gary mac Posted September 21, 2014 Share Posted September 21, 2014 (edited) One of the input sockets on my Mark Bass 2 x 10" has failed. Not a huge problem because there are two inputs but I would prefer to fix it. I've had a look inside, expecting to find a failed solder joint/loose cable but there is nowt visibly wrong. So, any ideas as to the likely cause please? Edited September 29, 2014 by gary mac Quote Link to comment Share on other sites More sharing options...
bertbass Posted September 21, 2014 Share Posted September 21, 2014 Jacks or Speakons? Quote Link to comment Share on other sites More sharing options...
yorks5stringer Posted September 21, 2014 Share Posted September 21, 2014 They are speakons on MB Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 21, 2014 Author Share Posted September 21, 2014 Yes, speakons. Quote Link to comment Share on other sites More sharing options...
icastle Posted September 21, 2014 Share Posted September 21, 2014 Reflow the solder joints to make totally sure they're good. If that doesn't fix it then it's going to be a replacement socket. HTH Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 22, 2014 Author Share Posted September 22, 2014 Thanks Mr. Castle, will do that. Quote Link to comment Share on other sites More sharing options...
Grangur Posted September 22, 2014 Share Posted September 22, 2014 (edited) [quote name='gary mac' timestamp='1411369707' post='2558716'] Thanks Mr. Castle, will do that. [/quote] I just did that for my MB LM2. I got the socket from Maplin for about £5 inc postage. This is what I ordered. http://www.maplin.co.uk/p/speakon-jack-combi-pcb-mount-vertical-a57qt Edited September 22, 2014 by Grangur Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 22, 2014 Author Share Posted September 22, 2014 Thanks for that Rich. If one is needed that will save a big search, good man. Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 22, 2014 Author Share Posted September 22, 2014 I[quote name='icastle' timestamp='1411341025' post='2558644'] Reflow the solder joints to make totally sure they're good. If that doesn't fix it then it's going to be a replacement socket. HTH [/quote] Ian I've just been having another look and listen. The faulty socket is actually working but is much quieter than the other one. No crackling or cutting in and out, it just doesn't put out anywhere near the volume of the other input. I've actually got two of these cabs, so I thought I would look under the hood of the other one, to get a comparison. Didn't help much as the panel in the other has one less component. Take a look at the pics for a better idea. The first pic shows the panel in the cab with the fault. The second pic is just for a comparison and is from my other cab which is all functioning as it should. [url="https://flic.kr/p/p4dJvT"][/url] [url="https://flic.kr/p/p4cGwB"][/url] Quote Link to comment Share on other sites More sharing options...
icastle Posted September 23, 2014 Share Posted September 23, 2014 Ah. You know that saying 'a picture is worth a thousand words'? The first picture shows a PCB that has been played with by someone. The soldering on CN2 isn't great, the capacitor near the R1 label has had the hotglue scraped away and that capacitor strapped onto the back of CN2 doesn't look like it was originally there. I'd be inclined to desolder one leg of that red capacitor and see what happens. Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 24, 2014 Author Share Posted September 24, 2014 [quote name='icastle' timestamp='1411502336' post='2560217'] Ah. You know that saying 'a picture is worth a thousand words'? The first picture shows a PCB that has been played with by someone. The soldering on CN2 isn't great, the capacitor near the R1 label has had the hotglue scraped away and that capacitor strapped onto the back of CN2 doesn't look like it was originally there. I'd be inclined to desolder one leg of that red capacitor and see what happens. [/quote] Thanks Ian. I wonder why the capacitor was added. Anyway, I will do as you suggest, although will leave it until after this weekends gig. Then if I get any bother, there will be a little more time for me to sort it before the next gig. Quote Link to comment Share on other sites More sharing options...
icastle Posted September 24, 2014 Share Posted September 24, 2014 That sounds suspiciously like a cunning plan. Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 24, 2014 Author Share Posted September 24, 2014 My wife would say " procrastinating again" Quote Link to comment Share on other sites More sharing options...
stoo Posted September 24, 2014 Share Posted September 24, 2014 [quote name='gary mac' timestamp='1411542303' post='2560425'] Thanks Ian. I wonder why the capacitor was added. Anyway, I will do as you suggest, although will leave it until after this weekends gig. Then if I get any bother, there will be a little more time for me to sort it before the next gig. [/quote] Are they 4 pole speakons? Could someone have tried to set it up for something like the GK amps which power the tweeters from a separate power amp maybe? Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 24, 2014 Author Share Posted September 24, 2014 The BC'er I purchased it from didn't tell me about any "improvements", so don't know the answer to that Stoo. Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 25, 2014 Author Share Posted September 25, 2014 [quote name='icastle' timestamp='1411543926' post='2560437'] That sounds suspiciously like a cunning plan. [/quote] Ian, I had the soldering iron out this morning for another job, so thought I might as try your suggestion on that capacitor. Unsoldered the leg to the tag. The result being no sound at all from that input, the other still worked as it should. I'm a bit stumped really Quote Link to comment Share on other sites More sharing options...
KiOgon Posted September 25, 2014 Share Posted September 25, 2014 Hi Gary, The only thing I can suggest is that the metal contact inside the Speakon has moved/broken/fallen out & I'd say a replacement socket will most likely fix it! Cheerz, John Quote Link to comment Share on other sites More sharing options...
BassBunny Posted September 25, 2014 Share Posted September 25, 2014 If you look at the connections on the offending speaker, the driver/horn are connected to HF1 and HF3, whereas on the OK one it is HF1 and HF2. Still reckon John could be right, a new Speakon socket from Audiospares and then hopefully it can all go back as it should be. Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 25, 2014 Author Share Posted September 25, 2014 [quote name='KiOgon' timestamp='1411640686' post='2561386'] Hi Gary, The only thing I can suggest is that the metal contact inside the Speakon has moved/broken/fallen out & I'd say a replacement socket will most likely fix it! Cheerz, John [/quote] It is working though John, just not as loud as when using the other input. Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 25, 2014 Author Share Posted September 25, 2014 [quote name='BassBunny' timestamp='1411642437' post='2561417'] If you look at the connections on the offending speaker, the driver/horn are connected to HF1 and HF3, whereas on the OK one it is HF1 and HF2. Still reckon John could be right, a new Speakon socket from Audiospares and then hopefully it can all go back as it should be. [/quote] I thought it might be that but swapping them over made no difference. Thanks though. Quote Link to comment Share on other sites More sharing options...
Grangur Posted September 27, 2014 Share Posted September 27, 2014 As you have the luxury of having 2 almost identical cabs, have you thought about swapping the boards over? Doing that ould identify if the problem is located on the board or is the difference between the 2 a red - herring. Quote Link to comment Share on other sites More sharing options...
gary mac Posted September 27, 2014 Author Share Posted September 27, 2014 Morning Rich. I had considered that but haven't actually tried it yet. After tonights gig we have a two week break, so I will take the opportunity of further investigation then. Thanks for the suggestion. Quote Link to comment Share on other sites More sharing options...
HowieBass Posted September 27, 2014 Share Posted September 27, 2014 I know very little about crossover design and even less about Mark Bass gear but could there have been some fault on the PCB affecting one speakon input such that the blue capacitor went out of circuit for that input only and a second capacitor (the brown one) was added to the circuit in substitution? As has been suggested someobody's looked at the blue capacitor (was there some fault at one point) and then had to make a workaround. I presume the cap is there to cut high frequencies from the signal going to the 10" drivers. I can't tell if the blue and brown caps have the same values. I wonder if the soldering for the brown cap is where the volume drop/loss problem originates? Quote Link to comment Share on other sites More sharing options...
icastle Posted September 27, 2014 Share Posted September 27, 2014 Having a working cab as a template makes this a service engineer dream come true. As the non-working cab has been blatantly fiddled with: 1) Check that the wiring is the same on both cabs and correct it if not. 2) Remove the added on parts and make both PCBs look identical - including the terminals that the wires are connected to. If that doesn't fix the problem then you're looking at a component fault (suspect the blue capacitor) or a broken track or bad joint on the PCB - easily fixed. Quote Link to comment Share on other sites More sharing options...
goingdownslow Posted September 28, 2014 Share Posted September 28, 2014 (edited) It looks like the pcb around the 1+ connection on CN2 has been scraped away to isolate it and the capacitor then added. Maybe they have made speakon 2 as an output to a tweeter or some other HF unit... Edited September 28, 2014 by goingdownslow Quote Link to comment Share on other sites More sharing options...
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