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Audio Repair Restoration Project: Klipsch ProMedia Ultra 2.0 Computer Speakers.

By Jestine Yong on January 30, 2015

These speakers have a cult following worldwide, due to their compact size with outstanding sound.

1. Clean the On/Off/Volume Potentiometer-Switch.

They have had a very reliable history, with usually only the On/Off/Volume Potentiometer-Switch being faulty, and that is an easy fix, using a spray such as DeOxit FaderLube, which cleans the crud, and removes the dropouts and scratchiness.

Some people have chosen to replace the potentiometer entirely, which is a matter of free choice. As far as I am concerned, unless you are selecting $100 gold-plated MilSpec components, any other $1 Chinese potentiometer is not going to be any better, than the potentiometer which was factory-installed.

My customer brought me this unit, with the complaint that it does not power on. Immediately, of course, I suspected the On/Off switch. But a quick test proved that this switch was perfect, and so this was a problem which I’d not seen before with this unit.

This is NOT at all a user-friendly unit to disassemble, even for a skilled technician. The double-decker PCB’s are soldered together via 11 pins, which requires tedious desoldering and separation. Not to mention having to fabricate wiring between the 2 PCB’s to facilitate troubleshooting and testing. It may be cheap for production, but it’s a pain to repair.

2. Upgrade the Electrolytic Capacitors

My first Go-To solution is checking all the electrolytic capacitors. On this unit, they are made by Capxon and Orient, two well-known players with well-deserved reputations for sub-standard components.

But once again, their ESR tested OK – not great, just OK. So that was not the problem.

However, I decided to replace them anyway with Nichicon HE and KT audio capacitors, to ensure reliability and long-life after the repair.

3. Check Power and LED

I connected power and did a quick check of the power circuits – everything looked OK.

So, now I proceeded to check the On/Off rail. Of course, one end of the rail terminates at the LED. I tested the LED, and it illuminated just fine, so that was not the problem.

I had to remove the On/Off/Volume Potentiometer-Switch from the PCB to determine which traces went where, in order to locate any possible problems.

I scratched the green mask off a couple of traces, in order to check continuity, and here I ran into a problem.

4. Check for Continuity

The On/Off rail disappeared under the TIP32 transistor. So I removed that. I checked for continuity again, and there was none!

Here, as is quite common in Chinese electronic assembly, the factory assemblers had been very liberal with glue to hold down the TIP32. And I’m sure that there were plenty of scratches in the green mask, from less-than-careful assembly.

So we have a well-known and deadly combination for electronic components – Burnt glue (due to the heat of the adjacent TIP32) is conductive and highly corrosive, and it caused a break in that On/Off rail.

As a probable random occurrence, this is not a problem which I would expect to be too common with this particular unit.

However, the destructive results of burnt glue are more and more prevalent these days, and so broken copper traces are an increasingly common occurrence in electronic equipment sourced from China.

If a technician sees burnt glue on a PCB, it pays to investigate that area for likely shorts or breaks.

5. Repair the Corroded Trace Break

I cleaned up the area to fresh copper, and then repaired the break, which connects the LED and On/Off rail to Ground in order to complete the circuit, and the unit returned to full-working condition.

6. Upgrade the Bridge Rectifier Diodes

I did an additional upgrade according to the customer’s request. In the separate Transformer-PSU block, the bridge rectifier is made up of 4 1N5400 3A silicon diodes. There is nothing special about them, and they do the job.

I replaced those with 4 Vishay SB3H100 Scottky diodes, with far better performance for audio, and with a small side benefit – because they have a VF Drop of only 0.3V, there is an additional 1 volt on each of the +18V and -18V power rails. It’s always nice to get a tiny bit of extra power in an active speaker!

Parts for this restoration

Parts and advice are available for owners who wish to tackle this project by themselves.

http://www.condoraudio.com

This article is contributed by Menahem Yachad and for more information about his other repair articles please visit the link below:

https://www.jestineyong.com/author/yachadm

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14 Comments

Phumlani

January 30, 2015 at 1:56 pm

Well done sir,I've learn a lot on this article

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Robert Calk

January 30, 2015 at 2:09 pm

Good job Menahem and thanks for the article. I have some Bose laptop speakers and they sound really good. The laptop doesn't output much power though. The speakers will turn up real loud when I plug a radio up to them.

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Mark

January 30, 2015 at 6:32 pm

Hey Menahem,

Thanks for a well written and logical diagnostic path that was easy to follow.

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Corriete

January 30, 2015 at 8:07 pm

well done article.thanks

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Yogesh Panchal

January 30, 2015 at 10:02 pm

Good experiment!
thanks for sharing.

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Humberto

January 30, 2015 at 10:20 pm

Good job Menahem Yachad, thanks for sharing your knowledge.

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Mario

January 30, 2015 at 11:14 pm

Interesting articles well done

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Josie s. koker

January 31, 2015 at 12:44 am

Your articles are so interesting that I really studied electrical installations technology which has some components of electronics which I had not liked at all for some very precise problems which has been always had to figure out for me, which has not made me like the electronics parts of things, but i think i just have to please prescribe suggested books of understanding electronics components better in circuits when good or bad. thanks.

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t.kingsley

January 31, 2015 at 12:05 pm

i am very much interested in audio service, but your experience is giving me more experience. thanks for your sharing.

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Kiet T. Le

January 31, 2015 at 10:05 pm

That was a good piece of work Menahem. Continue to rock on as you are!

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Albert Hoekman

February 2, 2015 at 6:38 pm

Nice job and explanation.

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Amir Mukhtar

February 6, 2015 at 3:25 pm

Thanks you Mr. Menahem Yachad to share Restoration Project of Audio Speakers.

Keep Sharing your Expert ARticles to Learn and Experiences.

Good JOB

Amir Mukhtar Ashrafi

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Taring

March 30, 2015 at 3:23 pm

Thank you for your nice article.

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Ian Johnson

May 25, 2020 at 9:22 am

Thanks so much for taking time to publish this information. I picked up two of rmthese sets (=4 total speaker units) at a local thrift store. $4.00 a set! $8 total. When I test and they didn't function I planned to rip the speakers out and trash the cases and amps. Glad I didnt! Saw this and dug them out. Exactly the problem on both sets! I didn't want to reassemble once repair was made(thanks to your info) so I decided to build my own sound bar with the two sets. Birch wood with plexiglass viewing window. Interior of bix lighted in blue. And finished with an espresso color stain topped over with 4 coats of polyurethane! One of the most beautiful projects to come off my bench. Thank you for your unaware assistance.

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