Phoenix Gold Phorum

I could not sleep the other night and did one of my many searched on ebay and was surprised when this little sucker popped up. IT was listed as non-working for parts but I am hoping that they didn't notice the ground switch was on common instead of floating and just did not wire it right if they did test it(I am awaiting their response to find out). I would like to put it in action in the mustang so a cap change is a must and wondered if the cap experts could give some guidance on what is needed and what else to look for when I get inside of it?



its been a while since I have seen an MS/MPS in this good of condition. This style will just never get old to me especially with the new black box style everyone is doing.

Let me know if you change your mind on this , I might need to use it for my tweeters,thanks !

I might be tempted... Let me see if it works or not and we can go from there. Anyone think these caps are original? the paper test was dry under it.

Looks to be recapped. Dead giveaway is if they are 2200mfd and 16v though

16v 4700 microfarad nichicon caps and 15k sprague 16v

It's already recapped, the rails are original but are not 16v are 25v.

I saw this amp as soon as it was posted a week ago for 140.00 and offered the seller 120.00 for it and he never did replied (so kinda bummed out that he ended up listening for 120.00 without any notice lol, oh well). I can say that having the com/float switch set to float won't cause one channel to fail or have issues, is either both or neither when it comes to the float/com switch.

I have a gut feeling it will need repair hence why I was trying to get it for a bit cheaper.

Those are not original caps, so you are in luck.

The cap change may be why the amp does not work. It is actually pretty easy to make an MS amp nonfunctional by replacing its caps. Generally something ends up shorted when putting it back together.

Well since the caps were not a problem I powered it up, or tried to and nothing. No power led no output. Any advice on where to look, what to test is greatly appreciated. I have all the tools but have not done much circuit board repair.

Check the fets and fet gate resistors in the power supply, check for any shorted output devices (mounted on the heat sink).

the larger fets have sil pads, the smaller look to have grease behind them. What voltage should I be looking for on which legs of the fets?

Right now you are not looking for voltage you are looking for shorts (dead shorts) between the pins of each device, no power applied to the amplifier.


I asked about the fuse because I don't know if you have a current meter/clamp and wanted to know if there was excessive current draw upon trying to power it up. I always recommend using a small 5amp fuse when testing amplifiers with known issues. If the fuse pops then there is excessive current which clearly indicates and issue.

no it did not appear to draw anything as its a small power supply and the led dims when I use it to charge rc batteries. Ok dead short on the pins - will check it out in the morning. all the fets or just big/little?

I took a good long look at the board to see if I could see any issue and its really clean. There are a couple of spots that look worn and makes me wonder what is under those but no breaks/shorts or components that look to have been hot or smell smoked.

ttocs wrote:I might be tempted... Let me see if it works or not and we can go from there. Anyone think these caps are original? the paper test was dry under it.

Let me know what you find or if you just want to sell it like it is . I have a recapped M50 if you are interested. I need a ms or mps to run tweeters in white.

I am willing to put a few hours into getting it running as being disabled I have time to fill. After thinking about putting it to work in the car the last little amp I need is for the center channel. Needless to say the mps is overkill and a small ms would be just fine so I am looking a into a small ms and then this would be for sale. You were the first to show interest so I will let you know if/when it does go for sale.

Just need to get new batteries for my meter to start, of course its dead for the first time in 4 yrs when I need it....

Thanks, just let me know !

ok I finally found a battery for my meter. are the power supply fets the 6 one the same side as the power wire? If so Q7-10 show a short between the center pin and the pin to the right of it. D8-9 show a short on all 3 pins.

D8-D9 are the part of the bridge rectifier (these rarely fail), the fets Q7-10 should not have any shorts between the middle pin and either outer leg/pins. Are you checking it with the dmm set to ohm or diode mode?

diode check is how I normally look for shorts.

Check the middle pin of the fets in the power supply with one of the test leads on the chassis ground. Is there any shorts or low resistance between them? Perhaps of one of the silpads got damage and the fella who recapped it just didn't know or bother.

the all show a short to ground on the pins to the right and q9 shows a short to ground on all 3.

Remove the board completely then check them again, perhaps there was a short between the chassis and device. If Q9 is still showing a short then remove it completely and check out the remaining 3 (there's a chance you'll have more than one shorted fet, best to replace all four).

Once removed from the board check the rectifiers, should allow current/voltage to flow one way and block when meter probes reversed/swapped. If you have a short in the diodes as well then those will have to be replaced. Don't forget to check the gate resistors for the fets, they are near the PWM IC and are either 33 or 100 ohm resistors.

will do. any words of warning about removing it? Stupid things to watch out for? Thanks fer yer help by the way.

You may have a bit of a hard time removing the devices that are attached to the heat sink, use the largest allen key you can fit in the device's screw/mounting hole and slowly pry the allen key towards the center of the board (downward). Just enough to separate the device from the sink, don't bend it too far otherwise you'll create a weak point on the pins and the device may completely fall off leaving pins behind (snap right in the middle of the pins from creasing too much).

Remove the screws that hold the pcb down as well before trying to lift board up (I know this sounds stupid, but trust me if you forget one screw and start prying the board hard enough the you can cause serious damage). Once all devides mounted on the sink are completely loose, then slightly lift board up without too much force remember if you have to use force then something is wrong.

Once board has been remove observe the insulator sheet placed below the pcb to see if it has any penetrations (from component pins making contact with them) as well as any obvious damage sparks burnt marks or hershey squirts.

Here is a really high quality drawing of how I remove these devices off the heatsink.

I have both standard and metric Allen keys, and I find the one which fits into the screw hole of the device the tightest. I then put the short end of the key into the hole and orient it as you see in the high quality drawing.

Now push on the key at the point and direction you see the arrow. If you do it right, the device will "pop" off the heatsink, and the key will likely jump out of the hole at the same time.

It should be easy to tell from the drawing (as it is so high quality), but if you cannot tell, that is looking in the direction of the end of the amp where an endplate would be.

I am not sure my education is high enough to understand such precise/technical drawings but in all seriousness I thank you very much for taking the time

My pops is a perty fart smeller I will see if he can translate!