Post by sub on May 30, 2019 13:49:35 GMT 12
Taken things as far as I am able. Removed wires from connector box - a simple plug in - and while the copper/brass terminals and springs looked clean and without tarnishing or corrosion, gave them all a good clean with deoxit.
Then did a complete continuity test, starting at first capacitor in MF circuitry. Each cap tested positive for continuity to its neighbour, and the last cap in the chain also tested positive to the base of +tive pin.
Are the caps bipolar? If so, couldn’t get a read for continuity on any of the -tive ends of the caps to the -tive pin. Although the wires from the connector box, both from the pin side and the wire side, to the PCB distributor all tested positive for continuity.
Going to take to a tech to sort out!
|
Post by Owen Y on May 30, 2019 14:04:13 GMT 12
Capacitors by nature, pass only AC current & will not show continuity across them, with a DC Ohm meter.
|
Pundit
Post by Mike A on May 30, 2019 14:16:26 GMT 12
Have you tried swapping the crossovers to see if the fault follows the board, it may help to nail down where the problem is.
|
Pundit
Post by Mike A on May 30, 2019 14:49:40 GMT 12
Just double checked my meter and I can test the caps for you.
Let me know and I’ll drive up to you and we might be able to solve the problem.
|
Post by colinf on May 30, 2019 18:19:18 GMT 12
Good luck, let us know how you go! I’d check L9 and L10 for continuity and/or soldering integrity. They run the upper midrange. The crossover to the upper midrange rolls off much sooner than the lower one so it will sound more dull.
AMR-iFi R&D
|
Post by Owen Y on May 30, 2019 21:04:34 GMT 12
Testing capacitors can be a little involved - Capacitance (uF) is one thing, but also Leakage (applying rated DC voltage & measuring any current leakage) & ESR (Equivalent Series Resustance).... but all of this should be kosher if, as I understand correctly, these caps are new & have been expertly installed right? If the coils are old, then as colinf says, check them out. Hopefully no internal shorts/insulation breakdown over time & reduced inductance. Tricky to troubleshoot - have inductance (uH/mH) meter?
|
Pundit
Post by Mike A on May 30, 2019 21:31:15 GMT 12
Let’s hope sub has the chance to swap boards before it all gets too complicated.... Are matching coils even available now?
|
Post by sub on May 30, 2019 22:33:35 GMT 12
Hi team, interesting comments. I guess swapping boards will prove where the trouble lies. I doubt that any of the caps are at fault - all the caps in the MF circuit tested fine for continuity checking from the soldered side of the xover board. Will also check the inductors at L 9 and 10. I am guessing they are what you refer to as coils?
Will check to see if replacements are available, just in case.
Will report back in a couple of days.
MikeA, great offer mate, will let you know.
As an aside, if the inductors are faulty, and cannot be replaced, would jumper leads from the lower MF driver to the upper work, or would that create more problems?
|
Pundit
Post by Mike A on May 30, 2019 22:53:51 GMT 12
No problem whenever you’re ready.
I was thinking about the actual physical size of the coils as if the only equivalent is bigger or a different shape then you will have to be a bit creative when it comes to fitting...
|
Post by colinf on May 31, 2019 0:11:05 GMT 12
In order to measure the caps they need to be unsoldered from the circuit board, as there are other inductors (also called coils or crossover chokes informally) that are in parallel that will make the cap appear as a short circuit. When measuring C12 in circuit the current from the multimeter will flow through L9, L7, L6 and L5, making C12 appear as a short circuit, something which C12 itself definitely shouldn’t be. With it unsoldered from the board it should measure as an open circuit with a normal multimeter set to resistance. (And measure 4.2uF with the meter set to capacitance.) But as the caps are new there wouldn’t be much reason to suspect them. Caps almost never go short circuit, they normally just lose capacitance and increase ESR (equivalent series resistance) slightly over time as the liquid electrolyte inside slowly dries out. I’d still check L9 and L10 for continuity. Another more convenient way to check them would be to just put a multimeter across the wires that go to the upper midrange, without both the midranges connected. It should be about 1 ohm or less. Measuring that will check that L5, 6, 7, 9 and 10 are soldered onto the board ok. It looks like replacement coils are available from Falcon as well, if necessary. If everything is measuring just fine with a multimeter, but there still isn’t any sound coming from the upper midrange and the lower midrange is ok, suspect C12 as a short circuit. Try removing it. It’s ok to connect the two midranges together temporarily and make them run off the wires for the lower midrange. Although then the upper midrange won’t sound right from that speaker.
AMR-iFi R&D
|
Post by Owen Y on May 31, 2019 9:48:09 GMT 12
Yes indeed, at least one end of the caps and/or inductor coils would need to be lifted to isolate & measure.
|
Post by sub on May 31, 2019 11:42:55 GMT 12
Caps are new and should be good, especially since the issue occurred spasmodically before new caps installed.
First checks just completed -
Continuity test between L9 and L10 good, taken from soldered side.
Impedance test across wires to upper MR, reads 0.0 i did a comparison test across wires to lower MR = 2.0
I measured impedance of both inductors in situ, even though I know result not accurate - L9 = .6, L10 = .1
Looks like either L9 or 10 is faulty? Will have to decide which one to remove from the xover board first for testing.
|
Post by Owen Y on May 31, 2019 13:21:21 GMT 12
(Minor point of learning - 'impedance' means AC resistance, 'resistance' refers to DC resistance or 'DCR' - the latter is what is being measured with a simple digital multimeter ) As colinf says, not that useful measuring the Ls in situ, as other components will interfere, eg... Attempting to measure DCR across L10 in situ, you will also be measuring L9-L7-L6-L5 in series/parallel with the 2 x MF drivers! L9 similar. However in this circuit, think that you can isolate & measure the DCR (ohms) of L10 & L9 by disconnecting both MF drivers first - try that
|
Post by sub on May 31, 2019 13:37:02 GMT 12
However in this circuit, think that you can isolate & measure the DCR (ohms) of L10 & L9 by disconnecting both MF drivers first - try that Thanks Owen Y. All measurements, as above, were done with both MF drivers removed and wires disconnected.
|
Post by sub on May 31, 2019 14:19:32 GMT 12
For a comparison, I repeated the resistance test proposed by ColinF, in the 2nd para of his last post, that is putting multimeter over wires leading to upper and lower MR, with drivers removed, on the loudspeaker known to be good, with following results -
Upper MF on good spkr = 2, (on bad spkr = 0) Lower MF. “. “. “. = 1.4. (2) HF. “. “. “. = .2 (0)
|
Post by Owen Y on May 31, 2019 16:01:52 GMT 12
A little baffling.... Zero ohms of course indicates a 'short'. I have not a lot of experience here, but I'd expect that inductor coils could measure as little as a fraction of an ohm, 0.5 ohms say, as they are simply a coil of conductor wire. Esp the heavier bass Ls. Measuring across the MF lower driver connections would put L5+L6+L7 in series - so 1.4 - 2 ohms seems OK. Measuring across MF upper would put L5+L6+L7+L9+L10 all in series - so a bit higher ohms, 2 ohms or so would seem right. (All assuming that the LF bass drivers are also disconnected?) The MF upper 0 ohms measurement looks suspect - check the board near these MF upper connections, maybe a short across the board somewhere near this driver? Similarly the HF 0 ohms measurement looks odd, this is measuring L12 essentially, the HF hi-pass coil, still only in the region of an Ohm or so? Does your meter resolve down to fractions of an ohm?
|
Post by colinf on May 31, 2019 18:56:05 GMT 12
Ok, good. So good speaker measures 2 ohms for the upper midrange wires (with the midranges disconnected), an ok measurement. And the bad speaker measures 0 ohms on the upper midrange in the same situation. Suspect C12 is a short circuit (not very likely as it is new), or something on the board is shorted together on those particular tracks, perhaps even at the solder side of the connector pins. If you unsolder L10 off the board, try seeing if the short still exists across the upper midrange wires. If it does, you have a short on the board or connector somewhere on those tracks, and C12 is ok.
AMR-iFi R&D
|
Post by sub on Jun 1, 2019 14:07:40 GMT 12
Desoldered L10, and measured it’s resistance in ohms, = 0.1
Measured resistance across upper MF terminals = 0.0, so short circuit still exists!
No obvious signs on the circuit board. Looks like time for a tech to take over. Like to go to Axent, but another trip to Auckland not on cards at moment. May try Searle in Whangarei, they have been around for years, and fixed a Proac tablette spkr for me once and did a good job.
|
Pundit
Post by Mike A on Jun 1, 2019 14:47:18 GMT 12
If you're coming down to Whangarei then drop by here first and I can have a look, a fresh pair of eyes may see something that you missed.
|
Pundit
Post by beeman on Jun 1, 2019 16:25:49 GMT 12
As you say a good scrape deoxit & tighten of all spade connectors would not hurt as well. May not solve your problem but will make everything else sound better
|
Post by Owen Y on Jun 1, 2019 17:59:06 GMT 12
Audiomark (Mark Brumby) in AKL - did he get back to you? Did you do that last ohms test across upper MF terminals with L10 out?
|
Post by colinf on Jun 1, 2019 19:12:18 GMT 12
You’re almost there! Just examine the crossover board closely for shorts. Maybe a stray wire, a solder blob connecting 2 connector pins together inadvertently etc. Where the midrange wires connect onto the connector block on the board, look around there. Also the track that L10 solders to, the one that goes to the connector. Take a close up photo of the underside of the board if you like and put it on here, and I’ll see if I can spot anything.
AMR-iFi R&D
|
Post by sub on Jun 1, 2019 19:15:24 GMT 12
Audiomark (Mark Brumby) in AKL - did he get back to you? Did you do that last ohms test across upper MF terminals with L10 out? Mark did reply, but was away on holiday when my trip to Tauranga happened - and I dropped my woofers at Axent instead. yes, last ohms test was with L10 out, as per SimonF instructions. In fact it is still out of the circuit, as my soldering skills not up to replacing it.
|
Post by sub on Jun 1, 2019 19:43:51 GMT 12
You’re almost there! Just examine the crossover board closely for shorts. Maybe a stray wire, a solder blob connecting 2 connector pins together inadvertently etc. Where the midrange wires connect onto the connector block on the board, look around there. Also the track that L10 solders to, the one that goes to the connector. Take a close up photo of the underside of the board if you like and put it on here, and I’ll see if I can spot anything. Used a magnifying glass and could see no issues on any of the wires soldered to the board. there is something though, now you mention it, there is a trail of solder running from an inductor diagonally across the underside of the board, but it does not seem to be affecting anything in the MF circuit. Will try to take a photo in good light. may take MikeA offer up as his experienced eyes will see things I don’t understand!
|
Post by sub on Jun 1, 2019 19:44:10 GMT 12
You’re almost there! Just examine the crossover board closely for shorts. Maybe a stray wire, a solder blob connecting 2 connector pins together inadvertently etc. Where the midrange wires connect onto the connector block on the board, look around there. Also the track that L10 solders to, the one that goes to the connector. Take a close up photo of the underside of the board if you like and put it on here, and I’ll see if I can spot anything. Used a magnifying glass and could see no issues on any of the wires soldered to the board. there is something though, now you mention it, there is a trail of solder running from an inductor diagonally across the underside of the board, but it does not seem to be affecting anything in the MF circuit. Will try to take a photo in good light. may take MikeA offer up as his experienced eyes will see things I don’t understand! Edit: I presume the ohm reading of 0.1 on the detached L10 is ok?
|
Post by colinf on Jun 1, 2019 19:48:44 GMT 12
The measurement of L10 looks ok. If it was a short circuit the midrange would still work. See if you can measure a short on the connector pins.
AMR-iFi R&D
|
Post by Owen Y on Jun 1, 2019 20:09:49 GMT 12
yes, last ohms test was with L10 out, as per SimonF instructions. In fact it is still out of the circuit, as my soldering skills not up to replacing it. Well that's interesting. If you look at the schematic, the -ve pin of MF upper connection is connected to Ground (pcb track). The +ve pin to the MF upper connection is connected to only L10 & the MF upper driver - and if both of those are removed, then that suggests that this MF upper connection pin is shorting (0 Ohms) to Gnd. Seems unusual however.
|
Pundit
Post by Mike A on Jun 1, 2019 20:24:23 GMT 12
Owen, I was just thinking exactly the same thing
|
Post by Owen Y on Jun 1, 2019 20:27:02 GMT 12
Or, the track that it is attached to, including the L10 end.
|
Post by Owen Y on Jun 1, 2019 20:35:14 GMT 12
Edit: I presume the ohm reading of 0.1 on the detached L10 is ok? Yes, remember that L10 is simply a coil of copper wire, so should measure 0 Ohms. But on the meter, 0.1 ohms is probably as low as it resolves.
|