Marshall Stanmore Repair

[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

[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?

[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

[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!

[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

[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.

[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

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

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

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.

[ZOrd_Z]

Re: Marshall Stanmore Repair

Hi. I'm repairing a Marshal Stanmore.

It's de second time i'm repairing this one. First time I've replaced the TAS5342LA an a diode, witch i cant remember what kind it is. It's a smd close to the primary big cap.

Can anyone give me a help?

[6krray]

Re: Marshall Stanmore Repair

I have a Marshall Stanmore AMP that's 2 years off warrantee and have started to make a low pitch > High pitch noise upon power on and stopped playing audio.
It might have been a bad practice but by turning on > off the device a multiple times (like 3 times), it was able to return to it's normal state for a while but seems it's not able to do that anymore.

I've opened the backpanel and noticed these 2 points as seen on the attached image.

1.R232-Q202 Cap seems to have exploded.
I'm not fond of these but is this a cap fuse? Does anyone have any info on what I should be using as a replacement?

2.C8 Seems to be an empty slot which seems to have had a cap.
Anyone have any information on what was/should be placed there?

[tolpow]

Re: Marshall Stanmore Repair

@cpt_electric
Black inductor L1 marked is 22uH

[cpt_electric]

Re: Marshall Stanmore Repair

Thanks for the reply VanDivX! It doesn't look like I damaged it too much, there's only a little scratch on one of the wire turns, so I probably didn't short anything.

I think the resistance of this inductor is going to be too small to measure. I estimate that there's 200 mm, at most, of 0.5 mm diameter copper wire. Resistance is probably like 0.017 ohms or less (although I'm not sure how much the ferrite core would affect it). When I try to measure it, there's no significant difference to if I just short the leads of the ohmeter.

I'll most likely just plug it back in and hope my house doesn't burn down lol.

[VanDivX]

Re: Marshall Stanmore Repair

In the post #68 above here is a scheme where your coil would be at the bottom of it, joining two of those three 1000 uF caps. It is L1 as marked on the PCB.
I don't a goop there but because of those caps surrounding it, I can barely make out that there is any markings on the coil.

I would hazard to guess, if you didn't interrupt the coil wire, then it will be OK. Measure across it if you get some resistance, it will be OK. I can measure on it tomorrow to give you resistance value which I would guess will be close to short since the coil has thick wire with just a few loops, at least judging by the outline of wire on the shrink wrap tubing enclosing it.

[cpt_electric]

Re: Marshall Stanmore Repair

Hey all, does anyone happen to know the specs on the black cylindrical inductor located near the lm317, between the three blue caps? I was trying to cut away the black goop, and accidentally punctured that inductor. The black goop is covering any identification markings for me.

[VanDivX]

Re: Marshall Stanmore Repair

Sorry for the long delay.
...
They replaced the entire main PCB. I asked if they could offer any information on what part was defective, or if I could even have the defective board shipped back, but they said that was not possible.

That's OK, myself also pop on here only once in a long while, like when checking my open tabs in the browser. It is nice when people return to say what worked for them.

They had no idea what was wrong with because they didn't troubleshoot it. Given how it is plastered with the gummy black goo, it was never meant to be fixed. Mine is not as badly sealed as what I've seen in pictures others posted here but still, it is a pain to work on. Double sided PCB is also not friendly when it comes to parts removal for testing and replacement - as you found out too .

I suppose that shipping charge is worth it (unless you are a pro troubleshooter, the time you spend on it... only saving grace is we do it for fun ), I will contact them, thank you for info.

[pbakai182]

Re: Marshall Stanmore Repair

I wonder if you are still around, if you could report how the repair went. I am in Toronto and guess 'out of province' likely meant to Quebec, Montreal?

Sorry for the long delay.

Marshall had me send the speaker here:
38152 2nd Ave
Squamish BC
V8B0C4 Canada
8445671464

If I recall correctly, this cost me about $65 to ship both ways.

They replaced the entire main PCB. I asked if they could offer any information on what part was defective, or if I could even have the defective board shipped back, but they said that was not possible.

[alelkes87]

Re: Marshall Stanmore Repair

ZD3 on pcb with blue band, ss14 check out in the circuit, zd1 is ok.

Hi, please write ZD3 parameters, thanks

[VanDivX]

Re: Marshall Stanmore Repair

I did some measurements around the diodes to make sure they are not blown they seem alright. Now the speaker is just eating fuses. It looks like a dead short but i cant find the short.

Hi, just dropped in, I have the same thing happening, posted on it last August or September here, then I put the troubleshooting aside and didn't get to it yet, even if in meantime some parts I suspected and ordered from China came in the post...

Your post motivates me to maybe start tinkering with it some more. I am pretty weak in measuring on electronic parts but I tested the diode bridge last fall and it looked OK to me. I ordered the FET transistor that sits near the power supply components and I think it could malfunction to change the working p/s into the fuse eating monster. I think the order was for ten of those FETs but it wasn't expensive. Also bought a pack of diode bridges just in case I don't know how to measure them and why not replace it if that's also not expensive. I took out the big capacitor and measured it outside and it looks OK, not sure now if I ordered that one too.

Above on the thread, I was advised to put a light bulb in series with A/C main supply... I dropped the project by then and didn't try it, but I believe the idea behind it is to prevent the fuse blowing and so make the faulty part to reveal itself by smoking... or maybe you put bulb in series on input and short the fuse to force the offending culprit to betray itself, probably by smoking because of overheating.

As it is, the fuse I suppose doesn't let things go that far and nothing gets heat damaged due to its malfunctioning. When I pull it out again, that will be the first thing I will do, the bulb method.

I went over PCB in minute detail and don't see anything wrong with anything. I do have some experience and know theoretically how most parts work, just lacking in knowledge how to measure on components when they are part of a circuit.

Also got this handy parts tester and already it paid off on another job.