Sign in   |  Join   |  Help

First attempt at Beomaster 2400 'refurbishing'

rated by 0 users
Answered (Verified) This post has 3 verified answers | 48 Replies | 2 Followers

jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member
jesperb posted on Thu, Apr 26 2018 12:39 PM

Hello All,

Starting my first real repair project on a Beomaster 2400 - no previous BeoFixing experience, but lots of electronic DIY. This model came from my Dad, which is why i said yes to try to fix it, besides always having wanted to having fixed a Beomaster by myself (counting on a little help from my friends). It will be a rather long project, because summer is creeping up, but if it rains as much as last year, could be a quick fix after all.

Problem is 'no audio - hissing sound in both channels - volume control does not work'.

Took the lid off last night, things of immediate notice :

-End panel (left) missing - anyone got a spare in dark rosewood ?

-Sliders in really good condition, no dust, no coffee spills - nice and clean.

-Bass section, ceramic caps are 'crushed' (see pics) ?

-Output trannies (IC200,201,300,301) have been repaired previously and BADLY resoldered.

Cheers,


Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

Answered (Verified) Verified Answer

Dillen
Top 10 Contributor
Copenhagen / Denmark
10,725 Posts
OFFLINE
Founder
Moderator
Answered (Verified) Dillen replied on Thu, Apr 26 2018 2:50 PM
Verified by jesperb

The polyester caps are not part of the kit. They are usually still fine.
And it's not uncommon to see cracks and flaking off of the outer layer of the "tropical fish" types - though in this case it
seems to be a bit more than usual. You could replace them, but I wouldn't suspect them at this point.

Capacitors and balance control slider much more likely.
But of course, any and all signs of previous repairs should be looked at - and in this case tidied up a bit.

If the lamps are still the original, you will need new ones when you are done servicing the rest.
The filaments in the old lamps become brittle from heat and age and the unavoidable vibrations from servicing will
break some. Replacing those will then break more. You have a fresh full set, might as well replace the lot - but wait until
repairs to the Beomaster is about done.

Martin

Dillen
Top 10 Contributor
Copenhagen / Denmark
10,725 Posts
OFFLINE
Founder
Moderator
Verified by jesperb

The balance potentiometer is special in that it operates from the center outwards, - and with the channels in antiparallel, rather than
from one end to the other in parallel.
In other words, at center position both channels should read zero ohms.
As you move the slider left the resistance in the right channel increases while the left remains at zero - and vice versa.
You lower the signal in one channel in each direction from center. At center no channels are lowered.

The resistive tracks only varies from the center towards each their ends. The other ends (respectively) of the tracks doesn't vary.

Martin

Dillen
Top 10 Contributor
Copenhagen / Denmark
10,725 Posts
OFFLINE
Founder
Moderator
Verified by jesperb

If the Beomaster will switch on briefly - even if only for a fraction of a second - you should be able to tell if one output has
a high DC level, pointing to a problem in that channel.

Martin

All Replies

jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member

Output stage bad soldering

 


Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

Beo_Jean
Top 200 Contributor
QC, Canada
284 Posts
OFFLINE
Bronze Member

Great!  Another project showing up!

Things I'm noticing from the pictures are:

- ROE red capacitors --> changed them asap.

- The cracked capacitors are not ceramic but metallized polyester (MKT):  Depending on the values, you can use Vishay MKT1822 or MKT369 but you can also use MKT brand as well.

- Really bad soldering on the output transistors but you may want to check them to see if they were properly matched...

jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member

Hey,

Thanks for the input - i simply couldn't remember what that type of caps were called in techspeak :-)

I will check the output stage transistors, before or after recap ?

Already got a kit of caps + lamps + slider holders from Martin/Dillen. Lamps and sliders will not be needed though, both parties look to be in really good shape.

Thanks,

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

Beo_Jean
Top 200 Contributor
QC, Canada
284 Posts
OFFLINE
Bronze Member

Ask Martin but I don't think the cracked capacitors are part of his standard cap kit...

Dillen
Top 10 Contributor
Copenhagen / Denmark
10,725 Posts
OFFLINE
Founder
Moderator
Answered (Verified) Dillen replied on Thu, Apr 26 2018 2:50 PM
Verified by jesperb

The polyester caps are not part of the kit. They are usually still fine.
And it's not uncommon to see cracks and flaking off of the outer layer of the "tropical fish" types - though in this case it
seems to be a bit more than usual. You could replace them, but I wouldn't suspect them at this point.

Capacitors and balance control slider much more likely.
But of course, any and all signs of previous repairs should be looked at - and in this case tidied up a bit.

If the lamps are still the original, you will need new ones when you are done servicing the rest.
The filaments in the old lamps become brittle from heat and age and the unavoidable vibrations from servicing will
break some. Replacing those will then break more. You have a fresh full set, might as well replace the lot - but wait until
repairs to the Beomaster is about done.

Martin

jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member

OK, polyesters are just flaking - never seen them so bad before though.

Looking at the rows of caps in the kit, it's like i'm the richest man in the world - uncharted territory ahead.

Will clean sliders.

Will swap the lamps as the last task - but first a long weekend off.

Nice hint about the lamps, and common sense, put in another context : I recently busted my last glow lamp, bumping it around a bit with the vaccuum cleaner.

Thanks very much, enjoy.

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

Rich
Top 50 Contributor
Orlando, Florida, USA
2,570 Posts
OFFLINE
Bronze Member
Rich replied on Fri, Apr 27 2018 1:53 AM

I may have an end panel.  Are you in the US?


jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member

Thanks for offering, but we found the missing panel in the attic. Turns out the panels are black - not wood 

Cheers,

PS I am in Denmark

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

Dillen
Top 10 Contributor
Copenhagen / Denmark
10,725 Posts
OFFLINE
Founder
Moderator
Dillen replied on Fri, Apr 27 2018 7:57 AM

Not original in black.  They were painted then.
The serialnumber label will usually tell the original finish. 

Martin

jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member

Didn't notice - nice paint job or i need better glasses (probably the latter) ...

Model/type : NR 2400/2901

s/n says : No 15130001 SIGN E4 (in blue ?)

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

Dillen
Top 10 Contributor
Copenhagen / Denmark
10,725 Posts
OFFLINE
Founder
Moderator
Dillen replied on Fri, Apr 27 2018 12:35 PM

Originally light oak.
So the backsides of the plastic panels will be a beige color.

Martin

jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member
jesperb replied on Fri, Nov 16 2018 12:25 PM

Update : So the 2400 has been in the closet for more than six months, awaiting dark and cold nights, best fit for a soldering iron etc.

But come November, I am well into recapping, with the kit from Dillen (thank you!).

A practical question : Does anyone have an easy way to locate which soldering points belong where, when unsoldering ?

For reasons unknown, i have some trouble hitting the right points. Could be lack of practice.....

New slider bridges (also from Dillen) were quite easy to swap, lamps also went fine.

In the meantime, I got a really (really) old Metric variac,i plan to/hope to use for the testing. All including dust, spiderwebs and black fuses. New 3A fuses took care of that, at least for now.

Have a nice weekend :-)

 

 

 

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member

 

Looks like the previous 'repair person' was somewhat of a brute for quick (& dirty?) solutions.....

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

jesperb
Not Ranked
64 Posts
OFFLINE
Silver Member

Not all of the old caps were happy-campers...

Beogram TX, Beovox S45, Beovox MC 120.2, BeoSound 1, CX50, Beovox S75, Beomaster 2400

Page 1 of 4 (49 items) 1 2 3 4 Next > | RSS
Beoworld Security Certificate

SSL