Trace Elliot RAH300SMX issues

Discussion in 'Amps and Cabs [BG]' started by Lumbergh, Jul 20, 2009.

  1. Lumbergh


    Feb 21, 2008
    So as a few of you might have seen, I just bought a TE rah300smx (or it might be a 250, i'm not sure as it says 280W on the back). Well I got a KILLER deal on a cab (Ampeg SVT 8x10 for $250 =) ) and I finally got to crank up the TE.

    Well, when I did, there really wasn't much volume. I had it at 10 at one point and it wasn't super loud... it sounded like it should have been on 2. So I opened it up and sure enough, on the power section circuit board there's a burnt capacitor and a burnt resistor (i think, it didn't look like a resistor but its labeled R## so it must be).

    Here's 2 pictures of the burned cap/resistor:

    Would fixing it be as simple as finding those 2 parts and re-soldering them on? I'm very good with a soldering iron so thats not a worry. I'm very confident I could do it, i'm just not sure that more stuff isn't broken. Also, would the underlying circuit board be okay, or could it have easily burned that out too?

    Could someone find a schematic for me (I googled for a while but couldn't find one), or open up their ah300 and look at what the values should be? I'd appreciate it.

    Thanks guys!
  2. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    I'm also very handy with electronics. I design and build all sorts of electronic gadgetry. BUT, I wouldn't go poking around inside an amplifier. It's a completely seperate skill set. Take it into a good amp tech, and have it serviced professinaly.
  3. BassmanPaul

    BassmanPaul Inactive

    Agreed. Resistors and capacitor don't just fail for the sake of it. Something has blown and the damage you see is the result. Just replacing those parts will not fix the original problem and the new parts will just blow again.

    Tech time!

  4. BassmanPaul

    BassmanPaul Inactive

    Can you at least post a photo of the inside of the amp. I don't have a schematic for anything with RAH in the title.

  5. fish bulb

    fish bulb

    Jul 20, 2009
    RAH is the rack mounted version of the AH models so check for AH300smx.

    Also could we possibly buy a new power section or would that be impossible to find?

    FYI: i'm lumbergh's brother, we're in this mess together.
  6. BassmanPaul

    BassmanPaul Inactive

    I have a AH300 Series 6.

    A new board can be purchased IIRC from british Audio Service. I seem to remember a price of $99. Check them out.


    Post the phote of the inside of the chassis anyway.
  7. Lumbergh


    Feb 21, 2008
    I'm pretty sure I found the part we need on British audio service... its the replacement for the Bipolar Bear right? (# C11-MOD-K3-12)

    I'll grab pics of the chassis when I get home hopefully
  8. fish bulb

    fish bulb

    Jul 20, 2009

    Beat ya to it.

    The cabinet we ran it through said 4 ohms on it so that would be fine with this amp correct?

    I checked the impedance of the cabinet by connecting a speaker cable to it and using a multimeter and it gave a reading of 2 ohms. The seller of the cabinet said he recently rewired it so my guess is that he accidentally wired it to 2 ohms and that blew our amp out.

    When lumbergh gets home we'll open it up and see how it was done.
  9. fish bulb

    fish bulb

    Jul 20, 2009
    Turns out the cabinet has 4 32ohm speakers and 4 8ohm speakers all wired in parallel. The top four in parallel would come out to 8 ohms, the bottom four in parallel would come out to 2 ohms and if you parallel the 8 ohm and 2 ohm sections you get 8/5th ohm for the whole thing right? (1/res = 1/8 + 1/2 -> 1/res = 5/8 -> res = 8/5).

    To get the bottom four to eight ohms you just have to parallel 2 sets of series, right?
  10. BassmanPaul

    BassmanPaul Inactive

    Your statements are correct. How the cabinet will sound with mismatched drivers is another matter.

    Your amp is safe to 4Ω. The PCB and heatsinks look much like those in the GP7 I own. The original output transistors, TIP35/36 IIRC, have been changed to 2SC4468 and 2SA1695. You will need two of each. You will have to replace the damaged parts.

    I consider this cooling arrangement very poor. It could have been designed so much better. My GP7 was supposed to be 300W but it turns out that is peak. 150W is more realistic. My amp has just two output transistors but has space for four which I installed. The method of mounting the bias transistor is terrible. It depends on a dollop of heatsink compound for conducting the heat from the sinks. Very badly done.

    With mine I replaced the sinks with a much larger unit and clipped the bias transistor directly to it. I wired the outputs themselves on flying leads.

  11. fish bulb

    fish bulb

    Jul 20, 2009
    Are those the burnt out parts that need replacing? C15 and R30 and possibly R31 need to be replaced, what are their values?
  12. BassmanPaul

    BassmanPaul Inactive

    PM me with a proper Email address (not TB) and i'll send you the PDF.

  13. fish bulb

    fish bulb

    Jul 20, 2009
    Is there any way i can test the rest of the amp before i replace the powersection? I'd hate to install that and have something else blow it up again.

    I was thinking of sending the effects loop out of the T.E. into my brother's guitar amp's effects loop in so we could test the preamp at least. Any objections? That would test most everything else correct?
  14. lauriastral


    May 19, 2011
    I've also got problems with AH300SMX power section losing watts. Normally you can play gig with main volume in 2 or so - sometimes the power drops and volume 5 is not enough. The sound becomes also very distorted when this happens.

    I've owned this for 7 years now, the problem has always been there but nowadays it's much too frequent to play with the amp. Took it to a local tech couple of years ago who claimed the problem was a bad contact (no it wasn't).. Last week opened it up, cleaned all the contacts and re-soldered all the susicious spots, with no help.

    Could the problem be the output transistors? Power supply? Something else? Guess that easiest (but not cheapest) solution would be to buy Trace Elliot 150W Bipolar Board Upgrade Kit from British Audio Service..

    Any ideas how to proceed? Schematics would be very helpful too. Like this amp too much to get rid of it.