Tune up procedure

From tubes to solid state.
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riverbasin
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Tune up procedure

Post by riverbasin »

Amp is a MV75A. It needs brought up on a variable power supply, I am instructed. I haven't pulled it out of box in a few years, but tubes were recent when I last boxed it. I do have bench equipment to do this, just like some advice first. Or I fInd a shop a couple states away still doing work.

Stepping stone to a new choice, but that step is getting pretty big now that I shopped the best. Have hungry Magnepans to feed.
jeffreybehr
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Re: Tune up procedure

Post by jeffreybehr »

Welcome.

Is there a question in your note?
Tin-eared audiofool, large-scale-Classical-music lover, and damned-amateur fotografer.
William Bruce Cameron: "...not everything that can be counted counts, and not everything that counts can be counted."
riverbasin
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Re: Tune up procedure

Post by riverbasin »

It would be my first if I do this power up. It would be helpful to hear from a fellow tech how to set that up.

The concern would be current at outputs, or measure points I need to monitor. Would I need a oscilloscope. I have looked around web, not seen any pointers so far.
plurn
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Re: Tune up procedure

Post by plurn »

I am not a tech so excuse me if I get this wrong. My understanding is that if a device has not been used for a long time, it can be good to power it up on a variac ( variable power supply ) at a lower voltage than your standard mains voltage, and you slowly bring it up to standard voltage. I think this is so that you don't send a lot of current to the empty power supply capacitors and damage them. If they are fine after that, they will be charged and might be ok from then on.

When doing this, might be an good idea to have some cheap/expendable speakers connected - or something like a suitable 8 Ohm load. I have heard it is bad to operate tube amps without a load connected as it can damage the output transformers. I would guess it would be ok for a short time though - say a minute - as long as the transformers don't overheat? That is just a guess.

Another simple thing to check if you have a multimeter is DC offset - see the first post here:
http://audiokarma.org/forums/index.php? ... -you.5634/

Hopefully someone with better knowledge than me can respond.

edit: just thinking - as I understand it, output transformers should block any DC so probably no need to test DC offset.
Big Dog RJ
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Re: Tune up procedure

Post by Big Dog RJ »

Nice one Plurn!

I'm still trying to figure out the question... better enrol in an electronics course so that I could be up to speed!
cheers mate, RJ
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