Babelfish XA252 / Babelfish XA252 SIT / Babelfish XA252 SET

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#2,181
cwlo said:
Russell, see if you can cleanup that whole area. R21 solder pad looks like it could be touching adjacent c6. BD sandwich missing mica? I got a Hakka desoldering tool when I had my issues, and it made the removal of components so much easier and cleaner. Also, I was able to test probably 95% of the components installed, so using your dmm and super gizmo tester should find the problem.
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Mica there, I think a desoldering station is in my future! I get why it blew up, flat out careless on my part. confused as to why "fix" failed. Obviously, something about repair is different than it originally was. Almost hope I screwed up Q1 and Q2 locations...
 
#2,182
For now, I devised next gen, having 2 LEDs in series as base spreader, allowing use of 2*91R in between emiters, at least partially decreasing Poof possibility


Knowing this, should I wait on getting XA 252 number 2 until changes made? Or staying like it is? I just want another all mosfet/puck amp for other system.

Russellc
 
#2,184
Q1 and Q2 are removed and measure fine. Will replace anyway. R24 only thing looking cooked.

Will also post pics of boards once parts are removed, and again once parts swapped out.

Will remove and test T6. Anticipating it is fine, but will replace along with R19 and other parts, like last time ..
 
#2,185
Zen Mod said:
stay with changes you made for one you have, just avoid nasty plops

I'll soon make batch of pcbs for iteration with current limiting, so hopefully no smoke with even most wakoo gremlins
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Apparently I have wakoo gremlins. Should I replace everything again and do board off pucks testing?

It is puzzling that first off, previously amp worked great. Changed parts. First channel works fine. Second channel not so much. Must have mistake in second channel. I really thought I may have reversed Q1 and Q2, no such luck.
 
#2,186
you need practically to check every passive and active part, ref. to linked/nested schm, starting from R17 down and then going through numbers to right, ending with Q1 & Q2 with their common emiter resistor (which you redid to 2 series ones)



babelfish-xa252-sit-sch-png.958925
 
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#2,187
Zen Mod said:
@william2001

Study Papa's New Stasis FE - there is limiting cell (Q4) where it needs to be
When I asked Pa about that detail, his answer was pretty much like "prevention of disaster in case of..."

Now you know and I know ........

Though, ZM need to build more cleverness to implement any sort of no-invasive limiting zingy in existing emiter follower stage in XA252

For now, I devised next gen, having 2 LEDs in series as base spreader, allowing use of 2*91R in between emiters, at least partially decreasing Poof possibility


that enables next step - no other way than adding few smd bjts and few smd resistors, monitoring current through each 91R emiter resistor, and clamping BD bases when current goes to - say 40mA


attached Papa's Stasis FE

Clever Pa.......
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I like the sound of decreasing poof possibility.
 
#2,189
Zen Mod said:
you need practically to check every passive and active part, ref. to linked/nested schm, starting from R17 down and then going through numbers to right, ending with Q1 & Q2 with their common emiter resistor (which you redid to 2 series ones)



babelfish-xa252-sit-sch-png.958925
Click to expand...
So R17, R18, R19, R20, R21, R22, R23? And R24. Any other passives?

Besides T6, Q1 an Q2. Should I add the other "T" actives, and any others. Not sure what is meant by "going through the numbers on the right" all includes? I assume All the T active devices, 1 through 7?

Thanks. I believe I have all parts on hand...
 
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