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2019 State of the Art - Penta MKIII restoration

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Chris
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Chris posted on Tue, Aug 27 2019 3:22 PM

Hello,

I am about to be given a pair of Penta MkIII, photos show that all the foam is rotted.  They haven't been used in years.

 

What is the value in going through a full restoration? Is at absolutely unrealistic, or are there still supplies and materials available such that these can be brought back to life?

Foam, amps, electronics, cones, there are many things possibly needed repair/replacement.  Are there things that are simply no longer obtainable?

 

Thank you

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BEOVOX141
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IMHO well worth the effort!

There are simple ways of doing it, but you can also turn it into rocket science. Schematics and tips are available here on Beoworld.

Almost all parts are readily available, either as originally specified or equivalent parts. And for the really ecsotic parts like the display you can always find a donor speaker. Refoaming the midranges is a DIY job with plenty of instructional videos available. 

Best of luck Smile

Chris
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Chris replied on Wed, Aug 28 2019 3:25 PM

This is a remarkable community. Thanks for the encouragement and information.

 

I've seen other discussions here about "Good HiFi" replacement foam for these Penta MKIIIs.

How much would be accomplished of the restoration if these are refoamed, and the amps are freshened with Dillen's service kit?  What else typically needs to be repaired or replaced in these speakers to have them back to making beautiful music?

 

--Chris

Dillen
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Dillen replied on Wed, Aug 28 2019 4:54 PM

chris_in_cal:

What else typically needs to be repaired or replaced in these speakers to have them back to making beautiful music?

Capacitors in the crossovers.
Readymade kits are available for some versions.
I would need to see a photo of the filter circuitboards so tell if a kit is available.

With regards to foam surrounds, my personal experience is that Audiofriends' surrounds are the least bad.

Martin

 

BEOVOX141
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chris_in_cal:

I've seen other discussions here about "Good HiFi" replacement foam for these Penta MKIIIs.

How much would be accomplished of the restoration if these are refoamed, and the amps are freshened with Dillen's service kit?  What else typically needs to be repaired or replaced in these speakers to have them back to making beautiful music?

Hi Chris

If the drivers are still intact, I wouldn't refoam them. My MK IIIs still show no sign of foam rot, It all depends on the environment they have been subjected to.

The two big 10000uF electrolytic caps in the power supply (not in the replacement kit) will eventually fail, and I would recommend replacing them asap. 

The choice you make here is where thing turn into rocket science,- the price range is 10-75$ a piece, Perhaps Dillen has a good suggestion?

As long as you stay away from EBAY parts (Use Mouser or Digikey) you should be fine.

If you have no equipment available I would recommend leaving the R95 trimmer alone.

A hint: When you start swapping components do it in small groups and then do a test, It makes it a lot easier to isolate an issue if you can narrow it down to a few parts to begin with.

Make sure you have a PAPER copy of the schematic where you can make notes and markups, I cannot stress this enough!

The PCB material is FR2 Phenolic paper and the peel strength is close to zero, always extract pins from the component side AWAY from the board.

... And be careful you are dealing with 150V across the supply rails. With the 10000uF caps there is 110j of energy stored.

If in doubt,- its always better to ask another question than wreck the whole thing beyond repair.

 

Chris
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Chris replied on Fri, Aug 30 2019 3:21 PM

BEOVOX141:
If in doubt,- its always better to ask another question than wreck the whole thing beyond repair.

Truer words have never been spoken...thank you all again. I'll probably be bringing them home this Sunday. I'm excited.

Chris
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Chris replied on Sun, Sep 1 2019 10:38 PM

I got the speakers today.

BeoLab Penta 3

Type: 6633

12752602 US 10 SW 1.1

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They do not have speaker cords.

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