Trace Elliot 715 2006 BX007 board

[JonnyP]

Hi chaps, chapesses,

I've got a 2006 Trace Elliot 715 in for repair, with one of the newer BX007 F amps in - all switched mode and Class D.

They (Peavey / TE) were letting people send these back and swapping the board / modules over a while back, but I've had no joy with them.

The fault is a low frequency buzz / hum (not UK mains - around 108 Hz) coming, (I think) from the switched mode end. I'm suspecting switched mode caps, but does anyone have any info on this?

I've got the schematic, but no TP data, and would be most grateful if anyone has any idea of a common cause.

thanks, J

[Enzo]

108Hz is darn close to 100Hz. In any case, the SMPS runs at many times that frequency, as in well above the audio spectrum. In fact, you can set your scope probe right next to the switcher transformer to pick up the switching signal and see its freq. You cannot scope the primary side without an isolation system, but you can certainly scope the secondary, as it is all earth referenced. If you really think filter caps are failing, it should be apparent on a scope.

Isolate the problem. Is the noise in the power amp? In the preamp? In both? Use your FX loop or pre-out and power-in jacks to do this. Do ANY controls affect the hum in ANY way? That would point to a preamp issue.

[JonnyP]

Ah, ok, it's not really a SMPSU - it's a complicatedly FET switched VRS.

The main filter caps, AC rectified C5 (3300uF 100V) and DC C6 (1000 uF 63V) sides have been pulled and checked on an LCR meter, and are a bit low, but within spec.

None of the cans have burst, bulge, or rattle.

The noise is a variable sawtooth, starts of at 108 Hz, but moves around, and is only on the power amp section, post VRS.

Most of the work seems to be being done by a 2sK3216 n-channel mosfet

All the other regulator circuitry is linear.

This really is too complicated - Peavey and their part numbering system, and lack of part numbers on the board make it too hard to service old gear.

[J M Fahey]

Is this what you are talking about?
Straight from Guitar Center user reviews:

This family of combos has been renamed the 715X because there is a horrible noise issue with the regular 715. Every single amp has the same buzzing sound. The 715X does not have the problem.

Please post the schematic to know what are we talking about, I didn´t understand:

it's not really a SMPSU - it's a complicatedly FET switched VRS.

also:

, AC rectified C5 (3300uF 100V) and DC C6 (1000 uF 63V)

thanks.

[Enzo]

Did you get the schematic from Peavey? generally Peavey drawing sets include layout, which will have part numbers.

[JonnyP]

I have requested the service docs, twice, but they have ignored me. The schematic I have is in this: http://music-electronics-forum.com/a...-715-2009-.zip

It's the BX007 F 200-250W power amp schematic.

[Enzo]

Not to belabor it, but did you use this address?
customerservice@peavey.com?

it is a large company, and if you get the wrong address, the email gets lost.

[J M Fahey]

Ok, now I get it.
According to your schematic it is a Class D amplifier, so far not that bad except they do NOT show the schematic of "mystery custom IC" IC6 which they just call BX001-D and which they probably sell as a replace only prebuilt module.

Big problem is that power supply seems to be a conventional transformer fed one (they do not show it, please post some picture) which feeds a horribly complicated switching *regulator*.

Worst of all worlds, all the weight of standard 50/60 Hz iron with about 3 times the complexity of a straight SMPS, and 20 times the weight.

And to boot, looks like it didn´t work properly , that infamous 108Hz sawtooth wave about many complain might have been a poorly compensated regulated supply, hunting around expected output voltage under load.

[JonnyP]

I sent it to customerservice@traceelliot.com

[Enzo]

Try the peavey address then.

[JonnyP]

Done. Will keep you updated.

[JonnyP]

...still nothing...

[Enzo]

OK, then pick up the phone and call them.

[JonnyP]

I've got my mate at a Peavey Authorised place to contact them. Can't really be bothered with £2 (GBP) a minute call to a GMT -6h place in Mississippi on election day.

[Enzo]

Fair enough, why not include your UK location in your profile then?