[Dillen]

davidross222 wrote:

New thread: what is best solvent to remove the gunk left by perished belts in tape drive??

IPA.
(Isopropanol alcohol, that is. – Not the beer).

Martin

[Dillen]

It’s B&O alright.
Not sure for what, though, but could be a RIAA, so perhaps an input adapter for a TV or a tape recorder.
Late 1960s or early-mid 1970s, I’d say.

And the 56K resistor has a bad solder joint. Perhaps the reason it was replaced.

Martin

[Dillen]

Apparently, the height matters to some extent – or Bang & Olufsen wouldn’t have made different stands.
Your speakers will play regardless – of course – though it may not be at the most ideal height, which is usually centered vertically around the height of your ears when listening (usually in a sitting position).

Also, – the S45-2 stands came in two versions; One has the vertical part assembled with a screw from below to the base part, the other is permanently welded.
I think the version with screw wouldn’t be strong enough for MC120.2 to be safe.

Martin

[Dillen]

All components can fail.

Is the TC9177P IC a typical problem and a well-known trouble maker IC?
– No.

Have I seen TC9177P ICs fail?
– Yes, once or twice in thirty+ years.

Considering the amount of work done to the module you show, I’d say check the work that was done as that alone could have caused the problem.

Oh, – and don’t forget to replace that speaker relay. Cleaning its contacts will only provide a temporary solution, and leaving it open like that won’t help it in any way.

Martin

[Dillen]

Beovox S45 (Type 6302) and Beovox S45-2 (Type 6312) does not suffer from foam rot as they use rubber surrounds.

Beovox S45 (Type 6427), however, does.
Fixable, though.

Martin

[Dillen]

These Beomasters (5500, 6500, 7000) will run a little warm at the cooling fins when powered up, even when not actually playing anything but silence.
This is mainly because the cooling fin also holds the power supply voltage regulators.

If the cooling fin is also warm in standby, it is most often caused by one or more
cracked solder joints at the amplifier power supply relay, keeping it from drawing and cutting power to the amplifiers, which means that the amplifiers will still be powered in standby.
Not good for the electric bill either.

The fan will normally only activate when playing at loud volumes with heavy passive speaker loads.

Martin

[Dillen]

Adjustment of what?

Martin

[Dillen]

Check the supply voltages to the Dolby ICs.
Particularly the Vref (a dead C2 wouldn’t be a first).

Martin

[Dillen]

You could try setting the tracking force very low (0.2-0.3g) and see what happens.
The needle may not track correctly, and it may jump around a bit, but it would also
merely be to test if sound is produced from both channels.

Another test could be to take off the cartridge and put it aside, start the Beogram (play)
without it and while it is “playing”, insert a small strand of copper wire into
the cartridge socket, one hole at a time, listening for a healthy buzz from the amp/speakers.
The L+ and R+ socket pins respectively, should give that if the deck, leads, amplifier and speakers are fine.

Martin

[Dillen]

The record/playback relay should only draw when record is pressed.
Do the VU-meters react while playing a tape?

Martin

[Dillen]

The smell is caused by airs moisture (most often down to bad storage).
The smell will never go away again, even if vented thoroughly and kept completely dry for years.

If it doesn’t smell when the speaker is closed, you may want to just leave it alone.
But if it smells “out” of the speaker, it will be annoying, and the solution is to remove it all, clean the cabinet inside using a disinfectant/smell remover (as the smell will also be in the wood) and put in new damping material.

Martin

[Dillen]

“Martin, I agree but the diagram is still wrong as a single pin cannot have 1480 and .2 ohms. It would be 1480 and 740 ohms.”

When muted all pins are connected. That’s where the 0,2-0,3 Ohms come in.
When unmuted, the L- and R- are still connected (signal ground), so when measuring between L+ and R+ you are measuring the two coils in series.
Their common center connection to ground doesn’t matter, seeing as you are not measuring with respect to ground.

OP: Any access to another Beogram to test the suspect cartridge with?
Where are you based?

Martin

[Dillen]

Do you have access to another cartridge for testing?

Martin

[Dillen]

Mark-sf wrote:

Those do not look right. Measure the cartridge pins when it’s not installed. The pins are looking from the back: L+. R+ L- R- The 740 ohms should exist between L+ to L- and R+ to R-. There should be no resistance between R+ and L+.

Unmuted; When the cartridge is fitted to the arm, the two coils have their respective negative ends connected to signal ground.
This means that if you measure from L+ to R+, you measure the two coils in series (2x 740 = 1480).
All fine.

Muted; All cartridge pins are connected to signal ground.
All fine.

Martin

[Dillen]

All fine so far.
The fact that you actually have sound from the affected channel, even if only briefly, suggests that the wiring is fine.
The problem could be with the cartridge itself.
I have seen cases where sound is lost when the needle is on a record.
Perhaps a dying cantilever suspension.
Do you have access to another cartridge for testing?

Martin

[Dillen]

It has been a while since the last Beogram 5000 on the bench, but I seem to remember
when you lift off the dustcover hinge block, a small connector becomes visible.

Martin

[Dillen]

Cracked solder joints near the relay?

Martin

[Dillen]

herrit wrote:

Firstly, would I be right that the power relay is by the large transformers, and the muting relay is close to the speaker outputs?

Yes.

(See attached image). I have never got involved with such transformers – might I ask for a bit more detail for “cleaning the contacts” and a view on the resistances shown attached. Some of them are very approximate as they were slowly falling during my measuring them.

Replace the relay. Cleaning will not be a long lasting solution.

I have not yet removed the transformer…

You don’t have to.

Martin

[Dillen]

So, basically, you are comparing a 45 year old speaker still running on its original
capacitors that, ideally, should’ve been replaced 20 years ago, to two speaker models
that are currently available new in shops – and you find them lacking a little treble?

Well… replace the capacitors to grant it just a hint of fairness.
Kits are readily available.

Beovox S45-2 is an incredibly well balanced and sounding speaker, but it is not “audiophile” and will never be.
Keep in mind it was merely somewhere in the middle of the Beovox model range at the time.

Martin

[Dillen]

MINI 41K? – Are you sure?

Martin

[Author]

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