Marshall MF350 Mode Four - No power up

[BurrMan]

Also, I dont want to make it too painful for you, but will the wiring be the same? ie; the same amount of wires going to the same spots? I'm not an electrician. I have a buddy who is, but not nessasarily a guitar amp guy. Maybe if it's not exactly apparent I'll show up here and ask for a bit of direction? thanks again.

[Enzo]

Um...

I don't see 19v or 18v, what are we talking about? Wherever it might be, one volt difference is not likely to matter.

For that matter what do you mean confirm the power supply?


I can't tell you anything about the wiring, I don't have one here, you have one there though. I don't remember the transformer layout, hard wired or terminals, nor any color schemes that might pertain.

[Jazz P Bass]

What you are attempting to do, change out the power transformer in a Marshall Amplifier, is not going to be a walk in the park.
There is not any "this color wire goes here" documentation available.
And what info is available from Marshall is really hard to decipher.
I would kindly suggest that you take the whole affair to a competant tech that can handle the job with grace & ease.

[BurrMan]

For that matter what do you mean confirm the power supply?.

I was refering to the one that was suggested a couple posts ago. I just wanted more than one confirmation.

I don't see 19v or 18v, what are we talking about? Wherever it might be, one volt difference is not likely to matter.

It's written on the top of the transformers. I'm going to take Jazz P's advice and go see if a guy in a guitar shop down here will work with me.

Thanks. Maybe I'll be back to see if anyone will hold my hand if I need it.

[soundguruman]

Well I've gone and screwed up...

I was trying to replace the AMP2 fan on my MF350 because it was making a lot of noise. I ended up forgetting to unplug it and touched the back panel wall with the heatsink... a little tiny spark...

i figured maybe all is well still, so I unplug, keep working and put in a replacement fan (not stock but figured it would work... although it's a 12v instead of the factory 24v ones)...anyway I finished the fan install and powered up.

POW!!!!! and A BUNCH OF SMOKE COMING FROM THAT HEATSINK AREA!!!

Damn. I guess I probably blew an IC (what does that stand for anyway!!!) based on what I've read on this forum. I can see dark staining on the legs of one.

First off, where the heck is the fuse on this thing?

Second, I noticed the IC chip is soldred at about 15 spots to the little board it's attached to... If I change the IC's, do I have to de-solder all those, and rede it for new one? or will the main part of the IC slide off and leave the legs attached to the mini board?

Third, who is this "Mouse" i keep hearing about who sells stuff? By the looks of it, I need 4 new IC's and 1 new 24v fan.

Go&&am it!... All of this because of a noisy fan....and me being brain dead.

The plastic fan IS the insulator. The heatsink is HOT (energized HOT)
But don't feel too bad. A guy just dropped one off....he plugged the speaker out of another amp into the speaker out of the Mode Four. (KA BOOM!)
Need part Numbers? The KDOG will help you.
Kevin (Kdog) Drury

Marshall USA Service
1000 Corporate Grove Dr.
Buffalo Grove, IL 60089
800-877-6863
kevin.drury@USMusicCorp.com

[BurrMan]

Need part Numbers? The KDOG will help you.
Kevin (Kdog) Drury

Marshall USA Service
1000 Corporate Grove Dr.
Buffalo Grove, IL 60089
800-877-6863
kevin.drury@USMusicCorp.com

I'll take you up on that Kdog! I'll send an email tommorow!

Burr

[soundguruman]

I'll take you up on that Kdog! I'll send an email tommorow!

Burr

You need to go thru a Marshall dealer. I am getting parts for this other one, so if you want to lump these together,
I know a dealer that will probably help. (if you don't have one already)
I need 4 output modules too...
check the control pots, they wear out pretty fast. I'm changing about 10 pots on this other one.

[BurrMan]

You need to go thru a Marshall dealer. I am getting parts for this other one, so if you want to lump these together,
I know a dealer that will probably help. (if you don't have one already)
I need 4 output modules too...
check the control pots, they wear out pretty fast. I'm changing about 10 pots on this other one.

Thanks brother!

[soundguruman]

Marshall Mode Four Part Numbers

Four terminal control pots: (these are un-threaded, no bushing, plastic shaft, PC mount)
2X A50K M-POTP-00096
2X B50K M-POTP-00081
4X B20K M-POTP-00086
3X A1Meg M-POTP-00100
2X C 20K M-POTP-00079
2X B 200K M-POTP-00087
1X B5K M-POTP-00098
1X C5K M-POTP-00101
4X Power Amp Module Board (stuffed): M-KITS-00004
Red rocker power switch: M-SWTM-00031
Control Knob: M-KNOB-00037
1X Footswitch Jack (looks like RS232 computer connector) M-SKTP-00040
2X Scoop Switch (push button Switch) M-SWTP-00055

Schematic Attached:
Marshall Mode Four.pdf