Topics

28V PSU?


Robin Szemeti - G1YFG
 

My 13cms PA needs 28V to feed it, around 600W input would be good with some headroom for safety.  In the shack I can of course use a bench PSU, but I'd like to box it up and finish it off as a stand alone system I can take out portable.

Any recommendations?   Ideally something suitably switch mode and tolerant of a good range of mains voltages to facilitate operation on a generator would be good.

48V PSUs to drive 50V LDMOS are easy enough, but 28V seems to be a bit more of a challenge to find surplus stuff ... maybe 24V and tweak it up a bit?

--
Best regards,

Robin Szemeti

Redpoint Consulting Limited

E: robin@...
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--
Robin Szemeti - G1YFG


Neil Smith G4DBN
 

I use Meanwell 27V units, they go up to 30V without trouble. I have an RSP 1500-27 and some RSP 500-27s.  The 500s will happily run 22A without sagging.  The 1500 is a complete beast of a thing, I haven't managed to upset it so far, even with a pair of Spectrians or a pair of DF9ICs pulling 45A or more at 30V.

Other approach is a couple of tweaked surplus 12V server supplies in series, but that's getting a bit heavy for /P.

The Meanwell RSP-500-27 is what I use portable. £70 plus VAT with free carriage from Mouser.

Neil G4DBN

On 05/09/2020 17:00, Robin Szemeti - G1YFG wrote:
My 13cms PA needs 28V to feed it, around 600W input would be good with some headroom for safety.  In the shack I can of course use a bench PSU, but I'd like to box it up and finish it off as a stand alone system I can take out portable.

Any recommendations?   Ideally something suitably switch mode and tolerant of a good range of mains voltages to facilitate operation on a generator would be good.

48V PSUs to drive 50V LDMOS are easy enough, but 28V seems to be a bit more of a challenge to find surplus stuff ... maybe 24V and tweak it up a bit?


Robin Szemeti - G1YFG
 

That looks promising, cheers Neil.  A very reasonable price for a PSU with PFC too.


On Sat, 5 Sep 2020 at 17:25, Neil Smith G4DBN <neil@...> wrote:
I use Meanwell 27V units, they go up to 30V without trouble. I have an
RSP 1500-27 and some RSP 500-27s.  The 500s will happily run 22A without
sagging.  The 1500 is a complete beast of a thing, I haven't managed to
upset it so far, even with a pair of Spectrians or a pair of DF9ICs
pulling 45A or more at 30V.

Other approach is a couple of tweaked surplus 12V server supplies in
series, but that's getting a bit heavy for /P.

The Meanwell RSP-500-27 is what I use portable. £70 plus VAT with free
carriage from Mouser.

Neil G4DBN

On 05/09/2020 17:00, Robin Szemeti - G1YFG wrote:
> My 13cms PA needs 28V to feed it, around 600W input would be good with
> some headroom for safety.  In the shack I can of course use a bench
> PSU, but I'd like to box it up and finish it off as a stand alone
> system I can take out portable.
>
> Any recommendations?   Ideally something suitably switch mode and
> tolerant of a good range of mains voltages to facilitate operation on
> a generator would be good.
>
> 48V PSUs to drive 50V LDMOS are easy enough, but 28V seems to be a bit
> more of a challenge to find surplus stuff ... maybe 24V and tweak it
> up a bit?





--
Robin Szemeti - G1YFG


Colin Ranson
 

Robin,

 

I have a Farnell 75amp 28v unit......  clean as a whistle, not been able to find any crap off it, on the other hand I have an Advance 50v, 32amp SMPSU that I use with a 2m Enigma pallet amp and the filth it outputs from 26MHz to 38MHz is incredible.   Strange thing is all the other HF bands below and 50/70MHz are clean !   Weird.

 

Back to giving points away on 2m,

 

Regards   G8LBS

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 05 September 2020 18:19
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 28V PSU?

 

That looks promising, cheers Neil.  A very reasonable price for a PSU with PFC too.

 

On Sat, 5 Sep 2020 at 17:25, Neil Smith G4DBN <neil@...> wrote:

I use Meanwell 27V units, they go up to 30V without trouble. I have an
RSP 1500-27 and some RSP 500-27s.  The 500s will happily run 22A without
sagging.  The 1500 is a complete beast of a thing, I haven't managed to
upset it so far, even with a pair of Spectrians or a pair of DF9ICs
pulling 45A or more at 30V.

Other approach is a couple of tweaked surplus 12V server supplies in
series, but that's getting a bit heavy for /P.

The Meanwell RSP-500-27 is what I use portable. £70 plus VAT with free
carriage from Mouser.

Neil G4DBN

On 05/09/2020 17:00, Robin Szemeti - G1YFG wrote:
> My 13cms PA needs 28V to feed it, around 600W input would be good with
> some headroom for safety.  In the shack I can of course use a bench
> PSU, but I'd like to box it up and finish it off as a stand alone
> system I can take out portable.
>
> Any recommendations?   Ideally something suitably switch mode and
> tolerant of a good range of mains voltages to facilitate operation on
> a generator would be good.
>
> 48V PSUs to drive 50V LDMOS are easy enough, but 28V seems to be a bit
> more of a challenge to find surplus stuff ... maybe 24V and tweak it
> up a bit?




--
Robin Szemeti - G1YFG

 


Robin Szemeti - G1YFG
 

I have a pair of Farnell rack mounted supplies, 60V, 50A fully variable current and voltage limits etc ... as you say, clean as a whistle.  Lovely bits of kit, but I prefer not to use them for stuff that is relatively permanent, otherwise I end up with them tied up "In use" rather than available as test equipment.

I got them on eBay, £50 the pair as non workers ... the fault was that they refused to come into enable mode, and simply sat there in standby. An easy fix, the cover that goes over the output terminals was missing, there is a microswitch behind one of the screw holes, if the cover is missing, it won't let it come on ;)


On Sat, 5 Sep 2020 at 19:50, Colin Ranson <g8lbs@...> wrote:

Robin,

 

I have a Farnell 75amp 28v unit......  clean as a whistle, not been able to find any crap off it, on the other hand I have an Advance 50v, 32amp SMPSU that I use with a 2m Enigma pallet amp and the filth it outputs from 26MHz to 38MHz is incredible.   Strange thing is all the other HF bands below and 50/70MHz are clean !   Weird.

 

Back to giving points away on 2m,

 

Regards   G8LBS

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 05 September 2020 18:19
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 28V PSU?

 

That looks promising, cheers Neil.  A very reasonable price for a PSU with PFC too.

 

On Sat, 5 Sep 2020 at 17:25, Neil Smith G4DBN <neil@...> wrote:

I use Meanwell 27V units, they go up to 30V without trouble. I have an
RSP 1500-27 and some RSP 500-27s.  The 500s will happily run 22A without
sagging.  The 1500 is a complete beast of a thing, I haven't managed to
upset it so far, even with a pair of Spectrians or a pair of DF9ICs
pulling 45A or more at 30V.

Other approach is a couple of tweaked surplus 12V server supplies in
series, but that's getting a bit heavy for /P.

The Meanwell RSP-500-27 is what I use portable. £70 plus VAT with free
carriage from Mouser.

Neil G4DBN

On 05/09/2020 17:00, Robin Szemeti - G1YFG wrote:
> My 13cms PA needs 28V to feed it, around 600W input would be good with
> some headroom for safety.  In the shack I can of course use a bench
> PSU, but I'd like to box it up and finish it off as a stand alone
> system I can take out portable.
>
> Any recommendations?   Ideally something suitably switch mode and
> tolerant of a good range of mains voltages to facilitate operation on
> a generator would be good.
>
> 48V PSUs to drive 50V LDMOS are easy enough, but 28V seems to be a bit
> more of a challenge to find surplus stuff ... maybe 24V and tweak it
> up a bit?




--
Robin Szemeti - G1YFG

 


--
Robin Szemeti - G1YFG


Colin Ranson
 

Robin,

 

Two words – ‘neat’ and ‘jammy’

 

Regards   Colin.

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 05 September 2020 20:24
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 28V PSU?

 

I have a pair of Farnell rack mounted supplies, 60V, 50A fully variable current and voltage limits etc ... as you say, clean as a whistle.  Lovely bits of kit, but I prefer not to use them for stuff that is relatively permanent, otherwise I end up with them tied up "In use" rather than available as test equipment.

 

I got them on eBay, £50 the pair as non workers ... the fault was that they refused to come into enable mode, and simply sat there in standby. An easy fix, the cover that goes over the output terminals was missing, there is a microswitch behind one of the screw holes, if the cover is missing, it won't let it come on ;)

 

On Sat, 5 Sep 2020 at 19:50, Colin Ranson <g8lbs@...> wrote:

Robin,

 

I have a Farnell 75amp 28v unit......  clean as a whistle, not been able to find any crap off it, on the other hand I have an Advance 50v, 32amp SMPSU that I use with a 2m Enigma pallet amp and the filth it outputs from 26MHz to 38MHz is incredible.   Strange thing is all the other HF bands below and 50/70MHz are clean !   Weird.

 

Back to giving points away on 2m,

 

Regards   G8LBS

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 05 September 2020 18:19
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 28V PSU?

 

That looks promising, cheers Neil.  A very reasonable price for a PSU with PFC too.

 

On Sat, 5 Sep 2020 at 17:25, Neil Smith G4DBN <neil@...> wrote:

I use Meanwell 27V units, they go up to 30V without trouble. I have an
RSP 1500-27 and some RSP 500-27s.  The 500s will happily run 22A without
sagging.  The 1500 is a complete beast of a thing, I haven't managed to
upset it so far, even with a pair of Spectrians or a pair of DF9ICs
pulling 45A or more at 30V.

Other approach is a couple of tweaked surplus 12V server supplies in
series, but that's getting a bit heavy for /P.

The Meanwell RSP-500-27 is what I use portable. £70 plus VAT with free
carriage from Mouser.

Neil G4DBN

On 05/09/2020 17:00, Robin Szemeti - G1YFG wrote:
> My 13cms PA needs 28V to feed it, around 600W input would be good with
> some headroom for safety.  In the shack I can of course use a bench
> PSU, but I'd like to box it up and finish it off as a stand alone
> system I can take out portable.
>
> Any recommendations?   Ideally something suitably switch mode and
> tolerant of a good range of mains voltages to facilitate operation on
> a generator would be good.
>
> 48V PSUs to drive 50V LDMOS are easy enough, but 28V seems to be a bit
> more of a challenge to find surplus stuff ... maybe 24V and tweak it
> up a bit?



--
Robin Szemeti - G1YFG

 


--
Robin Szemeti - G1YFG

 


i2NDT
 

I bought a couple of these PSU:

https://www.ebay.it/itm/2PC-Power-Supply-28V-43-1200W-Linear-Amplifier-Army-Surplus/173939932721?
they are 27.2V and were made for Ericsson.
I opened one but couldn't find any trimmer to adjust the output...but I guess that it's possible to do it!

best 73
de
i2NDT Claudio


Robin Szemeti - G1YFG
 

Do you know if it is 120 to 250 volt .. (ie it switches between 120 and 250V mode, depending on the input, this is common in older supplies to switch in a voltage doubler)  or if it has PFC and is any voltage from 120 to 250?

On Sun, 6 Sep 2020 at 10:55, i2NDT via groups.io <i2ndt=yahoo.it@groups.io> wrote:

I bought a couple of these PSU:

https://www.ebay.it/itm/2PC-Power-Supply-28V-43-1200W-Linear-Amplifier-Army-Surplus/173939932721?
they are 27.2V and were made for Ericsson.
I opened one but couldn't find any trimmer to adjust the output...but I guess that it's possible to do it!

best 73
de
i2NDT Claudio


--
Robin Szemeti - G1YFG


Mike Willis
 

I suspect you do it in software, but no doubt somewhere there is a voltage monitoring system that can be suitably tricked. 27.2V is enough for most PAs I suspect. I have a similar PSU that's very nice also 27.2V. There is a permanent fault light which relates to it not being attached to it's network but that does not stop it working. Maybe I will order one, though it looks like you have to order a pair.
--
Mike G0MJW


Robin Szemeti - G1YFG
 

Mike: want to go halves?

On Sun, 6 Sep 2020 at 13:35, Mike Willis <willis.mj@...> wrote:
I suspect you do it in software, but no doubt somewhere there is a voltage monitoring system that can be suitably tricked. 27.2V is enough for most PAs I suspect. I have a similar PSU that's very nice also 27.2V. There is a permanent fault light which relates to it not being attached to it's network but that does not stop it working. Maybe I will order one, though it looks like you have to order a pair.
--
Mike G0MJW


--
Robin Szemeti - G1YFG


Mike Willis
 

Might be a good idea.
--
Mike G0MJW


Mark - M0WGF
 

The Ericsson PSU are good value.  

You can adjust the output voltage up to 28.2V using a pot located under the heatsink.  I can't remember which one but I can open the unit and have a look if it's at all useful?

They run hot even under idle (approx 50C) so you need a fan to keep them cool a single fan over the top of the heatsink would do.  I used two fans which on hindsight was overkill. 

If you can find the same style of binding posts they screw tight into the original socket which is handy and saves some modifications.  

73 Mark
M0WGF


i2NDT
 

sorry no idea!
the label says: 120 - 250 VAC 50/60 Hz.


Mike GD6ICR
 

I wonder if you know what type of 27v Plugs they use

--
Mike GD6ICR IO74PF73TW


Robin Szemeti - G1YFG
 

I'm thinking 4mm banana plug will do it.  Just ran my 1200W ones, off load there is negligible heat output, I could barely detect they were on.

On Sat, 12 Sep 2020 at 13:36, Mike Webb <gd6icr@...> wrote:
I wonder if you know what type of 27v Plugs they use

--
Mike GD6ICR IO74PF73TW


--
Robin Szemeti - G1YFG