ads 910 crossoever component values

[srivats]

Can someone please tell me the value of big blue inductor in the ADS-910 crossover? One of my crossovers is busted (no sounds from midrange), and I have checked and confirmed that the drivers and the pin connector/fuses are all fine (all drives have sound with the working crossover in both the speakers, so it's not a connector/driver issue).

The 3 other coils are 0.18 mH, 0.5 mH and 3.0 mH as you can see on the labels. Looking at the crossover schematic (from sporstbil/ads website), how can it be that the big inductor is also 3.0 mH?

 

[dshoaf]

Since it is the biggest choke in the picture, I'd suggest this would be part of the woofer circuit. That would make it L1. According to the schematic, model 910 crossovers would have a 3.0 henry choke at that position.

Since I can't see the whole crossover board, I'm still guessing on this, though.

Cheers,

David

 

[nerdorama]

They can both be 3.0 mH with different wire sizes. The big inductor needs to have much lower wire resistance for use in the woofer circuit while the smaller 3.0 can work very well for the midrange with a higher resistance.

 

[toxcrusadr]

Regardless of its value, you can check an inductor quite easily with an ohmmeter. If it's open it will read high or infinite resistance. But this rarely happens.

Have you checked the caps? C3 is in series with the mid, as is resistor R2. Capacitors are the culprit fairly often.

 

[srivats]

R2 measures fine; I suspect C3 also. Here is a bigger picture of the xover ..

The values of all the inductors are in mH according to the schematic below - that's what is throwing me off. If the wire gauges are different, that would make sense.

I know ADS used good quality components but even film caps age after 30 years.

http://sportsbil.com/ads/xoverschematic.pdf

 

[nerdorama]

Fuses ok? How about a broken solder joint on the bottom of the pcb? Were the speaker wires from the amp connected to the two terminals with the screws missing? For full range running, the hot lead from the amp should go to the connection nearest the 3 pole common jumper.

 

[dshoaf]

Just re-read the OP's original post.

- Check the midrange with an ohm meter to be sure it isn't open.

- Check the switches - clean them with DeOxit.

- Then, pull that jumper board and clean the pins with the same stuff on both the board and the socket.

I doubt the components are at fault.

Cheers,

David

 

[srivats]

Fuses ok? How about a broken solder joint on the bottom of the pcb? Were the speaker wires from the amp connected to the two terminals with the screws missing? For full range running, the hot lead from the amp should go to the connection nearest the 3 pole common jumper.

Fuses are good, first thing I checked, and I replaced them for good measure. Solder traces all check out for continuity. I'm making the connections properly.

I've listed out replacement parts for all the components except the big choke, still amazed that the size is so large for the same 3mH value.

 

[srivats]

Just re-read the OP's original post.

- Check the midrange with an ohm meter to be sure it isn't open.

- Check the switches - clean them with DeOxit.

- Then, pull that jumper board and clean the pins with the same stuff on both the board and the socket.

I doubt the components are at fault.

Cheers,

David

David - the midrange is fine; it works with the crossover from the other speaker. I have cleaned the switches and the jumper board to no avail. I am guessing that one of the capacitors is not working properly (don't have equipment to check caps) since the resistances measure fine after I pulled them from the board.

 

[nerdorama]

I wouldn't discount the connector socket which connects to the driver cable. Mine were both very flaky and I had to replace them. Have you tried wiggling the driver cable while playing music? Just another idea.

If you have an ohmeter, do you measure resistance in the midrange circuit? You should measure 5 or 6 ohms from the input terminal to the upstream side of the C3 (3 parallel caps) and low resistance from the other side of C3 to the driver side of the midrange fuse.

 

[srivats]

nerdorama - haven't checked the connector socket, good call. Will check that. Have not measured the impedances of the circuits separately .. will work on that too when I get home.

Can you tell me where you got the replacement connector socket? Will a a molex replacement work (provided I wire up the male part also)?

 

[nerdorama]

I couldn't get the pcb mounted version of the socket so I used an inline wired version with short wire tails to the pcb. The Mouser p/n is 538-38331-8006. I didn't use the back shell. Mouser lists them as discontinued by the manufacturer but still has over 200 in stock.

 

[srivats]

I couldn't get the pcb mounted version of the socket so I used an inline wired version with short wire tails to the pcb. The Mouser p/n is 538-38331-8006. I didn't use the back shell. Mouser lists them as discontinued by the manufacturer but still has over 200 in stock.

Thanks .. I will get a couple while they are still available. BTW, wiggling the socket/connector (while music was on) did not have any effect

 

[ChrisNC]

What do you see if you take off the blue cover? Can you visually see if the wire gauge is very different. That seems like the most likely reason, but the size difference is SO great that it would be interesting to see.

Also, you might contact Richard So. (I don't have the contact info, but google will.) Don't know if he would answer such a question since he also repairs ADS speakers, but it is worth a shot.

 

[nerdorama]

You didn't mention about the missing screws in the main terminal strip where I asked above. Were those screws used for the incoming speaker wires or have they always been missing? The middle screw in the common jumper is the terminal for the midrange common connection. If it's always been missing, then it might not be making good connection.

 

[srivats]

What do you see if you take off the blue cover? Can you visually see if the wire gauge is very different. That seems like the most likely reason, but the size difference is SO great that it would be interesting to see.

Also, you might contact Richard So. (I don't have the contact info, but google will.) Don't know if he would answer such a question since he also repairs ADS speakers, but it is worth a shot.

Unfortunately, the blue cover seems to be glued on (or, has become stuck over the years) and I can't get it out after removing the screw/nut holding the part to the PCB. When I eventually get it off the board, I'll cut it open and post a photo.

 

[srivats]

You didn't mention about the missing screws in the main terminal strip where I asked above. Were those screws used for the incoming speaker wires or have they always been missing? The middle screw in the common jumper is the terminal for the midrange common connection. If it's always been missing, then it might not be making good connection.

They have always been missing. I read the ADS 910 manual, and made sure that I connected +ve wire correctly; and since the -ve terminals are jumpered together, I just hooked to one of the other ones. The working x-over also has missing screws; but this is worth checking and I will do that now .. thanks for helping me troubleshoot, I would not have thought of this. Will report back shortly ..

edit: Putting a screw there does not help Ah, how I wish that had worked!

 

[toxcrusadr]

If all the inductors have continuity and no more than a couple ohms DC resistance, I would leave them alone. No need to take that blue one off the board. Just replace any bad caps and resistors, clean up connections and you should be good. Those square caps are probably film caps (anyone?) and might be just fine. I don't know how old these speakers are, but probably not older than 1990s right? If the caps are not electrolytics (they would have + and - ends marked) I don't know that I'd go replacing them all.
One test you can do on a cap with an ohmmeter: it should go from low resistance to high as the cap charges up. If the cap is not too huge. If it's instantly at infinite resistance and stays there, the cap may be open somewhere inside. That would be consistent with a silent driver. If it was shorted, or drifted way off its value, the driver would get the wrong range of frequencies, but it would play.

 

[srivats]

Replaced just C3 with a cheap cap of the right value just to test and we have sound!

I will definitely put new caps and resistors. Still thinking about the coils ..

 

[srivats]

Also .. The crossover posted above is the modified series ii version, that goes with this version of the PCB I found on AK. The one I posted is slightly different .. I will share a ckt diagram of the version I have with values.