QSXM2 problem

[zayance]

Hi Again,

Allright, fired the thing up, and  tested all points, for now with Lab PSU.
The build is a mix between SMD and TH., and using SSM for now for ease of troubleshooting, i'l try the BC847BS and 857BS tough for
comparing.
Here are the values, if you have some time? I have some values low and some higher because of BC's beeing CG, but not sure of the lower ones, and i could maybe better match some points, any suggestion is welcome.

Thanks for your help, and sorry to bring this back after all this time  :-)

[zayance]

Hi Again,

So, i'm only able to work on this one during week-ends, so i slowly just keep at it.

Plugged your SSR03 PSU, after this one working good without any load, meaning H1 / H2 lighted up,
output voltage within specs no prob (+/-15V).
But as soon as this one is hooked up to the QSXM2 (Both channels), H1 / H2 lights up for a sec and then lights go out, since there is around
1V voltage drop, from 15V to 13.5/14V on both rails.
Didn't want to post on the PSU section, since this one seems to work as is.
I tried to the PSU to only one channel, and the PSU behaves well, no voltage drop.

Anyway, hope you can find some time to shed some light on this. Even if the T51-54 section seem to be having different behavious then yours since your tests were with 550/560's and not 850/860... (might try to match BC550/560 in this section and see if it gets better values), the circuit seem to be doing fine, and so i wanted to hear if it was passing Audio etc.. but stumbled on this with the SSR03 + QSXM2 so...

Thanks for the help and clarifications,

T.

[peranders]

The SSR03 should be rock stable if you aren't in the current limitation mode. Make sure that your incoming voltage is at least 20 V. Your sense inputs are both connected, tin blob on the solder side.

[zayance]

Make sure that your incoming voltage is at least 20 V. Your sense inputs are both connected, tin blob on the solder side.

I'm using 15VAC Transformer, this one exhibits 17VAC wich give around 24VDC after Bridge, so.... edit: 22.5VDC To be precise at X2
Blobs are there yes.

Thanks

[peranders]

Check that the SSR03 really regulates. Measure the voltage at pin 2 and 3 on the opamp. Those pins should have the same voltage with a millivolt or so.

[zayance]

Hi,

Under no load attached  Pin 2/3 are exact:
Positive Voltage
pin2: +7.41V
pin3: +7.41V

Negative Voltage
pin2: -7.36V
pin3: -7.36V

Under load (both channels of QSXM2) they are off:
Positive Voltage
pin2: +7.31V
pin3: +6.79V

Negative Voltage
pin2: -6.62V
pin3: -7.21V

Those this means both IC's dead?  :-o

[peranders]

The regulators are out of the regulating range. Make sure that you have 20 V in and "in" means on pin 3 of the LM317 (IC1). Check also that your current is under the limit. Check the voltage over the current shunts (R47/R49). It should be under 600 mV

[zayance]

Yes Vreg is at 18VDC at pin 3
Voltage over R47/49 is at about 550mV.

hmm so i guess i should get a 2x18VAC Tranny here.

Thanks for the support Peranders, i'll keep in touch on this one, and hopefully
will be working as it should and ready for fitting in case etc....

[zayance]

Allright, have some days off, yippy....
Used a 2x18VAC SSR03 is doing fine now...

Audio is passing and sounds nice, all seem to be doing well, at least to me ears...
Very dynamic, had an hour listening to various stuff, mainy listening  on headphones (neighbors thank me)
consisting of an Audeze LCD-X, was a nice hour of listening....
EDIT: I have the same oscillation on Preamp out, but it doesn't seem to affect the overall sound as some have mentionned,
so not sure what to think about that....

Still needs an enclosure, it was just dummy metal plate for now....


Thanks

[peranders]

You should try to locate where you have the oscillation and try to cure it. Start with only one channel active and shorted input. If you can measure the frequency or even better having a FFT measurement you may come to the conclusion that it's a radio signal you picking up.