65V means sum of rails ?
as at +/-32V5?
I can't see anything wrong on picture
have mica put to BD transistors, to have them isolated from each other?
of course, it's implying to have all components in proper places .... but in this case first thing to check - are BD transistors not swapped?
one thing more, generally - when working on new amp, it's clever powering up (and setting) one channel at a time
as at +/-32V5?
I can't see anything wrong on picture
have mica put to BD transistors, to have them isolated from each other?
of course, it's implying to have all components in proper places .... but in this case first thing to check - are BD transistors not swapped?
one thing more, generally - when working on new amp, it's clever powering up (and setting) one channel at a time
Sorry, was referring to Variac voltage, not rail voltage. Mica is installed. I will double check the BD transistors orientation. I replaced the resistors and retried one channel at a time. Same result unfortunately.
Wade
Wade
test each and every semiconductor in situ
if in doubt, desolder and test out of pcb
I know that each big heatsink is having holes deburred, so slight chances of perforated mica..... but check that too with ohmmeter
there must be something amiss, in both channels
if LED is lit, bases of BD transistors are at proper potentials, so current through BD string is set by value of 43R resistor
if 43R is toasted, only possible explanation is short somewhere or improper part
I hope you did follow short setting procedure from post #1
if in doubt, desolder and test out of pcb
I know that each big heatsink is having holes deburred, so slight chances of perforated mica..... but check that too with ohmmeter
there must be something amiss, in both channels
if LED is lit, bases of BD transistors are at proper potentials, so current through BD string is set by value of 43R resistor
if 43R is toasted, only possible explanation is short somewhere or improper part
I hope you did follow short setting procedure from post #1
Thanks ZM. Initial issue fixed...tied to BD error as you predicted. Amp now powers up fine. Following short setting procedure from post #1:
Left Channel: IQ maxes out at 175mV. Offset is stuck at 26.2V and doesn't budge regardless of Offset Trimpot adjustments.
Right Channel: IQ set at 200mV; Offset at <5mV
So I need to figure out what's going on with left channel.
Left Channel: IQ maxes out at 175mV. Offset is stuck at 26.2V and doesn't budge regardless of Offset Trimpot adjustments.
Right Channel: IQ set at 200mV; Offset at <5mV
So I need to figure out what's going on with left channel.
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power off, check all semis in FE
something else gone south
power up again only when you're sure that you fixed all bad components
something else gone south
power up again only when you're sure that you fixed all bad components
Q: The XA252 US FE is the addition card needed for Ultrasymetry / Balanced .. but this schematic was never released, only the simplified ?
Does the US version still have stability issues ?
I would like to support your work and buy a XA252 US FE set (one chn) and incorporate it in my SMT work if the circuit is stable. If the US is not ready, I will wait for that one.
Does the US version still have stability issues ?
I would like to support your work and buy a XA252 US FE set (one chn) and incorporate it in my SMT work if the circuit is stable. If the US is not ready, I will wait for that one.
Hi ZM,
before I start heating up the soldering iron, I would like to ask if this schematics is correct for the SET version (your post of 12/18/2022). If so, are the annotations "do not mount..." irrelevant to the SET version? What does "C15 not fitted" mean - should it be left out (because it's not fitted anyway) or should it be fitted because it's not fitted yet?
Many thanks in advance.
before I start heating up the soldering iron, I would like to ask if this schematics is correct for the SET version (your post of 12/18/2022). If so, are the annotations "do not mount..." irrelevant to the SET version? What does "C15 not fitted" mean - should it be left out (because it's not fitted anyway) or should it be fitted because it's not fitted yet?
Many thanks in advance.
bridged XA252 is waiting for my time for final developing work
it consists of 3 pcbs - FE + 2 OS pcbs (each going on one side/heatsink)
when it's done, it's done
until then, consider it as writing on Tom Sawyer's plank fence
it consists of 3 pcbs - FE + 2 OS pcbs (each going on one side/heatsink)
when it's done, it's done
until then, consider it as writing on Tom Sawyer's plank fence
yeah, post #624 https://www.diyaudio.com/community/...2-sit-babelfish-xa252-set.373443/post-7206721
that's pretty much final SET schm
only difference you can find is - do you have 3W resistors groups of 3 (0R33) or 5pcs (0R56)
caps - not fitted means - not needed
so, consider that I did all necessary smd work, through hole is up to you
Got it. I know you have a lot on your agenda and things take time... No worries, I more or less only need a SE version atm.
Well, it's fairly unfair...
As soon as I decide to build the SET version, a bridged version is announced... and triggers the cramped "want to have" effect... 🤪
as double Gemini .......... consider that 15 ZMs are busy having wild ideas, while only me - 16th ZM is actually producing them
so, plenty of things on everchanging list, prior to Mighty XA252
not overly believer in Horoscope, but some things in my life are easiest explained that way
I was told - "if you're Gemini, that's same as there are two of you, but if you're also Gemini in sub-sign........ that's not as there are 4 of you, rather 16......... "
O plethora, O mores!
I keep hearing about ordered PCBs that are sitting on the shelf. I can imagine what that shelf looks like!as double Gemini .......... consider that 15 ZMs are busy having wild ideas, while only me - 16th ZM is actually producing them
so, plenty of things on everchanging list, prior to Mighty XA252
not overly believer in Horoscope, but some things in my life are easiest explained that way
I was told - "if you're Gemini, that's same as there are two of you, but if you're also Gemini in sub-sign........ that's not as there are 4 of you, rather 16......... "
O plethora, O mores!
Oh, that can be complicatedas double Gemini .......... consider that 15 ZMs are busy having wild ideas, while only me - 16th ZM is actually producing them
so, plenty of things on everchanging list, prior to Mighty XA252
not overly believer in Horoscope, but some things in my life are easiest explained that way
I was told - "if you're Gemini, that's same as there are two of you, but if you're also Gemini in sub-sign........ that's not as there are 4 of you, rather 16......... "
O plethora, O mores!
But as long as you don't fight each other...
And being a Cancer, I understand the meaning of a horoscope... and the explanation of the weird things in life 🤪
Pulled T1-T7 off board and did basic multimeter voltage drop test. They all passed. Also did same for JFETS on board and they also passed.
well, something is wrong
having one channel behaving, you can at least do some ohmmeter/diode test measurements, comparing good vs. bad channel
check resistors around/up/down BD transistors; trimpot too
having one channel behaving, you can at least do some ohmmeter/diode test measurements, comparing good vs. bad channel
check resistors around/up/down BD transistors; trimpot too
well, trimpots are used as variable resistors, so one outer and wiper pins are shorted
similar you have in current mirrors in OS biasing circuit - two transistors are having base connected to colector, but through 100R base resistor
besides that, no deliberately shorted pins on components
again, you have one working channel, as reference for troubleshooting other one
similar you have in current mirrors in OS biasing circuit - two transistors are having base connected to colector, but through 100R base resistor
besides that, no deliberately shorted pins on components
again, you have one working channel, as reference for troubleshooting other one