Looking for M25 schematic and close up picture of circuit

[Virtue]

Hi, I am looking for the schematic of the M25 amp and a very good picture of the circuit board, concentrating in the area of the speaker terminals. I got an amp that has a lot of parts missing and I am wanting to transfer parts from a blown M50 to the M25.
Thanks you so much!

[ttocs]

Can't remember for sure but pretty sure that there are a couple different revisions of that amp with minor changes. It might be helpful to look on the board to see if its listed and let us know.

[trickyricky]

Lets just hope its not the first gen....the second series had a larger transformer so it would easily do rated power and more ( I believe a total of 100-120watts bridged at 4ohm).

I just bought a few extra spare boards from a member here, pm me if you would rather purchase a working one with the filter and rail caps already replaced.

[Virtue]

I am missing these parts. It is version II. I would like to know what these parts are first before I buy a new board... thanks!

[zeropoint0.5]

this is a board coming out of a route 66 amp

[trickyricky]

Those are mosfets...itfz44 but you can use irf3205 as they handle more current...more reliable. Your also missing a rectifier.

[Virtue]

Great that helps me with the power supply part. Are there any photos out there for the preamp part of this ( front left corner under the speaker terminal)? And yes, this came out of a route 66. I am just using this for a center channel amp. Thanks for everyone's help so far!

[trickyricky]

The M25 from the Route 66 is missing the preamp section because it uses the signal from the M44. You'll have to add quite a few resistors and a couple of op amps in order to get that side working, not to mention RCA's, Gain and bass pots which are not easy to find especially since Aleks is no longer in business.. I know this may be a project for ya but it may be cheaper to purchase another working board because those pots were 15 bucks EACH when they were available. Op amps, resistors, rectifier, caps will cost you another 10.00 so you'll end up spending over 40.00 just to get this functioning as a normal M25, not worth it in my opinion. Don't get me wrong fun project to take on if you have the time and patience, just something I wouldn't consider today.

[ttocs]

gosh I am still just not use to our go-to guy for repairs, parts and info not being here/there anymore.... Doesn't feel right like there is something in the force that is off balance.

[trickyricky]

I could list exactly every resistor value and cap needed as well as the rectifiers, I just don't feel like the op will ever finish this project because of the gain and bass pots being a bit too expensive or impossible to find at this point. I gave him the option of purchasing a working recapped board for 75.00 shipped.

If he has a M-series burnt damaged board he could easily salvage those parts from that.

[Virtue]

Just to restate my original comment. I have a burnt out M50 that has all the parts to be put on to the M25. I have spent a lot of money getting the M25 and I can't spend any more... So I am hoping someone has a M25 and can take a beautiful, clear, up close picture of the pre amp section. Located where the speaker terminals are. Then I can complete this M25 in one night. Thanks!

[trickyricky]

Hope Eric doesn't mind, but have you checked here ( http://www.soundbuggy.com/Eric/Car%20Au ... index.html )?

[Virtue]

Hi Tricky, thanks for the picture. If it is possible, could you get a picture of the left OP amp area. I cannot make out the resistor colors. (shown by my picture)
Thanks!

[trickyricky]

This should help out...

10k; 102, 103, 104, 106, 108 , 202, 203, 204, 206, 208
1K; 101 , 201
1.2k; 107 , 207
510; 109, 110 , 209
1.1k; 210
330; 105, 205

caps
33uf 16v: 101, 103 , 201, 203

[trickyricky]

You have two resistors that are wrong value on your last picture. They are the 7.5k (purple, green, orange, gold), also C116, 102, 216, 202 are 150pf.

[Virtue]

Thanks Tricky, I got the old girl going! I just wish it had more power... Kind of gutless...

[ttocs]

You have two resistors that are wrong value on your last picture. They are the 7.5k (purple, green, orange, gold), also C116, 102, 216, 202 are 150pf.

if I am not mistaken, purple green orange = 75k not 7.5k? I can't remember the last time I did this though so sitting here with the whole fingers count with the bad boys memory aid and I could very well be wrong but pretty sure purple green red would be 7.5k

[trickyricky]

You're right, its 75k and hopefully our friend replaced those with 10k otherwise those op amps will have a bad gain circuit (may explain the low output).


These amps are 100watt, you may get another 20watts out of it but thats about it. It's not a M100, that sucker can do 500watts. These are perfect for tweets and mids, even though many been used for woofer duty. Glad you got it running.

[machinemike]

I had a pair of m25s in high school, a friend bought one and ran 2 xmax 12s off of it. I was always amazed. Wish I had them back, had a zx200 that went with them.

[ttocs]

I was right?! Damn I am surprised I still remember that crap I only needed it when I installed stereos/alarms funny enough my career at intel it was never needed. Ah if my high school electronics teacher would be happy I guess it could be learnin all of us the resistor color bands. I can still remember how he didn't want to teach us the bad-boys way to remember it but 20+ yrs later, I can still use it

[Virtue]

I did correct those two resistors. This is crazy. I looked at your photo and noticed that a number of resistors have orange in them. The ones I installed have none... I was confused. So I checked the resistors I bought... And look what is wrong. All the 10k I bought were actually 1k, so I have a bunch to change now... That's NTE for yah.

[trickyricky]

NEVER EVER BUY NTE!!! For this very same reason (well many more, especially the lack of QC and how many components are just rebranded), I know you would think "well this is just resistors, shouldn't matter that much AS LONG AS THEY ARE CORRECTLY PACKAGED". If in doubt always double check them with your DMM.

I order all my components from Mouser, they are 15-20 minutes away or I can have them ship (when they are very small orders, such as a few resistors).

That should explain the low output, if the preamp section is screwed up then you might be attenuating the input signal instead of amplifying it.