Marshall Stanmore Repair

[SkyHeart]

Re: Marshall Stanmore Repair

Update:
The power amplifier was fried and the 7812 IC together withthe shorted D7 located underneath. Everything replaced except the amplifier.

The unit started up and this time the bluetooth worked as well Could easy pair it so there is hope for the unit but we see when I receive the power amplifier.

The amplifier IC has the marking 42TTI A87CG4 (?) but someone else suggests that it could be a TAS5342A IC?

Has anyone information what the amplifier IC could be?

Hey @Chris_J
were you able to fix your issue?
I also replaced 7812 IC and the D7 including the TAS5342A IC, R23 and 3.3 cap but still no sound, I can pair with bluetooth and everything seems to work but still no sound coming.

[kros]

Re: Marshall Stanmore Repair

Thank You @kros, yes I found it on ebay after posting and I did order it, though i'm not sure if the cause of the issue is from that IC but it's good to have it just in case

Thanks again.

For me, the best option was to buy a new motherboard, in mine there was a burned hole in the laminate where the TAS5342A chip is, it was completely burnt. Earlier I wrote to marshall asking for a new motherboard, they said they can't sell me, but they can fix it, it will be around 200 euros plush shipping costs

That's why I was able to buy a new motherboard for half the price that Marshall was offering

[SkyHeart]

Re: Marshall Stanmore Repair

Hi
I don't know where you are looking for this chip ,but there is a lot of it on ebay in europe

https://www.ebay.de/itm/223882780254...kAAOSw-xJisx1S
https://www.ebay.de/itm/133518480526...gAAOSw7dth4q19
https://www.ebay.de/itm/361705477744...QAAOSwCehi36eR

Thank You @kros, yes I found it on ebay after posting and I did order it, though i'm not sure if the cause of the issue is from that IC but it's good to have it just in case

Thanks again.

[kros]

Re: Marshall Stanmore Repair

Hey Guys,

has any one found any diagram or schematics for this PCB?
I have 2 of this Stanmore on my table with the same issue, both light up and everything work except from no sound output.

the area around OB2269 looks a bit hot but I wasn't able to find the OB2269 in our local stores, couldn't find it on digi-key as well, any help or more information is appreciated.

Hi
I don't know where you are looking for this chip ,but there is a lot of it on ebay in europe

https://www.ebay.de/itm/223882780254...kAAOSw-xJisx1S
https://www.ebay.de/itm/133518480526...gAAOSw7dth4q19
https://www.ebay.de/itm/361705477744...QAAOSwCehi36eR

[SkyHeart]

Re: Marshall Stanmore Repair

Hey Guys,

has any one found any diagram or schematics for this PCB?
I have 2 of this Stanmore on my table with the same issue, both light up and everything work except from no sound output.

the area around OB2269 looks a bit hot but I wasn't able to find the OB2269 in our local stores, couldn't find it on digi-key as well, any help or more information is appreciated.

[kros]

Re: Marshall Stanmore Repair

Hi
If someone needs a New working board Marshall Stanmore Main PCB, it can be bought at this link:

https://reverb.com/item/48237590-mar...e-main-pcb-cpi

I bought the last one and everything works, the board is completely new

If someone needs it too, Marshall Stanmore Front Panel with PCB (cpi)
https://reverb.com/item/48234877-mar...l-with-pcb-cpi

Thanks

[jonathandean]

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 My 3.3 uF Cap seems to be reading short, it looks like this goes to a winding on the transformer,could this be the problem? Has anybody changed the transformer on their stanmore?

[dannybloe]

Re: Marshall Stanmore Repair

Can somebody tell me what the value is of L13? Turns out while assembling everything together, this one was broken (no burn marks). Can't exactly tell what the colours have been. Looks like it is similar to L7 next to it but I'm not sure.
Is this an inductor?

[dannybloe]

Re: Marshall Stanmore Repair

Intersting follow up: after placing the bluetooth module back in the Stanmore, all seems to work again. Guess the module had to get a proper connect somehow.

[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.

[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?

[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.

[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

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

[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!

[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!

[halford_fight]

Re: Marshall Stanmore Repair

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

[VanDivX]

Re: Marshall Stanmore Repair

I found interesting post regarding this PCB on the elektroda forum

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

[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...

[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