JUMA PA1000 input attenuator repair
In case you have accidentally over driven JUMA PA1000 you may have burned some of the adjustable input attenuator resistors. The attenuator is handling user interface gain (Gx) setting. It is using three binary (1dB, 2dB and 4dB) attenuators which are sequentially taken in to use with the small SMD relays by firmware control. Typically a burned resistor can be seen visually. See here an example of over driven burned resitors.

If your PA1000 has a nominal bias (idle) current (1.5A-2.4A) but it is not transmitting you may have burned the attenuator.
In case of zero bias current follow this instruction.
JUMA PA1000 input attenuator schematics
The adjustable input attenuator can stand max 25W RF power but 100W is absolutely too much. The attenuator is using rather big 2512 size SMD 3W resitors. There is also a fixed 4dB attenuator (R16, R17, R18). You need to replace only the resistors which have visual marks of failure.

Here is a list of suitable 3W/5% size 2512 SMD resitor part numbers available from DigiKey and Mouser.
12 ohms 2EA 352212RJT
22 ohms 3EA 352222RJT
47 ohms 2EA 352247RJT
220 ohms 3EA 3522220RJT
470 ohms 4EA 3522470RJT
820 ohms 2EA 3522820RJT
JUMA PA1000 input attenuator layout (location in center top of main board)
To remove a burned resistor use two soldering irons and heat both ends of a resitor until it will be freed. After that gently remove residual solder from the pads with a solder wick. You may wash the area with a brush and isopropyl alcohol if you like. Add then fresh solder to one pad which after place a new resistor and reheat the pre-soldered pad. Finally solder the other end of the resistor.

To open and close the top cover follow this instruction

Update 2023-11-24 OH7SV

Back to JUMA PA1000 support information