Novatron 440 Plus Schematic

[jim10219]

Does anyone know where I can find a Novatron 440 plus schematic or perhaps a similar model. I’m talking about the power pack. My issue is I bought a used one some time ago and the variable power switch doesn’t do anything. Every setting produces the same wattage. This makes sense since I opened it up to look at it, because the way it’s wired, it won’t do anything. The switch is basically wired out to bypass everything regardless of its setting. I’m thinking the previous owner had it repaired by someone who didn’t really know what they were doing, and just rewired it for one setting just to get it working.

So if no one has a schematic, does anyone have a picture of how the switch is supposed to be wired or has someone worked on these before and have an idea how these are supposed to vary the wattage? I’m guessing it probably used some bleed resistors, but of what value? I’d like to get it rewired back to factory defaults, but I don’t think it would be worth sending it in. I could likely get a new one for less money. Plus, I already replaced the capacitors myself, meaning I have enough money sunk into this as it is.

And before anyone brings up the “you’ll kill yourself” routine, I’ve got decades of experience around high voltage electronics. I used to design and repair tube amps and also have experience working on giant industrial equipment, so I know all about the dangers of working around caps this large and how to protect myself.

[Leigh]

I used to be a warranty servivce station for Novatron.

Before they sent out the service lit, I had to sign a non-disclosure agreement.
I expect that was true of anyone else who received that info.

- Leigh

[jim10219]

I used to be a warranty servivce station for Novatron.

Before they sent out the service lit, I had to sign a non-disclosure agreement.
I expect that was true of anyone else who received that info.

- Leigh

Yeah, that’s what I’m noticing. I can’t even find a picture of the inside of one online. Maybe I can find another unit to compare it against. At this point, I’m not even sure it didn’t come from the factory like this. The other four contacts on the switch don’t look like they’ve ever been soldered. It’s basically just being used as a junction box right now. Or maybe the switch was replaced (though it looks original). Oh well. I’ll figure something out sooner or later.

[jim10219]

I found a schematic for the power pack from another brand. The switch in theirs just switches power capacitors in and out from the circuit. I’m going to try looking around for a while longer, but if I have to experiment, this may be my best route.

Still, if anyone would care to snap a quick photo of the underside of the top panel on one of these, I’d greatly appreciate it. At the very least, it may point me in the right direction, and then I could take it from there. I don’t want to reinvent the wheel here if I don’t have to.

[Leigh]

Be VERY careful when working inside one of these power packs (of any brand). Those capacitors can hold a significant charge even after the pack is turned off. If you're not familiar with these capacitor banks, the charge can re-form over time.

The switch may have been disconnected due to carbon tracking.

- Leigh

[jim10219]

Be VERY careful when working inside one of these power packs (of any brand). Those capacitors can hold a significant charge even after the pack is turned off. If you're not familiar with these capacitor banks, the charge can re-form over time.

The switch may have been disconnected due to carbon tracking.

- Leigh

Yes they can! I have a set of shorting cables with different value resistors (for different sized caps) because I’ve spent so much time working on big electrolytics. I’ve been burnt (literally) before by one (in a guitar amp) while trying to hastily move some wires around trying to figure out the source of some parasitic oscillation (while it was unplugged). I’m also familiar with dielectric absorption. And just in case I make a mistake somewhere, I always keep one hand “in my pocket” to keep the current off my heart.

And carbon tracking may have happened to the old switch, if this one is indeed a replacement. But I doubt it effected this one. It looks really clean in there. No dust to be found anywhere. And like I said, I don’t think the other contacts on this switch have ever been used. They’re pristine. I thought the old caps I replaced were original. They were all USA made Mallory’s which haven’t been made in quite a while. But who knows. Without a schematic, I just rewired them the way they were. And it works, great, outside of that one problem. I have a ton of circuits experience with audio equipment, cars, household appliances, and industrial machines, but none with flash units. They’re not too complex compared to some of the stuff I’ve done, but since I don’t have another power pack to compare to, and I can’t hardly find any information about any of them online, I’m kind of flying blind. Like I said, I’m trying not to reinvent the wheel here. There are a bunch of ways to limit the power going into something. But I’m betting the makers of these units have come up with better ways of doing that in circuits like this than what I’d likely come up with on my own. So I’d rather learn from them than my own mistakes.

I’ll just have to wait until I can get my hands on one, or someone provides me a picture. I know it has to be something simple, because there isn’t room in there for anything complex. However it was done, it didn’t require a separate board. And then once I figure out the method they used, I can take it from there.

[Leigh]

Hi Jim,

I think you'll find the power level was changed simply by switching capacitors into or out of the circuit.

That's why to change power levels you MUST turn off the pack, fire it into at one or more heads of proper power rating, change the switch setting, then turn it back on. Changing power settings with the pack charged can damage the switch.

Those caps are in sets, matched by ESR. This is a situation where ESR really matters.

- Leigh

[jim10219]

Hi Jim,

I think you'll find the power level was changed simply by switching capacitors into or out of the circuit.

That's why to change power levels you MUST turn off the pack, fire it into at one or more heads of proper power rating, change the switch setting, then turn it back on. Changing power settings with the pack charged can damage the switch.

Those caps are in sets, matched by ESR. This is a situation where ESR really matters.

- Leigh

Excellent! Thank you for that! That is exactly what I needed to know. I'll have to dig out my ESR meter, and probably have to rearrange the caps that are in there. I hope I don't need to buy any more due to inconsistencies, as they're not cheap.

[Leigh]

Excellent! Thank you for that! That is exactly what I needed to know. I'll have to dig out my ESR meter, and probably have to rearrange the caps that are in there. I hope I don't need to buy any more due to inconsistencies, as they're not cheap.

The caps are also matched by capacitance at rated voltage.
The match need not be precise, but it should be close to change output consistently.

To measure that, you'll need an instrument like a Sprague Tel-Ohmike TO-6 or similar.

- Leigh

[Bob Salomon]

Have you tried asking one of these? Be sure to read the statement at the top:

https://system.na1.netsuite.com/core...t=.pdf&whence=