In this thread I will try to document and tell about the repair and
restoration of a vintage Bang & Olufsen radio, namely
the JET Present 607.

Built in late 1960 for the 1961 season model range, the
JET Present 607 is somewhat large but still categorized
as a mid-sized table radio with several good features and a
superb build- and sound quality as would normally be expected from B&O.
The MINI Present 607 of the same year was almost the same build
and chassis but didn't have the extra "luxury" functions such as f.e
the extra row of buttons just below the speaker grill
with tone-controls and a direct button-operated choice of using an
eventual extra speaker (possibly in another room - hello Beolink !).
The JET was meant for use in the livingroom and is stylishly designed
in real teak veneer to match the contemporary furniture fashion.
Typical of the period is also the piano-type keys and the
round knobs each end of the dial indicating that B&O was
still following other brands though they actually managed to make a
high-quality radio that didn't look as "clumsy" or "alien" as many others.
No wonder the modern looks and ease of use made it a quite popular
model despite the fact that all lettering is in danish suggesting
that this model was not meant for export.

 

 

The Jet Present 607 has FM but also a quite extensive AM coverage
with both FM and AM antennas readily built-in, both very good.
The FM antenna is a dipol made of alu foil glued to the inside cabinet
with soldered wires running out the back to two plugs allowing the
use of either the built-in FM antenna or an external.
The AM antenna is in the form of a ferrite rod with coils,
cleverly mounted so that it can be rotated inside the radio by turning
a knob on the front.
In practice AM is much more sensitive to direction than FM so making
the AM antenna this way is the better alternative to rotating
the whole radio to get the best signal.
The JET Present 607 features an arrangement of two speakers;
The large oval KINO 160TV woofer from B&O's own production along with a
Peerless MT20HFC tweeter. A simple crossover, not unlike that
of the later Beovox 1000 is mounted directly at the baffleboard.

A quite extensive tone control was available with two combinable
filter positions for bass and the same for treble plus the
extra settings for "Speech" (Tale), "Music" and both together "Orchestra".
An input for a grammophone (GR) is present and a similar
plug at the back is for an optional external speaker.

 

 Some call them valves, in the US they are named tubes but since
this is a UK site I will go with the english and stay with valves.

The valve line-up brings no surprises;
UCC85 / UCH81 / UBF89 / UABC80 / UL84 and "magic eye" UM84.
The rectifier is of the metal-type and the radio is built on
the early pertinax type PCB boards.
One large board holds most of the components and one smaller
board is found inside the screened VHF (FM) metal can.

 

Little marks of the passing years and daily use is fine in my opinion,
it's part of the radio's history and this particular unit is in
great shape, obviously loved and cared for from the first day
and 46 years have passed leaving only a couple of
minor chips to the veneer at the sides, all the way back
at the rear edge, nothing major and the rest is absolutely beautiful.
All in all a good project, definitely worth restoring.
The restoration will be aiming at making the radio work like new again and also be safe to use.

 

Regarding the safety, everything with valves always bears a risk of personal
injury if poked the wrong places.
This radio is no exception. There are two leads in the mains flex and
after the mains switch one goes directly to the
metal chassis so the chassis can potentially be the bearer of live mains.
Furthermore, voltages greater than that of the mains can be
found elsewhere inside, even after power has been turned off
so don't poke around the inside unless you know what you're doing !
(The red circle indicates where the green wire goes directly from the mains
power switch to the chassis).

Wonderful project! I'll tell Tim to log in to have a look! I am sure this would interest him.

Before powering up a valve radio for the first time after standing
unused for years it's always a good idea to do some initial checks
to insure that nothing drastic is about to happen.
This is a matter of personal safety and also a matter of insuring that
no components are becoming damaged, possibly totalling the radio.
A few initial checks and measurements proved that even if probably
not readily working, the radio would at least be fairly safe to apply power to.
Connected to one of my trusted B&O RT12 variac's, the voltage was
slowly brought up, keeping an eye on the current-meter which didn't
really show anything...
The radio was not drawing any mains current and, not suprising, didn't do a thing.
The upper part of the chassis is accessible by removing the back and
the solder side can be reached from underneath where a panel can
be dismounted, so at least accessing the innards of this little
beauty is fairly easy.
The back came off and I took a look inside.
As with many other 60's B&O's the schematic diagram was found in an
envelope placed inside the cabinet, very nice !
As an important part of the radio, the original schematics will
of course be placed back in it's envelope after servicing.
I will probably be working mainly from the original service manual anyways.
Inside, the cabinet was stamped "10 Nov 1960", precisely confirming the
dating of the set.
Finding production dates stamped inside the older B&O's actually is very common.
A brief look around revealed that two valves were missing, namely the
UCH81 Mixer/oscillator (or "Frequency changer" as some like
to call it) and the output valve UL84 but no other signs of any previous "service".
The valves heaters are all in series so with one or more valves
missing it was no wonder that it didn't do a thing.
Now the access panels were off, it allowed me to do a couple more checks prior
to powering up again. Everything looked if not fine then at least safe
which is good enough for now.
Down the dungeons to find two replacement valves from a scrapped set.
Fitted them and checked that the rest of the valves were of the correct
types and in the correct positions which they were.
Up with the variac again, carefully monitoring everything.
Feeling for hot components, watching the current flow ....
- nothing !
I decided to check the internal mains fuse, it didn't look too good.
Clamps all green by oxidation and along with the fuse holder
the fuse itself came completely apart when touched.

 

I wanted to keep the appearance fairly close to the original, also
inside so the fuse holder needed to be repaired rather than replaced.
A newer part was found with holding clamps looking exactly like
the original so these clamps were transferred to the remains
of the old holder and a new fuse was mounted. Much better.

 

Up with the variac again, monitoring the amp-meter...
- nothing !
In came the voltmeter, showing that the voltage reached- and passed
the fuse now and the high voltage (HT) was present at the main
smoothing cap and filter caps but the valve heaters didn't glow.
The heaters are all in series and the ohm-meter showed that all
heaters had good continuity. What failed here was the dial lamps,
which are also connected in series with the valve heaters.
The ohm-meter showed that both lamps were burned.
The lamps are bridged by some kind of thermistors, allowing the current
to bypass one broken lamp but with both lamps out there was no current flow.
In most cases, the dial lamps are standard 6.3V but not in this case.
Here the lamps were only marked Philips 8005D which didn't give
much hint to the voltage and current ratings.
The internet is a good thing and the Philips code was soon decoded as
18V 100mA with E10 socket. This type of lamp is found elsewhere in
1960's B&O's, Beomaster 1000 and Beomaster 5000 to name a couple so
I had some in stock.
Two new lamps were mounted and the variac was slowly turned up again...
Both lamps lit up, brightening up the dial for the first time in years
and, a brief moment later an amount of hum was emitted from the speaker.

 

It can be considered normal for a valve radio to hum a
bit during warm-up but then it's supposed to fade out,
allowing programme sound through.
Not here. The hum only increased, accompanied by slight crackle and
it remained at the same level regardless of the position of the volume control.
No programme sound could be heard anywhere on the dial.
The magic eye was lit but stood frozen, indicating no change in signal
strength as the dial was travelled.
Well, at least we had some reaction from the radio now with at least
the output stage doing something which, along with the fact that the
speakers were probably also OK, made the best news so far.
Replacing capacitors is an essential step in any restoration and this
little beauty is no exception. Especially the smoothing- and filter
caps is of interest in this aspect but also the caps around the output
stage valve is known to cause trouble.
The output valve grid coupling capacitor in this radio was of the
mustard-colored axial type. I always considered these caps extremely
reliable and a quick check revealed no DC on the grid of the output
valve so this cap was still doing fine.
The cathode decoupling cap is of the electrolytic type and is also
a wellknown troublemaker. It sits in parallel with the cathode
resistor which is of a rather low value (270 ohms) so the cap
was desoldered and checked outside the radio.
The ohmmeter showed that even if the cap wasn't quite dead, it was
leaking current and a reading of a couple of hundred kilo-ohms suggested
a replacement was adviceable though it clearly wasn't the reason for
the radio not working.

The photo shows the old cap and it's modern replacement.
Had this been a rarer or much older radio I would probably have
hid the new component inside the emptied shell of the old one to
preserve the original look.

 

 

Humming can be caused by several things; Leaking smoothing- or filter caps
and too high output valve anode current just to name the main causes.
In series with the metal rectifier a 47 ohm ceramic resistor is mounted
to slow down the rush-in current in case the radio is switched off
and then back on again while the valves are still hot.
This would otherwise place a huge stress on the rectifier and the fuse may even blow.
This resistor comes in handy when measuring the current drawn by the radio.
A voltmeter revealed that the resistor was dropping apprx 3,4 Volts.
Using Ohms law we have a current of (3,4/47) ~ 72mA.
The service sheet gives 83mA so this is clearly not a case of excess
currentflow anywhere, quite the opposite in that we are apprx 11mA short ...

With the oxidated fuse in mind, the valve pins and sockets
were checked next.
The sockets all looked fine but some valve pins showed signs
of oxidation so all valves were dismounted to have their pins cleaned
using a glass-hair brush.
What a difference it made !
With the radio on AM, it started playing as the variac was turned up
but the sound was quite distorted and fairly low in volume.
The hum was still present but the radio was, apart from this, completely
dead on FM (VHF).
I now concentrated on the FM front-end which is housed in a
screening can, mounted in rubber supports to avoid mechanical
vibrations coupling to the front-end UCC85 valve (microphonics).

 

The UCC85 is a combined valve and has two anodes.
The service sheet gives the anode voltages as 144 and 154 Volts respectively.
The voltmeter showed 143.5 (close enough) and 112 Volts (no good) so
a replacement UCC85 valve had to be found.
The replacement gave 145 and 143 Volts so was clearly better.
Still not spot-on but should at least be able to bring some life into
the front-end but the radio wasn't working any better...

A good idea is to measure the AGC voltage (Automatic Gain Control)
which is here to compensate for stronger and weaker stations.
This is especially important on AM since the amplitude of the signal
is otherwise directly related to the programme sound volume requiring
you to turn up and down the volume according to the signal strength
of the currently tuned station.
Without AGC stronger (or geographically nearer) stations blasts through and weaker stations
won't be heard unless the volume is turned way up making travelling
the dial an unpleasant experience.
The AGC signal goes to the front-end, setting it's amplification
but also goes to the magic eye for showing the strength of
the signal from the station currently tuned.
A negative voltage is to be expected here, varying according to the
signal strength, somewhere between 0 and -15 volts (negative to chassis)
the stronger signal the more negative.
AM showed a good variation of the AGC voltage across the bands but
at FM it remained very close to zero.
Back to the front-end and the still-fairly-good-but-not-quite-up-to-spec UCC85.
Whereas most valves are actually fairly reliable and long-lived,
this is not the case with the UCC85. It's comparatively short-lived
and I wouldn't be surprised if after 40+ years it had given up the ghost.
The one last mounted showed low grid voltages so a NOS UCC85
was mounted.
This was much better, all voltages at the valve now tallied
almost precisely with the service sheet. I was now
rewarded with one single station on FM, drastically distorted and
almost drowned in the background humming.

 

Back to the missing 11mA. With the introduction of the NOS UCC85
that brought the front-end to life, the current now looks much
better, measured and calculated to apprx 80 mA.
Very close to the service sheet but still not spot-on
and the radio still wasn't working very good.

The old coal-type resistors are usually very reliable.
Having said that, in some stressed positions, especially high-value
resistors working with high voltages can cause problems.
Resistors of 100Kohm or more tend to go even higher in value with age
resulting in a reduction in current flow and often an otherwise
unexplainable disfunction.
The radio was allowed to cool down and I brought out the ohm-meter,
working my way across the board I set out to check each and
every resistor I could find. Especially the anode resistors
are of interest here since they are working with high voltages and
are often of high resistance values, typically 470Kohm or more.
All measured with results within reason...
Power up again, this time to check the anode voltages.
Starting at the output stage where the current flow is greatest
and working backwards.
The output stage voltages were all spot-on but the triode-part
(pre-amp) of the combined valve UABC80 showed an abnormal anode voltage.
Some 4 volts were found where the service sheet suggested 72 Volts
so here was definitely something fishy going on.
The anode is fed from a single 220Kohm resistor and since
all resistors were just checked, a replacement UABC80 was fitted.
This brought about ....
- no change at all.
What is going on here ?
Measuring from the solder side, it seems as if the anode
resistor is open circuit.
Looking from the component side, the resistor...
... couldn't be found.
Out came the Sherlock Holmes cap, only to find that the resistor
was indeed there but put up against the back of an IF coil screening can so
neat and tightly, it was practically not visible unless using
a dentists mirror.
Obviously, exactly this one single resistor was overlooked when I thought
I checked them all.
It was desoldered and checked, completely open-circuit.
The service sheet gives the current flow to the triode as 3mA,
precisely what was missing.
A new resistor was mounted and I was greeted with lots of stations
at, initially, VERY HIGH VOLUME.
The sound was pleasant, undistorted and the bands were all
filled with stations. The radio was played the whole next day, showing
no further electric problems.

 

While repairing, I noticed that the chassis was mounted
slightly offset towards the right side. The group of piano-type buttons
was not centered within the wooden frame cutout, causing
the far right treble control buttons to rub the wooden frame and
even bind to eachother occasionally.
This was corrected by losening the two screws holding the chassis
to the cabinet and sliding the complete chassis apprx one millimeter
towards the left.

 

The dial string arrangement was very lose, often causing slippage.
The chassis bracket holding the AM antenna also holds a couple
of little dial string wheels. The bracket was bent
at an angle. This was corrected and the bracket given a slight
bend in the opposite direction to introduce a tiny amount
of string tension which cured the problem.

 

While inspecting the valve pins, I noticed that the UL84
had a crack around the base of the glass envelope.
I left it in circuit while repairing as it was still
working but since it probably won't stand the vibrations of
future moving around and eventual shipping it was
replaced with a NOS Telefunken UL84 which should guarantee good
functionality for many years.

The diode transient capacitor is often found to have blown
itself to pieces. Not here but it did look a bit sorry for itself.
The isolated end seemed to have leaked something and the pins were
showing signs of oxidation.
It's a high-voltage 4.7nF capacitor and was replaced with a new
orange-drop 2KV component for safety.

 

The appearance of the JET was fine from the start though the wooden
surfaces looked a bit dry in some places.
The glass dial was cleaned gently on the outside.
It's not adviceable to clean the printed side of the dial unless
you are absolutely sure that what you do won't ruin the lettering.
All knobs were cleaned in handwarm soapy water using a dedicated toothbrush.
The teak surfaces was treated with a generous amount of teak oil, applied
using fine steelwool, rubbed in along the lines of the woodgrain, never across.
It was allowed 15-20 minutes to soak in and the excess was wiped
off using a soft cloth, leaving the radio a silky shine with a nice glow.
Restoration is now finished and the radio has temporarily substituted
the wallmounted Beomaster 1900 in the kitchen which is on the bench for
recap'ing and general overhaul after 14 years on the wall.
The JET entertains and impresses all house guests with it's warm sound and sheer presence.

Martin

Thank you Martin. That was a very informative thread. It must of taken a long time to type all that and do the pictures. What a beautiful piece of B&O. So are you keeping it? Please say yes.

 

Craig

What a beautiful set, and such a labour of love! I am sure you would have many takers if you did decide to sell it - myself included!

Just shows the immense knowledge and ability you have in this field. Really enjoyed reading it and appreciate the time and effort you took share it with us. I only wish I knew how to do half of what you can do!!! Even a quarter  would do!! 

Thanks guys for the nice comments.
If you had only half the fun reading it as I had doing it, it was all worthwhile.

The radio comes out of my own private collection and is in daily use as of this writing but like the majority of things in my collection
it will eventually be sold. I simply have no room for the things any longer.
The radio has a veneer chip on the rear edge of the sides, the rest is practically mint.
It has it's original backside and underside covers in perfect condition and the envelope with schematics preserved inside.
Will run fine on 220-240V, power consumption is only 45 Watts. It has it's original mains flex, a brown figure-of-eight cable which is safe and sound.
The radio has a lot of power, it can play surprisingly loud without distorting.
More photos can be taken if needed.
Packing and shipping is possible at buyers expense.
If there's interest, I will of course consider any offers on PM.

Martin

Hi Martin,

Thank you so much for taking the time and effort to write down your experiences in a way that reads like a novel, and no doubt inspires others to undertake similar (or -in my case- simpler) repair projects. Being able to bring a piece of beautifully designed vintage equipment back to life must be a very rewarding feeling.

This is highly enjoyable reading and certainly a story that further lifts the level and value of this already valuable website and community!

Already looking forward to similar experience sharing stories we might see in the future!

Kind regards, Eric

Dillen:

Thanks guys for the nice comments.
If you had only half the fun reading it as I had doing it, it was all worthwhile.

The radio comes out of my own private collection and is in daily use as of this writing but like the majority of things in my collection
it will eventually be sold. I simply have no room for the things any longer.
The radio has a veneer chip on the rear edge of the sides, the rest is practically mint.
It has it's original backside and underside covers in perfect condition and the envelope with schematics preserved inside.
Will run fine on 220-240V, power consumption is only 45 Watts. It has it's original mains flex, a brown figure-of-eight cable which is safe and sound.
The radio has a lot of power, it can play surprisingly loud without distorting.
More photos can be taken if needed.
Packing and shipping is possible at buyers expense.
If there's interest, I will of course consider any offers on PM.

Martin

Can I just say - if anyone intends to do something up and then sell it then this the sales pitch to beat

Show them the goods before and after (some after!) - let them lust after it - and then announce its for sale!

Masterful.

And a splendid post/restoration!

A credit to Dillen (and his undoubted skills).

The radio will have to go to a new home.
I have no room for my collection anymore and more projects will
follow but when I wrote the above story, my mind wasn't on the selling of the radio at all.
It was a mild attempt at making Beoworld cover an even wider
range of B&O interest and the workbench section opened the
opportunity and seemed like the right place for me to share the story.

It was never my intention to make this a sales
add, lurk people into buying or even make people lust for the radio, "clever" or not.
I have no problem selling on f.e. Ebay and in case I would try
to sell it on Beoworld I would have taken it to the
sales forum section but after I posted the story, the interest
was very intense, emails, PM's and even a pleasant
overseas phonecall so it more or less turned out this way by itself.

Having said that, I can easily see what you mean by clever advertizing;
Several sellers list vintage radios for sale, some even checked
at a B&O workshop (one wonders) but in this case you can actually see,
almost feel, what you're buying.

Martin