Please help repair a Makita jobsite radio BMR 102 - Page 1
Forum section: electronics / repair

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 10, 2022, 12:18:21 am
content: Symptom: Does not turn on with DC from the original adaptor. The LCD display works, as well as setup of clock and alarm etc. with backup batteries installed but won't turn on when pressing the power on button, it gives "E" with the low battery indicator flashing.I've exhausted all I could find online, webpage or youtube videos but have not found or figured out a solution.Problems often happens with the DC input jack but it's ok.Apart from the small boards for DC input/audio output and for battery pack input, there are two main boards. I would assume one is for the radio another is for the microcontroller/user interface. There is a flat cable connecting both, I would assume it's largely one way - from the LCD board to the radio board except perhaps a signal (or power) input from the radio board, to which the DC input jack board is connected, at least for the LCD board to know whether there is power. This is based on the fact that, without connecting the DC adaptor or installing the main battery, connecting the cable from the backup battery to the LCD board will cause the LCD display's to reset (briefly showing all the segments). And with only the backup battery, I can set up the clock and the alarm.Its user manual can be found here:https://media.makita.co.nz/_media/user-manuals/B/BMR102-UG.pdfI couldn't find a service manual or its schematics online.Thanks for any help.

author: sean0118
author_rank: Frequent Contributor
timestamp: March 10, 2022, 02:46:46 am
content: Check the power rail voltages at the ICs

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 10, 2022, 06:41:54 am
content: Thanks for the hint.There are two dual op-amp chips 4580. What are the design Vcc and Vee? Can they be as wide a range as +/-2 ~ +/-18V (based on the feature "operating voltage (+/-2 ~ +/-18V)")? I only got very close to 0 on both of the Vcc and Vss pins of both chips. This does not seem right.There is a voltage regulator SA78RL05F. But I only found the datasheet for SA78R05F (without an "F" in the middle). According to this datasheet, its input power rating is 7V (but the absolute maximum rating is 35V). My input is approx. 17V (wait - why is it 17V when it's said on the case to be 12V output?). Almost 0V on the second pin (output), which is supposed to be 5V according to the datasheet of SA78R05F (assuming they are largely the same?). would this voltage regulators probably be the culprit?Tried to feed a 5V DC directly between its output pin (#2) and GND but there was no miracle happening.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: March 10, 2022, 08:10:05 am
content: Such op-amps would normally have something like +12v/-12v supplies, or 15v is also pretty common.Sometimes they will only have one positive supply though, so you may see something like 15v or higher on the +ve rail and the -ve rail is at 0v.In this case the input and output pins will be at half the +ve rail voltage.If it does use a dual supply and the negative is missing, so it looks like +15v on the +ve rail and zero on the negative, the op amp outputs will be slammed at either full supply voltage or zero, not at half the supply voltage as in the single rail case.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 10, 2022, 09:37:40 am
content: Quote from: Audiorepair on March 10, 2022, 08:10:05 amThat makes sense. No need to have a 12V adaptor if the circuit does not need a voltage higher than 5V. It's likely the positive rails of the op-amps are supposed to be +12V?One strange thing is the AC adapter gives 17V DC but its label says 12V. Surely this is not right?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: March 10, 2022, 09:48:33 am
content: Ah, I replied without looking at the photos.I assumed, like most contemporary equipment, there would be some internal power supply generation from DC converter chips and the like.Yours looks pretty simple, so most probably there is a single supply rail to the op-amps, which will probably not be 5v, but somewhere between 5v and 12v.A 12v linear transformer may very well put out 17v if it is not loaded, in circuit and supplying power this will drop to more like its nominal 12v.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 10, 2022, 10:03:22 am
content: Quote from: Audiorepair on March 10, 2022, 09:48:33 amThanks. So I don't need to look into the AC adaptor (which is difficult to open).

author: Audiorepair
author_rank: Frequent Contributor
timestamp: March 10, 2022, 10:47:11 am
content: Is it a Switch Mode Power Supply or a transformer in a plastic box?

author: timenutgoblin
author_rank: Regular Contributor
timestamp: March 10, 2022, 11:34:05 am
content: Quote from: max.wwwang on March 10, 2022, 12:18:21 amIs the backup battery on the PCB or in a separate holder?Check diode D301 and connector JW301 both located on the small PCB. Check for connectivity/conductivity between JW301 (small PCB) and CN1 (large PCB).

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 10, 2022, 08:46:05 pm
content: Quote from: Audiorepair on March 10, 2022, 10:47:11 amThe latter.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 10, 2022, 08:52:40 pm
content: Quote from: timenutgoblin on March 10, 2022, 11:34:05 amThe latter, with the 2 wires going to a small board coordinating all the inputs from the main batteries (not used by me) which has a cable of 3 wires going to the LCD board. Reconnecting this cable (with backup batteries in) will cause the LCD reset - that's why I believe the LCD/control board is ok.Quote from: timenutgoblin on March 10, 2022, 11:34:05 amThis is very detailed and specific, and sounds promising! Thank you. Will check it out later today.It also came to me that I need to check the capacitor connected to the output pin of the voltage regulator, its 0V output can be caused by its failure?

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 11, 2022, 04:42:06 am
content: Quote from: timenutgoblin on March 10, 2022, 11:34:05 amAll checked. No problems. But thank you. Obviously, you know this model very well. Did you repair one of this before, or at least you looked closely into it? Are you aware of its schematics anywhere?

author: timenutgoblin
author_rank: Regular Contributor
timestamp: March 11, 2022, 05:28:25 am
content: According to the User Manual it mentions that the main battery and backup battery may need to be replaced. Check page 5 of the User Manual (I have attached a screenshot). It also mentions that the power adapter does not charge the battery. Also check page 4 regarding battery installation.Unfortunately, I don't know about any schematics or service manuals.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 11, 2022, 05:39:49 am
content: Quote from: timenutgoblin on March 11, 2022, 05:28:25 amThank you. I’m aware of this. I also noticed that there is a difference from the signal for low backup battery and what I got. For the former, as described in the manual, it’s a flashing “E” letter and a low battery sign (that probably does not flash, but this is not specified in the manual). In my case, it’s an “E” letter that does not flash but with a flashing low battery sign.Strictly speaking, these two are different. But there is no description of what exactly this means, which is a bit strange. I'm using two new AA batteries (according to the manual).

author: timenutgoblin
author_rank: Regular Contributor
timestamp: March 11, 2022, 05:50:56 am
content: Quote from: max.wwwang on March 10, 2022, 06:41:54 amDid you get the radio working? Maybe the voltage regulator is faulty or is not switching on. How many pins does the voltage regulator have; 3 or 4?

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 11, 2022, 10:21:18 am
content: Quote from: timenutgoblin on March 11, 2022, 05:50:56 amSorry, I missed a "no".Not working.Yes, I think the voltage regulator is possibly the culprit. It is a SA78RL05F but I can only find the datasheet for SA78R05F (without an "L" in the middle). It has 4 pins: Vin, Vout, GND, and Vdis/Vadj, according to the datasheet of SA78R05F. Trying to replace it, but I couldn't find either SA78RL05F or SA78R05F on sale online.

author: timenutgoblin
author_rank: Regular Contributor
timestamp: March 11, 2022, 01:39:42 pm
content: I noticed that there is another small PCB in the bottom right hand corner of your second photo with black/red twisted wires and grey coloured wires connected to it. I think this is the same PCB shown in a YouTube video. I have attached a screenshot from the video.Here is the link:https://youtu.be/Vt0xrWyUyJ8

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 11, 2022, 06:52:00 pm
content: Quote from: timenutgoblin on March 11, 2022, 01:39:42 pmYes, that’s the board for the various kinds of main batteries. I watched this video though didn’t quite get what the fix was. Since I’m not using main batteries (I’m using the mains adapter only), I think this is not relevant to my case. No matter whether or not I connected this main batteries board to the (another small) DC input board, I got the input power voltage of 17v on the radio board.A new thought is - it appears to me that the voltage regulator is possibly used in the disable mode (as opposed to the adjustable mode, according to the data sheet). Because all the 3 pins other than Vin gives 0V, it’s possible that even if the chips is not broken it’s disabled (making Vout 0V, as opposed to 5V). There must be a way on this radio board to send the status of the main DC power to the LCD board through grey flat cable (which is the only one between these two boards) to it for it to be able to determine whether or not to show a low battery sign. If for whatever reason it sees a main battery fault (then shows a low battery sign), it will probably not send an ‘enable’ (I.e. high, which is 2V according to the data sheet) to the Vadj/Vdis (4th) pin of the regulator.So there is probably a problem here.

author: timenutgoblin
author_rank: Regular Contributor
timestamp: March 12, 2022, 11:03:28 am
content: There is a component labelled ROT200 on the LCD board which might be a rotary encoder for the volume control and radio tuning. I'm wondering if it might be faulty and preventing the radio/amplifier from working properly. At first, I thought it was a potentiometer.Have you checked if the speakers are working? Do you hear any hissing or clicking when connecting or disconnecting power? Is the audio amplifier IC getting any supply voltage? You mentioned in an earlier post that the op-amps are measuring 0V. Maybe check them for short circuit?

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 13, 2022, 04:33:00 am
content: Quote from: timenutgoblin on March 12, 2022, 11:03:28 amYes, it's a rotary encoder not a potentiometer. It's working without a problem. After pressing the setting button I can use it to adjust the clock and alarm (So I think the micro controller module is working fine).Quote from: timenutgoblin on March 12, 2022, 11:03:28 amYes, speakers are good. When reconnecting the backup battery (with or without the AC adapter connected), I can hear a short beep from the speakers, along with a brief display of all the segments on the LCD (sort of self-test I think).Along my thought of input +17V going from the radio/amp board to the LCD board, yes, there is a line feeding this voltage and this for sure has come to the LCD board. No further findings suspicious along this line. Maybe I should look along another line - why the positive rails of the op-amps give 0V.

author: amyk
author_rank: Super Contributor
timestamp: March 13, 2022, 04:43:16 am
content: Could you post good aligned photos of both sides of the baords? That looksvintagewith the through-hole components and single-sided boards. It won't be hard to create a schematic.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 13, 2022, 05:01:40 am
content: [ Specified attachment is not available ]Quote from: amyk on March 13, 2022, 04:43:16 amSure.Radio/amp board frontTwo pairs of wires (bottom right) go to speakers.CN4 (not clear, the one below JP 28) goes to Aux in 2. CN1 goes to the Aux in 1/DC in board. CN2 goes to the LCD board.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 13, 2022, 05:03:25 am
content: Radio/Amp board back

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 13, 2022, 05:03:57 am
content: LCD board front

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 13, 2022, 05:04:32 am
content: LCD board backThe bottom right corner is the socket for the 3 wires coming from the batteries board. The left one and right one are for the backup battery input. The middle one I suspect is for detecting the main battery position switch. With DC plugged in, it gives 5V (1.9V when without DC in). it's pulled to 0V when manually pressing the micro switch (pretending there is a battery).

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 13, 2022, 05:19:05 am
content: The Aux in 1/DC in boardFront/JW301: Left 4 wires are from the Aux in 1 jack, the right 2 are for main DC power in (white +/blue GND).CN301 comes from the battery board carrying - two wires for the main battery. Inserting the DC plug will break the power from the main battery (from CN301).(This is a common problem of this model but this unit does not have this issue.)

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 13, 2022, 05:20:20 am
content: The batteries board and a tiny switch board (for sensing a main battery in position).# wires on the top go to the position switch (the second photo). When there is no main battery (one type of the many that are acceptable) the right two points are connected, otherwise the left one and the middle.Top-left corner, the top 3 wires go to the LCD board - the top and bottom ones are wired to the backup batteries (3V) by the traces.The socket below goes to the backup batteries compartment (3V, 2x AA).

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 13, 2022, 05:52:39 am
content: The audio power amp chip is LA4631. Datasheet here:https://pdf1.alldatasheet.com/datasheet-pdf/view/439056/SANYO/LA4631.htmlOne thing is that the physical specs of the chip in the radio/amp board is different from this datasheet. Also mine has only 12 pins, the datasheet has 13 (though #13 is N.C). Otherwise the wiring is similar: pins 8/12 go to the speakers. So pin 7 should be Vcc. I got only 5V here (with or without DC in). The datasheet requires 14V.

author: timenutgoblin
author_rank: Regular Contributor
timestamp: March 13, 2022, 01:34:07 pm
content: I think that the reason the op-amps are measuring 0V on the power supply pins is because they are powered by the 5V voltage regulator which is 'disabled'. Perhaps you could confirm this with your DMM. V+ is pin 8 and V- is pin 4.On the Radio/Amp board there are two transistors Q8 and Q9. I think this is a DC/clipping detection circuit for the audio amplifier IC. The circuit connects to the LCD board via the grey flex cable.On the LCD board, there are zener diodes that may have something to do with battery voltage detection; ZD201, ZD202 and ZD203.Could you check IC203? It's located under the shield. It looks damaged in the photo.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 14, 2022, 05:09:52 am
content: Quote from: timenutgoblin on March 13, 2022, 01:34:07 pmBoth rails of both op-amp chips measure 0V. This obviously does not seem good.Quote from: timenutgoblin on March 13, 2022, 01:34:07 pmYes, both transistors are connected to the speaker outputs and audio amp IC.Quote from: timenutgoblin on March 13, 2022, 01:34:07 pmThese diodes look good with the diode test function of my MM (though only tested inline without taking any of them off - no short circuit detected through these diodes).Quote from: timenutgoblin on March 13, 2022, 01:34:07 pmGood spotting! There is indeed some dirt on it but after cleaning, it does not appear to be physically cooked. But I'm unable to read its label.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 14, 2022, 05:20:28 am
content: Is this transistor (B1143) the culprit (highlighted in the photo)?From the top downwards, the pins are E/C/B with C going to the audio amp IC (pin 7, expecting 14V). They measure 16.7V/1.2V/16.5V, respectively.(I remember once I got 5V on pin 7 of the amp IC. Don't know why I got only 1.2V now.)Is there a bad smell here? (Is the V drop between B/E, 0.2V, OK?)

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 14, 2022, 06:04:45 am
content: Found a unit with the same problem on sale on eBay

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 14, 2022, 06:07:19 am
content: Asked makita service with this:I have a Makita Jobsite Radio BMR102 that does not work. I plugged the AC adapter without using a main battery (I've put in two new AA batteries as backup battery according to the user manual). It does not turn on when pressing the power-on button. The LCD gives an "E" with a flashing low battery sign.I checked the user manual. It only says when the backup battery is low, it will show a low battery sign with a flashing "E", which is different from what I got. The manual does not include information about a flashing low battery sign and an "E" (that does not flash).Would really appreciate if you can let me know what this means and how I can possibly fix this.Thank you very much for your help.I got this:That’s likely a fault with one of the main boards, if you send it down to us we can assess and fix it for you. If you could also provide a copy of your proof of purchase that would be good.

author: Muttley Snickers
author_rank: Unknown
timestamp: March 14, 2022, 06:53:41 am
content: Quote from: max.wwwang on March 14, 2022, 06:04:45 amThe local council recycle center/ tip shop had an entire wall stacked with these job site radios about a month ago. They would all be warranty returns and likely deemed beyond economical repair, possibly due to an inherent fault or bad batch. I haven't been back there since but might go for a look this week, it's amazing the stuff that gets chucked out.

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 14, 2022, 06:56:38 am
content: Please have a look. Haha

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 15, 2022, 06:45:50 am
content: New development --After a careful close examination and some fiddle-around measuring the connectivities and voltages, it cameto be that a fine trace under the belly of a transistor seemed broken - measuring different voltages at its two sides. After connecting it with a jump wire, as shown, now the low battery sign is gone, and when pressing the power on button, the LCD backlight lit up!Also, the +ve rails of the two op-amp chips all give 5V (presumably this is a good one?), #7 pin of the audio amp chip gives 14V (correct), the Vdis/Vadj pin of the voltage regulator give 2V (enable) and in turn, its Vout gives 5V (also correct)!All good. However, the front panel does not respond further and there is no radio or noise coming out of the speakers. And it can not even be turned off by pressing the power button.Also, the voltage regulator chip is very hot (it does not have a heatsink with it).Is this closer?

author: timenutgoblin
author_rank: Regular Contributor
timestamp: March 15, 2022, 06:56:56 am
content: Are you able to tune the radio frequency with the rotary encoder (ROT200)? Try pressing in the rotary encoder to select between volume and tuning. Maybe the volume is muted?

author: max.wwwang
author_rank: Frequent Contributor
timestamp: March 15, 2022, 08:04:48 am
content: I tried turning it, pressing and long pressing. But no responses whatsoever.