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president HR2510 high swr spikes

Then likely it's the disc caps under the final. I would install the insulator, and fully remove the 2 - 561 disc caps under the final. Your output power will drop a little, but that also means your impedance is matched on the final, and you're not reflecting wattage back into the final. Should fix your issue. Let us know how you get on.


~Cheers~
 
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Was just playing around with it and took a multimeter set it for continuity with sound and ran one probe into the antenna socket and the other around the ground side the the so 239 jack and there was continuity so there is a definute short to ground somewhere dont know if the disk caps would cause this or now was just checking for other possibilitys
 
Just tryed removeing the screws to the main board and still has a short so i removed the synthesiser board and short was still there so i rwmoved the screws to the final driver and pre driver one at a time and moved them back a little so they werent touching the chassie and short was still there
 
Wow, this thread got busy, Hi gang!

Well, to catch me up, yes - the radios' antenna connector WILL SHOW SHORT - why?

Locate L136 - toroid...Because it has a toroid wind "coupling" that allows DC and static to drain off and not get into the rest of the radio - think of it as a Hi-Pass Filter - Keeps DC and those noises off the antenna RX/TX line - or at least from doing any damages to the radio when you run a dipole - the static from the wind strumming thru the wires and it's open separator - it can generate enough voltages in static to poke - if not kill someone if they are not careful, let alone RF energy from an AMP and it's RF when it unkeys, that energy has to go somewhere to get quenched - might want to keep that outside of the radio.

Here's the location of what we're trying to show you...
upload_2020-7-20_9-44-12.png
upload_2020-7-20_9-55-13.png​

Now, to me, the 560pF (561 Discs) are necessary, but not too much of a fussy REQUIREMENT.

There is a spot or them on the BASE lead below on the foil side. The MRF477 is a BEC configuration - meaning it's EMITTER is BOLTED to GROUND at the Chassis - and the Center leg of the part is solder to foil GROUND.

Note the use of Insulator on the part - above MRF477 is NOT using a Heatsink insulator - that is Heat sink goo - the part is botled to the rear panel ...
  • What they suggest you do is to use a Mica insulator on that part - the EMITTER portion of this - to keep it's ground to the main foil pad below on the Foil side.
There is also your SWR problems - that is further over to the left - the SO-239 and it's made out of nickel and plated chrome - in an Aluminum HEAT SINK rear panel
  • - so remember to also PROPERLY TIGHTEN the SO-239 connector, it uses a solder lug - keep it and properly solder it well to the foil ground. The rear panel is aluminum so it can oxidize and show a resistive impedance to RF that can and will inject SWR issues - hence my thoughts added to this thread...
So when problems do occur, be sure to keep an eye and ear out for erattic operation if the Final were to ever "latch up" - due to noise proximity that can make it go into self oscialltion - hence the 560pF's to keep RF off the Base lead - so don't put / place too much worry of Part exactly - but the LOCATION of them is important - just use some form of RF shunt to keep RF from ruining your day...

Part of the problem? Alloy and Galvanic events of corrosion - never gives good results - Steel and Aluminum don't mesh well...
 
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