higher current capacity, the voltages are within a couple of volts. There are pre-reg and post-reg voltages listed on the 1B/M schematic so maybe some extrapolation can be used. My friend in the office next to me has an XXX but he's in Greece at the moment and I can't get to it to measure what you need.

Craig
 
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The transformer on mine has a 62v output but wasn't powering the unit. After checking all board components finding them to be good, I then touch soldered all connection points on the boards. The unit now powers up and functions as it supposed to. Issue must've been due to corrosion on the solder joints.
 
The SAE Mark XXX Preamp is one of the best preamps ever made. Those who have them KNOW. It is nothing short of a masterpiece of audiophile engineering. I have compared it to QUAD, Bryston, Marantz among others and the XXX is far and away better.
 
taineasy said:
The SAE Mark XXX Preamp is one of the best preamps ever made. Those who have them KNOW. It is nothing short of a masterpiece of audiophile engineering. I have compared it to QUAD, Bryston, Marantz among others and the XXX is far and away better.
Click to expand...

I'm curious. How so?

I've never heard one of those preamps and never seen the schematic. What makes it so fantastic? I checked out a picture of it. It looks very basic. Is it more passive than other preamps? I don't care for the slide controls. I have an SAE Tuner which is fine. I bought it to go with my GAS amp and preamp because I could not find a GAS tuner. The SAE was similar and looked decent racked with the GAS.
 
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