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Old 13th Oct 2022, 6:54 pm   #1
Steve G4WCS
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Default Diawa power supply PS304-II

Picked this up cheap off ebay. There hadnt been much interest, possibly because it was listed as a dowding and mills power supply. It was possibly a skip find, it had been dropped and the mains lead cut off.

Straightened the case out, fitted a new mains lead, and gave it a good clean.

I also fitted a power led as the on off switch wasnt illuminating.

Its a go-er and Im very impressed with it, its a lot of unit for its size. The voltage pot has a detent at 13.8 volts.

Gave it a soak test and the power switch neon decided it was going to work again.
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Old 13th Oct 2022, 6:56 pm   #2
Steve G4WCS
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Default Re: Diawa power supply PS304-II

Some after its clean up
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Old 14th Oct 2022, 7:30 am   #3
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Default Re: Diawa power supply PS304-II

good find/fix these is a circuit here if you have not already found
https://usermanual.wiki/Pdf/DAIWAPS3...PPLY.286793869
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Old 14th Oct 2022, 8:46 am   #4
Bazz4CQJ
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Default Re: Diawa power supply PS304-II

These seem to have a good reputation. I think I have one of the clones which is also good.

B
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Old 20th Oct 2022, 6:20 pm   #5
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Default Re: Diawa power supply PS304-II

Nice find i also have one here in Jo'burg!Now mine has lost the 5a fuse cover and below the fuse cover on the rh side are the battery charging output connections .I am getting zero volts DC .the analogue dial seemed to work and registers voltages .but no outputs dc voltages on both sections The internals have lots of PCBs and components so not sure if this is economically viable to fix as labour rates expensive in Za any suggestions
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Old 20th Oct 2022, 6:57 pm   #6
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Default Re: Diawa power supply PS304-II

I have always found Daiwa stuff to be of good quality and well made.
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Old 20th Oct 2022, 7:42 pm   #7
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Default Re: Diawa power supply PS304-II

Agreed, I have the earlier Daiwa model, I purchased it around 25 years ago & it's still going strong.

David.
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Old 20th Oct 2022, 8:35 pm   #8
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Default Re: Diawa power supply PS304-II

That is indeed a good quality PSU. It uses three power transistors running in parallel with proper current sharing resistors. Not only that, it averages the currents the three transistors are doing to operate the over-current limit. Some cheapo supplies sense only one transistor and just hope!

The averaging method is not flawless, if one transistor fails, it causes the remaining two to make up for it, and then when one of those pops, the last transistor is expected to carry the full load. Not Ideal but better than one transistor which if it goes, there is no longer any overcurrent protection.

The devices aren't the inevitable 2N3055 so probably won't be the dumping ground for rejects from the manufacture of far fruitier devices and all the instabilities that can bring.

What I don't see is a walloping great thyristor and a trigger circuit as a last ditch saviour of your radio if an output device fails short circuit.

Your radio is likely worth a lot more than your power supply.

If you have a look at Trio and Yaesu's PSUs to match your rig, you'll find some rather horrible circuit design. They often rely on the power transistor Hfe to set the current liit level and still no crowbar.

David
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Old 21st Oct 2022, 6:01 pm   #9
Jimwall
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Default Re: Diawa power supply PS304-II

Some nice positive feedback on the amentioned. And they where built and designed for quality usage. What for example can you test with these I know ham radios use them in Za. But as a bench testing device what is the best use for them as output voltages to DC motors radios etc or what load can you connect for testing?
As now I am keen to repair and put this to use!
Jim
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Old 21st Oct 2022, 8:48 pm   #10
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Default Re: Diawa power supply PS304-II

They really are intended to power radios. They're not general purpose lab bench supplies.

There isn't much protection from EMF spikes from motor commutators, or from attempts to charge batteries (a big killer of lab supplies)

Best keep it close to 13.8v and non-sparking loads.

David
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Old 22nd Oct 2022, 1:40 pm   #11
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Default Re: Diawa power supply PS304-II

The PSU which I have is the "Mydel 304"; to what degree it is similar to the Diawa, I'm not entirely sure (it looks very similar, which I suspect is intentional).

I bought it to use with an Icom IC718 and was slightly surprised by some switch-on effects with the transceiver.

There's a thread about the issue https://www.vintage-radio.net/forum/...ransient+spike, which may or may not be of interest to anyone reading the current thread.

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Old 22nd Oct 2022, 2:26 pm   #12
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Default Re: Diawa power supply PS304-II

Daiwa stuff has a reasonable reputation built up over quite a few decades supplying radio or electronic stuff. In the late 70s I had a Daiwa SR9 VHF receiver that covered 2M, used with a magmount on my father's car.

Daiwa are, intriguingly, also well known as manufacturers of fishing tackle!!
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Old 23rd Oct 2022, 6:45 pm   #13
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Default Re: Diawa power supply PS304-II

I've had one of those for years when I got it it needed the rectifier replacing and its been fine since.
Different meter though.
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Old 23rd Oct 2022, 10:36 pm   #14
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Default Re: Diawa power supply PS304-II

It could be argued that amateur radio gear is just another sort of fishing tackle

David
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Old 23rd Oct 2022, 10:40 pm   #15
Bazz4CQJ
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Default Re: Diawa power supply PS304-II

Quote:
Originally Posted by Radio Wrangler View Post
It could be argued that amateur radio gear is just another sort of fishing tackle

David
Perhaps, but I wouldn't want to stand in water up to my thighs when working on or operating something with mains or HT on it .

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