Voltage drop with power supply when in use problem -

[radio grief]

01-22-2k25
An unusual problem, power supply related -

1)...I have a Texas Star DX500v, brand new from factory (purchased possibly 10 years ago with true Toshiba "reds" and converted to "high-drive" from same...I put on only 25 min total talk time and then, packed away...

2)...I have connected the amp (base use) to a 100 amp rv power regulated supply putting out approx 14.6v dc. recently purchased new...

3)...With a connected dc volt meter, I noticed that when I transmit on SSB. (approx 15w pep input to amp), the voltage drops to about 8volts dc!.....

ohhh, it gets better!

4)...I watched a few popular vids via U-Tube about computer power supply use/conversion, in my case the 100 amp versions, however, I left the dc output voltage of mine at 12.6vdc since I had much difficulty with affixing the required/suggested resistors and associated modifications....The amp at "balls to the wall" is believed to be drawing 60-65 amps.

**WHY is the voltage dropping so much and, with each aforementioned power supply since both are supposed to be regulated?**

**I had heard of large capacitor(s) being placed in the dc line to the amp and do not know if that would benefit me or not and, would not know how many mF's rating it should have. Any assistance with this issue?

 

[sp5it]

Where do you measure voltage: PS connectors or inside amp?

 

[nomadradio]

100 amp rv power regulated supply putting out approx 14.6v dc.

Unless I'm mistaken, that power supply is meant to be used with a 12-Volt deep-cycle battery connected to it. It has no standalone regulation circuit and will exhibit a voltage drop without the battery.

73

 

[linearone]

Who makes the supply

 

[linearone]

You have a power supply issue. Buy a meanwell or better yet a megawatt brand

 

[BC Coyote]

Unless I'm mistaken, that power supply is meant to be used with a 12-Volt deep-cycle battery connected to it. It has no standalone regulation circuit and will exhibit a voltage drop without the battery.

This. These types of "power supplies" are the modern equivalent of the old-school RV battery chargers with an iron transformer and half-wave rectification.

There is also no regulation whatsoever. Using such a "power supply" without a battery in the circuit will fry your equipment very quickly. Running a deep cycle battery in the system as a ballast will limit the power drop but you will still be dealing with an unregulated supply and it will almost certainly cause hum in your received and transmitted audio and as well the excessive AC ripple is hard on electronics (especially electrolytic caps).

As Linearone said.....Buy a meanwell or better yet a megawatt brand.

 

[9C1Driver]

I agree with the above, it's a power supply issue.

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[Captain Kilowatt]

Unless I'm mistaken, that power supply is meant to be used with a 12-Volt deep-cycle battery connected to it. It has no standalone regulation circuit and will exhibit a voltage drop without the battery.

73

You beat me to it. I was thinking that it needed a battery to basically smooth out the output from the supply. That battery will act like a filter capacitor.

 

[Eldorado828]

Not to debate with some of you, but for years I used a couple of those supplies or converters as they call them. The first was a 60 amp iota and the second was a 100 amp by powermax. At that time they were all the craze, especially for the big amp running guys.
Anyhow, I used both for a few years no problem, but they were heavy and huge so eventually went to smaller switchers.

Maybe that's what the op is using?

 

[Cable Guy]

I think campers have multiple 12v deep cycle batteries, increasing the charging requirements hence 60 amp or 100 amp chargers. I too have used one as a supply and it worked well. However, it may have battery monitoring and/or smart charging and without a battery to give it it's needed feedback it may switch into a different mode. Without knowing the model he is using, we can only speculate.

 

[Shadetree Mechanic]

The one I have, has a switch to select battery charging mode. Maybe yours has a little switch somewhere?

 

[nomadradio]

The power supplies I'm thinking of are the old school heavy-iron types. The inside will have a big transformer, a fairly-big paper-in-oil capacitor wired directly to one transformer winding, a rectifier and an electrolytic filter capacitor, typically the size of a Foster's Lager can. No fancy circuit board with chips, transistors and such.

If this one has a circuit board full of fiddly stuff, it's newer then the type I'm thinking of.

73

 

[Amperex]

RF is likely killing the power supply Meanwell power supplies perform well with RF amps/

 

[Greg T]

I've been using Megawatt PSUs for some time. I parallel two 50A to run my DX-500 and I use #6 cable to tie them and [power a hub that connects my Amp to the power. My idle voltage is 14.2V and during full output I drop to 13.9v. Never lower. These readings are taken at the hub where the amp is connected. I also use an independent 50A Megawatt to run my SR-955. It idles at 14.6 and drops to 14.5v when TXing. I know you'd like the answer as to why you have this issue, but if you decide to change PSU I would just recommend Megawatt.

 

[CbRadiosPRONTO]

Just FYI: I’ve sold close to 1,000 of those units over the years.

Try using an analog reading meter. 9 times out of 10, it’s not dropping in voltage (at least that much) it’s the RFI causing the digital multimeter to react. Sometimes, especially when modulating, you can see the meter “freak out” and show all kinds of crazy readings. Might not be the issue in your case.

With that said, they do drop a little in voltage. Through the years they’ve had different designs and some are better than others.

Off topic: : I tried running my Icom 7300 with it but it would shut down immediately upon key up and restart. These units drop in voltage on sudden current draws and then recover. That’s no big deal for an amp like that (or shouldn’t be) but it is for a piece of ham equipment.