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NAD - Trace Elliot GP12 SMX 250


ahpook
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After messing around with pre and power amps for many years and growing ever more tired of the sound of fans, I decided to go back to all-in-one peace and quiet amps.

This arrived today - built mid-May 1993 (about the time I met Mrs. Pook as it happens) and in good condition bar some crackles that some switch cleaner sorted out very quickly.

Sounds lovely, except for one niggle - there's a slight buzz though the speakers even when the unit is on standby - I'm guessing this is the call for new power supply capacitors, an easy fix and I think overdue for an amp this age.

There, back in the Big Green club :)

 

GP12.jpg

Edited by ahpook
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3 hours ago, burno70 said:

Get in - love these amps. Had one back in the day, sold it to go to uni and wanted to get a replacement ever since. Seeing this makes me want to scratch that itch.

Years ago, I used to have a 150W GP7 - as I unpacked the new amp I got a little touch of excitement at seeing the green livery again :)

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Ha, only gone and broke it haven't I ?

The output knob was sticking a long way out of the fascia, so I gave it a gentle push (yes, a gentle one) and the control shaft crunched straight through the back of the pot. I suspect it's had a knock at some point - there wasn't a great deal of resistance to it being turned before.

Oh well, another job to do when I re-cap it

Best it happens now, at home, rather than later, and it's not like I don't enjoy a bit of tinkering :)

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I've read a couple of threads recently where GP12 SMX owners report noise coming through independent of volume settings. I wonder whether the SMX series is more susceptible to mains hum or other interference than the earlier less featured series? 

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56 minutes ago, Sparky Mark said:

I've read a couple of threads recently where GP12 SMX owners report noise coming through independent of volume settings. I wonder whether the SMX series is more susceptible to mains hum or other interference than the earlier less featured series? 

It could be the case, it would be a shame though.

I can't remember if my old GP7 did the same - when I get the new volume pot I'll give it a proper once-over, see if some more intensive TLC could help.

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On 20/08/2019 at 13:41, ahpook said:

After messing around with pre and power amps for many years and growing ever more tired of the sound of fans, I decided to go back to all-in-one peace and quiet amps.

This arrived today - built mid-May 1993 (about the time I met Mrs. Pook as it happens) and in good condition bar some crackles that some switch cleaner sorted out very quickly.

Sounds lovely, except for one niggle - there's a slight buzz though the speakers even when the unit is on standby - I'm guessing this is the call for new power supply capacitors, an easy fix and I think overdue for an amp this age.

There, back in the Big Green club :)

 

GP12.jpg

Welcome Home! Tell me how do you find the Kustom gear? 

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On 23 August 2019 at 14:30, stewblack said:

Welcome Home! Tell me how do you find the Kustom gear? 

It's OK, certainly not brilliant, but perfect for what I wanted it for - a small cab for my little home studio/spare room which won't swamp the room with bass.

I've used it at two rehearsals and it doesn't fill the room like my SWR 2x12 but is more than audible and did fine.

For £45 it was hard to argue with !

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I've been a Trace user since 1989 when I purchased a Series 6 GP7 Combo which I still use today, a great amp, serial number ends in 419, anyone know the year ?

It's not that long ago since I replaced the caps in the power supply, they were starting to bulge !

I came across this article about Clive Button who designed all the trace amps and speakers, some great reading.   http://www.clivebutton.com/

Thanks for this post, all good trace stuff lol 

 

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5 minutes ago, whamni said:

I've been a Trace user since 1989 when I purchased a Series 6 GP7 Combo which I still use today, a great amp, serial number ends in 419, anyone know the year ?

Usually the best way to check the year is to look inside the amp as there should be a QA label with a date on it affixed to the board. Although if you've already been inside I'm suspecting yours doesn't.

Edited by Deedee
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Little update - I removed and desoldered the popped potentiometer from the PCB that connects it to the rest of the circuit and gave the whole thing a right proper clean - even took out the glowy green plastic control surrounds out and gave them a wash. Ooooh, they were grody.

Sorry, forgot to take any photos - I'll post some when I get the replacement parts and start putting it back together.

 

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38 minutes ago, ahpook said:

Not this one I fear - it's in about 5 pieces !

Ah ok. Definitely dead so!

Those SMX heads are great. Thick and punchy. I still have a great love for Trace. Have a few heads here. This is the main one. Have it since 1993 more or less (sold it for a short while and bought it back). Still a great thump, despite weighing a ton.

 

20170224_185205[1].jpg

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1 hour ago, LennyP said:

Ah ok. Definitely dead so!

Those SMX heads are great. Thick and punchy. I still have a great love for Trace. Have a few heads here. This is the main one. Have it since 1993 more or less (sold it for a short while and bought it back). Still a great thump, despite weighing a ton.

 

20170224_185205[1].jpg

Nice, I bet it sounds as solid as it looks !

I've got most of the bits of the pot - when I do the surgery pics I'll see if I can take one of the remains.

 

 

Edited by ahpook
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Right then, back up and running....and a saga. Oh how we love a saga !

As promised @LennyP there's a pic of the busted pot. Or at least the biggest bits :)

Also the head with the fascia off. I like the bent bits of silver metal to keep the light from the lamps in the right places to illuminate the labels and logo from behind.

So then...why the saga ? And why did he have the main board out if he was just changing a pot ?

Well, after putting the new pot in, strange things started (and didn't start) happening. The 3-LED level indicator didn't work and the EQ was in a mess - constant cracking in the background when it was engaged and moving the sliders did a) nothing b) made the sound get distorted and disappear or c) acted as strange volume controls. Harrrumph #1

Next step - I pulled the EQ/Level indicator board and gave all the sliders a thorough clean. They were filthy. Two rounds of switch cleaner and isopropyl alcohol were needed to get them ship-shape. Checked the board and reflowed some of the less savoury connections. Back together....still the same problem. Harrumph #2.

After some pondering of the circuit diagram and removing the feeds to and from the EQ board I realise that it's most likely the problem is on the main PCB, not the front slider/level indicator board. Time to get some proper disassembly done (Pic 3). It's built like a tank, so this was quite good fun.

Soldering iron on, pot of tea made and some Suzanne Vega to listen to and I started on the clean-up and partial reflow. Did all the pots and switches as well as a couple of strange-looking solder joints in the EQ circuit. Everything else looked very solid so rather than make problems I stopped there and reassambled.

And it works ! Whoo-yay !

Sounds spiffing too, still has the background noise on standby, but it's not too bad and I may still give it another service at a later date, but for now Matthew, I'm off to be Tony Levin for a bit :D

BustedPot.jpg

TEFront.jpg

TEBigBoard.jpg

Edited by ahpook
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52 minutes ago, ahpook said:

Right then, back up and running....and a saga. Oh how we love a saga !

As promised @LennyP there's a pic of the busted pot. Or at least the biggest bits :)

Also the head with the fascia off. I like the bent bits of silver metal to keep the light from the lamps in the right places to illuminate the labels and logo from behind.

So then...why the saga ? And why did he have the main board out if he was just changing a pot ?

Well, after putting the new pot in, strange things started (and didn't start) happening. The 3-LED level indicator didn't work and the EQ was in a mess - constant cracking in the background when it was engaged and moving the sliders did a) nothing b) made the sound get distorted and disappear or c) acted as strange volume controls. Harrrumph #1

Next step - I pulled the EQ/Level indicator board and gave all the sliders a thorough clean. They were filthy. Two rounds of switch cleaner and isopropyl alcohol were needed to get them ship-shape. Checked the board and reflowed some of the less savoury connections. Back together....still the same problem. Harrumph #2.

After some pondering of the circuit diagram and removing the feeds to and from the EQ board I realise that it's most likely the problem is on the main PCB, not the front slider/level indicator board. Time to get some proper disassembly done (Pic 3). It's built like a tank, so this was quite good fun.

Soldering iron on, pot of tea made and some Suzanne Vega to listen to and I started on the clean-up and partial reflow. Did all the pots and switches as well as a couple of strange-looking solder joints in the EQ circuit. Everything else looked very solid so rather than make problems I stopped there and reassambled.

And it works ! Whoo-yay !

Sounds spiffing too, still has the background noise on standby, but it's not too bad and I may still give it another service at a later date, but for now Matthew, I'm off to be Tony Levin for a bit :D

BustedPot.jpg

TEFront.jpg

TEBigBoard.jpg

That pot was definitely busted! I've seen them with a lot of dry solder joints in the past. Great sounding amps though. Always found them very reliable when treated well. The EQ balance control is superb in these when switching between genres of music.

Well wear with the amp.  Still love a good old MKV though - That's my favourite Trace tone. Very hard to find a good one these days though. 

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18 hours ago, Sparky Mark said:

Unless you look at my Mk V head for sale on here!

20190831_171636.thumb.jpg.12ed495ccad6198c6689c385c3e0fcd1.jpg

😄. Good one! Great condition. Very clean faceplate with all knobs present. 

The cost is a bit prohibitive to bring it from the UK to Ireland unfortunately. I have the MK4 version which was taken from a 410 combo like yours. Reminds me that I need to get a sleeve for it!

Ideally, the AH250 is the one for me. Plenty of poke. 

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39 minutes ago, LennyP said:

Ideally, the AH250 is the one for me. Plenty of poke. 

When you compare the power amp sections from the AH200 and the AH250 they appear to be the same. I wonder whether Trace Elliot realised they were understating the AH200 and for marketing differentiation specified the later model as 250 watts?

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See...now I've put it back together (well, bar getting the front panel off again as one of the level LEDs was out of whack....didn't mind at first, but after a couple of hours it became too much :D ), I'm starting to wonder again about the background noise.

I gave all the boards a good flexing when it was powered up and nothing seemed to affect the noise then, but maybe a reflow on the power side might help...I'm wary of applying too much tinker !

lovejoy_uk.tinker_dill.jpg

Edited by ahpook
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