Marshall Stanmore Repair

[VanDivX]

Re: Marshall Stanmore Repair

It's a smd close to the primary big cap.

That diode is D5, is labeled S3M and its marking strip is on the right side as in your picture, away from the transformer. I can post a picture tomorrow.

Somewhere back on this thread, someone posted a partial scheme and the diode is on it, also marked S3M.

[nekken]

Re: Marshall Stanmore Repair

Hello everyone,

I have recently started trying to repair my board, but to be frank I am slowly loosing hope as i have tons of resistors and capacitors that have been shorted due to U15 blowing out (and so did the bridge rectifier, the shotkey diode right near it).
Because marshall provides no technical documentation what so ever I decided to start making my own BOM, and maybe later if I feel brave enough to reverse engineer the board. Please feel free to add in any information that you have on any part and help me make the most accurate BOM possible.

If i am unable to repair this little piece of junk Im thinking of throwing a raspberry pi in it and turning it into some kind of airplay/web radio.

[VanDivX]

Re: Marshall Stanmore Repair

i have tons of resistors and capacitors that have been shorted due to U15 blowing out (and so did the bridge rectifier, the shotkey diode right near it).

I feel with you.

As I posted last fall, my pcb blows fuses and I found that the MOSFET (10n60nz) on that big heatsink is shorted. I replaced it and when I powered up, the fuse held and I wanted to check if I am actually sending power in past the fuse and went to touch one meter probe to the solder point under the power connector and just as I touched it, it blew like if you short 120V AC. But it wasn't my doing, that replaced MOSFET blew up, shorted again. My hope for the board lasted all of one minute.

Obviously something else is at fault and from your post, it looks like it may well be the U15 and or the diode. Are those the parts I indicate on the picture I just took? There is U1...(the rest is under the goop) next to that flat 8legged thing, it could be that U15 you mentioned.
I am not too good at repairs like these, identifying parts or measuring on pcb when under power to find out what is wrong. Even the MOSFET I had to look up how to measure on it.

I suppose I could remove and check the Schottky diode (if I identified it correctly) but I doubt I'd want to attempt to do anything with that U15 part, except maybe measure resistance on its legs. You can see the goop it sits in.

I make a stab at fixing this board once in a while, if only for the education value LOL (I used to be radio amateur in my teens, tubes and later transistor era, but my practical circuits know-how ended when integrated circuits came in sometimes in 1970s , I lost interest)

[nekken]

Re: Marshall Stanmore Repair

Hey there VanDivX,
Yeah tubes were deadly and high voltage but damn at least they were more serviceable than this smd crap.
So I checked your picture and U15 is the amplifier board that is underneath (with the heatsink that goes to the back of the chassis) what you are pointing is U1 which is the PWM controller. I don't have a diode as you on my board it is a small Zener Diode the shottky diode was in D15 just near the AC Bridge.
For my board I now know it is officially dead, i have removed the PSU components to replace the AC Bridge and to my suprise when the bridge blew out it destroyed the 2mm copper pathway. I can't repair this anymore and i am thinking removing all the components (except SMDs) and scan the board so it could help you guys out.
I seem to have another board version than you,

[VanDivX]

Re: Marshall Stanmore Repair

On top of that smd crap, there is also two sided pcbs... removing parts can easily rips copper pathways. You can replace those with a piece of wire like I did when I removed the diode bridge for testing - found it was OK but replaced it anyway (I guess you mean that big one, KBL 406).

You are a professional when it comes to these things, compared to me. I don't even know how the two sided pcbs work - it seems you don't need to solder on top because there is a copper 'neck' connecting the bottom to top pathways, right? Also find it annoying that the solder used commercially has some higher melting point. I even resorted to using my electric gun (the one that heats a wire loop to de-solder). I set my micro soldering iron from standard 300 to 360 degree and it still hardly touches that solder, maybe I should go still higher? I have Sain Smart Pro32 soldering iron.

Anyway, I have also pretty well written the thing off. Moral is, stay away from Marshall brand, it may have had reputation in past but that is no more. I include some pics of my board to maybe help somebody. They are not too good, it is surprisingly hard to make good ones.

[Revenge89]

Re: Marshall Stanmore Repair

Hi all,
i have a problem with this marshall stanmore, after repair his power supply and restore 30V i can't read PWM output voltages from TAS5508..i've tried to change it because it's original was burnt and also the PCM1808 but nothing change..can you help me? Vdd and PLL voltages are present..
Thank you so much

[Revenge89]

Re: Marshall Stanmore Repair

Problem solved, i found that PWM IC TAS 5508 didn't work because Master clock MCLK was missing and it was generated by BB DIR9001, changing this one it worked!

[hann]

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).

its near on the pwm IC

[Fasse-sweden]

Re: Marshall Stanmore Repair

I’ve fixed the 31V by replacing the flyback diode (d5?) and the overvoltage protector (d15?). The 7812 does not give any output so that is next. Anyone who knows which dc voltages that are needed. 5V for bluetooth U8?, 3,3 for uC. What is the lm317t for?

[michel91]

Re: Marshall Stanmore Repair

It's done !!! Yeahhhh, I've fixed my problem and the Stanmore plays again.
First, it's important to distinguish which model you have, for me it's the european one, with the switch "PowerSaver/Standard" at the rear of the box. The importance is that on this PCB, there is no resistor R23.
So, as wrote Chris J in the post #62, I put a resistor R23 (220 Ohms) as he did (see the post #62). What a miracle !!!
Please, don't replace any other component before soldering this R23 and test.
Before I find my solution, with the big help of this thread, I've replaced several components : the diode bridge, Caps C36, C49, the MC34063A, the LM317T and FMG23S, but I'm almost certain it was not necessary.
Just add the R23 and see.
My symptom was the n°4 explained in the post #1.
I really thank Chris J and Hann for their explanations, and hope this will help for many other people.
Michel.

PS : for the Marshall team who never helps us

[Jipis]

Re: Marshall Stanmore Repair

Hi,

Interesting thread. I have replaced the burned R23 (220 ohm) with a bigger resistor underneath the PCB. I have attached a picture so you can see how I have done it.

I have also a picture for you who have problems finding the 3.3 uF capacitor.

PS still broken but faultfinding is still in progress.

Hi. Look like you put resistor to wrong pin on D669AC. Must be on middle pin...

[VanDivX]

Re: Marshall Stanmore Repair

I found interesting post regarding this PCB on the elektroda forum

https://www.elektroda.com/rtvforum/topic3430940.html

[halford_fight]

Re: Marshall Stanmore Repair

Hi Stanmore repair people, What voltage do you have on gate pin nr 8 for OB2269?

[Filip_U]

Re: Marshall Stanmore Repair

Hi,

Could you please help me identify the following diodes? All of them are shorted. I have also marked them on the attached schematic.

ZD1
D4
ZD3

Appreciate your help!

[SKP]

Re: Marshall Stanmore Repair

Old thread, I know..
I have one of these speakers on my bench.
Previous owner said it doesn't power up anymore and last time it did, it took a long time before powering up and then worked for a while until it died completely.

I did some measurements like shown on username hann's schematic and found out that 100/63 cap had only 12.3 volts, 3.3/50 had 11.5v, 22/50 had 12.0v and OB2269 pin 3 had 16.68v. Fet drain had full B+ 325 volts. OB2269 looked a little suspicious so I decided to change that and also 3.3/50 cap.
Unfortunately it didn't power up after these changes, 'chirping' noise could be heard after switching it on though. Voltage on 100/63 got up to 18 volts, but not the mentioned 30 volts which it should have?

So I measured some more and accidentally slipped the probe and shorted Q7 fet! Well… Both .1 resistors burned, fet shorted, ceramic cap 101k shorted, fuse blew and OB2269 shorted. All other components seemed to be/measure ok.

Now I've replaced those burned components and also 100/63, 22/50, 3.3/50 and 150/400 caps. Voltages are a bit higher, but still it doesn't power up.

OB2669 pin 3 17.48v
C4 3.3/50 17.48v
C28 22/50 17.95v
C49 100/63 18.42v

Could it be a faulty transformer? How do I check that?
Any help would be appreciated!

[sessingø]

Re: Marshall Stanmore Repair

Hi everyone.

Great thread! Just picked up a marshall stanmore that has a weird problem. It powers on - but every 5-6 seconds a loud static noise comes from the speakers. Volume doesn't seem to work and each time the noise is present the led indicator light will dim like it doesn't have enough power.

I've taken it apart and can faintly hear the noise on the board with only the power connected. It's hard to pinpoint but i think it's coming from one of the transformers or on the hot/power supply side.

I can see two capacitors are bulging at the top c23 and c85 (50v 220uf). I've ordered some up and will try to replace them.

Is there any way to power this unit with a bench power supply. I can't seem to find the correct voltage specs anywhere and i want to make sure im doing it right so i don't create more issues. Where would be the best place to inject DC voltage and bypass the power supply? This way i can be certain the issue is in the hot side.

Thanks

[sessingø]

Re: Marshall Stanmore Repair

I suspect my transformer is bad too. I was thinking about injecting voltage directly into the cold side and bypass the power supply/hot side. Not sure how the best way to approach this is and can't find any information on the TriStar transformer.

[sessingø]

Re: Marshall Stanmore Repair

Hell Yeah! I fixed mine by replacing both 220uf caps that was bulging and the 3.2uf capacitor on the hot side. Also added the 200 ohm resistor like recommended by others as my board had the resistor removed from factory.

The board is a pain. Was struggling removing the soldering from the capacitor holes. Found that using hot air and solder sucker worked best for this thick board.

Make sure the connector to the control board is pushed in correctly, the gunk can make it look like it's connected. This was the reason I had no power and NOT the transformer, spent hours pulling out my hair and it turns out the connector wasn't seated properly.

Have a nice day everyone and thanks for the detailed help.

[haydster7]

Re: Marshall Stanmore Repair

Hi everyone.

Great thread! Just picked up a marshall stanmore that has a weird problem. It powers on - but every 5-6 seconds a loud static noise comes from the speakers. Volume doesn't seem to work and each time the noise is present the led indicator light will dim like it doesn't have enough power.

I've taken it apart and can faintly hear the noise on the board with only the power connected. It's hard to pinpoint but i think it's coming from one of the transformers or on the hot/power supply side.

I can see two capacitors are bulging at the top c23 and c85 (50v 220uf). I've ordered some up and will try to replace them.

Is there any way to power this unit with a bench power supply. I can't seem to find the correct voltage specs anywhere and i want to make sure im doing it right so i don't create more issues. Where would be the best place to inject DC voltage and bypass the power supply? This way i can be certain the issue is in the hot side.

Thanks

Getting the exact same issue

Mine has been working for the better part of 4 years so it's a recent issue

Will consistently start up with 1 static pop, sound will come through fine from any source for about 20 seconds, then will have 3 static pops in quick succession and it will act as if it turns off and restarts (Bluetooth disconnect and reconnect, sound stop). takes about 10 seconds to 'reboot'.

Light is also dimming during that period, when sound starts again light looks normal.


I measured the voltage on the 4 pin connector coming from the shield, got 3.3V pretty consistently except for during the restart goes down to about 2.9. OP mentions it should be 5V, haven't replaced the MC34063A yet.

Any ideas?
Any luck with your caps?
Anyone know how to test the MC34063A?

[dannybloe]

Re: Marshall Stanmore Repair

Hey folks.
Some of the problems I've seen with these devices:

1. Power LED, no audio through Bluetooth

1. Seems to most commonly be fixed by nuking all Bluetooth devices that have been assigned to the device and then re-pairing a specific device. Less frequently, it could mean the Bluetooth card (soldered to the PCB) has become damaged in some manner. There's a 4 port header on the PCB in the middle of the raised panel labeled "shield" that can be measured for proper voltage: The one closest the Bluetooth module (and right next to a capacitor also poking through the shield) should measure around 5VDC, the next pin being ground. If this voltage is much lower, one person discovered that the voltage to the MCU is too low and traced it back to the 8-pin surface mount DIP MC34063A in the middle of the board. These are cheap to replace.

-Jeff

Today I am trying to fix this one from work that has the problem that the bluetooth source is on for a brief moment and then goes off. Everything works but bluetooth.

After Googling, poking around and doing measurements I discovered that the pin mentioned by Jeff should be 3.3V and not 5. That pin leads directly to the bluetooth breakout board and also to MC34063A. That pin on the breakout board is labeled as 3.3V.

I found this site: http://www.sicken.ch/pi/en/Marken/Au...0-e224772.html and after desoldering the bluetooth module I saw exactly the same pinout:



Next step was to see if the module would work standalone so I used a bread board and started playing around:



And lo and behold: it works. I had to connect On to ground (active low obviously) and Off to 3V. Put 3 and 12V to the proper pins, attached a LED and the LED was flashing when powered on. Then I connected Pair to ground (clearly also active low) and on my iPhone I saw the STANMORE speaker in my list! I connected succesfully, the LED stopped flashing and I streamed music. Then I hooked up a speaker to one of the output pins (Left or right) and... music!



So, the next step is figuring out why it doesn't turn on when inside the Stanmore. It looked like the pins received the proper values but now that I know how it should work I can check again when I put it back in the device.