Amp help!

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XXL
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Amp help!

Post by XXL » Mon Sep 02, 2019 1:35 pm

Hi can anyone help me with this amp ?

It’s running red hot and only doing 80w.
50w runs cool. The 2 trimmers are matched. Is there anything that would be causing this ?

Is there anything I’m missing ? Thanks
https://pasteboard.co/IvxJUgx.jpg

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teckniqs
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Re: Amp help!

Post by teckniqs » Mon Sep 02, 2019 3:08 pm

Those two trimmers on the output are very insufficient for the amount of power that amp should produce and the wire of coil between them looks to thin to handle any more than 50w.

...Oh and SD2933 is a 300w device!

s2000
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Re: Amp help!

Post by s2000 » Mon Sep 02, 2019 3:56 pm

If its running red hot, probably means you have poor efficiency. You can work it out by taking the rf wattage out and dividing it by the supply wattage (voltage x amps). That will give you the percentage of the rf converted from the input supply. I would imagine it's low meaning the amp is probably not matched well.

I notice theres a blob of solder on the 3 turns (after the hairpin), is that intentional?

What have you set Idq too and what about the input wattage?

As Technics said, those trimmers are well weedy for 300w, they'll probably blow up after 100w :lol:

s2000
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Re: Amp help!

Post by s2000 » Mon Sep 02, 2019 4:03 pm

Also where did you get the device? According to Mouser its obsolete, did you get it from China?

XXL
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Re: Amp help!

Post by XXL » Mon Sep 02, 2019 7:50 pm

They still make this fet I think.

The blob of soldier on the coil is because the power went up, so it’s a quick fix to remove a turn.

The wattage is around 500ma. I’m just trying to get it to run efficiently really.

The trimmers will be replaced with caps once it’s tuned to the set value.

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Re: Amp help!

Post by nrgkits.nz » Tue Sep 03, 2019 5:33 am

Using trimmers on the output is what you’d expect from Paul Hollings, they’ll just flash over and melt as Albert has mentioned. Buy some high voltage ATC capacitors, they will work fine.

SOTS 87 7
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Re: Amp help!

Post by SOTS 87 7 » Tue Sep 03, 2019 10:19 am

Forgive me for butting in, but that heatsink doesn't look really big enough either. Maybe it's the picture?
Some years ago I had similar problems with a PA of similar design. Bigger heatsink cured it.

Albert H
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Re: Amp help!

Post by Albert H » Tue Sep 03, 2019 11:48 am

Yes - bigger heatsink and get rid of those output trimmers - I've had those melt at just 20 Watts (with a mismatch)! The shorted turn isn't usually a good idea either. It's a quick and expedient way to remove a turn, but you really should change the coil out.
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"Because it doesn't know the words!"
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Re: Amp help!

Post by Albert H » Tue Sep 10, 2019 12:11 am

So what are your "qualifications", Monitor?

Mine include a first University degree and further degree, Marine Radio Officer ticket, Chartered Engineer status, Amateur Radio Licence, forty years' experience working with RF and other electronic equipment.....
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

monitor
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Re: Amp help!

Post by monitor » Tue Sep 10, 2019 12:57 am

Albert H i was not talking about you!!
But as you are helping, building or supplying for illegal activities, this is against the law and you could be prosecuted.

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Re: Amp help!

Post by Albert H » Tue Sep 10, 2019 1:01 am

I couldn't possibly comment. The "authorities" like Ofcom have no jurisdiction where I live and where I work, so I'm not concerned about them at all. The PTT near my European home can be a bit officious, but can't usually be bothered with "enforcement" unless someone's causing interference.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

XXL
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Re: Amp help!

Post by XXL » Tue Sep 10, 2019 1:08 am

Clearly your from offcom, or just a jobsworth. Piss off and annoy someone else. Using the radio spectrum should not be a crime. You don’t own it, nobody does.

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Neckmin
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Re: Amp help!

Post by nrgkits.nz » Tue Sep 10, 2019 2:24 am

He’s been banned

SOTS 87 7
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Re: Amp help!

Post by SOTS 87 7 » Tue Sep 10, 2019 5:28 pm

Either he's from ofcom or he's one of those stuffy old amateur radio operators who uses 2 meters and talks about Landrovers.
That's why I never renewed my licence, haha.

goneho
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Re: Amp help!

Post by goneho » Wed Sep 11, 2019 12:52 pm

Ofcom is responsible for the management, regulation, assignment and licensing of the electromagnetic spectrum in the UK.
If you want to have a go at building transmitters, please do it the correct way and apply for you ham radio licence.

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yellowbeard
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Re: Amp help!

Post by yellowbeard » Wed Sep 11, 2019 9:17 pm

goneho wrote:
Wed Sep 11, 2019 12:52 pm
Ofcom is responsible for the management, regulation, assignment and licensing of the electromagnetic spectrum in the UK.
If you want to have a go at building transmitters, please do it the correct way and apply for you ham radio licence.
Oooooh responsible... Who died and made you the pontiff? Some of the contributors on this forum are making their living from radio, that busts your hypothesis about amateurs being correct. Having soldered up their kits, read their posts and decompiled their code I can tell you that they are doing a lot better than "having a go".
Image

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sinus trouble
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Re: Amp help!

Post by sinus trouble » Wed Sep 11, 2019 11:02 pm

How about Ofcoms 'Mafia style' of regulation! Based on who can line their pockets with the most pieces of gold!! Fair use is forbidden!!
I am as stupid as I look! :|

XXL
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Re: Amp help!

Post by XXL » Thu Sep 12, 2019 4:38 pm

Looks like we need to ban another jobsworth. Goneho.

Ofcom are only there for money making purposes, they’re like little kids “I want what they're having”. They see there is money to be made, so they setup a bullshit organisation to regulate anyone who switches on to pay them money, or they will come for you. This sounds awfully familiar to a mafia gang doesn’t it ?

If they were really trying to keep the airwaves clean, you would be able to apply for a radio licence for FREE, and allow you to do whatever you wanted with your station, on what ever frequency you come to an agreement to. Instead, they keep turning you down, to gain more money, make it ridiculously hard to even apply, and for what, 25w ? Limited antenna height ?No thanks.

To put it bluntly, they are the most corrupt bunch of cunts that exist. Like anything, it’s just to grab more of your hard earned cash. £££££

I’m going to setup an organisation to regulate oxygen. Anyone that wants to breathe oxygen needs to pay me revenue or I’ll send the boys round and have you dealt with. You must sign an agreement to say you can only use oxygen in your area, you must not breathe over the approximate measurement of 1000l.

AGGHHH I HATE THEM.

SOTS 87 7
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Re: Amp help!

Post by SOTS 87 7 » Fri Sep 13, 2019 1:01 am

XXL wrote:
Thu Sep 12, 2019 4:38 pm
Looks like we need to ban another jobsworth. Goneho.

Ofcom are only there for money making purposes, they’re like little kids “I want what they're having”. They see there is money to be made, so they setup a bullshit organisation to regulate anyone who switches on to pay them money, or they will come for you. This sounds awfully familiar to a mafia gang doesn’t it ?

If they were really trying to keep the airwaves clean, you would be able to apply for a radio licence for FREE, and allow you to do whatever you wanted with your station, on what ever frequency you come to an agreement to. Instead, they keep turning you down, to gain more money, make it ridiculously hard to even apply, and for what, 25w ? Limited antenna height ?No thanks.

To put it bluntly, they are the most corrupt bunch of cunts that exist. Like anything, it’s just to grab more of your hard earned cash. £££££

I’m going to setup an organisation to regulate oxygen. Anyone that wants to breathe oxygen needs to pay me revenue or I’ll send the boys round and have you dealt with. You must sign an agreement to say you can only use oxygen in your area, you must not breathe over the approximate measurement of 1000l.

AGGHHH I HATE THEM.
Mr. XXL, agreed 100%.
I'm wondering if this could be the ghost of Mr. Gotts or his junior.

nrgkits.nz
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Re: Amp help!

Post by nrgkits.nz » Fri Sep 13, 2019 2:35 am

It looks like a different guy as the ip addresses are from different countries, unless a VPN is being used. I checked "monitor" the ip address is from Germany, "goneho" is using an ip address from Texas, US.

Its unlikely Ofcom would register on the forums, if anything they would just observe.

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