Trace SMX faults for repair

[Deedee]

I’ve just purchased a ‘spares or repair’ AH250 GP12 SMX, purely because it was local, has all the correct (hens teeth) buttons, knobs and switches and sports an unmarked faceplate.

Anyhoo, opened the case up to have a nosey (not that I know what I’m looking at) and there’s a post-it note in there that says:

Requires TR1, TR2 plus output rebuild.

Does anyone know what that means exactly and whether it’s as big a job as it sounds? I’m not fussed either way as I bought it for spares should I ever need them, but I must admit to being very curious.

Thanks

 

Edited March 4, 2019 by Deedee

[3below]

 

Depending on how diy electronics you are, the following website looks useful. TR1 and TR2 are TO92 packaged BF423 about 12p each. Lots of good pics and even better ,big pcb tracks and full size components. Repair heaven

 

https://www.circuitsonline.net/forum/view/121282/1?query=doe+hand&mode=or

Output mosfets can be found,  they seem pricey or modern alternatives  https://www.diyaudio.com/forums/parts/9502-j50-k135-mosfet-replacments.html

 

https://www.ebay.co.uk/itm/ECF10P20-ECF10N20-BUZ900-BUZ905-PAIR-TRANSISTOR-TO-3-SOLD-IN-PAIR-/192263936928  it will be £45 to £50 for two pairs. 

 

Sorted, this will be an amp for life   let me know if you want to send it to a good home....

Edited January 15, 2019 by 3below

[itu]

3below sent an excellent link, although you may need translator for a moment...

If you look at the picture (or probably the actual unit), there are those four big transistor up left. Under the two rightmost big MOSFETs there are two parts missing, so those transistors. You can find them by reading the PCBA.

Transistor type is BF423.

https://www.onsemi.com/PowerSolutions/product.do?id=BF423

I have to say that there may be something else that is faulty, too, but trial surely is not very expensive.

[Deedee]

Many thanks. I’m useless with electronics so it’s probably not something I’d attempt myself.

EDIT - Although now I can see on the image that they’re just plug in, even I may be able to manage that 😂.

For the record the unit powers up. All the switch lights work and all the knobs and sliders feel solid and secure. It’s just that there’s no sound from it.

I’ll take the lid off my other SMX (same model) and compare and contrast.

Edited January 15, 2019 by Deedee

[itu]

Not just plug in, but they need to be soldered. And as there is something with the output, please contact your tech.

[PaulWarning]

I had the output transistors replaced on exactly the same amp, total bill was £130 (with labour), someone else on here got it done for £110 if my memory serves me correctly (not sure if it was the same amp though), get it done, money well spent. IMO, I don't regret it, great  amps and not that heavy either

Edited January 16, 2019 by PaulWarning

[Deedee]

2 hours ago, PaulWarning said:

I had the output transistors replaced on exactly the same amp, total bill was £130 (with labour), someone else on here got it done for £110 if my memory serves me correctly (not sure if it was the same amp though), get it done, money well spent. IMO, I don't regret it, great  amps and not that heavy either

I'll certainly get it done at some point. I'm a big fan of the SMX and used to have several of these in various guises (see pic). I still have one as my main workhorse plus another incoming, plus my MkIV AH250 and now this one for spares/repair so there's no great rush at the moment. 

[Deedee]

This is now for sale on the forum as spares or repair if anyone is interested:

 

https://www.basschat.co.uk/topic/338237-trace-elliot-ah250-gp12smx-spares-or-repair-£50/

 

Edited March 2, 2019 by Deedee

[paul_5]

well worth repairing IMHO. Not sure why transistors are labelled TR1 & TR2 instead of Q1 and Q2, as per standard electronics nomenclature, but still worth doing.

[Cook1e]

I'd like to take that off your hands, if it's still available?

Where in South Yorkshire are you? My old Mum's in Rotherham, could be an excuse for a visit...

Edited March 2, 2019 by Cook1e

[Japhet]

I had one of these and there was apparently a manufactureing issue where there was an earth wire that was prone to coming loose which took out the output section. I had mine repaired for around £100 but it's worth checking and improving the earth to stop it happening again. Lovely amp by the way.

[TheGreek]

I've mailed my Tech guy for a quote on the cost or the repair. I'll let you all know when I do...

[Deedee]

Thanks all. It sold last night anyway so it’ll be winging it’s way to a new owner tomorrow.

Edited March 3, 2019 by Deedee

[Deedee]

EDITED

Forget that, I'll open another thread 🙁

Edited March 4, 2019 by Deedee
Deleted

[rmorris]

On 02/03/2019 at 20:45, paul_5 said:

well worth repairing IMHO. Not sure why transistors are labelled TR1 & TR2 instead of Q1 and Q2, as per standard electronics nomenclature, but still worth doing.

Both 'TR' and 'Q' have been commonly used for transistor component references.

Similarly an integrated circuit may commonly be 'U' or 'IC' etc... 

[Davy]

On 16/01/2019 at 11:51, Deedee said:

I'll certainly get it done at some point. I'm a big fan of the SMX and used to have several of these in various guises (see pic). I still have one as my main workhorse plus another incoming, plus my MkIV AH250 and now this one for spares/repair so there's no great rush at the moment. 

Good lord! I hope that's a concrete floor beneath the amps!