I have a Maxpro 2015+ v3 August 2015 (DIP board ONLY) that has worked flawlessly for many years. I wanted to up date the DC supply connection. All was working fine while testing with homebrew cabinet lid off. After reinstalling cabinet top, I noted NO RF output. All looked good upon inspection after I reopened the lid.
I have found the following issue: the LDMOS output device is getting HOT. I have unit fully heatsinked to cabinet and all ground points connect through metal screwd standoffs etc. It tested fine and full power before I reassembled the lid.
I have tested the connection to my 50ohm dummy load and through my SWR PWR meter and connections and RF load seem fine. At RF connector at cct board connection I show 50 ohms. Removing RF load from BNC and testing only at board (power off) I am getting HIGH (infinite) resistance betweeng BNC grnd and RF centre pin. ..as expected?
I am at a loss as to what may have happened. Only possible thing MAY have been a lose RF BNC chassis grnd connection during iintial test, however I would have expected the SWR Foldback circuit to protect the unit, but I saw full 15watts output on RF meter and 1:1 swr.
In all cases, testing was for less than 20 seconds or until heat up of LDMOS PD85015 was noted (using finger on LDMOS case only) The first heat up did get extremely hot and I shut down quickly.
I have checked obvious things like NO solder splashes, NO burnt or damaged traces or components etc.
Using a transistor tester Mega328 type device tester with LDMOS still in cct and got good results .(although I note your post warning not testing LDMOS (-except by replacement ? ) .Just the fact it is overheating leads me to believe
1. The LDMOS is defective
2. Something in the Microcontroller cct is defective and not protecting the LDMOS.
Again, how this may have happened from simply reinstalling the cabinet top, I cannot understand. No long screws, no lose uncovered wires etc
I don't know if an alarm is shutting the unit down, but it is doubtful if the LDMOS is overheating while seeing a non-inductive 50 ohm dummy load.
This is a DIP Switch ONLY used board. I do NOT have or use any of the accessory boards.
I am very disappointed with myself for not finding what caused this problem.
Any advice and details on how to return to PCS for repair would be appreciated. Shipping from Canada with insurance and return shipping cost plus repair may approach an expense not worth the PCS repair.
Not having a schematic nor ability to test the Microcontroller or output power control circuit makes professional repair seem likely. If you suspect a LdMOS failure, I can repair that myself.
Note that the unit was never powered with more that 13 volts DC.(5 amps available)
Any testing or repair advice is appreciated.
Tnx
Repair Policy Maxpro 2015 +
Moderators: Sir Nigel, Nina, pcs, 5r, phpBB2 - Administrators
-
- New registered user
- Posts: 6
- Joined: Thu May 07, 2020 6:07 pm
Re: Repair Policy Maxpro 2015 +
Hi,
I would recommend getting in touch with us, send us an e-mail and include a high resolution photo of the board.
I think we can fix this together with some luck
Best regards,
Marko
I would recommend getting in touch with us, send us an e-mail and include a high resolution photo of the board.
I think we can fix this together with some luck

Best regards,
Marko
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128