Help repairing my Logitech Z-5500s - Page 1
Forum section: electronics / repair

author: adsada
author_rank: Newbie
timestamp: March 29, 2017, 08:19:32 am
content: Hi there, so I'm really gutted, but basically I purchased a bypass cable from ebay to allow you to bypass the control pod and use the system with a 3.5mm jack, however when trying it out it worked for a couple of minutes then suddenly stopped. I tried plugging back in the control pod and it works for a about 10 seconds then freezes displaying squares on the screen...I'm not sure if this was the cable that caused this issue, or just a really timely coincidence, but somewhere in the subwoofer (which houses the amp) something is now broken...So I have two questions, firstly is can anyone reassure me that this cable didn't cause the fault, because if it did I'm going to gocrazy to the ebay seller, what's the likelyhood here?and secondly, where on earth would I begin trying to diagnose where the issue lies in the sub? I have taken the back off and inspected all the parts with no obvious signs of any issuesI love these speakers, so any help would be much appreciatedthanks

author: Zbig
author_rank: Frequent Contributor
timestamp: March 29, 2017, 09:34:03 am
content: Why would you buy some unknown eBay bodge while the system is perfectly able to accept analog line-level signal via the 3.5mm jack on the control pod dedicated for this very purpose?It's impossible to answer your question without reverse-engineering both the Z5500 and the kludge you've got on eBay. Also, why not provide an eBay link?

author: jeroen79
author_rank: Frequent Contributor
timestamp: March 29, 2017, 09:54:17 am
content: QuoteWithout knowing what you bought: No.What kind of equipment do you have?You would need something to generate a known signal -a simple MP3 player would do- and something to trace that signal around the amp -a multimeter with AC and frequency measurement or better a line to another speaker-.What I gather from a brief googling is that the control pod connects with a DE-15 connector.Pinouts are provided:Can you measure anything out of the ordinary on the connector?High or no supply voltages?

author: adsada
author_rank: Newbie
timestamp: March 29, 2017, 10:01:26 am
content: My thinking was the control pod at present has a slightly dodgy cable, and these pods are notoriously known for gaining faults. As such I thought it would be good to have this cable as a spare, when and if the pod does eventually break.Here is the link:http://www.ebay.co.uk/itm/320741280010?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITas you can see, the seller has sold bucket loads of them and the feedback seems to be positive, so I had no reason to think that it would cause any issue.thanks

author: Zbig
author_rank: Frequent Contributor
timestamp: March 29, 2017, 11:10:10 am
content: Quote from: adsada on March 29, 2017, 10:01:26 amI owned Z5500 and used it daily for years before I sold it and the only fault it developed was that the LCD backlight has failed on one side (one of the two LEDs gave up). The trouble with internet forums is you'll only see people reporting problems with their gear and that could very easily skew your perception of how good or bad something is. How often do you post on a forum that your TV/car/washing machine/whatever is still working perfectly fine and you were using it happily for another year? If anything, the number of Z5500 talk is a testament of it being a terrific value for money. As you have probably realized by now, it's a bit silly to do things like that anticipating a failure that could have very well never happened. As per marginal control pod cable, probably the right thing to do was just to test it and replace or fix if needed. But enough preaching. I don't know how the eBay cable bodge is supposed to work but it seems there's many things wrong with it to me. First, whacking a potentiometer on the amplifier input (and varying the input impedance as seen by the signal source) is very crude approach and I don't consider it proper means of volume control. Secondly, as far as I understand, the control pod serves all the crossover/bass management duties, sending separate sub/satellite signals to their respective amps. By trying this cable bodge, you could have very well applied full-range signal to both satellites and subwoofer for all we know. Sorry I couldn't be more helpful but let this be your lesson that not everyone who is selling something does actually know what he is doing and you should stick to the well known and true "if it ain't broke, don't fix it" principle.EDIT:Also, it's my 666'th post

author: Zbig
author_rank: Frequent Contributor
timestamp: March 29, 2017, 11:38:09 am
content: As per the connector pinout provided by jeroen79, you turn the amp on by tying pin 7 to 5V. Unless there's a voltage regulator/divider in the cable you bought, it could have just shorted it to what's available on the connector and that'd be 8V. I'm only speculating here but this could be one reason why the cable has borked your set.

author: adsada
author_rank: Newbie
timestamp: March 29, 2017, 11:52:37 am
content: Appreciate your bluntness hah, I guess when you put it like that it was a bit silly, however I still not toally convinced the cable caused said issue, the seller sells a plethora of cables and seems to have sold thousand for similar logitech systems and yet his feedback it almost all hugely positive... plus the cable was working fine for about 10 minutes before the issue happened...surely damage to the sub would have been instant as soon as I plugged it in? The amps dont seem to be damaged either as the whole system works fine for about 10-20 seconds before the crash.Anyway I would still like to give a shot at fixing it, maybe if I outline more detail of the issue would help:The system still turns on and works perfectly for up to about 15ish seconds. I can turn them up full and almost lose my hearing but they still give off a flawless sound...After this time the system basically freezes, the control pod shows all black squares. If I unplug the control pod and plug it back in (leaving the amp powered on) the control pod is still just frozen, displaying all black squares.If I unplug the control pod before the amp freezes (say 5 seconds after turning it on) and plug it back in the control pod still works fine and i can play music/sound for another 10 seconds or so, then freezes.Thus its definitely the sub at fault... my friend has the same speakers, so I would be able to do tests and compare them boththanks

author: Zbig
author_rank: Frequent Contributor
timestamp: March 29, 2017, 11:58:29 am
content: Do you have a multimeter so you could check that the voltages present on the control pod connector agree with those on jeroen's schematic (8V, +18V, -18V)? Keep in mind there could be differences between hardware revisions as the eBay guy mentions, though. Can you open the sub box up and visually inspect the electrolytic capacitors for leaks and/or bulges?

author: adsada
author_rank: Newbie
timestamp: March 29, 2017, 12:04:34 pm
content: I can get my hands on a multimeter, but it will be some time next week. I've already had a look inside and inspected the various caps and cant see any issues, everything looks good

author: Zbig
author_rank: Frequent Contributor
timestamp: March 29, 2017, 12:13:19 pm
content: Quote from: adsada on March 29, 2017, 12:04:34 pmGood, when you manage to check the voltages, I'd advise to do it both loaded and unloaded, that is without and with the pod connected. That would reveal the potential voltage sagging problems when the pod is connected. You could probably do this from inside the sub box. But please be careful if you decide to do so as there's dangerous mains voltage exposed inside the sub enclosure. Ask someone more experienced if you don't feel comfortable and/or aren't sure you can do this safely.

author: adsada
author_rank: Newbie
timestamp: March 29, 2017, 12:36:40 pm
content: Quote from: Zbig on March 29, 2017, 12:13:19 pmOk, yeah I might get my friend to help who's a bit more clued up on electronics, this is what the solder points on the board looks like from the insidehttps://ibb.co/nrBUFaCan I assume that layout is the same as the image jeroen79 posted? And I take these readings to the ground right?thanks

author: Zbig
author_rank: Frequent Contributor
timestamp: March 29, 2017, 12:55:49 pm
content: Quote from: adsada on March 29, 2017, 12:36:40 pmYes, you measure the voltages relative to ground. You keep the multimeter's GND probe on the GND pad and probe the voltages with the other one. For -18V you should also get "-18" on the meter (assuming it's a digital one). Double check the meter is on the voltage range and the probe cables are in the correct multimeter sockets beforehand.

author: adsada
author_rank: Newbie
timestamp: March 30, 2017, 04:52:21 pm
content: Quote from: Zbig on March 29, 2017, 12:55:49 pmGreat, I've ordered a volt meter so will report back with results!Got an reply from said cable seller,"Sorry to hear that. The cable does not supply any power to the system. All it does is turning on the subwoofer and feed in audio signal into the sub. Couldn't really know what caused the problem since we don't have your subwoofer to diagnose. Please let me know if you have any further questions."So I don't really know what to believe ahaathanks for your help btw

author: adsada
author_rank: Newbie
timestamp: April 09, 2017, 05:05:37 pm
content: Ok, so a wee update. I just spend this morning taking it apart with a friend whos more clued up on electronics. I checked the 8v regulator on the pcb, and this seems to be reading 6 1/2 volts, but as I was doing this I noticed smoke coming off the board. It seems a couple of resistors at (R21 and R22) are burning, and they're roasting hot.Even more odd, the fault is different how, the pod no longer crashes, it works and then after a minute the sub speaker produces a noise which gets progressively higher pitched... not really sure what to do!Does make me less think it was caused by the cable, in other news I bought a new set of ebay, managed to get them quite cheepbut I'd still like to try and get this fixed!

author: Astaldoath
author_rank: Contributor
timestamp: April 11, 2017, 10:38:07 pm
content: was the board smoking while you had probes on it or while it was just sitting there with nothing touching anything that it shouldnt?Maybe you caused a short with your leads or something im not as knowledgable as others. I fixed my old altec speakers today only problem left is a jack on the PCB is a little messed up but the set works fine if the plug isnt pushed in to the port all the way so im happy with that.Either way smoke is not good lol, will be checking back, curious if you figure out whats wrong

author: LeWidget
author_rank: Regular Contributor
timestamp: April 12, 2017, 07:07:34 am
content: Noobi here, so forgive me if i'm incorrect.. but maybe replace smoking resistors and try again in case they're failing? If the new ones smoke, maybe try tracing back the circuit, see which component(s) are next, find specs on each component (what their voltages are, amps etc..) then measure each one ?To me, could possibly be a component failing, outputting a higher voltage/Amps causing resistors to smoke? Could it possible be failing component/resistor that's causing the issues OP is having ?I personally don't see how a cable could cause failure, even if it is a cheap cable, unless there's some sort of power input regulation in the cable that's faulty?Sorry if I don't make much sense, just something I thought could be the case

author: adsada
author_rank: Newbie
timestamp: April 12, 2017, 05:23:18 pm
content: Quote from: LeWidget on April 12, 2017, 07:07:34 amThanks for your replies, it sparked separately once on the metal rod because I forgot to reattach the earth cable and the rod was touching the top of one of the amps...hahaa, but that wasn't what cause the burning resistor they did that on their own I'm pretty sure...does anyone know what voltage is outputted from the transformer? was getting some crazy high readings when measured it at that point.I'm equally fairly nobbish about electronics but my friend knows more and he was equally baffled, will have another go this weekend and report back!

author: LeWidget
author_rank: Regular Contributor
timestamp: April 13, 2017, 12:17:05 pm
content: Quote from: adsada on April 12, 2017, 05:23:18 pmHave a look on the transformer, there's usually writing (?), should give a model/component/serial etc.. number. Type into google, should be able to find the manufacturer and a spec data sheet.

author: Demosthenes
author_rank: Newbie
timestamp: February 15, 2019, 09:52:30 pm
content: My cable has been playing up, seems to be dodgy connections in to the amp... Can I just splice it to a new connector?

author: Zbig
author_rank: Frequent Contributor
timestamp: February 15, 2019, 11:34:32 pm
content: Quote from: Demosthenes on February 15, 2019, 09:52:30 pmCan't see why not...

author: Demosthenes
author_rank: Newbie
timestamp: June 10, 2019, 01:45:53 am
content: I eventually opened the controller box and it's hard wired / soldered inAny ideas? How hard is it to just chop the end of the cable and wire in a new connector?I am hoping it is the cable and not the port. If it's the port I may as well throw it in and send this off to recycling which is a HUGE shame and waste!

author: senso
author_rank: Frequent Contributor
timestamp: June 11, 2019, 01:14:23 pm
content: What makes you think that the broken wire is near the plug and not in the middle of the cable where there is a lot more movement?