De-APOCing my B&W 802 Series 80s - Question

[Zonker92]

OK, here's the schematic for my crossovers, including the APOC protection circuit (at the bottom), which is powered by my amp, and is not battery powered:

http://www.bwgroup-support.com/downloads/techmanuals/bw/802-TM.pdf

Photos of the crossover appear here:

http://www.head-case.org/forums/do-yourself/9007-b-w-802-series-80-repair-5.html#post404176

and here:

http://www.head-case.org/forums/do-yourself/9007-b-w-802-series-80-repair-3.html#post402352

and here:

http://www.head-case.org/forums/do-yourself/9007-b-w-802-series-80-repair-5.html#post404221

I can see which points to connect on the PC board to bypass the relay; that's no big deal. My question is, is it true that the only other thing I should do, to bypass the APOC circuit, is remove the three diodes?

Bonus question: Why would this procedure have any sonic benefits, as I keep reading?

Thanks!

Eric

[Zonker92]

Update: Per this page, all I need to do is cut out all the diodes. Looking at the PC board I see six diodes lying flat and a few more of the little tripod ones. Should I remove (or clip) them all? Thanks.

[Zonker92]

<crickets>

[Zonker92]

I may be the only one posting in this thread, but that's OK; I think I found my answer, which is indeed, just to unsolder one end of each of the three diodes. (I also remembered that the little three-lead devices are transistors, which I used to know.) Optionally, I can also bypass the relay.

[The Monkey]

Zonker, unfortunately I am a mess when it comes to DIY, but I am following this thread with interest. I look forward to the results.

[Zonker92]

Monkey, it SEEMS, per one Jerry S and this page, plus my amateur study of the PC board and schematic, that the ticket is to unsolder one end of each of the six diodes shown in orange below (I said three, but there are really six). This depowers the APOC circuit. You can do it without even removing the PC boards from the speakers.

Optionally, you can also bypass the relay, too, but that isn't necessary. You would do it only if you worried about it someday losing continuity. I have studied it, and I can see that to bypass it, you would want to solder a jumper from the center lead of the relay, to the lone corner lead, ignoring the two corners that feed the coil.

I think I'll take that step, too. I can post a photo when I do it.

I decided not to recap the crossovers. My research indicates that electrolytic caps dry out when subjected to too much heat, or when they physically leak. The 802 crossovers should not see much heat (unlike what they might get in an amp or a PC) and mine show no leakage. Plus, they are branded LCR and ALCAP, and my research indicates that those are both solid English brands. If they're not broken, I do not intend to fix them, and Jerry S says it makes little improvement anyway.

So in sum, I'm going to unsolder the six diodes, bypass the single relay, and while I'm at it probably upgrade the binding posts, but I'm leaving the caps alone. I'm also going to leave off the crossover cover plates or put some weatherstripping around the edges to make sure they don't buzz. Any maybe put spikes on the cabinets, too. I'll also oil the cabinets and clean up all the black cloth with a damp rag.

[Zonker92]

OK, I did the unsoldering and jumper last night; pretty easy. I did it on only one of the two speakers so I can play them against each other using a mono test tone, before and after. I'll use my iPhone dB meter to see if the levels change. Maybe this weekend?

[jacknk]

Was curious how the modification worked. I have some 801's and the APOC is bad on one, thinking of doing the same mod that you did.

[livewire]

[auriian]

i just did a pair of 801 series 80, replaced all the caps with solen 400v fast caps, and two bennic 1000mf 100v ones.. yes it was a great deal of stacking, drilled a couple of holes and made sure it all fit good and snug with zip ties and silicone.  

 i also removed allot of the protection circuit ( from looking at it as a section on the board) i removed the 82 ohm & 1k ohm resisters (which had burn marks on them), all the diodes, the two 100mf 40v caps (both dry and junk)  and two of the wire jumper leads that connected the resistors.. that appeared to be all the 'connections' from the cross over traces to the protection circuit!  I  hope i did it right!     i just am not able to get measured ohm load at the speaker terminal with my volt meter.. not sure why?  they sound good so far,  

;-)

i think i might need to put that 82 ohm 10 w resistor back in there.... not sure  B& W has no schematics available

[grawk]

Please read this post:                   Welcome to Head-Case                 

 

[Pars]

You can't find it in here?

http://bwgroupsupport.com/manuals/bw-service

Not to encourage this, BTW.

I would read the welcome if I were you.

[auriian]

so what can i post and can't , i dont get it

awesome, thank you 

 

this is B&W reply to me...

Paul S. (03/30/2017 04:03 PM) Hi Ian, hope you're doing well.   I did some thorough searching, and we don't have a crossover schematic or owners manual for the Matrix 801 Series 80.           Kind regards, Paul Bowers & Wilkins