Harman Kardon 395 Sub Woofer & Satalite speakers

[groovejet]

I ve noticed a change in the quality of sound from my Hk 395 speakers.
The 2 satalite speakers seem fine, its the sub woofer i thinks to blame?

When turning the woofer volume pot there's a lot of distortion / crackling.
Also this week, when i was watching a movie there was also heavy distortion on the lower bass sounds, with a lot of vibration.

I noticed taking the back off the speaker seemed to ease the unwanted noise, and then i noticed a couple of caps i wasnt happy with!
I tested these with a multimeter as i hav'nt got a esr meter. My readings were pretty suspect, as i could'nt differentiate from a leaking cap of glue type substance from manufacture?

Anyway i changed these caps (25v 470uf) (50v 2.2uf) and what do you know? A big improvement.
I thought i'd got it but couple of days later i heard more distortion??

From what a friend said the caps on the board were audio ones and i changed them to something else?? (They were blue color, i changed to black ones)

Now? Ivé stripped the speaker down and removed the volume pot and trebble pot from the board, and im going to swap them over!
My thoughts were that the volume pot has had more hammer than the trebble, so changing them will give me decent volume control.
But i want to clean them up also? Markings on them say B503

Any help to get these bad boys working 100% most appreciated

[lti]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

Cleaning the potentiometers will help. Spray contact cleaner in them and turn the shaft until it turns smoothly. It will feel rough after the contact cleaner is sprayed in.

Replacing all the electrolytic caps is a good idea. Harman/Kardon used the cheapest caps they could find back then, and their amps run warm. I had to recap some little HK-206 speakers a few years ago. Just use good 105°C caps like Nichicon VZ series. The old ones definitely weren't audio grade, and you don't need audio grade caps anyway.

I think B503 indicates a 50K ohm linear pot.

[Kiriakos GR]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

In audio you need branded caps and not 105°C, they make no difference.

I have Yamaha http://usa.yamaha.com/products/audio...ems/ystm20dsp/ which need recaping 100%.

[lti]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

You're right. This amp probably doesn't get hot enough to need 105°C caps. Good quality caps will last longer than the originals, no matter what the temperature rating is.

[groovejet]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

Removed the pots.
The volume pot was clean but when i pulled back the metal tabs holding it together i noticed very small pieces of the plastic body cracked off.
This broken part would of held it secure in its metal enclosure, which is why there was so much interference.
Anyway i havnt got replacements and its Sunday so i stripped, cleaned and put them both back together, then swapped the dodgy one for the treble pot which doesnt get any use.
Works much better, although at very high volume a problem still exists. Its a vibrating popping noice(pissing me off)
Thanx for help up to now

[groovejet]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

How do i identify good and bad caps?
Meaning good quality made ones?

[Kiriakos GR]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

How do i identify good and bad caps?
Meaning good quality made ones?

By comparison of their named specifications ( specs sheet) by using a 200$ portable LCR bridge.

[lti]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

If you're wondering what brands are good, look here:
https://www.badcaps.net/forum/showthread.php?t=414

Anything from those brands (except Mallory - they're made by Teapo now) will work. You don't need expensive caps.

There is the possibility that one of the chips is bad, but changing those cheap caps would be good to try first. I don't know exactly what kind of noise you're talking about. If there is a constant hum in the background, replace the caps. Other types of noise could be caused by bad caps or another component failing.

[JJR]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

Panasonic & Rubycon caps here http://cpc.farnell.com/aluminium-ele...etResults=true

Both top quality & free delivery from CPC Farnell.

[groovejet]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

I know its difficult to explain the types of noice im experiencing over a thread, but thanks for all the help thus far

[budm]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

You can improve the power supply peak current demand by changing that 470uf 25V filter cap to one with low ESR and higher current ripple spec, you can also go to 680uF if it will fit the board.

[budm]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

BTW, you should also remove those brown glues.

[groovejet]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

I will remove glues but Why??

The 2 poly caps closest to the heat sink were stuck together. I pulled apart to check whether they were leaking or were actually glued!
So my question ....Why glue these 2 and not other components? Whats the reason for all this glue, because it doesnt seem to be helping in any way?

[budm]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

https://www.badcaps.net/forum/showthread.php?t=34692
They use glue to hold down components during wave soldering process.

[momaka]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

You can improve the power supply peak current demand by changing that 470uf 25V filter cap to one with low ESR and higher current ripple spec, you can also go to 680uF if it will fit the board.

470uF only? For a speaker setup like this?! Man, that's some cheap build quality there. I wouldn't go with anything less than 2200uF. If the cap doesn't fit on the board, it's okay to have it sitting high on its legs. After all, this is not high-frequency PSU, so ESR and long leads won't affect the operation.

Then again, that transformer is puny too!

[budm]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

@2200uF it may trip the fuse due to high inrush current, have to measure the inrush current to find out.

[lti]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

I think C34 (the largest cap on the board) will be the filter cap. It's at least 2200uF, based on its size. There's no way that the filter cap is only 470uF. Even the little HK-206 speakers (using a TDA1517) have a 2200uF cap in the AC adapter and an extra 470uF cap next to the power input jack in the amp. This isn't Cyber Acoustics.

[budm]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

From post 1 "Anyway i changed these caps (25v 470uf) (50v 2.2uf) and what do you know? A big improvement" unless he did not change C34 which is the big filter cap.
You may be right that it is 2200uF based on the size of the rectifier diodes and the heatsink, the 470uF will not be able to handle the current demand.

[poconoman]

Re: Harman Kardon 395 Sub Woofer & Satalite speakers

Hi all, great site!

Was wondering, what size woofer is in the hk395 subwoofer and would upgraded driver improve the bass? If yes, what woofer do you suggest?

Thank you!