Troubleshooting a Harman Kardon TS-8

[goller]

Hi I am new to the forum and looking for some help with a Harman Kardon TS-8 Subwoofer. Initially the issue was an intermittent fault but has recently become a permanent fixture of the Sub.

The issue I am having is when the sub is switched on it make a thumping noise randomly every few seconds regardless of the mode (i.e. AUTO/ON, Reverse/Normal, Filter on or off) and also regardless of whether there is an audio source connected or not. When it thumps the light will switch to ON (blue) when back to standby (amber). I know these amps have issues with bad caps so have disassembled the sub and looked it over but can't see any obviously bad caps. There is some darkening on the PCB but given its proximity to the heat sink I suspect this is pretty normal.

I am happy to replace all the caps is necessary but just wanted some thoughts on which caps might be the likely culprit for the fault.

[ben7]

Re: Troubleshooting a Harman Kardon TS-8

You could try replacing the small caps near those hot discolored areas.

Of course, check for bad resistors too.

[lti]

Re: Troubleshooting a Harman Kardon TS-8

Remove the glue. It looks like the glue that becomes conductive.

The caps in the discolored areas are probably bad. You might end up replacing most of the caps.

[goller]

Re: Troubleshooting a Harman Kardon TS-8

Thanks guys will let you know how it goes.

[goller]

Re: Troubleshooting a Harman Kardon TS-8

I have swapped out all the caps and removed all the glue but have the same problem. Still getting the sub popping every 30 odd seconds then I can here what sounds like something clicking on the PCB (the same sort of click which you first get when the amp turns on or it come out of auto mode).

Any ideas would be appreciated.

[budm]

Re: Troubleshooting a Harman Kardon TS-8

I do not know which version you have, but one of this service manual should help, you can at least check the DC voltages on the filter caps first.

[goller]

Re: Troubleshooting a Harman Kardon TS-8

Thanks budm. I have the SUB-TS8/230 version for Australia and as such the service manual does seem to be for this model. I have looked around for the 230v service manual but can't seem to find it.

[ben7]

Re: Troubleshooting a Harman Kardon TS-8

I have swapped out all the caps and removed all the glue but have the same problem. Still getting the sub popping every 30 odd seconds then I can here what sounds like something clicking on the PCB (the same sort of click which you first get when the amp turns on or it come out of auto mode).

Any ideas would be appreciated.

Something clicking on the PCB like when you turn it on? That is very likely the protection relay that is making that clicking sound.

[budm]

Re: Troubleshooting a Harman Kardon TS-8

The primary side voltage does not matter, the secondary side will have the same output voltage since the turn ratio of the transformer for 120V or 230V will be used for proper output voltage on the secondary side. There is one speaker relay as you can see in the service manual.

[goller]

Re: Troubleshooting a Harman Kardon TS-8

Thanks budm for the replies. Looking at the manual posted, the schematic listed looks totally different from what I am seeing in my model. An example is single caps (6800U/50V) at C121 and 122, where as i have two caps at each location (4700U/50V and 4700U/35), but the rest of the PCB looks totally different also.

In reference to the clicking, I think I recall the clicking when the amp was working. Some sort of relay that clicks over from Auto to on mode, perhaps.

[speedylaci]

Re: Troubleshooting a Harman Kardon TS-8

Thanks budm for the replies. Looking at the manual posted, the schematic listed looks totally different from what I am seeing in my model. An example is single caps (6800U/50V) at C121 and 122, where as i have two caps at each location (4700U/50V and 4700U/35), but the rest of the PCB looks totally different also.

In reference to the clicking, I think I recall the clicking when the amp was working. Some sort of relay that clicks over from Auto to on mode, perhaps.

I had the similar issue but by switching the input to Line-Level Full-Range
Inputs connecting from receiver LFE to sub either L or R input now stopped making those popping noise and it turns off when no signal detected and on when is,before was turning on and off or just simply making noise when my receiver was off already ,I guess my Sub Line level input must be damaged somehow by my kids pushing the sub against the wall to often! I don't think this is your problem but I thought at least I share my findings!
Good Luck

[stj]

Re: Troubleshooting a Harman Kardon TS-8

resolder the relay & bridge rectifiers.
and whatever is under that very overheated part of the board in one of the foto's

[dkneyle]

Re: Troubleshooting a Harman Kardon TS-8

I've got one of these myself. Dear oh dear. Those power transistors look like they get bloody hot and should really have had a heatsink on them, don't they?

[Sparks88]

Re: Troubleshooting a Harman Kardon TS-8

dry joints on relay or relay shot

[jbs6053]

Re: Troubleshooting a Harman Kardon TS-8

am reading the thread, having similar problem, took it for repair, he said that a capacitor was changed and was working fine at his place, but took the thing home and same popping noises started coming out. called the guy and wants me to throw my sub mainboard and order a new one from Harman...is this for real

[redwire]

Re: Troubleshooting a Harman Kardon TS-8

30 seconds is a long time for problems.

Because subwoofer vibration can be hard on the electronics, I usually take a (plastic) pen and tap parts to check for broken leads or bad solder joints. Or a wack with a hand on the cabinet, to rule out a bad connection.

I'd watch for DC voltage on the amp's output and see if it is moving around.
It should be close to zero and stay there- unless there is a leaky cap in the signal chain. Anything beyond +/-1V would trip the protection relay.

There is a high-temperature trip (55°C EU/65°C USA) U101 with an adjust trimpot R138 and Q115 temp sensor on the main heatsink. It would activate the protection relay which then activates the mute circuit. Maybe this circuit drifts with age.

[Sundownee]

Re: Troubleshooting a Harman Kardon TS-8

Sorry all, I know this thread is old, but I was reading it for info, lo and be hold, I fixed my Harmon Kardon TS7 today, two Op amps with really bad solder joints and removed all the heated running glue that was shorting connections.
also changed a Cap, I need to change a few resistors as they have changed colour from heat, but do not have any of the correct size, will change later.....
Working great now with no popping or crackling.

Paul

[jiroy]

Re: Troubleshooting a Harman Kardon TS-8

It's better to know their resistance and change them before they do any damage . You can test them out of board .
I'm saying this , because i just changed one 150 Ohms 1 W in a Chinese crap power Mp3 player , and , surprisingly , they put the resistances values onboard , lol .

[snoobab]

Re: Troubleshooting a Harman Kardon TS-8

Sad day when my TS 8 stopped working.
Danged thing refuses to come out of standby mode even when set to on instead of auto.
It will however occasionally make a loud thump from the speaker even with no input connected, which gives me hope that somehow it can be resurrected, now if i just knew where to start...

[Moreno83]

Re: Troubleshooting a Harman Kardon TS-8

I would start with reading this thread haha.

You need to start with removing all the glue on picture 7 and then reflow most parts with fresh solder and see if it changes anything.