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Ericsson (ASTEC) 28V PSU? Anyone managed to adjust the output?


Paul Randall G3NJV
 

I bought two of these from Holland using the link given below by I2NDT Claudio.
Nice units, get pretty hot in one corner without load, 27.2V output, no visible pots inside.
Does anyone have a tweak to get them to 28v?
Thanks Paul


Colin Ranson
 

Hi Paul,

 

I would not bother, if you are powering a 28v amp you might not notice the difference by upping it by 0.8v.  I have two 28v amps but I run them at 26v.

Safer and a little less heat dissipation.

 

I do however have a 240w DB6NT 23cm amp that I have yet to use in anger, need to get a good C/O relay fitted to it. Now that does need a full 28v, power output drops off significantly at 26v., its the half watt drive version,  probably 2o years old with inefficient transistors.

 

Good luck.

 

Colin de G8LBS.

 

 

Sent from Mail for Windows 10

 

From: Paul Randall G3NJV
Sent: 03 October 2020 14:17
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ericsson (ASTEC) 28V PSU? Anyone managed to adjust the output?

 

I bought two of these from Holland using the link given below by I2NDT Claudio.
Nice units, get pretty hot in one corner without load, 27.2V output, no visible pots inside.
Does anyone have a tweak to get them to 28v?
Thanks Paul

 


Paul Randall G3NJV
 

Hi Colin, I think I'll need that extra 0.8v as well.
Not much progress, It looks a real pain to take the pcb off the heatsink and can't trace it out unless I do.
There's a uP near the output with 4 A/D input pins. A good chance one of them is supplying the micro with a sample of the output voltage.
I might try some resistance checks around those pins with power off, then select a reasonable shunt-to-0v resistor and dab it on.
If I get lucky I might load the divider circuit providing the o/p volts sample in which case ???in theory??? the o/p voltage should rise.
Crude but... any SMPS experts out there with a better idea or a schematic?

By the way, the pcb is marked as an Emerson product.
Paul


Andy G4JNT
 

It's probably got an overvolt trip - you may have to change the Rs in that, too.



On Mon, 5 Oct 2020 at 18:25, Paul Randall G3NJV <paulfrandall@...> wrote:
Hi Colin, I think I'll need that extra 0.8v as well.
Not much progress, It looks a real pain to take the pcb off the heatsink and can't trace it out unless I do.
There's a uP near the output with 4 A/D input pins. A good chance one of them is supplying the micro with a sample of the output voltage.
I might try some resistance checks around those pins with power off, then select a reasonable shunt-to-0v resistor and dab it on.
If I get lucky I might load the divider circuit providing the o/p volts sample in which case ???in theory??? the o/p voltage should rise.
Crude but... any SMPS experts out there with a better idea or a schematic?

By the way, the pcb is marked as an Emerson product.
Paul


Chris Gill
 

They are normally set by a controller module, as all the  outputs need to be same to feed the batteries. No experience of 28 volt. But 48 volt PSUs normally run about 55 volts, with a much lower voltage
when controller removed. From memory, retired 6 years ago, over voltage was 58.

On Mon, 5 Oct 2020, 18:28 Andy G4JNT, <andy.g4jnt@...> wrote:
It's probably got an overvolt trip - you may have to change the Rs in that, too.



On Mon, 5 Oct 2020 at 18:25, Paul Randall G3NJV <paulfrandall@...> wrote:
Hi Colin, I think I'll need that extra 0.8v as well.
Not much progress, It looks a real pain to take the pcb off the heatsink and can't trace it out unless I do.
There's a uP near the output with 4 A/D input pins. A good chance one of them is supplying the micro with a sample of the output voltage.
I might try some resistance checks around those pins with power off, then select a reasonable shunt-to-0v resistor and dab it on.
If I get lucky I might load the divider circuit providing the o/p volts sample in which case ???in theory??? the o/p voltage should rise.
Crude but... any SMPS experts out there with a better idea or a schematic?

By the way, the pcb is marked as an Emerson product.
Paul


Paul Randall G3NJV
 

Mmmm yes, good point Andy. A chance though, that will be done in software using the same sample input?
The uP's  4 A/D input pins are internally selected to a single on-chip A/D converter. Maybe one pin for o/p voltage, another for o/p current. Maybe one for temperature?

Apart from AC in and DC out, no other connections and no manual links/adjustents, The whole thing is controlled from the optical I/O bus,
Presumably designed to load share at 28V and in a default "no comms" state right now.
All guesswork...
I suppose a first check would be to see if it will take full load in this condition..
..40 amps, gonna need some thick cable and a bucket of water.

Paul


Andy G4JNT
 

Actually, you probably want thin wire to stick in a bucket of water, in order to get enough resistance.   But not plastic covered - use enamelled, or even bare



On Mon, 5 Oct 2020 at 18:57, Paul Randall G3NJV <paulfrandall@...> wrote:
Mmmm yes, good point Andy. A chance though, that will be done in software using the same sample input?
The uP's  4 A/D input pins are internally selected to a single on-chip A/D converter. Maybe one pin for o/p voltage, another for o/p current. Maybe one for temperature?

Apart from AC in and DC out, no other connections and no manual links/adjustents, The whole thing is controlled from the optical I/O bus,
Presumably designed to load share at 28V and in a default "no comms" state right now.
All guesswork...
I suppose a first check would be to see if it will take full load in this condition..
..40 amps, gonna need some thick cable and a bucket of water.

Paul


Clint Sharp <cjaysharp@...>
 

Is there a part or model number?

On Sat, 3 Oct 2020 at 14:17, Paul Randall G3NJV <paulfrandall@...> wrote:
I bought two of these from Holland using the link given below by I2NDT Claudio.
Nice units, get pretty hot in one corner without load, 27.2V output, no visible pots inside.
Does anyone have a tweak to get them to 28v?
Thanks Paul



--
Clint. M0UAW IO83

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