Question on SDA ICs

xoaphexox

I pulled and ohmed out all four surround drivers in the right channel. Each was the correct model, quality stamp August 31, 1989 and 3 ohms on the dot.

Haven't found any differences between the L and R xovers yet either, using a meter that reads capacitance, resistance and continuity.

I set out to get SDA working properly and because of all the DIY upgrade posts around here I ended up ordering some replacement binding posts and I got a quote from Polk for new RDO198-1's. I would really like to at least get SDA working first, though!

gimpod

It really sounds like you've got something wired out of phase. Remember that these drivers are wired in a "Series/Parallel" configuration. If I was you I would check how the right channel dimensional drivers (MW6511) are wired compared to the left channel. Make sure that they are wired the same as the left channel. Hope this helps.

xoaphexox

I'll buy that, gimpod. I didn't touch anything but the crossovers when I bought these a year ago, but I have no idea what the previous owner did to them during the 19 years he owned them.

Can I check the phase easily by (very temporarily) hooking up a 9v battery to the surround array to see if the speakers push out or in, and compare left vs right channels?

gimpod

That might work, but I think I would use a 1.5 volt, Drivers don't like DC and those 6511's are REAL hard to come by.

xoaphexox

Sounds good to me, thanks for the guidance!

gimpod

Your welcome.

If it was me i would physically check the wiring. possibly frying a 6511 is not something I would even take a chance on. I had a bad one in my 1C's (magnet slip) and it took 6 months and some horse trading to get one so be careful.

xoaphexox

gimpod wrote: »

Your welcome.

If it was me i would physically check the wiring. possibly frying a 6511 is not something I would even take a chance on. I had a bad one in my 1C's (magnet slip) and it took 6 months and some horse trading to get one so be careful.

I respect your desire to be on the safe side. I used the 1.5V test on the speakers and have confirmed that when + is hooked to blue (black for stereo) and - is hooked to green (white for stereo) the speakers push out as expected. I confirmed that all 16 drivers in both speakers act this way so I believe the wiring is in tact.

I guess I am back to the drawing board. I will play around.

gimpod

This is most perplexing . Make sure plugs P1 & P2 are clean and making a good connection also you might want to recheck the solder joints on the crossover. They should all be clean and shiny, if any are dull and flat looking (cold solder joint) re-do them. Also it might help if you can put up some pictures (Top & Bottom) if the suspect crossover and binding post plate both sides.

xoaphexox

I purchased new cardas binding posts and am in the process of putting everything together. I did have some so-so connections (stripped plastic end caps preventing a tight connection).

I am about halfway done. Once I get the binding posts installed I am going to try swapping the crossovers to see if the issue switches speakers, then at least I will know if the crossover is definitely to blame. I spent a while taking readings and haven't found fault yet.

Perplexing indeed - driving me half insane Thanks so much for your suggestions!

xoaphexox

I finished putting the binding posts on tonight and put everything together for a preliminary test. Much to my surprise the SDA effect now works. If I put the source on mono and fade the whole way left or right, only the opposite channel's SDA drivers are active. I think that's the correct function.

What a relief. Thanks for letting me think out loud here for a while and forgive me for derailing the thread. Excellent source of info here!

civilian

Thank you for thinking out loud and posting it. You think something was loose somewhere?

xoaphexox

That is my assumption. Either something wasn't making a good connection or a wire must have been touching a part of the crossover it shouldn't have. These speakers sat on their backs in a U-Haul truck for 2 hours on their way to my house and then got slid down two flights of stairs so it's entirely possible that is when it happened.

My guess is that the mere act of taking everything apart and putting it back together fixed the issue. And I have new binding posts now, to boot.

Since the stock binding post jumpers don't fit on these new Cardas posts, I am going to take advantage of the 20% sale Soniccraft is now offering and get a pair of the Rhodium/Silver Cardas binding post jumpers to match the Rhodium/Silver Cardas binding posts I installed (although I got those from Handmade Electronics in Allentown PA).

Next up on the 1.2tl upgrade roadmap are RDO198-1's. Then maybe I will look in to those steel rings you guys are using. Maybe.