Marshall Stanmore Repair

[VanDivX]

Re: Marshall Stanmore Repair

I have already sent the speaker to the authorized Marshall repair shop out of province for $35 CAD to get it fixed.

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?

I took several months off trying to fix mine, maybe will give it another go since in the meantime I got some parts for it I ordered from China. My speaker blows fuse and I hope it is something wrong with P/S part of the PCB, like the bridge diode or the MOSFET

[Chris_J]

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.

[Chris_J]

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?

[walzz]

Re: Marshall Stanmore Repair

I'm still looking for a schematic/ service manual for this amp. Hope someone can help with a copy or a link?

Posts in other repair forums mention the use of cheap chinese 'ChenX' caps on this board that leak electrolyte. Caps with Marshall goop poured around them had corrosion hiding underneath which destroyed a number of SMT components. I believe some of these design issues were addressed in the Mk2 version.

[walzz]

Re: Marshall Stanmore Repair

Update:
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?

As mentioned earlier in this thread U15 is a Texas Instruments TAS5342A (100w Class D amplifier with digital input) in a 44pin HTSSOP package.

Data sheet: http://www.ti.com/lit/ds/symlink/tas5342a.pdf

[Tamaska]

Re: Marshall Stanmore Repair

Hi Guys,

I have just joined this forum to be able to talk to you.
My stanmore is not powering up either.
Basically what happened:I unplugged it from the socket while it was playing, and ever since there's no pilot light and power.
I found the fuse blown so i replaced this, this gave not a lot of joy. While i was clapping happily for the fact the pilot light came up by the time i clapped twice it went out again.
I took out the big board and looked for damaged components but found nothing yet.
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.

Do you have any idea what it could be? What should i look 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).

pla see my drawn schem its near OB2269

[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).

pls see attached

[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).

whu are you changing that parts?
is it defective?

[kd6mtw]

Re: Marshall Stanmore Repair

I have one that is experiencing option #4

I'm going to change the 3.3uf 50v cap. OF course its marked C4! BOOM! lol

i'll post back if it works.

Thanks everyone for the contributions

[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.

[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

[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.

[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.

[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

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

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.

[tolpow]

Re: Marshall Stanmore Repair

@cpt_electric
Black inductor L1 marked is 22uH

[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?

[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?