Phoenix Gold Phorum

i just got myself a bargain of an ms2250, was supposed to be dead but it powered up ok so i attached some speakers and a source and hey presto it works anyway my question is regarding the big resistors i circled in red, they got rather hot after a short period of time and started to smell a bit. now the ones in my mint ms2250 are considerably bigger, was this a revision pg made to rectify this issue? also i think they're a little cooked and off value...

the board other wise looks mint and apart from the battered shroud the amp is in realy good shape too!

i've since straightened the should up and it's looking good, just needs re powder coating or painting! oh and i'm missing a deuz fastener as well if anyone knows of a source for them?

They should not be cooking off like they are. Please take a voltmeter and measure the voltage drop across them. And let me know what that number is.
Ill look up that on another amp I have here and see whats the spec......C

1moreamp wrote:They should not be cooking off like they are. Please take a voltmeter and measure the voltage drop across them. And let me know what that number is.
Ill look up that on another amp I have here and see whats the spec......C

how do i do that and where do i put the probes?

they get too hot to touch!! what do they do?

mark.

R345 and its partner are used as current limits on the +&-15 volt zener supply to the front end.

These can and do get hot to the touch due to the limiting they introduce to drop the rail to 15 volts. Ohms law will tell you if they are operating within there proper range. PG uses these throughout the MS series so its not something special to this amp. But they do have a hotter job in this amp because of the higher rail voltages for the original MS-2250 < a real powerhouse of a amp>

what are the 15 volt zener diodes reading ? they should be at ~15 volts each referenced to rca ground. LMK what you find but i think your OK here.....C


A simple mod is to look up and buy Vishay TO-220 packaged power resistors ( about 10 watt rated)and mount them under the board so that they lay against the case for sinking of the excessive heat they produce, If you do this do it to both channels and use high silver content solder to withstand the heat build up on the leads to the board connection points. I do this on some M series amps now just as a beef up of the existing design. < not cheap but effective for sinking these to the case and preventing bad solder formation at the contact points > ...

they are 1500 ohm resistors and i'm getting 1450 ish (cold, amp off)so they are ok i think. when amp is they read something loke 20.96 and the front one doesn't read anything! not sure if this is normal and they get so hot you can't touch them for long apart from this the amp runs fine.

EDIT- just tested my good amp in my car and it does exactly the same thing those resistors still get hot even the big ones but i can hold my finger on those a little longer (still hot!!).

shroud taking shape nicely, just needs polishing a little and jobs a good 'un, not bad for an aerosol job, i used radiator spray paint as this seams a good match to pg's white!

Nice work marko! That looks much better.

lookin good looking real good!

marko wrote: i used radiator spray paint as this seams a good match to pg's white!

Nice one!

finished result, still missing the 3 fans/plate and dzus fastener but have no immediate plans to fit it!

Droooooooooooooooooooooooooooooooool.....

nice job!

Man, that just looks very slick! Dam, I wish I could work with metal

Very nice man.

Kevin