Interpreting Electronics Schematics

[GRollins]

Bryan,
I'm not familiar with the ML-9 itself, but have heard other MLAS products that I could live happily with.
I have no guidance to offer on value for an ML-9, particularly an ailing one. Dead equipment can offer value, but can just as easily be a black hole for money.
First off--can you get a schematic for the unit?
Trust me, trying to repair a circuit without a schematic can be a serious pain in the rump. *Don't* assume that you'll be able to read the part numbers/values of the existing parts. Heat has a funny habit of cooking the markings right off of things. Worse yet, many audio companies deliberately deface the markings to make it difficult for those trying to reverse engineer their stuff. MLAS used to epoxy entire subsections of their circuits into monolithic black blocks with stickers on top. (I don't believe they do this any more, but could be wrong.)
Second--go into this *expecting* that something else is cooked, probably the output stage of one channel. It's possible that the power supply chose to fry on its own, but it's more likely that it had help. Assume up front that you'll be digging into at least one channel. Then you can be pleasantly surprised if it turns out otherwise.
MLAS is in your neck of the woods:
Madrigal Audio Labs
PO Box 781
Middletown, CT 06457
http://www.madrigal.com
Perhaps you can sweet talk them out of a schematic. Perhaps not. They used to be highly protective of their stuff. Mark Levinson himself is no longer with the company--hasn't been for years. Sandy Berlin was the honcho there, the last I knew, but that may no longer be the case, as I haven't kept up with the inner politics there in quite some time.

Grey

[Super]

After doing some further research, it seems damn near impossible to get those schematics. A few have tried, and none have succeeded. I'll still be on the lookout for any inexpensive amps to upgrade or repair though. Anyone have an amp with which they wish to part?

I also may be able to pick up the necessary toroids for the amps through the electrical repair company I mentioned earlier. I'll have to try and use that place to the greatest extent possible. A company discount or something of that sort would be more than welcomed...

Thanks again

Oh, by the way, still need sources for some beefy caps for the power supply.

[GRollins]

Bryan,
Does this mean you're back to the SOZ plan?
Toroids and caps will depend on the wattage you expect to get out of the thing. Choose a target wattage and work backwards from there. The best source for parts will vary depending on the voltage and VA ratings. Some places will have one thing, some another, particularly if you're seeking surplus. I don't have my list of surplus places with me, but they're all mentioned by someone or another in one of these threads, if you poke around.

Grey

[Super]

I was never actually off of the SOZ plan I was just hinting at something to refine some electronics skills while researching and sourcing out stuff for the SOZ's. In case your wondering, I plan on making them at about 30 watts each, so it seems that the power supply will have to put out about 700-800 watts continuous, and voltage of about +- 43 volts. I know what the toroids should be rated at, but how about the ratings for the caps?

Thanks again

[GRollins]

50V caps will do the trick.

Grey

[Super]

Thanks. I'll start looking around for them online tomorrow. But seeing as its 12:14 AM, I think I'll be off to bed now.

[Super]

After rereading some other posts in the SS forum and some other SOZ articles, another question popped up. Can someone please explain to me what is and what is the function of "rails" and the "rail supply voltage"? Thanks again

[paulb]

"Rails" refers to the power supply voltage(s). Amplifiers requiring a +/- power supply have two rails (or maybe three, if you include ground). I think the name comes from the way some circuits were built: two big bare copper bus bars running in parallel down a board.

[Super]

Thanks for clearing that up for me. I thought thats what it was, but wasn't sure.

[Super_BQ]

Hi Super!

I want to warn you that not many ppl have built 25+ watt /channel SoZ. GRollins said it right. 50 watts you'll need at least a 2KVA transformer. I've heard from others litterly frying their transformers trying to build large SoZ amps.

60w SOZ total may be the limit your house wire lines / circuit breakers could handle. What you don't want to happen is overloading your circuit breaker. Say in your living room if the power outlets are on a 30amp breaker. Excpect roughly a 3.6KVA max draw on the WHOLE circuit (that is not including your TV or what ever devices hooked up in that circuit).

I do not see how some SoZ owners can do 50 watts / channel in their homes without re-wiring the walls and installing a new breaker.

For capacitors - your V+/- of 43 may be a bit too high for 30 watt output ; 43 sounds like it will get closer to 40 watt output. Eitherway the supply voltage should be at least 20% below the rated capacitor voltage figure (safety margin).

The heatsinks will be the biggest cost - unless you choose to go electric fan cooling.