fed up with bosoz

[cowanrg]

well, as per poobah's suggestion, i replaced the 750ohm power resistors with some lower inductance ones. im not sure if they are non-inducting, but they are at least better than what i had.

sure enough, it really helped out. im not totally sure if it "fixed" the problem, but it certainly helped out a LOT. now i need to see if its a grounding issue or not. its still got a bit of noise, but it seems to be only a hum now. so, it could be a grounding issue.

BUT, i surely wont be putting those old resistors back. it still has the turn on issue though. however, its now fixed with the velleman unit. before it was so bad that the velleman couldnt even work. now it does. so thats nice.

i have another set of resistors to try that are supposedly zero-inductance, so ill try those to see if gets better, or fixes it. ill have to look at the scope and see whats exactly going on.

edit:

variac is totally right, this thing is possessed.

[poobah]

You can try... but don't hold any hope for those NH's in there... those are power resistors meant for different things. You just need a nice plain jane 3W metal film or metal oxide in there.

Oh, and ditch the big black heat sink, it ain't helping things...

Cheers...

[cowanrg]

Originally posted by poobah
You can try... but don't hold any hope for those NH's in there... those are power resistors meant for different things. You just need a nice plain jane 3W metal film or metal oxide in there.

Oh, and ditch the big black heat sink, it ain't helping things...

Cheers...

the big black heatsink hasnt been on for quite some time. and why is it not helping???

[poobah]

The big black heat sink is making a capacitor (a very small one) between all your outputs (drains), it probably isn't hurting things... but it is NOT helping anything either. The circuit will be just fine with little $0.50 heat sinks that sit flat on the board.

[Super_BQ]

One thing i've noticed on my BLS preamp is the transistors and 750/1.5Kohm resistors tend to give off a LOT of heat. So much that I had to upgrade my heatsinks and chassis mount the resistors.

Some simple checks if you have noise: check to make sure your transistors are completely isolated (ie. separate heatsink or fets isolated with sillypads or mica insulators).

http://www.geocities.com/super_bq/BLS1.html

My 4 channel BLS preamp appeared to be a disaster for ground noise. 2 power supply boards and 4 signal boards ALL off 1 toroidal power supply. I've upgraded to a much bigger 300VA donut and i'll agree, it's MUCH safer than what I had before.

BQ

[jh6you]

I use BOSOZ for unbalanced input and balanced output.
I had the unbalanced volume attenuator at input with ¡°somewhat¡± noise.
Later, I switched it into the balanced attenuator at output with ¡°dead¡± noise.

Good luck.

Regards
jh

[cowanrg]

i really wish i could test the preamp on a full balanced system. thats a LOT of work, as i dont have one here, so id have to make one, or find one... as much time as i have invested in this, i think its almost time to call it even.

a month or so ago, someone saw this thread and offered to sell me a P1.7 board fully populated and tested for a very low price. build quality was great and price was even better. not very DIY, i know, but at this point, this isnt fun anymore. i do this for fun, not for work.

i have a few other things on my plate, but im going to play with the new boards and see if they work ok. if they do, i will have a nice project for sale in the trading post for highest bidder...

i hate giving up on stuff, but for those of you who have been following this project, ive had this thing built for over a year, and been troubleshooting ever since. almost every single part has been replaced at least twice. its getting old...

[cowanrg]

Originally posted by Super_BQ
One thing i've noticed on my BLS preamp is the transistors and 750/1.5Kohm resistors tend to give off a LOT of heat. So much that I had to upgrade my heatsinks and chassis mount the resistors.

Some simple checks if you have noise: check to make sure your transistors are completely isolated (ie. separate heatsink or fets isolated with sillypads or mica insulators).

http://www.geocities.com/super_bq/BLS1.html

My 4 channel BLS preamp appeared to be a disaster for ground noise. 2 power supply boards and 4 signal boards ALL off 1 toroidal power supply. I've upgraded to a much bigger 300VA donut and i'll agree, it's MUCH safer than what I had before.

BQ

my transistors are FULL isolated. they have a little aluminum l-bracket for a heatsink right now, just enough so they dont fry or get too hot. they are not connected to eachother. even before, they had mica isolators, the l-brackets, AND, i used all nylon screws, just in case... but now, they are just kinda floating in free air. i dont have it on more than a minute at a time though, so they arent getting too hot...

also, i think my 800va xformer is big enough. i have tried it with lower power stuff too, a single 50va (for one channel, just as a test), and a 200va also. both had similar (or worse) results...

[lgreen]

It took me a full 2 years to get my 1st bosoz built and working. I understand the frustration, I was there about 5 times.

People might fault you for giving up, but not me, I barely made it.

[jh6you]

Originally posted by cowanrg

. . . , but at this point, this isnt fun anymore. i do this for fun, . . .

Fun not anymore . . . ? OK, here is more.

The original BOSOZ has one C of 1000uF just behind the bridge rectifier.
Replace it with CRCRCRC as shown in the sketch below, Fig.B.
Open you eyes wide and look at the location of the ground point.
Might be a part of help for cleaning up the noise.

Enjoy.

Regards
jh


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diyAudio seems to be getting ugly daybyday . . .