Gates 5 rebuild

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Gates 5 rebuild

Post by TPT » Mon Oct 15, 2018 9:55 am

Getting drawn into a choice of rebuild or downgrade and replace on a 5 kw AM. 1993 Gates 5, we were turning it off and on, off and on over several days while a cell installation was hoisted up the tower & tuning networks reset. Now makes about 2500 watts, PDM section looks like the national Christmas tree.

I suspect it will need a major re-cap. First question--before we tear into the PDM section--do those big V-8 Can sized caps need to be the same size or is it possible to use same value different sized caps. I am assuming if Gates Air even has the large caps they will want a ridiculous price.

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Re: Gates 5 rebuild

Post by RGORJANCE » Mon Oct 15, 2018 12:25 pm

It has been quite some time since I did the SX and Gates series recap. My old fuzzy brain is saying that the mounting is set for a specific physical size of cap...................

I was able to get an answer from a friend.

The caps need to be physically sized due to the mounting in the PDM area. They supposedly attach to the pc board, and are held tightly in place with a hose clamp arrangement. Physical spacing for the terminals is a fixed distance, and the diameter is also a factor. I recall that some also mount on the rear door, and those I believe are held with very long hose clamps, and physical size may not be as big a factor. Hope this is accurate.


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Re: Gates 5 rebuild

Post by ncradioeng » Mon Oct 15, 2018 2:37 pm

Have you checked the PDM and PA fuses and looked for shorted FET's?

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Re: Gates 5 rebuild

Post by Kelly » Mon Oct 15, 2018 3:19 pm

That's what I was thinking; blown fuses ahead of blown FET's.
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Re: Gates 5 rebuild

Post by ChuckG » Mon Oct 15, 2018 10:32 pm

Gates does stock the capacitor kits and the price is fairly reasonable. I've done several of these. I've read of folks getting caps from places like Mouser, but if you do- as Fossil said, watch the terminal spacing and physical size. There is no room for variance.

If the fuses are blown you can bet the associated FET's are. The fuses protect the PC board traces from a shorted FET.
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Re: Gates 5 rebuild

Post by RodeoJack » Thu Oct 18, 2018 7:20 am

I'd worked up a fairly intense dislike for the Gates series of solid state boxes, but I'm starting to come around to the conclusion that it's just another rig with a personality. Get to know its needs and it seems to stay fairly content. Unfortunately, Gates Air's getting out of the AM business and their level of support, compared to "type N", may do more to kill the Gates and DX transmitters than any performance issues.

When it's happy, the Gates 5 runs pretty well. When it's not, it will expand your vocabulary. Usually, the alarm lights show you the immediate problem, but the source can be elsewhere.

I spent over a year, fighting one such beast. It ate MOSFETs for lunch and, for appetizers, would enjoy a piece of PDM board. Sometimes, a PDM would blow a fuse without a corresponding MOSFET blowing, but not always. The PDM MOSFETs are a lot more expensive than the ones on the PA boards, which the transmitter was making full meals out of. The rig would ALWAYS wait until I had returned home (300 miles one-way), before ingesting something. Gates Air's suggestion was that we buy a new rig.

So... there are several service bulletins on the Gates series of transmitters They're worth looking into.

The big caps are a must-check. Gates says 5-7 years +/-. I've seen much more life, but when they're finished, the transmitter will do weird things, like not starting, stopping at random, power supply variations, MOSFET issues, etc. As the bulletin says; if you don't have a cap checker that will read that high, just take them out and give them a good shake. If they're obviously light or slosh like a half-filled water bottle, they're done. If anyone here runs a DX-10, this applies to you as well. Gates offers full recap 'kits', and they don't seem to be outrageously priced, given what your time would be worth, sourcing them yourself. Those kits are mentioned in the bulletins.

There are a couple other bulletins, regarding smaller caps in the oscillator and PDM boards. A couple of voltage checks will tell you if those are heading south, so pulling them out of the boards for testing isn't necessary, so far as I've seen.

If all else fails, check the mica caps in the bandpass filter, upper left at the top of the box, looking at it from the rear. They're hard to get to without pulling the top off, but you can use mirrors or feel around up there for any cracks. A problem in that section eluded me for most of the time I had fought with that model. Replacing those caps finally made the rig happy. I haven't lost a fuse or MOSFET in nearly a year now. Before that, it never went a month.

I don't know for sure if it matters, but... This station changes pattern and power levels. The installer set it up so the remote control shut the rig off while changing modes. In my tube days, we tried to avoid the on/off cycles as much as we could (anyone remember the old EBS procedure?), so maybe this is just me. I re-did the sequencing to use the transmitter's carrier mute, rather than a full off/on cycle. Don't know if that made a difference, but like I said, the box has had zero problems for longer than it had in the previous 5 years or so.

If you're directional, take a look at your contactor(s). I had one that would arc now and then. The transmitter doesn't like that.

If you're remoted and your control can save logs, keep those in a safe place. The transmitter doesn't drift around much, when given a stable power source and a solid load. You can see problems brewing if you can log the readings and look at them over time. I save my Burk and WVRC logs to an FTP computer I keep for the storage of EAS and transmitter stuff, and it has made a difference.

Otherwise, the basics apply to this rig... keep it clean, keep it cool, visit it once in a while.

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Re: Gates 5 rebuild

Post by Deep Thought » Thu Oct 18, 2018 8:49 am

RodeoJack wrote:
Thu Oct 18, 2018 7:20 am
Otherwise, the basics apply to this rig... keep it clean, keep it cool, visit it once in a while.
They also really *really* don't like open delta power feeds. One client was replacing fuses and FETs on a monthly basis until they installed a delta-to-wye transformer and haven't had a major problem since.
Mark Mueller • Mueller Broadcast Design • La Grange, IL •

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