Re: rv2- messed up setting and txing like mad!!!
Good advice. Yes, check the power supply voltage into the board.toggle quoted messageShow quoted text
But I would guess that after twiddling RV2 and RV3, the IRF510's are sucking too much current on transmit,
and so bring your power supply to its knees.
I would suggest that you remove power from the IRF510 drains by not supplying 12v to the PA-PWR pin
(the middle pin of the three pin power connector).
Leave it unconnected till you have the receiver working again.
Also turn RV2 and RV3 fully clockwise for minimum (zero) drain current. (Backwards of most knobs in this world)
RV1 should probably be about mid-range, determines how much drive the final transmit amplifier gets.
Find K1, which is the relay nearest the 3 pin P1 power connector near the left back corner of the board.
Find K1 pin 1, has the square pad on the bottom of the board, furthest from the board corner,
this is the TX 12v power rail, it will only have 12v when the rig is trying to transmit.
So your first debug step is to verify that K1-1 is zero volts when you power up the rig,
if it is 12v then the rig thinks it is transmitting, perhaps because of an issue with that 4.7k resistor.
Hopefully, the rig is not receiving.
Current draw should be around 150ma into the rig from the 12v supply.
Now re-attach the middle pin of P1 to 12v, so we are now supplying power to the IRF510 drains,
but monitor the current into that pin from the power supply using a DVM set to read up to at least 3 Amps
(probably the 10 Amp range). You are measuring current, so the meter is in-line, between the power supply
and pin 2 of that power connector. Attach a 50 ohm dummy load to the antenna port. Turn the rig on,
should be receiving. Press PTT, you will hear the relays click, and that TX rail at K1 pin 1 is now at 12v.
Current on the meter should be zero (I assume RV2 and RV3 are still fully clockwise).
Slowly slowlly turn up RV1 till the meter reads 100ma. Then slowly turn up RV2 till the meter reads 200 ma.
The transition to zero current to several amps is quite sudden, toward the end of travel for RV1 and RV2,
and running with several amps of drain current like that can quickly blow the IRF510's.
Check that the IR510 heatsinks are not getting hot, should never be uncomfortable to hold your finger on them.
If you were able to adjust the drain current at each IRF510 to 100ma (200ma total) in the above step
then you have not yet fried the IRF510's. Otherwise, it may be time to place an order for some IRF510's.
In addition to frying the IRF510's, you could also have fried L8 and L9, and the traces to them.
You can check for this by transmitting with no audio into the mike, and using your voltmeter from drain
(the top pin in the schematic) to ground on each of the IRF510's, should see 12v dc there if L8,L9 are ok.
At this point the rig should be working, and when speaking into the mike there should be power into
the dummy load. You can now adjust RV1, increasing it by turning counter-clockwise to where there is
a bit of distortion in the transmitted audio as reported in an on-the-air test when speaking in normal voice
into the mike, then back it off somewhat from there.
Moral of the story: Don't fiddle with RV1, RV2 and/or RV3 unless you have good reason.
On Tue, Feb 20, 2018 at 07:31 am, M Garza wrote: