Marshall Stanmore Repair

[hann]

Re: Marshall Stanmore Repair

You should have about 30 volts on the 100/63 cap connected to the diode and 5.1 resistor, The zener diode you have 5 volts on is too low.
Do you have full B+ on the fet drain pin? are the two 0.1Ω resistors on the source good?
When first connected to a/c, the ic should output pulses to drive the fet, that will induce a voltage in the secondaries of the transformer, The run winding should supply the run voltage (20~30v) to keep the ic operating. Check that the winding is not open, the diode is ok, the 5.1Ω is good and the 100/63 is good. Check that zener diode's number to get its value.

thank for the comment, i try measure it again.there is no markings on zener.

[R_J]

Re: Marshall Stanmore Repair

I also see ZD1 drawn in series with the optocoupler, are you sure this is correct? Ususlly the zener is across the opto's output, check that it's not shorted

[R_J]

Re: Marshall Stanmore Repair

You should have about 30 volts on the 100/63 cap connected to the diode and 5.1 resistor, The zener diode you have 5 volts on is too low.
Do you have full B+ on the fet drain pin? are the two 0.1Ω resistors on the source good?
When first connected to a/c, the ic should output pulses to drive the fet, that will induce a voltage in the secondaries of the transformer, The run winding should supply the run voltage (20~30v) to keep the ic operating. Check that the winding is not open, the diode is ok, the 5.1Ω is good and the 100/63 is good. Check that zener diode's number to get its value.

[hann]

Re: Marshall Stanmore Repair

tested some voltage mark with arrows, but still no output

[hann]

Re: Marshall Stanmore Repair

here is my board and i drawn a schem to find the culprit

[hann]

Re: Marshall Stanmore Repair

hi im hann, my problem with stanmore is no power. On supply section. Already replaced pwm chip ob2269. Still to success.

[sunnysocket]

Re: Marshall Stanmore Repair

Hi All , Have someone get success to fix stanmore ? I found mine met the same issue with R23 & still try to trace other problems
Thanks

[ToxicGumbo]

Re: Marshall Stanmore Repair

3) @ToxicGumbo: Can you share your experience when you say "the 50watt amp was a bad choice" ? I would have thought a 50w amp was a reasonable option. I was actually thinking of using this one.

Hey, Arno2. It's a daunting journey, but an enjoyable one and I learned a lot in the process. There are certainly several ways to go about it, too, and you've taken it a step further by trying to isolate the core parts of the existing hardware. I'd actually like to see that work out, but you're correct to point out the challenge of obfuscated design through all that anti-vibration/snooping goop they slopped on the PCB.

In my case, the 50W amp I picked turned out to take a stereo input and split it into two outputs for left and right speakers. Since the Stanmore has one speaker, the objective would be to have left and right combined into a single 50W mono output. One no-no of audio is never to splice stereo input signals together to force "mono" as it can potentially wreak internal havoc due to sound wave conflicts, so I was essentially forced to live with one channel output (left speaker?) for the woofer and rely on the tweeters for more noticeable stereo. No big deal, but it was a bit of a gut punch. I never could find a 50W amp that was guaranteed to output 50W of a combined stereo signal into mono for one speaker. There are hacks to sort of make this happen, but the safest approaches are a bit of a hassle.

I saw and liked the unit you spotted, particularly for the built-in Bluetooth, though I opted to add Bluetooth separately as an independent input choice for the pushbutton selection. Since that's all I use at this point, built-in bluetooth would have been less of a hassle. The one thing that worries me about that unit is the TPA3116 chip. That's the same one on the board I bought and if you read the spec sheet, you're likely stuck with the same situation I had:

https://cdn.badcaps-static.com/pdfs/...d5f959dd7b.pdf

From page 24:

"The TPA31xxD2 family can be connected in MONO mode enabling up to 100W output power."

In other words, the only way to get both Left and Right in a single mono output means you're forced with 100W, which will overpower that driver. You can see in the block diagram on page 13 how the chip takes L & R inputs (LIN*, RIN*) at the very start and produces L & R outputs (OUT*L, OUT*R) under normal 2x 50W mode.

Maybe there's an easy solution to this, but just combining signals before or, especially, after, can possibly turn out nasty. For me, I just gave up looking for an alternative and went with one channel. Would love to hear your thoughts.

[Arno2]

Re: Marshall Stanmore Repair

Hi there,

I am willing to not scrap my marshall stanmore as well and reuse the existing enclosure as well as the drivers.
I understood ToxicGumbo and others (https://techfindings.one/archives/3375) have explored this option .

My questions to the group:
1) Has anyone tried to reuse the original crossover ? If yes can you share your experience ?
2) Could anyone identify the crossover itself ? The goop does not help and in case (1) is doable, I may not want to remove the goop to avoid damaging the crossover.
3) @ToxicGumbo: Can you share your experience when you say "the 50watt amp was a bad choice" ? I would have thought a 50w amp was a reasonable option. I was actually thinking of using this one.

Thanks !!

Arno

[ToxicGumbo]

Re: Marshall Stanmore Repair

Please excuse this poor photo, but after scraping off Marshall's glue and rubber absorption material, I believe I found R17, which is labeled "1004".

According to...

https://www.hobby-hour.com/electroni...-resistors.php

...and...

http://www.kiloohm.info/smd4-resistor/1004

1004 = 1MOhm

[cpanshey]

Re: Marshall Stanmore Repair

Hi Everyone,
Can anyone advise the value of R17, actually its not clear in the image.

Thanks in advance
Regards
Chandrakant

[Viikari]

Re: Marshall Stanmore Repair

Hi,

In my speaker main amplifier is totally fried also some pcb tracks are missing. I traced that everything else is working even PWM signal processor/driver TAS5508C (below the shield) is outputting correct pwm signals to powerstage.

Has anyone measured powerstage input voltage? Mine shows about 31 volts. Other voltages seems to be ok, but is that 31 volt correct?

Do anyone any clues what else might be broken when amplifier chip is broken? Has anyone one anyled why that powerstage fries itself?

Br Kari

[Jaume]

Re: Marshall Stanmore Repair

Hey everyone,
Can anyone help me identify this chip that I have circled in orange. I also have the Q7 broken but thanks to your thread I have the information I need to replace it.

Thanks for your help

[ToxicGumbo]

Re: Marshall Stanmore Repair

R23 is a 220 ohm. mine was damaged but still readable.

Thank you! Much appreciated.

[Outlier Audio]

Re: Marshall Stanmore Repair

R23 is a 220 ohm. mine was damaged but still readable.

[monpana]

Re: Marshall Stanmore Repair

For Q7 = FQPF2N60C - Transistor MOSFET, Canal N, 2 A, 600 V, 4.7 ohm, 10 V, 4 V (farnell)

[ToxicGumbo]

Re: Marshall Stanmore Repair

Amazing to see others with R23 problems.

Wiru, here's info for U15 (note that the full 100W isn't directed to any single speaker):

TI TAS5342A 100 watt amplifier
HTSSOP package (44 pin)
Tech sheet: http://www.ti.com/lit/ds/symlink/tas5342a.pdf

Kimera, here's info on Q7:

Fairchild FQPF10N60C MOSFET
TO-220F package
Tech sheet: http://www.onsemi.com/pub/Collateral/FQP10N60C-D.pdf

Hedefalk, how did your repair efforts go?

[ToxicGumbo]

Re: Marshall Stanmore Repair

I had no idea anyone had replied to this thread until Kimera wrote me a private message (which triggered an email alert). Very glad to see some activity and people helping each other out. I'll find my board tonight and answer as best I can where questions went unanswered.

As far as my PCB, I never found assistance, gave up on repair, and built an entirely new system using cheap parts over eBay. Here's what I came up with for reference.







It works quite well, but has a very low level of hiss - most likely due to the obnoxiously lengthy cable runs - that's only noticeable when up close. I don't recommend this route to anyone due to the amount of time and research it takes, but it taught me a lot and is at least an option for those who feel so moved. I think the individual parts cost up to $75 (the 50watt amp was a bad choice, but all of this is now modular and replaceable).

[Kimera]

Re: Marshall Stanmore Repair

What Q7 number ? my q7 missing

thank.

[Fla]

Re: Marshall Stanmore Repair

Hello, I am e new member, I have a problem with the same product. The label/value of resistor R23 is damaged, black. The resistor is near of r22.
Can you help me?
Thanks