BTL2101 by Wang Qiao

[klc-audio]

I have a System Audio SA 175 subwoofer which from time to time puts out a lot of DC for about a sec or so. Not good!
I have isolated the fault to the power amp board. There is a black box named BTL 2101 and the output stage is IRFP260 (4 pcs)
Powersupply seems OK so I believe the black box is somehow messed up.

Does anybody know anything ?

Thanks you

 

[ManUtd]

Hi,
Do not know if You got it repaired, did you?
I suggest changing all capacitors on amp board before changing BTL chip.

 

[sloop81]

same problems with same sub...

I have the same issue...
On top of this... the HUGE transformer has single output of around 60V ... sooo... not dual power supply...
I don't know why they use this **** in a nice piece o equiptment (and expensive).

Any options (BTL 2101 chip is dead) ... the rest is fine... it s only this final amp board...

 

[sloop81]

Anyone? I can't find similar schematics (+62V single supply)

 

[Bruce@bluff]

There is a simple bridge mode circuit in LT spice that could easily be modified to run off a single 60volt single supply and with a few more modifications could work with the mosfets on the board, but it mostly depends on your electronics knowledge and experience. I don't have any experience in using LT spice a gentleman by the name of Mooly would be your resident expert, but I do have a lot of experience with single supply amplifiers

 

[sloop81]

There is a simple bridge mode circuit in LT spice that could easily be modified to run off a single 60volt single supply and with a few more modifications could work with the mosfets on the board, but it mostly depends on your electronics knowledge and experience. I don't have any experience in using LT spice a gentleman by the name of Mooly would be your resident expert, but I do have a lot of experience with single supply amplifiers

I think it need to be BTL type to get the needed power from 60V. Also no output cap schematics is a must for a subwoofer amplifier.

 

[Bruce@bluff]

The LT spice model is a BTL type amp with a single supply ( app 20v). There is also a single supply amp in the October 1970 issue of Wireless World which you can download from American Radio history read the article it will give you a good insight into single supply BTL amps. There are no caps in that design as the outputs are or should be at the same dc potential

 

[sloop81]

The LT spice model is a BTL type amp with a single supply ( app 20v). There is also a single supply amp in the October 1970 issue of Wireless World which you can download from American Radio history read the article it will give you a good insight into single supply BTL amps. There are no caps in that design as the outputs are or should be at the same dc potential

I know the schematics but they are no were near 300w/4ohm ... very low power, also low voltage... i need over 60V DC.

The only schematic that has some power si Autona AL125 but this uses output capacitor. Schematic it s here with modern parts (4xMJL4281 on output) but still no were near the original amplification that has 300w ... the original transformer is huge at 407VA.
https://www.diyaudio.com/forums/solid-state/236256-retro-amp-50w-single-supply-33.html#post5447476

 

[Bruce@bluff]

You can bridge the autona al125. I have done it before and it works well at 60v I am quite sure you would get 200 watts into 4 ohms with a 60v supply however I would replace the 2n3055 with mj15003 or MJL4281 and use Rod Elliots simple bridging adapter. You can leave out the caps as in the Wireless World circuit as the output is at the same dc potential. You could use the AX6 shown in the retro amp 50w single supply but I have not tried it in bridge mode, but the article in WW says it would be better to use a differential pair for the phase inversion the article explains in detail why.

 

[Bruce@bluff]

a 470Va transformer will easily give you 200watts into 4ohm load

 

[Bruce@bluff]

I have attached a pic of the WW circuit unfortunately the whole article is too big to load but will give you and idea of how a single supply BTL circuit works

 

[Bruce@bluff]

I have attached the WW single supply circuit

 

[HansMio]

I have the same sub (SA175) and the same problem.
It stated with cracking and popping and now it outputs DC and makes some seconds brake.
Has someone succeeded in changing the BPL2101 brick???

 

[sloop81]

I have the same sub (SA175) and the same problem.
It stated with cracking and popping and now it outputs DC and makes some seconds brake.
Has someone succeeded in changing the BPL2101 brick???

Nothing soo far... nothing to came close the 380W claimed.
No similar schematics found... after a full year of research.