Connect with us

Trace Elliot GP12 amp

Discussion in 'Electronic Repair' started by N Cook, Feb 21, 2007.

Scroll to continue with content
  1. N Cook

    N Cook Guest

    Cut out because owner was connecting to speaker with lead connected to amp
    and touched the plug-tip to guitar strings.
    I cannot find anything wrong with it now.
    I downloaded , something like the schematic version here from
    www.britishaudioservice.com/schem/12%20band/GP12%20300%20watt%2012%20band%20
    series.pdf

    I cannot see how any protection circuitry would work/ reset themselves in
    this fault mode.
    Anyone familiar with these amps.?
    I'm surprised the Cockroft Walton pump cirrcuit is enough to power the HT of
    the ECC83.
     
  2. It does/doesn't work?
    Not a pump, a full wave bridge.

    --
    ..

    --
    ..
    ..
    ..
    ..
    ..
    ..
    ..
    ..

    --
     
  3. Arfa Daily

    Arfa Daily Guest

    As Homey says, look again. Although it's peculiarly drawn, it is just a
    simple full wave bridge, with 250v AC input. The caps are just spike
    bypassers to protect the diodes. As to why it cut out, it may be that
    something locked out that complex soft-start circuit. Give Trace Idiot a
    call and just ask. I've found them pretty helpful in the past ...

    Arfa
     
  4. Ron(UK)

    Ron(UK) Guest

    How did you find the circuit diagrams from the main site ?

    Ron(UK)
     
  5. N Cook

    N Cook Guest

    I see what you mean , either cyber-squatters or
    duff connection etc, ie waste of time

    www.traceelliot.com/

    www.trace-elliot.co.uk/

    www.trace-elliot.com/

    unless you know of the correct URL or a genuine one that works with Firefox,
    i may try IE later.
    I've never got on with this new-fangled viewing schema on a monitor
    business, especially disjointed ones.
    I'll try printing off the first one but i've been there before as well.
    Yes the string of diodes and little caps is not a diode pump. Some strange
    HV stuff here, front panel "lamps" that are 3 legged phosphorescent bulbs -
    where would you go to get generic/ not main agent replacements ? no obvious
    HV wiring , a triac protection?/crowbar cct that i've not physically located
    yet, presumably under the rear panel or different model
     
  6. Ron(UK)

    Ron(UK) Guest


    I found the diag you refered to, I just wondered how you found it, and
    is there a way to navigate back from that url to an index of diagrams
    fro the rest of the range. I`m more interested in the small acoustic
    combos as they are fairly common around here.

    I repair quite a few of the TE bass amps, almost always they fail
    because they have been shaken apart rather than electronic problems.

    There`s a well blown up Bass head under my bench which was never
    collected by the customer after I declined to repair it. I think that`s
    a GP12.

    Ron(UK)
     
  7. N Cook

    N Cook Guest

    As i was, it is a diode pump, ladder steps 50V, 90V, 130V,170V , under load
    of ECC83. I just cannot make the whole thing not work now, damned annoying.

    Just downloaded the first schematic that turned up in a searchengine that
    was not 18Mbytes or such. I don't like the 2sJ50, 2SK135 mounting
    arangement. Cases electrically connected via black anodised? bolts and only
    one of those each, relying on the pcb not to deform under screw pressure/
    thermal effects. Exposed 230/110 mains select switch asking for trouble in
    the UK, nothing unusual there.
     
  8. N Cook

    N Cook Guest

    If it was used as i received it then the ground lift was in operation so if
    the guitar was connected to this amp then not earthed via the preamp so it
    was probably a static discharge. I'll replace the CMOS 4011 and 4066 as
    presumably they are the most likely to be affected. I still don't see why as
    the speaker output is earthed whether ground lifted or not.
     
  9. Perhaps they are a subsidiary of Lucas?


    --
    ..

    --
    ..
    ..
    ..
    ..
    ..
    ..
    ..
    ..

    --
     
  10. N Cook

    N Cook Guest

    gp12 "ah 250" "trace elliot " site:www.britishaudioservice.com

    pasted into the Google search bar found a more specific model in my case,
    the AH 250 ink on the paper label had faded to almost illegible on the back
    of the amp.
    I agree another useless site for accessibility.
     
  11. Arfa Daily

    Arfa Daily Guest

    But have you tried contacting Trace Idiot themselves ? Many of these
    manufacturers are a lot more helpful than you might imagine. I currently
    have a Traynor Custom 40 in for repair, with a standby switching problem -
    easy one you might think, but the output stage HT is actually switched by a
    FET / opto isolator arrangement (!!). I could not find the specific model on
    the Yorkville website, so I mailed their technical department. In less than
    an hour, I had a mail back from one of their engineers, with some useful
    suggestions, and a pdf of the service manual attached. Now that's what I
    call support !

    Hey Ron, how's it going ? I also do a lot of Trace Idiot bass heads. Have
    you had a lot of trouble with the main smoothing caps hanging out of the
    board ? I had one just yesterday with an odd smoothing problem. The reported
    problem was that it "cracked up when a bass guitar was put through it, and
    an open E was played". On idle, it sounded fine, no hum or other nasty
    noises. With normal music going through it, again it sounded fine. But when
    40Hz from a signal genny was put in, it sounded harsh like a ripped speaker
    cone. On the scope, you could see a disturbance on the waveform - but
    nothing *really* significant. Turned out that BOTH the smoothing caps on the
    negative rail to the output stage, were COMPLETELY open circuit ! A new pair
    sorted it. It's amazing that it didn't show more obvious symptoms to point
    to caps this badly defective.

    Arfa
     
  12. Ron(UK)

    Ron(UK) Guest

    I,ve seen them mechanically out of circuit due to the solder joints
    being fractured but so far not seen an actual faulty cap. I have seen
    lots of Peavey Impulse powered cabinets with internally intermittent
    o/c smoothers, even replacement ones have failed after a time, yet
    Peavey technical say they haven`t heard of the problem.

    Usually the Trace Elliots come in with the graphic eq board hanging off,
    and the little switches broken. Bass players drive em till they stop
    working!


    Ron(UK)
     
  13. Meat Plow

    Meat Plow Guest

    I owned a Trace 250 head. It was very reliable and I did not baby it. I
    sold it when I acquired a Crown Microtec 1000 amp and a BBE bass preamp
    back in the 90's and have been using that combo for going on 11 years.
    I know when I hit the Crown's on switch it's going to work but I still
    take an old BGW 350 missing a channel along just in case.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-