Voltex, Inc.
Quality Assurance and Reliability Notes
Voltex Inc. of Colorado Springs, formerly Plasmatronics before our move from California, has been growing stronger over the last few years, and in the last several years has developed several models that effectively leave our competitors behind. We are now arguably the leaders in the HeNe power supply world.
Starting in 1991 with the new technology contained in the "R" and the "U" models, we began to surge ahead of the others. These two models contain technology which is unmatched in the industry. With an output having a dynamic range of at least 25:1, nothing else even comes close to the capabilities of these models. Our U, or Universal Test Station, is now in service at several of the HeNe laser manufacturers, where they are used all the time and are very popular, to say the least.
In 1993, we solved the two fundamental problems which have plagued the 240 Volt input, or dual AC input supplies. We first learned of these perplexing problems several years ago when, for a short time, we made a small family of 240 - V input types. The problems that emerged were:
(1) Just occasionally, on startup, a supply would instantly and inexplicably fail.
(2) This problem, with competitors' units and not with ours, was a troubling one: - Just occasionally, a supply would violently explode, sometimes with disturbing and expensive results.
We wanted to make very sure that these problems were well understood and dealt with thoroughly before we went to market with a dual-input supply. In 1993, we went to work on these phenomena and came to understand their causes. This work allowed us to design in circuitry which has effectively eliminated both of these problems.
The first problem is caused primarily by the limited capabilities of the switch transistors available today. During the first millisecond or so of operation, the switch is exposed to stresses which it should not be asked to deal with. We have designed "soft start" circuitry which firmly controls the switch through the start - up period, until in full operation, everything comes into normal control.
The second problem turns out to be caused by catastrophic failure of the input capacitors; in a dual input supply, there are two of them, in series. We have built in circuitry which eliminates the cause of their breakdown and subsequent explosion. During the development of the entire "D" series, that is with dual AC input, there has not been a single failure of this nature in a supply which had these protective circuits in place.
We wish to emphasize here that, in our original family of 240 - V input supplies, there were never any explosions. The reason is that those supplies had only one input capacitor; the problem arises with dual inputs.
Following is a discussion of specific steps taken by Voltex to assure quality and reliability which put us head and shoulders above the others in the field.
1. The Circuit Board
All of the lessons learned by us since 1984 go into the design of every P.C. board layout. We use double-sided, plated-through boards for fail-proof solder joints. We design all boards so that there are no marginal high voltage creepage distances. As far as we have seen from our few Customer Returns, failure of the potting material just has not happened in recent years.
Additionally, all boards are laid out and circuits designed so that all our products exceed all requirements of UL and CSA, such as input-to-output isolation - even without the potting material.
2. Agency Approvals
All of our DJT series are approved by TUV Product Service as stand-alone power supplies; that is, they all have appropriate input-output isolation, ensured by 4 mm input-output creepage distance. This distance is maintained throughout the board layout and the transformer itself. Even without the potting, this is more than adequate for TUV approval.
Some of our competitors have approval only to the "Component" standard, putting the burden of isolation on the laser itself. This will only work if you are dealing with enclosed laser heads that have the required isolation, and not with bare laser tubes (bottles). Then, safety is compromised.
TUV approval was issued in April 1995 for our model DJT-22. Since then, we have added all the rest of the DJT series, to operate almost all of your HeNe’s with TUV approval. Incidentally, all the rest of our AC input units are designed to the above standards. As time goes by, more models will be added to those with agency approvals.
3. The Input
Input rectification is accomplished by the stoutest bridge rectifier available today for this job, since it is becoming more and more apparent that the AC power out there in the world is sometimes exceptionally dirty with transients. Inrush currents to the input capacitors are well managed by resistors that are particularly adept at handling surges.
4. The transformer
We wind all our own transformers, placing a layer of tape between all layers to prevent arcing between layers. From input to output, we place a minimum of three layers of special transformer tape, which is capable of withstanding at least 10.5 KV theoretical, far more than adequate input-output isolation. A proprietary method of winding also maintains 4 mm of creepage distance from input to output. In addition to these precautions, they are all vacuum impregnated in transformer varnish to prevent corona and subsequent failure.
5. Output capacitors
Some makers of HeNe laser supplies use inadequate output capacitors, with the idea that they are only subjected to start voltage for short periods, thus they can be rated at less than start voltage. We use only capacitors rated 10 KV continuous, and resultant failures of output capacitors are virtually non-existent in our products.
6. Inspection and Test
All products are fully tested prior to potting and again after potting. At this time, all AC input units are burned in for a minimum of eight hours with a maximum load and repeatedly cycled off and on.
7. Customer Returns
Throughout the analysis period, our total return rate under warranty (eighteen months) was 2.1 percent. Adjusting for units damaged by customers, for example some which had the H. V. output lead tied tightly with tie wraps, causing arcing through the insulation and subsequent failure, and some which were specified incompletely by the customer, etc., resultant real failure rate for the year was only 1.3 percent. This rate is unprecedented in the industry in North America, indeed in the world, to the best of our information.
Elden Peterson, President
© 1994 Voltex, Inc.