Pure Evoke H3 DAB/FM Radio not powering on and no sound or muted erratically - Page 1
Forum section: electronics / repair

author: rh100605
author_rank: Regular Contributor
timestamp: October 04, 2020, 05:37:13 pm
content: Hi,I have repaired 3 and failed to repair 3 of these radios. Faults fall into two definite categories. Firstly will not power up and secondly sound comes and goes1. Will not power upThese radios use a 5.5volt supply but it seems that many people fail to notice this and plug in a higher voltage. It is polarity protected by Schottky diodes but not voltage protected.This results in damage to the regulators (8Kxxx which is Diodes Inc. AP2318 DFN-3x3-8 goes short) , pass transistors (1F and 3F), glass diodes (1N4148) and even ferrites, all of which which may be repairable but check the resistance to ground of the 3.3v lines, which if low points to the Kino 4 chip itself. The Kino4 chip 3.3v power input on the display connector side, is prone to shorting.Damage to the Kino 4 chip (which is inside the can) is evident as a small hole or crack in the plastic. This not repairable as I cannot source chip + the code stored in flash memory.2. Sound comes and goesThe final amplifier is on a small board soldered directly to the speaker terminals. I have not seen this failI found out that replacing the connector board ( USB/power/headphones/aux in) or removing the plug CN6 (7way) clears the problem. There seem to be two causes.You will have to remove rubbery glue to get at the components. I used flux remover to soften it first.Firstly the switches in the headphone socket are unreliable. They are unusual as there are two SPDT switches internally that are connected in parallel to pin2 of CN6 (yellow wire) and ground the yellow wire when a plug is inserted. Pin2 is normally pulled up to 3.3v.I have extracted two sockets and found that grounding sometimes does not happen or a high resistance approximately 1Meg to ground can occur without the plug being in.I dismantled one and found green crystals on the metalwork inside. So corrosion......I cannot source a replacement socket except in 5,000's. The manufacturer is Kunming Electronics Co Ltd Taiwan.Vertical Headphone Stereo Jack Earphone Socket ISO Connector 3.5mm Stereo Jack PDA Socket Model Number: HTJ-035-17 series-#0528Yes I am considering putting a switch on the back to perform the mute function.!Secondly Pin2 of CN6 has a ESD protection diode (D403) marked E6 to groundThese are PESD5V0S1BA , bidirectional 5 volt TVS clamps from Nexperia. They fail in strange ways and can even change characteristic when in use .Vishay have written a pdf "Failure Modes and Fusing of TVS Devices" if you want more information.UPDATE 8th NOV 2021I have found a headphone socket from LUMBERG 1503-18 which is the same form factor and fits the PCB however the switch is a normally closed single pole type, what is needed is a normally open to gnd.So I put a 20v 1amp schottky diode between the yellow wire and a 4.7k resistor to ground (cathode bar to the resistor) and then wired the junction to the switch and the other side of the switch to the +5v supply on the same board (3v3 would be better from the main board. So when powered up the yellow wire is pulled down through the diode and resistor until a voltage 3v3 or above is applied when it rises to the internal pull up voltage. In this way I used the Lumberg part... and due to the blocking diode did not destroy the 3v3 input to the mute switch.For those of you who would rather have swapped the aux socket for the headphone socket, I have found that if one is corroded so is the other.It is also worth checking the soldering to the centre pin of the DC jack for cracks at the same time.Happy debuggingRob

author: geneticplasma
author_rank: Newbie
timestamp: October 07, 2023, 06:26:53 pm
content: Hello Rob,I also have an Evoke H3 and my problem is, if the Evoke is on Standby for some minutes (or longer) and then it will wake up, there isno sound.So if I remove the power cord for some minutes and plug it in again, then sound will work (until I put the Evoke into standby).Any idea what could be the problem?GreetingsJo