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Roll Call: Who's building, built, or thinking of building a beta22? - Page 161

post #2401 of 2890
2/16/10 at 11:39am
really, just 200ma for the gnd channel, if its not in use? ok, that's small enough to just leave on, I guess.

but I can still use a DPDT to switch the 2 non-gnd connections between the front phones jack and the rear spkr 2 + jacks, right? then the 2 rear - speaker jacks go to the 3rd amp channel (always) and the phones gnd wire also goes to the 3rd amp channel (always). no need for 3 poles in my spkr/phones relay, right?
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post #2402 of 2890
2/16/10 at 3:56pm
Quote:
Originally Posted by LeMat View Post
Finally finished my 3 boards B22... fired up... 2 boards working perfectly but the ground channel .. quite the opposite. Leds are on, r9 is 4.5v but i have 0mv across R34... damned !
If there is something obvious coming to your mind, please share ! Otherwise, what's the better way to debbug it / narrow down the possible issue ?
Quote:
Originally Posted by amb View Post
LeMat, tried looking back at past posts in this very thread?
I didn't have the time to browse 3100 posts so I sticked to the schematic and did some tests.. Oddly one of the Mosfet wasn't working properly and after replacement, miracle.., my last board works ! In the process I've lost Q25 which blew up for I don't know what reason.
I found it quite rewarding to solve the problem by myself
Now i have to order a BJT550 to enjoy my amp ! A chance I also realized i messed up when ordering a part for the e12 (wrong dpdt relay).. I didn't want to pay 8$ of shipping for 0,02$ part !
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post #2403 of 2890
2/16/10 at 4:53pm
LeMat - I can mail you a couple 550's if you want. PM me your address.
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post #2404 of 2890
2/16/10 at 8:54pm
Quote:
Originally Posted by linuxworks View Post
but I can still use a DPDT to switch the 2 non-gnd connections between the front phones jack and the rear spkr 2 + jacks, right?
Yes.

Quote:
then the 2 rear - speaker jacks go to the 3rd amp channel (always)
If you want the ground channel amp to source/sink the return current, then yes. Otherwise, these go to the PSU 'G'.

Quote:
and the phones gnd wire also goes to the 3rd amp channel (always). no need for 3 poles in my spkr/phones relay, right?
Yes. A DPDT switch is all you need, either way.
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post #2405 of 2890
2/16/10 at 11:56pm
Over the last few weeks I've noticed a quiet hiss that lasts for maybe a tenth of a second and occurs every few seconds (not at a constant rate, seemingly random in occurrence and exact sound). It doesn't occur all the time, sometimes it does it a lot, usually not at all, sometimes just a little. It is volume knob related and when the volume is at zero it's totally silent, and at max the noise is very loud. At listening volumes it's quite quiet but definitely there. Does this mean it's outside of the volume knob? Even with source unplugged it does it and I don't understand how the wire from the knob to the RCA jacks could do this. I didn't change anything, It's just started doing it recently.
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post #2406 of 2890
2/17/10 at 12:04am
So guys is this amp worth the price?
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post #2407 of 2890
2/17/10 at 12:21am
Quote:
Originally Posted by dude_500 View Post
Over the last few weeks I've noticed a quiet hiss that lasts for maybe a tenth of a second and occurs every few seconds (not at a constant rate, seemingly random in occurrence and exact sound). It doesn't occur all the time, sometimes it does it a lot, usually not at all, sometimes just a little. It is volume knob related and when the volume is at zero it's totally silent, and at max the noise is very loud. At listening volumes it's quite quiet but definitely there. Does this mean it's outside of the volume knob? Even with source unplugged it does it and I don't understand how the wire from the knob to the RCA jacks could do this. I didn't change anything, It's just started doing it recently.
Sounds like a minor joint has become cold, I’d check around the pot especially the ground wiring, make sure all joints are secure. Give each wire a good tug and make sure each connection has a good contact. The hiss is from both channels?
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post #2408 of 2890
2/17/10 at 12:25am
Quote:
Originally Posted by johnwmclean View Post
Sounds like a minor joint has become cold, I’d check around the pot especially the ground wiring, make sure all joints are secure. Give each wire a good tug and make sure each connection has a good contact. The hiss is from both channels?
Seems a tad louder in the left side but it's in both. I'll run over the solder joints and report back if I'm still having problems
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post #2409 of 2890
2/17/10 at 1:46am
Maybe cell phone interference?
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post #2410 of 2890
2/18/10 at 2:57am
Hey guys, i've got a random thought. I have read that the beta 22 runs real hot. So, is it possible to add a fan in the casing, such as what little dot do to the mkvi+?
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post #2411 of 2890
2/18/10 at 3:21am
Quote:
Originally Posted by DemonicAngelz View Post
Hey guys, i've got a random thought. I have read that the beta 22 runs real hot. So, is it possible to add a fan in the casing, such as what little dot do to the mkvi+?
Sure it runs hot it’s heavily biased class A, but properly ventilated and cased this is not a problem, unlike the LD MKVI which is not and needs a silly fan IMO.
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post #2412 of 2890
2/18/10 at 4:39am

that is at approx 140mA on the output stage...it was connected for about 30 minutes to see how much the everything drifts. I would say that the b22 is pretty sensitive to temperature it takes about a good 20 minutes to warm up and stabilize. the input stage and output stage readings are all over the place until it warms up fully.

has anyone Water cooled their b22 yet? i think they make mosfet copper water jackets that could span across a mosfet quad.

seeing how sensitive to temps the JFETS are, i noticed that people orient their b22 boards across or in line from each other #O #O #O #O (each Jfet is close to a hot heatsink except the first or last). that would mean 3 JFET quads are hot and 1 is cold is that optimal?
maybe oriented like this #O O# #O O# you would have all equally warm quads. # represents the hot heat sinks and O are the JFET side
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post #2413 of 2890
2/18/10 at 5:20am
I wouldn't worry about equalizing the temps around the input JFETs across the boards. As long as the temperature gradient between Q1/Q2 and Q3/Q4 is minimal (and they should be due to the close proximity), all would be well.

Btw, the #O O# #O O# arrangment that you mention is how many people have built their balanced β22s. including the group-build β22 (see pics in the β22 website gallery) .
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post #2414 of 2890
2/18/10 at 8:46am
I was moving my setup into a more permanent case and doing some rewiring / testing...

long story short there was a loose wire and the v+ from the sigma shorted to the signal ground on the beta i believe i am not 100% sure thats what happened but judging from the wires positioning and my glancing looks i think thats what i saw...

the sigma wont power up now... so just wondering if any have had this happen before so i dont have to start testing each thing any help would be appreciated....

thanks
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post #2415 of 2890
2/18/10 at 8:50pm
boinger, "won't power up" isn't very much info...
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