Hello everyone,
now that 50xx series has been fully replaced with the new 60xx and 2015 (yes 2015 and 60xx are all based on new architecture) with only a few 5050 boards left so I believe it is time to escort the 50xx series to the annals of history. As much as 50xx series improved upon the 3000 series massively it still suffered from some drawbacks that were finally eliminated in the new 2015 and 60xx series. Primarily the large drain coil was slightly microphonic so strong mechanic vibrations could manifest themselves as audible modulation. Also, the reference oscillator was not supressed as much as in the new 2015 and 60xx series. Other than that these proved to be very reliable workhorses. Since the new 60xx series shares the same LCD display and same form factor it is a worthwhile upgrade to consider.
Over the next years people will be coming back to us for tips on repairing these units so it may be best to write these up now while the old model is still fresh in our memory. Lets list them here model by model:
All 50xx models:
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P: (problem): Unit draws huge amounts of current (4A or more or whatever the power supply can give) or blows fuses constantly.
S: (solution): The output transistor is dead, please replace. They are listed on our website under MAXPRO5000 series product listing.
To replace output transistor first remove the heatsink. IMPORTANT: Also the bottom part of the heatsink. The heatsink removes the heat so removing becomes impossible!
Once the heatsink is removed you can heat up the transistor until you can remove it. You can also connect the transmitter to 12V/5A power supply, it will heat-up by itself and after 20-30 seconds it'll practically fall off the board by itself, if you turn it around and shake it.
P: Unit displays I2C error in an endless loop1
S: You have probably connected stereo encoder into RS232 port. This probably damaged the microcontroller both on LCD display and main RF board. Usually first we try to replace the microcontroller on LCD module, this is easy to do since it is in the socket. Next, if this does not work, the RF board needs the same fix. Unfortunately microcontroller on RF board is SMD component so this needs to be done in our lab.
P: Unit displays I2C error in an endless loop2
S: Some early models sometimes developed a problem with quartz crystal. Sometimes moving the trimmer next to it or replacing the quartz resolves
MAXPRO5015:
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Failure of this model usually comes down to final transistor or I2C error due to mis-connected stereo encoder (see above).
If supply voltage exceeds 16V this can also result in burning of opamps (ti2372). With burned opamp you'll have no output power.
Burned final is usually a result of unsuitable cooling or poor antenna (bad SWR).
MAXPRO5025/5040:
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Failure of this model usually comes down to final transistor or I2C error due to mis-connected stereo encoder (see above).
Burned final is usually a result of unsuitable cooling or poor antenna (bad SWR).
If supply voltage exceeds 16V this can also result in burning of opamps (ti2372). With burned opamp you'll have no output power.
MAXPRO5050/5050LP:
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This model is more sensitive than the others for four reasons:
- On-board DCDC converter is a bit sensitive
- It generates a lot of heat so efficient cooling is critical (if not cooled the final may die)
- Antenna connection are just solder posts so failures occur here with people not used to making short leads and not using PTFE coax.
- There is a sensitive SMD resistor close to the LED diode in the centre of the board.
But once all these things are carefully taken care of it will work for you for years to come.
Fixing the 5050/5050LP
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1. Fixing DCDC
DCDC is located close to the power connector in the top right corner. On-board DCDC just turns the 24-28V into 12V for the control circuitry and LCD.
How will you know that it failed? Well, the LCD will remain completely off when you connect power.
Why does DCDC fail? One possible reason is when more than 32V are connected. This can be just a very short transient, it is quite a sensitive IC.
Luckily if the DCDC fails you can simply connect 12V from external source. How? Well, look for the large surface mount coil close to the DCDC circuit close to power connector. Take this coil off the board (heat on both sides). Now note the (+) sign next to the electrolytic capacitor. Connect +12V to this pad where the SMD coil used to be. Also note a 1 ohm 1/4W resistor just below the fuse. Cut this resistor off the board as well. By doing this you effectively disabled faulty on-board DCDC and switched to external 12V source (12-15V is acceptable). Make sure this voltage never exceeds 15V! Also ensure it is RF blocked meaning the power supply for both 24V and 12V need to be isolated with metal shield from the transmitter board and the supply wired through feed-through capacitors.
You can also ask us for this IC, we have spares.
2. Efficient cooling
You will need a metal enclosure and a suitable 80x80 fan or two small 40x40 fans (stronger since they are small). Without this unit won't last long.
3. Very good example of correctly wired coax to the circuit board:
http://i.imgur.com/hUXLo8Rl.jpg
Note leads need to be kept short also on the connector side! Use PTFE/Teflon coax such as RG142, RG178 or similar.
4. There is a size 1206 SMD resistor right next to the manually mounted LED diode. Usually this is 330R or 390R. Since the manually mounted LED diode is causing some stress on the resistor sometimes its end contact can break off. In such cases just place a new one on top of it or replace the old one. This problem manifests so that the output power remains zero.
If you get stuck do let us know, we're here to help.