Dirland 3900f ,variable power knob doesn't work ?

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original45
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Dirland 3900f ,variable power knob doesn't work ?

Post by original45 » 28 Sep 2018, 16:20

Any ideas please.is this a mod ? Or does it look like theirs a fault that has been bypassed ?

Obviously it had the facility out the box apparently it's not functioning but still putting out good power ?.
Apparently 12 w am fm and 18 ssb ?sounds high ?

This is a radio I consider buying but don't wish to get in too deep.

Thank you

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by 14CS06 » 28 Sep 2018, 17:10

Hello

Variable power knob work only on AM FM no SSB

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original45
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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by original45 » 28 Sep 2018, 17:22

Thank you Claude. Any thoughts of reasons you are aware of as to why the variable knob would have been bypassed .

If indeed it isn't a case of it being broken faulty.
Just to confirm it doesn't work on fm
Thank you again

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by Black Spirit » 28 Sep 2018, 17:26

original45 wrote:
28 Sep 2018, 16:20
Any ideas please.is this a mod ? Or does it look like theirs a fault that has been bypassed ?

Obviously it had the facility out the box apparently it's not functioning but still putting out good power ?.
Apparently 12 w am fm and 18 ssb ?sounds high ?

This is a radio I consider buying but don't wish to get in too deep.

Thank you
If its doing 12w AM/FM then i would guess the variable power VR inside has been cranked up full and if thats the case the higher the VR is set inside the less response the variable power on the front has, As above the variable power only adjusts AM/FM.

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by original45 » 28 Sep 2018, 17:45

Thank you.
This could be the problem.

Would it be fair to suggest the front variable knob wouldn't show any effect then.

If so this is v likely the issue.

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by cb4ever104 » 29 Sep 2018, 06:30

12W is way too high. Even if the VR is wound up the front panel control should still reduce the power. Take the cover off and have a look. Sounds to me as if someone has jumpered one end of the VR to 13V. I uusually remove that feature if it's wired to the SWR CAL and put the radio back to the way it was.

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by Black Spirit » 29 Sep 2018, 10:37

original45 wrote:
28 Sep 2018, 17:45
Thank you.
This could be the problem.

Would it be fair to suggest the front variable knob wouldn't show any effect then.

If so this is v likely the issue.
Im not saying it is the problem im just saying its possible, I have a 3900F on the bench now and with internal power VR inside set to 8w AM/FM the variable power adjusts down to 2w, With the internal VR turned up full the variable power only adjusts a very small amount [around 1w].

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by original45 » 29 Sep 2018, 14:23

Thanks all, will look see .
Appreciated

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by cb4ever104 » 29 Sep 2018, 15:47

A couple of photos would go a long way too. :thumbup:
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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by original45 » 29 Sep 2018, 19:25

Yes once I get it in my possession I will do some images .

The seller seems to think this is done as a mod once it's expanded to the extra blocks ,same reason for its power increase seems the norm ?..
Apparently he said it makes power delivery equal through the blocks of 40.

Or something like anyway.

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by cb4ever104 » 30 Sep 2018, 09:07

That's rubbish. Someone's been messing about . The board is just the standard EPT3600 Ranger board , with twin finals. As I said. Some photos of the VR13 area on both sides of the pcb would help a lot.

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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by astradyne » 01 Oct 2018, 07:00

There could be the possibility that the regulator has gone open circuit. This would put the radio into full power mode on FM and AM as the output stage will be receiving a constant 12V. This would also explain the variable power not working.

An easy way to check if this is the case would be to see if you have any modulation on AM. If you don't try replacing the regulator, if you do then try the above suggestions.
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Re: Dirland 3900f ,variable power knob doesn't work ?

Post by original45 » 01 Oct 2018, 18:50

Thank you all for the input. I am awaiting a contact from the seller 're it's purchase.
Thanks again.

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