Results 1 to 22 of 22

Thread: SVT-7 Pro dead and free

  1. #1
    Old Timer tedmich's Avatar
    Join Date
    Apr 2008
    Location
    Sonoma CA
    Posts
    3,153
    Thumbs Up/Down
    Received: 13/0
    Given: 36/2

    SVT-7 Pro dead and free

    Local C list free section gave away Ampeg SVT-7 Pro that is totally dead, no nothing on power up.

    first off, fan header is disconnected on main board, so it got HOT, a 3 wire fan with a safety shutoff would be a good idea...

    sure enough Infineon SMPS IC (ICE2A165) looks scorched



    And R46 (removed) measures way more than 1 ohm

    Also over by the funky bare metal 0.02 Ohm resistors there is a cooked resistor and film cap (C16)



    schematic says resistor (R115) should be 22 ohms but it measures 54 ohms, bands are long gone...

    gotta clean up board



    several people think the tube heater causes SMPS chip to overheat, and recommend replacing with ICE2A265 with heatsink. Later versions supposedly got rid of the optos associated with the burned R115/C16


    Lots of problems on these units, people pay $700 for this ticking time bomb? jeesh...

    0 Not allowed! Not allowed!
    Last edited by tedmich; 04-06-2016 at 11:37 PM.

  2. #2
    Senior Member
    Join Date
    Nov 2006
    Location
    Sacramento, CA
    Posts
    503
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    What do you think of the class-d amps? I'm a little skeptical of anything that light.

    0 Not allowed! Not allowed!

  3. #3
    Old Timer tedmich's Avatar
    Join Date
    Apr 2008
    Location
    Sonoma CA
    Posts
    3,153
    Thumbs Up/Down
    Received: 13/0
    Given: 36/2
    They are a compromise, huge power, light weight but engineering wise they are balanced on a precipice, so many things can go wrong if the parts spec'd are a little bit too cheap or the design/mfg are too sloppy fast and untested. On many of them the end user is an unhappy beta tester, you're rolling dice, caveat emptor.

    0 Not allowed! Not allowed!

  4. #4
    Senior Member
    Join Date
    Nov 2006
    Location
    Sacramento, CA
    Posts
    503
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Thanks, I kind of got that impression but wasn't sure. I've read somewhere that the power ratings are measured in short bursts.

    0 Not allowed! Not allowed!

  5. #5
    Old Timer tedmich's Avatar
    Join Date
    Apr 2008
    Location
    Sonoma CA
    Posts
    3,153
    Thumbs Up/Down
    Received: 13/0
    Given: 36/2
    Well every amp Mfg is guilty of that, all the wattage inflation, very few use 20Hz-20kHz true RMS power output

    Mackie made fun of it,

    but probably uses it too now

    0 Not allowed! Not allowed!

  6. #6
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    29,909
    Thumbs Up/Down
    Received: 86/1
    Given: 0/0
    very few use 20Hz-20kHz true RMS power output
    Well, yeah, instrument amps don;t need remotely that much bandwidth.

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  7. #7
    Lifetime Member km6xz's Avatar
    Join Date
    Dec 2010
    Location
    St Petersburg Russia
    Posts
    1,840
    Thumbs Up/Down
    Received: 2/0
    Given: 0/0
    The SVT-7 is a well made amp, with solid construction. That said, it is complex in the power supply, the main defect seen by shops, because there are actually several switch mode power supplies there and they cascade in turn on in sequence so a number of feedback and protection schemes can halt turn on at any of those supplies. Getting one for free is a great deal, even if the whole board was replaced you would be ahead.
    Class D amps can't be compared directly to RMS rated amps and that is not a bad thing really. For a long time power was measured for RMS over a wide range of frequencies but that really is not how they are used or how we listen to sounds. Music or speech is nothing like RMS and headroom is limited on AB amps compared to the high peak to average amplitude ratios of normal program material.
    Class D are not great at generating high RMS values over a sustained period but in actual use, it is not even even a factor since a peak is usually short duration in sound reproduction/production. So basically the old much ridiculed Music Power rating is more realistic in quantifying the sensation of power of sound....if every brand used the same version of Music Power or Peak Music Power.
    There are standards for measuring and specifying power and the one for digital power amps uses a 4 cycle pulse and interpolated to 1 second for equivalent RMS power. For moderate crest factor music it translates well to perceived power. But for highly compressed music/sound, the burst value underperforms.
    A big problem has developed in the imbalance between speakers and power amps. It is very cheap now to build a 2000 watt Class D amp but very hard and very expensive to build a speaker system that can handle 2,000 watts. The only way to do it is make drivers very low efficiency so lower SPL. Matching a typical bass cabinet rated at 400 watts with any of the modern Class D, less than 10 lb, monsters is a disaster waiting to happen. Unless a new technology of moving air is invented, the mismatch between affordable drivers and affordable amps has pretty much reached a practical end point. Any bass or full range pa system buyer who is looking for louder levels by adding power is a fool and does not understand what the hell they are doing. Higher power requires lower efficiency so SPL might even be reduced. Besides, high SPL is killing live band work, few clubs or bars can tolerate the extreme levels and still sell drinks or keep customers coming back. For any other reason other than ego, why the very loud sound that prevents most bands from getting gigs and prevents most clubs from ever hiring live bands? The typical musician who claims they are pros but have no idea of being professional in earning an income. They have no business plan or clue on how to make themselves hirable. TOO much ego and not enough consideration of listener experience or the tough row to hoe by the club owner.

    0 Not allowed! Not allowed!

  8. #8
    Old Timer tedmich's Avatar
    Join Date
    Apr 2008
    Location
    Sonoma CA
    Posts
    3,153
    Thumbs Up/Down
    Received: 13/0
    Given: 36/2
    The Ampeg Pro series amps are wondrously complex products and (when they work) they are a rare combination of high performance for low dollars.

    Compare this amp in price (and weight!!) to John Champions 1kW tube amp
    Click image for larger version. 

Name:	const17o.jpg 
Views:	254 
Size:	77.9 KB 
ID:	38580

    with 20 x 807 tubes, even this beast has CONSIDERABLY fewer components than the Ampeg and their additive failure rate is tiny compared to the Ampeg's couple thousand SMD components (chosen for lowest possible price) slapped together by machines in a couple minutes.

    The wonderfully engineered, amazingly complex Ampeg, that represents the highest possible performance/price ratio, will necessarily have a quite high failure rate, and woe be the tech expected to fix it in a timely and cost effective manner!

    0 Not allowed! Not allowed!

  9. #9
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    29,909
    Thumbs Up/Down
    Received: 86/1
    Given: 0/0
    But it doesn't have a quite high failure rate. We hear of some, but what we don;t hear about is the tens of thousands of them that just work day in and day out for years on the road in the hands of professionals. The internet is not representative of any product line.

    The pick and place machines and automated soldering that goes into the boards in these things is the same process that is used to make that smart phone you carry everywhere. Those work. And that flat screen TV on your wall? Same thing. When was the last time the computer in your car broke? Made the same way.

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  10. #10
    Old Timer tedmich's Avatar
    Join Date
    Apr 2008
    Location
    Sonoma CA
    Posts
    3,153
    Thumbs Up/Down
    Received: 13/0
    Given: 36/2
    OK OK I'll admit to being seduced by "Internet Induced Spurious Magnification"!

    They may well have a tiny failure rate but the few seeking a fix are remarkably sad and pitiful in their (largely wasted) efforts!
    One was a guy at Talkbass who went straight from NAD chest thumping into "Wha happened??" lamentations that took nearly 40 pages!

    0 Not allowed! Not allowed!

  11. #11
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    29,909
    Thumbs Up/Down
    Received: 86/1
    Given: 0/0
    Sure, and I a while back had some "simple" little Laney amp I had been poking at for over 10 years off and on until I finally figured out its problem. it happens to everyone. A complex circuit like this can become devilish to repair sometimes. The internet is like the service counter at Best Buy. If you hang out there, you only see what breaks. No one brings in or gripes about all the ones that work.

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  12. #12
    Old Timer Tom Phillips's Avatar
    Join Date
    Jun 2006
    Location
    California, USA
    Posts
    3,468
    Thumbs Up/Down
    Received: 14/0
    Given: 14/0
    Quote Originally Posted by Enzo View Post
    ...The internet is like the service counter at Best Buy. If you hang out there, you only see what breaks. No one brings in or gripes about all the ones that work.
    In a similar fashion I often remind people that not everything was higher quality in the good old days. I was in an antique furniture store once when someone remarked that the furniture was better quality "back then." That may he partially true but they totally forgot to consider that the good stuff survived and most of the old crappy stuff ended up in the dump.

    0 Not allowed! Not allowed!

  13. #13
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    2,476
    Thumbs Up/Down
    Received: 24/0
    Given: 50/1
    Like all those "golden-age" amps with corrugated cardboard cabinets?
    (Cough-Lectrolab-Cough) for example...

    Justin

    0 Not allowed! Not allowed!
    "... If an older Boogie and classic Marshall had a (clearly illegitimate) child and you baked it in an oven set to clown shit crazy." - Chuck H. -
    "When receiving a shock I emit a strange loud high pitched girlish squeak." - Alex R -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  14. #14
    Old Timer Leo_Gnardo's Avatar
    Join Date
    Sep 2012
    Location
    Dogpatch-on-Hudson
    Posts
    4,862
    Thumbs Up/Down
    Received: 44/0
    Given: 32/0
    Hey I swapped out my VibroChamp for a LectroLab when the prices on the little Fenders went kookoo. (Paid a month's mortgage with the VC, not bad!) LectroLab's doing just fine thanxveddymuch, and that's authentic vintage cardboard, by the way.

    0 Not allowed! Not allowed!

  15. #15
    Old Timer
    Join Date
    May 2006
    Location
    Chill-Ville, VA
    Posts
    2,476
    Thumbs Up/Down
    Received: 24/0
    Given: 50/1
    Hey, I didn't say they SOUND bad, I just doubt most didn't survive their first backyard barbecue or frat party gig, after the cabinets dissolved when the first thunderstorm or beer pitcher fell on them! Personally, I love the little things, but darn, don't pull the chassis more than once, or all the screwholes will strip out!
    The one I got to work on (R500-B) sounded amazing with an efficient and decent-powered speaker hooked up!

    Justin

    0 Not allowed! Not allowed!
    "... If an older Boogie and classic Marshall had a (clearly illegitimate) child and you baked it in an oven set to clown shit crazy." - Chuck H. -
    "When receiving a shock I emit a strange loud high pitched girlish squeak." - Alex R -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

  16. #16
    Old Timer Leo_Gnardo's Avatar
    Join Date
    Sep 2012
    Location
    Dogpatch-on-Hudson
    Posts
    4,862
    Thumbs Up/Down
    Received: 44/0
    Given: 32/0
    Lots of old Danelectros, Sears Silvertones, Wards Airlines & who knows what else made with bent "beaverboard" aka "homasote." They don't like to get wet either, so keep 'em dry. 50+ years later many are just turning (back) into dust anyway, giving the local cab carp something to do. And whatever you do, don't stand on any of the above, especially while the amp's on!

    0 Not allowed! Not allowed!

  17. #17
    Old Timer tedmich's Avatar
    Join Date
    Apr 2008
    Location
    Sonoma CA
    Posts
    3,153
    Thumbs Up/Down
    Received: 13/0
    Given: 36/2
    In my defense the Musicians Friend reviews of this specific model describe 14 failures out of 31 total reviews, self reported but 45% is concerning.

    RevA is apparently worst but several failures were RevC (my unit is RevC) Its a complex design apparently held together by
    Crappy solder.
    Crappy solder.
    Crappy solder

    (credit to JBP!)

    0 Not allowed! Not allowed!
    Last edited by tedmich; 04-11-2016 at 10:33 PM.

  18. #18
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    12,214
    Thumbs Up/Down
    Received: 9/0
    Given: 5/0
    Crappy solder.
    Crappy solder.
    Crappy solder.

    0 Not allowed! Not allowed!

  19. #19
    Old Timer tedmich's Avatar
    Join Date
    Apr 2008
    Location
    Sonoma CA
    Posts
    3,153
    Thumbs Up/Down
    Received: 13/0
    Given: 36/2
    I replaced all the bad components I could find, plugged it in threw the switch and promptly blew a crater where the new ICE chip was...in the trash it goes! class D

    0 Not allowed! Not allowed!

  20. #20
    Old Timer Leo_Gnardo's Avatar
    Join Date
    Sep 2012
    Location
    Dogpatch-on-Hudson
    Posts
    4,862
    Thumbs Up/Down
    Received: 44/0
    Given: 32/0
    Quote Originally Posted by tedmich View Post
    I replaced all the bad components I could find, plugged it in threw the switch and promptly blew a crater where the new ICE chip was...in the trash it goes! class D
    What, no "lite bulb limiter?"

    0 Not allowed! Not allowed!

  21. #21
    Old Timer tedmich's Avatar
    Join Date
    Apr 2008
    Location
    Sonoma CA
    Posts
    3,153
    Thumbs Up/Down
    Received: 13/0
    Given: 36/2
    Anybody want to resurrect this Ampeg SVT-7 Pro? I'll send it to you for the price of shipping!

    Reduce reuse recycle keep this Chinese wonder out of the landfill!

    Earn your SMPS bonafides and flip it for a profit (if your time is worth "some low number") !

    PM if interested

    0 Not allowed! Not allowed!

  22. #22
    Junior Member
    Join Date
    Apr 2018
    Posts
    1
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    I'll take it

    0 Not allowed! Not allowed!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. behringer sl2442-pro dead effect
    By barthab in forum Music Electronics
    Replies: 2
    Last Post: 01-21-2016, 07:37 PM
  2. Ovation Op-Pro preamp tuner display dead
    By torlon2001 in forum Guitar Tech
    Replies: 2
    Last Post: 12-27-2009, 11:19 PM
  3. Fender Pro Tube Pro Reverb - Dead Tremolo and Noisy Reverb
    By pmwalk in forum Maintenance, Troubleshooting & Repair
    Replies: 1
    Last Post: 12-09-2009, 10:54 PM
  4. Free pro audio schematics
    By godzilla in forum Maintenance, Troubleshooting & Repair
    Replies: 0
    Last Post: 01-08-2008, 03:58 PM
  5. Fender Pro Tube Amp Completely Dead
    By macgonigle in forum Maintenance, Troubleshooting & Repair
    Replies: 5
    Last Post: 01-22-2007, 07:41 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •