Jedi MT2100/MT2000 - RX 10KHz off freq - faulty IF IC ???

[g8tzl2004]

I have an MT2100 , which is the European version of the MT2000.

The set originally suffered from instability (chuffing noise on weak signals). This was suspected to be a common fault with the IF IC - a uBGA device which is difficult to replace without special gear.

I decided to replace the RF board from a similar set (MTS1200) which used some custom firmware so I have never been able to read the codeplug. As a result , I was unable to note down any original softpot values - but I have enough test gear to realign the RF board - except deviation settings.

Anyway , I installed the replacement RF board - I needed to tweak the Ref Osc but the front end alignment was more or less OK - tuning was very "flat" with little SINAD difference for a big swing in softpot values.

However , there is a problem. Sometimes the RX is 10KHz off freq at power up. TX is spot on. BUT , if I power up and down , say 3 times , RX will be back on freq and will stay spot on all day!!

Also , when the battery is almost flat , if I TX , the set seems to lock on TX but way off frequency putting out around 1-2W . This only happens with a flat battery. To stop the set TXing , I need to power off. When fully charged , the battery is OK with a no-load voltage of around 8.4V - so I don't think my problems are due to a faulty battery !!

Any thoughts? I'm guessing that its the faulty IF IC problem again with the RX off freq issue. Not sure abut the TX issue - maybe VCO related?? Could be linked to dev balance compensation alignment??

Thanks

[wavetar]

I have no suggestions for the RX problem, but the locking up in TX with a low battery is a known issue with early version firmware versions (around 1.36 & earlier) for the MTX8000/MT2000. Sounds like your version does the same.

Todd

[Will]

- I needed to tweak the Ref Osc

Look at the Reference Oscillator's frequency in both TX and RX. It should not change. everything is tied to the Ref Osc.

[Karfield]

If you can put it into a breakout board and catch it doing that specific problem I'd take a look at the IF frequency with a monitor and make sure it's on freq. If that is off you're problem could be the U201 which is only tricky due to the two inductors that surround the U201 on the UHF models. (I'm assuming you have UHF) However if you have a VHF unit the U201 is simple and just a matter of carefully taking off the shield and replacing the U201 chip. I could get you the part number to that if you want it. If you do have a UHF and take off that shield keep your eye on the two gold inductors they will blow up like mushrooms and be very difficult to deal with. However if you order those parts as well you'll have nothing to worry about. A good hot air gun and suction pick up tool is all that's really needed to change the BGA parts on a Jedi.

[Andreas]

Change the RF board!
I´ve senn the problem often on the Jedi series.It´s the IF or mixer IC.

Andreas

[Karfield]

Suppose he could change out that RF board but the U3 is an easy repair where as the U201 is a little more difficult but both are doable (as long as there is a good heat gun involved). Harborfreight tends to have heat shrink guns for like 20 bucks from time to time.

[g8tzl2004]

Thanks for all the feedback.

I have a few more questions. My set is a UHF version.

- any idea what ref osc freq is ?
- any idea what IF offset freq is?
- what is U201? Maybe BGA IF IC?
- what is U3 ? Maybe mixer ??

I tried another RF board. This had clean TX and RX but was deaf (maybe 10-20dB down). Tweaking softpots had no effect. I guess this is due to a faulty front end FET? Any thoughts? Is this easy to replace?

Thanks

[Andreas]

Check the antenna switch and the spring to the antenna jack.Solder the spring to the RF board.It often have bad contact.

Andreas

[g8tzl2004]

OK on checking antenna switch.

However, front end softpot tuning has NO effect on sensitivity. While front end tuning is very "broad" on my other RF boards , you do notice a decline in sensitivity at the extremes of the tuning range.

With the deaf RF board , there is NO change in sensitivity , even at a softpot setting of 1 or 255. If it was a faulty antenna switch , I would still expect a change in sensitivity as you tweak the front end softpots?? Is this a correct assumption?

[IjeSJot]

I have exactly the same problem on my MC2100 and MT2100. I think it may be faulty reference oscillator. Have You programmed Your radios using wookie? I must try flash back MC2100 to GM1200 and see what will happen, maybe there where few firmware versions and few hardware revisions that were incompatible? For example, old firmware on new pcb?

[Andreas]

ON MC2100 never use the Wookie RSS!
Use always the 2100 series DOS RSS.
There is a bug in the software.You cannot tune the frontend!This can be a reason for low sensitivity.

Andreas

[IjeSJot]

Anyone tried to flash back MC/MT2100 to GM/GP1200?

[Andreas]

You can do this with the 2100 series lab flashtool and the GM/GP1200 lab firmware/codeplug kit.

Andreas

[Will]

Suppose he could change out that RF board but the U3 is an easy repair where as the U201 is a little more difficult but both are doable (as long as there is a good heat gun involved). Harborfreight tends to have heat shrink guns for like 20 bucks from time to time.

I have a few RF boards with the RX problem, do you want to fix them?

[IjeSJot]

I thought that my RF board from MT2100 UHF is faulty... so I decided to replace controller and i`ve created GP900 for UHF band and problem is gone! I suppose problem is with firmware or internal codeplug, not with RF board!