JUMA Amateur Radio Forum

Saku,

I think you found the main problem now
The OPAMPs A10 and A11 are installed 180 degrees in wrong position!
Remove them and check the +10V. If the voltage is ok you can try if those OPAMPs are still ok.

73 Matti OH7SV

Robert, The TRX2 rear panel has been changed to double sided PCB with thick copper layers abt one year ago. You can feel heat but that is ok because the final MOSFETs can easily handle the power dissipation although they are warm. 2 ea IRFI510 mosfets can dissipate more 40W at case temperature of 60...

Ok Saku, Let's continue with smaller steps. 1. I did not mean the RF Filter but the 1st AF filter which is plugged on the main board, marked FILTER1 on the PCB. Remove it and check if it helps with the +10V. 2. Is the +10V regulator REG2 getting hot when you keep power on for some time? 73 Matti OH7SV

Initial encouragement by Freescale in the choice of the device was strong but experience has revealed problematic levels of harmonic energy at the output. Freescale now acknowledge this problem to be significant when using these devices at HF. They have quoted H3 at -7dBc and H5 at -13dBc being the...

Saku, Good progress :D +5V is fine now. Most probably something is loading the +10V rail and the regulator REG2 is in current limit state. If it is overload, you should feel heat when touching the REG2. Pin 7 voltage will also go down if regulator is in current limit state. 1V output voltage indicat...

Robert,

Good to hear that

Readjust now the SSB gain trimmer R26 for 10W peak RF ouput. Typical proper value is in the middle position approx 25kohm which can be measured with ohm meter when TRX2 is OFF.

Enjoy QSOs with your JUMA TRX2.

Happy New Year
73 Matti OH7SV

John, During the design phase I tested several cap types for C4...C7 and C12...C15. Murata GRM31M5C1H473JA01D (grey in color) caps performed very well. I wonder if the brown caps you got with the kit are Murata type. Your modification idea is good. I have also sketched quite similar circuits. You ar...

Saku, By default ICs are not broken if you have not overstressed them with wrong polarity or some other "brutal" way. Additionally LP2951 is not very sensitive for ESD. There has not been any problems in TRX2 voltage regulators. You must have something wrong. Check carefully visually every...

John, The AF gain is huge but typically there has not been problems with acoustic feedback. I guess you have tested with an external speaker. Is it ok? Please check that the main board capacitors C4...C7 and C12...C15 are right G0G type. The G0G color is grey compared to the X7R brown color. X7R typ...

I have 0.9 volts on the electric mic hot side Robert, Something is wrong with the electret mic biasing or in the mic or in the wiring. The mic "hot side" voltage should be much more than 0.9V. Typical electret mic current is 200uA...300uA. That means 3V...4V on mic hot side. Please check ...