TFPro P3 problems

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    I’ve used the little red one as preamp and compressor for long. Quite satisfying its sound in the price.

    Until 3 days ago, there’s weird static noise (very low in level) in the preamp.

    I opened it and found the 100uF, 100V capacitor leaked.

    I replaced it with the same speced BC (Philips) 136 capacitor.

    And the sound is nice, more warmth, definition and solid mids. The original sound is more treble oriented.


    Since I live in Taiwan (Asian), a very humid area, I plan to replace all the old capacitors. From a great designer’s mind, what capacitor do you suggest for the TFPro P3 with less budget limit??

    And is there a schema available for reference?

    Question 2:” class=”bbcode_url”>

    Please refer to the picture above.

    The chassis is grounded by pin1, but the chassis paint is still on while the other paint in another screw wear off. I believe the chassis should be grounded with Pin1. Am I right?

    I actually dug bigger hole and put a Neutrik NC3FD-L-1 onto the chassis, the iron box has lots of contact with NC3FD. I’m not sure if it’s good (one contact via a screw as seems better with less different chassis noises), but the resulting noise is a lot less than the original unit.

    Question 3:” class=”bbcode_url”>

    On the back of the circuit board as indicated by the picture. Is the SMT resistor on the left supposed to connect with the capacitor C15 via solder??

    Question 4:

    I found the Kester (no lead with Ag) solder somewhat changed the sound a bit, do you have a solder suggestion for TFPro P3?

    Should I use lead solder for this older PCB?

    Thank you.

    And sorry for not mailing you the unit for fixing. International shipping here costs too much for me considering the price of the unit.

    Ted Fletcher

    The only capacitors in the P3 that could cause any problems are the input capacitors. These should be special low leakage types.

    Any leakage at all and you get additional noise and loss of low frequencies. I would recommend that you do not change any of the others unless there is an actual fault; there is no advantage.

    On the grounding, there should be a ‘shakeproof’ washer next to the paintwork that will cut through the paint and make a good ground contact. If there is not a good contact then it’s a good idea to clean away some paint…. it is essential that the ground contact is made. Yes the chassis should be grounded at pin 1.

    That solder joint is correct.

    As for solder changing the sound….. No! it’s your imagination! I use lead solder wherever possible because it’s easy to work with, but there cannot be any difference in sound. It’s like loudspeaker cables, weight is the important thing, not uni-directional or oxygen free. 60 amp cooker cable is best! 😮

    I’m glad you are enjoying the P3…. it’s a fine mic amp and the compressor is a genuine optical compressor with a superb sound. :)


    Thank you for the answers :)

    I meant the broken 100uF/100V output capacitor due to long time recording.

    The input capacitors are used whether phantom power is on or not, right?

    I read on the PCB, the input voltage indicated is 13V~15V.

    And the stock 120V->12V AC transformer is measured with 13.1V~13.4V.

    I got another new 110V->12V AC transformer measured with exactly 12V or 11.9V

    Interesting the new 12V AC transformer has a more defined sound.

    I wonder if the lowered input voltage damage the circuit?

    Ted Fletcher

    If you would like to email me at [email protected] I will email you back the correct circuit diagram.

    I have had a couple of instances of that output capacitor failing…. usually it’s caused by plugging the output of the P3 ito a mic input with phantom power on it (!) This usually damages the output capacitor and has been known to wreck the output stage!

    The power supply for the P3 is not critical….. the internal voltages are stabilised. It’s normal for the power supply to measure between 11.5 and 13.5VAC The symptom for having too low a voltage is severe hum on the output.

    Yes, the input capacitors are in use all the time.


    Thanks a lot for the detail information.

    Best customer support ever! :D

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