Beovox 1200 (type 6227)
From Helsingoer/Denmark
Owner has a complete Beosystem 1200 in beautiful oak, Beomaster, Beogram, Beovox.
One speaker had an intermittent tweeter. It got worse and worse and he decided to bring it to me.
A quick check confirmed that the tweeter itself was fine but it would only reproduce sound when the
cabinet was held face down.
A check of the filter board revealed that one of the two capacitors were only soldered properly at one end, the
other end pulled right up from the solder joint.
After more than 40 years on duty the old capacitors were retired and two fresh capacitors were fitted, the filter
board in the other cabinet had the same treatment to keep them identical and they both played on nicely again.
What a nice system this is.
Actually, the Beovox 1200 was produced in no less than three versions, both two-way and three-way versions exists
and to add to the confusion type 6227 can be either...
These were type 6227 in the two-way versions.

Martin

Beocord 2400 cassettedeck.
Based in Copenhagen, the owner brought this one in for repairs himself.
A nice and rather rare white design version and a very beautiful one at that but the deck showed no signs of life.
The mains fuse had blown. This usually happens for a reason and in this case the culprit was capacitor C20,
a 2200uF axial component in the power supply. It had turned into a dead short.
A nice blue replacement cured the poor thing. A nearby capacitor of the same brand, type and value
was replaced too for good measure.
Technically perhaps not the best deck in the history of recorded music but certainly not the worst either.
These decks are slowly but certainly getting rare. Worth holding on to.

Martin

A Beomaster 700K from my own collection.
At power up on the variac it was dead silent but pulling a little current.
The dial lamps were both burned. Two new lamps were mounted but that alone did not restore dial lighting.
The dial lamps have a dedicated fuse and fuse holder and both were completely green with oxidation.
New parts allowed the dial to be relit.
This always gives a good indication whether the radio chassis is powered or not.
A Beovox 1702 was connected as external speaker. It played something but sounded distorted.
FM stations were few and weak. Of AM stations there were none.
No reaction on the S-meter was noticed either.
The internal speaker leads was measured, leads were fine but the speaker was found o/c.
That is, measuring the speakers voice coil, across the thin leads running on the outside of the cone, the coil itself

measured fine.
The problem was narrowed down to a broken flex wire from the solder tag to the cone. It was soldered back in
place and the joint reinforced with a tiny drop of contact glue.
This brought back sound but didn't remove the distortion and the volume was still very low.
Sensitivity problems in the Beomaster 700K is often caused by the dreadful AF transistors used for the IF stages.
This case was no different. Two new IF transistors were fitted and I was rewarded with a dial now filled with stations
on all wavebands and volume was up to par as well.
Even a few stations could be found on shortwave which is almost always very quiet in my neck of the woods.
The S-meter was also back to being busy as the dial was travelled.
Four new rubber feet and a dose of teak oil ended this restoration.

Martin

Sony PS-T1 record player from a work colleagues daughter.
Speed had jitter, easily visible on the built-in strobo light. You could actually see that it was badly wrong by just
looking at the platter.
Looked like it was trying to switch between 33 and 45 twice for every revolution. Possible only because the platter was
very thin and lightweight.
Needless to put a record on this one at this point.
It even attempted to start backwards occasionally.
It's a very simple build.
The direct drive brushless motor was taken apart, all 4 coils measured fine which is good since they
look dreadfully machine specific and I have no Sony parts in the dungeons.
Driver transistors all measured fine but the signal fed to them looked very different on the scope.
The culprit was a simple little 8-pin IC 4558 where one of its dual opamps had given up the ghost.
This type of IC is also used in some B&O machines so the component drawer could provide a new IC which saw
it running fine, entertaining me for the rest of the evening.
I rarely do repairs beside B&O audio stuff but I thought I'd put it here since it was actually a recent repair and
it could come in handy for the odd surfer in need.
It was connected to a Beomaster 901 that has been soak testing for some days in an attempt to reproduce an
intermittent failure that I never experienced but the owner claims it has.
Ten days now without a single burp but that's a different story.

Martin

Beocord 8004 HX-PRO
This one arrived from the UK.
The owner claimed it had gone silent and the VU-meters no longer showed anything.
In an attempt to find the reason for this fault, the owner pulled some plugs and connectors around the
mechanical tapedeck section and put them back. This, however, merely resulted in a completely dead Beocord.
It arrived here in its original box, a very nice touch.
A couple of quick voltage samples showed that there were no connection to the regulators at the cooling fin.
This was caused by one of the ribbon cables not being fully inserted into its socket. They are kinda flimsy so this
was not a first.
Now, with power available again, the deck could be further examined.
The deck was silent alright, and on both channels so some common component was to be suspected.
All the major voltages were fine but the 7V reference voltage used for the Dolby ICs was missing.
A shorted 220uF capacitor of the dreadful black Roederstein type was duly replaced which restored sound and
VU meter action.
The record/playback relay was the original non-airtight type. I've seen this relay cause problems too often and
I like to replace it with an airtight type. It's a fairly cheap component and a 5-minute job so I replace it in
every Beocord on the bench.
A quick head clean, a good testing and it was returned to the owner.

Martin

I was going to comment that this is a nice feature Martin, then I saw that one of the items was mine!

Excellent stuff and please keep posting :)

John

Keep going!......

Great Idea Dillen!

I have been kind of wanting this for some time from you.

As you have my newly bought white Beosystem 6500 currently on the bench feel free to post any writeups or pictures you can. This goes for all B&O that you get from me.

Beolab Penta mk III
This pair was delivered to my door by the owner.
Very beautiful speakers that were both still playing but the owner was of the opinion that they were
no longer performing their best and he wanted me to restore them to their former glory.
A brief test proved one of them to actually sound somewhat alright while the other had a strange
midrange reproduction as if one or more of the midrange drivers had foam rot but I was told that they were
already refoam'ed so that couldn't be the case.
Work started and the crossover filters received new capacitors. So did the amplifier section and
the two large cans in the power supply in each tower was replaced with new 105degC types.
The signal path was upgraded with a couple of WIMA MKS-2 capacitors and the wonderful OPA2134 operational amplifier.
A check revealed the usual cracked solder joints to the driver transistors and the ribbon cable to the fold out front panel.
The midrange problem turned out to be caused by a bad refoam job; One driver rubbed badly on the center piece
when moved and all four had surrounds fitted that were cut down to size, presumably because the refoamer didn't
have the correct size at hand. Where the cut ends met up, there was just an opening, no glue or anything.
The glue used didn't hold on particularly good so the surrounds could be pulled right off.
When removed the original size of the foam ring could immediately be revealed in that the remains sprung
back to the size of what could easily have been a 5" ring. And this was a pro job ( ! ? ).
All internal cabling in the towers was then bypassed and new Van Del Hul Snowline cable was fitted.
All the spade-type plugs were cut off and the connections soldered instead. Let me say right away that it's
my opinion that those spade-type connectors are in fact very good and the original internal cabling adequate but
the owner wanted it this way and, well, it doesn't harm anything as long as cable lengths are kept long enough for
the crossover boards to be pulled out without desoldering anything.
New trimmers were fitted to the amplifiers and the idle current and DC offsets were set as per factory specs.
Three days of work and the final testing proved the job to be worthwhile.
The speakers now sounded considerably more fresh, open and ready and also much more identical. Gone
was also the strange midrange performance.
The restoration was rounded off with a fitting of fresh cloth to the four front grill panels. The original cloth was
actually still intact but it had faded and greyed badly as most of these have by now.
Everything now sounded clear, bright and undisturbed again and the speakers looked great.
The Pentas were always one of my own favourite speaker designs.

Martin