# Trace Elliot GP12 amp

N

#### N Cook

Jan 1, 1970
0
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.
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.

H

#### Homer J Simpson

Jan 1, 1970
0
I cannot find anything wrong with it now.

It does/doesn't work?
Anyone familiar with these amps.?
I'm surprised the Cockroft Walton pump cirrcuit is enough to power the HT
of
the ECC83.

Not a pump, a full wave bridge.

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A

#### Arfa Daily

Jan 1, 1970
0
Homer J Simpson said:
It does/doesn't work?

Not a pump, a full wave bridge.

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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

N

#### N Cook

Jan 1, 1970
0
Ron(UK) said:
How did you find the circuit diagrams from the main site ?

Ron(UK)

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
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

R

#### Ron(UK)

Jan 1, 1970
0
N said:
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/

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. Im 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.

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

Ron(UK)

N

#### N Cook

Jan 1, 1970
0
Ron(UK) said:
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. Im 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.

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

Ron(UK)

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.

N

#### N Cook

Jan 1, 1970
0
Arfa Daily said:
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

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.

H

#### Homer J Simpson

Jan 1, 1970
0
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.

Perhaps they are a subsidiary of Lucas?

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N

#### N Cook

Jan 1, 1970
0
Ron(UK) said:
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. Im 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.

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

Ron(UK)

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.

A

#### Arfa Daily

Jan 1, 1970
0
N Cook said:
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.
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

Arfa

R

#### Ron(UK)

Jan 1, 1970
0
Arfa said:
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

Arfa

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 havent 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)

M

#### Meat Plow

Jan 1, 1970
0
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)

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.

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