Marshall Stanmore Repair

[hann]

Re: Marshall Stanmore Repair

did you do as i do and see how long meter beeps for ?

the pointer of my multimeter go straight to zero ohm and slowly going back. i thought its ok. but i already suspected the ecap as i have read on the datasheet. that it should charge to make the ic run.

[dysk1]

Re: Marshall Stanmore Repair

Hello,

I also have a device that doesn't work. After switching on the power supply instead of 30V I have 8.3V.
I drew a converter feedback diagram. I came to the fact that it blocks the signal fed from the 12LE5A16S2 processor to the R147 resistor. After desoldering the R147 resistor, the inverter works correctly and has 30V, but this is not the solution to the problem.
I am asking for any suggestions.

[R_J]

Re: Marshall Stanmore Repair

Image is too small

[dysk1]

Re: Marshall Stanmore Repair

A larger picture is attached.

Edit:

I measured that instead of 3V on TAS5508C power supply I have 0.6V

[dysk1]

Re: Marshall Stanmore Repair

Update:

What voltage should come out of LM317??

[R_J]

Re: Marshall Stanmore Repair

Type this into GOOGLE: LM317 DATASHEET

[dysk1]

Re: Marshall Stanmore Repair

LM317 had the same protector signal as the inverter. After desoldering another resistor all voltages have already appeared correct.
Unfortunately, no functions are still working.

[VanDivX]

Re: Marshall Stanmore Repair

Hi there, new member... I have this expensive piece of hardware and when I opened it, I found the fuse blown but replacement blows again. Clearly I am the 'Case 3' in the original post - "no led, fuse blown".

My skills in this regard are very mixed, I know how basic electronic parts work but my radioamateur days ended when IC circuits came on scene. I did careful visual inspection but nothing looks bad. I was hoping for bulging capacitor top or something of the kind but it all looks OK.

I suspect some short in the area of power supply, in particular I suspect the big capcitor 150uF/400V. Also perhaps the rectifying bridge KBL406 perhaps?

The nature of this fault limits me to measuring only on un-powered PCB and I am aware that measuring resistance or continuity can be misleading...

I started by removing the above mentioned capacitor and when I got it out, it measures ~145 uF, which means it is OK.

Then I tried measuring on the rectifying bridge and I get continuity or about 1ohm across the +/- and (dc output) legs, the two inner legs to which AC is connected show now short, resistance is 'infinite', it is like the multimeter leads are not touching anything (0L).
Also no short to the two outside legs of the bridge from these two inner ones (I swapped multimeter leads polarity in case it matters - since diodes pass current only one way I presume.

The first transformer coils have continuity, the two yellow blocks on either side of it do not show short or any resistance (0L), so I am at the ends of what could be shorting the A/C input. I even tried 2A/250V fuse but it blows instantly as well.

Funny thing is, if I measure continuity or resistance across the AC input (the two prong socket where 120V comes in, with good fuse inserted, it shows no short, or resistance (infinite, or 0L). Maybe some semiconductor device mounted on heatsink when powered, it shorts instead of doing whatever it should be doing? So I don't measure the short circuit?

I took many photos of both sides of PCB, in Large format with my compact camera, in case it might helps somebody with their troubleshooting, like values of parts some people asked for. My PCB is luckily not that much plastered with the goop like what other peoples' pictures show. I uploaded the whole series of them to Mediafire here - I suppose the forum has upload but since these pics are large and many, I thought to upload them externally.

http://www.mediafire.com/file/8txzsi..._2019.rar/file

[VanDivX]

Re: Marshall Stanmore Repair

Can one edit one's posts here? Like at least to correct some spelling? I don't see how to do that.

Anyway, I measured across the two yellow blocks either side of the smaller transformer and they measure 0.8uF, I suppose then they are capacitors then and are OK. One of them is marked as CX1 on pcb.

I tried to take picture of the markings on the 'transistor' mounted on the black heatsing right behind that big capacitor I removed for measuring and it says 'F' 1FO5BR FDPF 10N60NZ

Googling around, I found it is FDPF10N60NZ ECAD Model
Fairchild Semiconductor MOSFET N-CH 600V 10A TO-220F

MOSFET is another possible culprit - all I know is it sensitive to electrostatic discharge and it passes current depending on input... that might be why I don't measure short on AC input, it needs powered up to short it (if it is faulty). I just don't know how to check it, if someone has an advice how to measure on it, I'd be grateful. Keep in mind I can't power the pcb up to measure voltages on it.

[RethoricalCheese]

Re: Marshall Stanmore Repair

Does anybody know what is the purpose of the NPN transistor in hot side next to the optocoupler, marked in red square?

I've got a speaker which has it missing. I have ordered a new one but I doubt it fixes the issue I have.

It does power on but no sounds coming from any input.

[VanDivX]

Re: Marshall Stanmore Repair

Does anybody know what is the purpose of the NPN transistor in hot side next to the optocoupler, marked in red square?

Just a guess - the OP mentions in 'case' #3 'blown fuse' some ""standby mode" circuitry thrown in for European compliance"

3. If a surge occurred and replacing the fuse doesn't solve the problem, this could be a fault of the primary (power supply) or secondary (cold) side of the PCB. ...The power supply is a 100-240V SMPS with some "standby mode" circuitry thrown in for European compliance.

Could someone have removed that transistor in some earlier 'repair effort'? It might well be superfluous but then again... again just guessing, maybe someone removed it, found it faulty but didn't get replacement and abandoned working on it?

As for my problem, I wait for the mosfet and rectifying bridge to arrive in mail but replacing them is just a shot in dark.
I think the big clue for fuse blowing might be my measuring 'open circuit' on A/C 120V input when there is no power supplied - yet once AC is connected, the fuse blows, indicating short circuit.

[RethoricalCheese]

Re: Marshall Stanmore Repair

Put a lightbulb in series before powering up.

[jabase]

Re: Marshall Stanmore Repair

Greetings...I was looking around for a schematic for the Stanmore and came across your discussion. I should pop in more often . I usually park my brain in some other forums :-)
Anyway ,the unit I received for service did not have audio. Unit came on with LED ,etc. I found that U15, audio output IC was cooked. I replace the IC, however I still have no sound. All voltages appear to be good. I can see audio at U19 (in/outs) . I see audio going into U4, but nothing coming out, data or analog. There could be a micro/software issue not enabling this IC, or something else. Seeing how U15 imploded pretty good, I suspect that it may taken out something else. Man , a schematic or even a block diagram would be great right now. It's fairly easy to obtain and replace U4 , which I'll do , but looking for other suggestions ...Thanks !!!

For reference:
U15 : TAS5342A(digikey)
U4: PCM1808 ( digikey)

U19 : HCF4052

[Andersswe]

Re: Marshall Stanmore Repair

Im trying to repair my Marshall now, and i see that c9 is burnt, what part is that?

[michel91]

Re: Marshall Stanmore Repair

Hi Hann,
I've read your post with great interest.
My Stanmore is also down, no led on at all, just earing a little click, for a few seconds, at the start.
No success after replacing the MC34063A, the LM317T and FMG23S.
So I would like to make your solution (replacing the 3.3/50), but I don't see it on the PCB...
Could you please give me its place and its reference ?
Thanks a lot.
Best regards.
Michel (from France).

[pbakai182]

Re: Marshall Stanmore Repair

Hello, I purchased a used Stanmore (1st edition) and while the unit turns on, LEDs working, Bluetooth connecting and staying a solid red LED, the sound will turn off when switching media apps (playing music, then playing a YouTube video, then back to music). The issue is very odd, as sometimes when I unpair and re-connect to Bluetooth, music will play, and sometimes it won't at all no matter how many times I try to unpair, unplug, and reconnect...

Speaker works just fine when connected to AUX... I have been able to replicate these no-sound issues with BT over 3 phones in total (Galaxy S7, A50, and iPhone 6S).

Marshall is willing to repair the issue (non-warranty repair), having me pay for shipping. But if I can repair by swapping out a 10 cent part, then I would prefer to try that. However, I'm not sure if Marshall would still repair if I opened up the back...

So has anyone here experienced my issues with speaker working fine with other inputs except no sound on Bluetooth even though it is connecting successfully?

Thanks.

[pbakai182]

Re: Marshall Stanmore Repair

Also, if anyone has had success swapping out the 8-pin surface mount DIP MC34063A who was experiencing my issues (Case#1, Bluetooth connecting but no sound), I would be very grateful if you could try to guide me in how to check the voltage on the part, and anything I need to be aware of when replacing. I have a basic multimeter, and an OK soldering iron kit. My experience is beginner in the electronics field, I've successfully swapped out a damaged micro USB port on a Logitech Bluetooth speaker, so I have confidence in my soldering abilities.

[pukipuki09]

Re: Marshall Stanmore Repair

sir R_J thanks for the input sir. i have found the fault. its the 3.3/50 volts e cap, replaced it then voila! power restored. i studied the datasheet on the pwm ic. the e cap doesn't charge that is why the ic wont start. a very big thank to you sir.

Hi,
I just got this device from my friend for repair.
Where this 3.3/50 cap is located on PCB?

[benzbenz]

Re: Marshall Stanmore Repair

hi everyone
i am new to fix my Stanmore
my Stanmore while playing music , sound went on and off all the time
with some strange noise before went off.
anyone know how to fix it?
appreciated

[pbakai182]

Re: Marshall Stanmore Repair

Hi all,

So I received the replacement IC chip (MC34063API) and after a long and arduous effort to solder this larger thru hole component onto a surface mount board, the original intermittent bluetooth problem persisted...

I have already sent the speaker to the authorized Marshall repair shop out of province for $35 CAD to get it fixed.
Hopefully they don't have an issue with the fact that I have a jumper wire from one of the IC pins to the connecting smd capacitor as the damn pin track came off as soon as I touched it with my solder wick