President Lincoln no power after thunderstorm.

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Breaklight
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President Lincoln no power after thunderstorm.

Post by Breaklight »

Radio Make and Model: President Lincoln HR2510
PCB Number: Main board PB-111AB
PLL Number: PCB PB 121 AC HCT 58 NY 94V-0
Test gear available: Watt meter, DC AM meter, oscilloscope
Symptoms: No power on FM/AM whatsoever. On SSB the is a very slight noticeable signal on an external reciever. This all seemed to have happened during a mild thunderstorm where a QSO wasn't possible all of a sudden presumably caused by static electricity.

What is working: Receiver and MPU

What has been tried: I received the Lincoln without the final where as the owner thought the culprit might be the final and unsoldered it. Before replacing any transistor I checked if there was any bias but none whatsoever... Maybe the bias diode gave way so I unsoldered the diode and it indeed was defective so it needed to be replaced. After this I tried to get a 50 mA reading between TP4 and TP3 but nothing yet. So I decided to place a brand new MRF477 there were the original was missing and do the test again. At that point I got stuck in finding the reason for this problem... At first my power supply went in a safe mode due to short-circuit :shock: . So I got the Volt meter on the two TP's and measured 13,89V between TP4 and TP3...? Is this normal? I don't have to guess what happens when the test pcb is placed back in this condition... :?

I have to say that I'm confident in making myself sure about the soldering job and checked all solder connections over and over again... I'm not a expert on this but I can do a lot to get a radio working again like many defective radio's before this Lincoln. But in order to avoid making matters worse I really hope that someone could give me a hint where to look for... If I made a stupid mistake or assumption... tell me :|

I just want to get this radio working again and I know I'm a step away... hopefully....

Any help would be very much appreciated!

Cheers!

John
RG2950DX, Lincoln, Imax2000
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13EL121
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Re: President Lincoln no power after thunderstorm.

Post by 13EL121 »

Hi!

Check C116 (150pf). This one sometimes blows when the radio is "tuned". :wink:

73,
Ralf
Breaklight
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Re: President Lincoln no power after thunderstorm.

Post by Breaklight »

Hi Ralph!

Thanks for the suggestion! I didn´t have the uppertunity yet to check this capacitor but as internet provides me with some info, this issue was mentioned a couple of times on different sites.

But if it is this capacitor, does it explain the 13,8v between TP4 and TP3?

Thanks!

19WAC495

John
RG2950DX, Lincoln, Imax2000
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13EL121
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Re: President Lincoln no power after thunderstorm.

Post by 13EL121 »

Hi John,

i don't really know, but C116 is one of the most problems in such cases. This can't be a big problem, but a hidden one :doh: .

73s, Ralf
Breaklight
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Re: President Lincoln no power after thunderstorm.

Post by Breaklight »

Hi Ralph!,

Yesterday I unsoldered C116 after a long search for this tiny component and tested it. (Un)fortunately the condensator passed the test and was soldered back in. I checked the other C115/114 and they worked fine too... Hmzz.. I guess this baby needs a real doctor, only if it was to find this tiny little bug that refused to be found or even fixed... :?

73's

Breaklight

19WAC495
RG2950DX, Lincoln, Imax2000
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13EL121
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First Name: Ralf
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Re: President Lincoln no power after thunderstorm.

Post by 13EL121 »

Hi John,

hmmm...hope that the rig doctor will find the problem. Maybe a small transistor is blown.
Good luck!
73s
Ralf
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