BeoGram

Re: Beogram 8002 - no damped lowering of the arm

chartz — Wed, 15 Jun 2011 08:27:22 GMT

I don't know.

It is very free to move and has no play.

Maybe the plastic part which pushed the lever is worn. Nothing I can see, but the 6006 has the same problem!

Re: Beogram 8002 - no damped lowering of the arm

Step1 — Wed, 15 Jun 2011 07:20:17 GMT

What do you mean by hiccup? If I take a hickup to mean the arm seems to get momentarily stuck, could your coil (only when energized), be slightly moving off center and catching or rubbing?

Re: Beogram 8002 - no damped lowering of the arm

chartz — Mon, 13 Jun 2011 11:08:01 GMT

Hello Martin,

No it doesn't rub on anything. Its translation is free when I push or pull it by hand. Anyway, it is fully enclosed in its own housing.

I must be stupid or something but that one makes me mad! Earlier on the arm was in bits and pieces, now re-assembled and better aligned than before. The problem remains. When monitoring the coil voltage it appears to be growing normally.

Re: Beogram 8002 - no damped lowering of the arm

Dillen — Mon, 13 Jun 2011 10:49:05 GMT

I suppose the subchassis is merely standing on the bottom plate now.
Is the solenoid thing rubbing on something ? Try lifting the subchassis away
from the bottom plate a bit.

Martin

Re: Beogram 8002 - no damped lowering of the arm

chartz — Mon, 13 Jun 2011 10:10:36 GMT

Hi,

I've dismantled everything, the solenoid works fine, it is totally free in its translation, with no play.

I don't see anything preventing the mechanism to run correctly.

The electronics have ben checked, they work just fine, and components have kept their values.

And yet. The solenoid has a hiccup half way out, which I can't reproduce by hand. It isn't arm-related, since with the arm manually kept up it happens too. I've seen several other Beograms, 6006, 8000 and 8002 with the same problem.

A solution has yet to be found then. Oh well, let's wait for Martin to have one with this fault to repair!

Re: Beogram 8002 - no damped lowering of the arm

Cleviebaby — Wed, 13 Apr 2011 01:29:57 GMT

Thanks to Martin and Jacques for this insight into the arm lowering process on the BG8002. It really demonstrates that I should have paid more attention to my Physics teacher.

When I was at school (many, many years ago), at the age of 14 I had to make a choice between continuing to study either Physics or History - I don't need to tell you which choice I made.

Cleve

Re: Beogram 8002 - no damped lowering of the arm

Dillen — Sun, 10 Apr 2011 11:10:18 GMT

Both a resistor and a capacitor can change its value over time so
we cannot rule out the need for replacing a component but check that the solenoid moves freely first.
If there is some kind of blockage, dust or the likes, the solenoid will not move freely enough to precisely
follow the DC slope.
If it binds near the beginning of its travel where the voltage is still rather low (read: until the magnetic
force is strong enough to pull it passed the blockage), it can cause the symptom you have of sudden lowering.
A scope across the solenoid would help monitor what's going on. A multimeter may also be sufficient.

If all that looks fine, I would check the values of that RC circuit and eventually replace the OPamp, the
resistor or the capacitor.
A slightly larger resistor or capacitor would slow things down a bit. Obviously, it needs to be completely
lowered when the muting relay releases the output signals.

Martin

Re: Beogram 8002 - no damped lowering of the arm

Step1 — Sun, 10 Apr 2011 10:42:53 GMT

Maybe try lowering r61 (assuming the 2u2 is still in place) slightly Jacqes? The muting circuit is controlled from the output of this section of the opamp and I would suggest the final charging of the capcitor slowed down sufficiantly that perhaps the mute circuit would have 'activated' sometime later than you would have been prepared to wait.

You may even have to adjust one of the resistors in the mute circuit, for instance slightly increase r54...?

I have to admit now that the damping on mine is not as smooth as the earlier decks but looks ok to me. Certainly consistant, but possibly a needless threat to aging cartridge suspension! I might investigate this myself :). Would be interesting to see if Martin has more to say on the subject!

Re: Beogram 8002 - no damped lowering of the arm

Cleviebaby — Sat, 09 Apr 2011 14:30:00 GMT

Peter :

You would appear to have picked the wrong cartridge! I believe you sent one back to Lee - I imagine that was the one Axel had just rebuilt!

I sent Lee the one in Axel's small plastic case on the grounds that this was the one from your BG7000 that Lee was selling as part of your 7000 system. There has been no evidence that the one in the 8002 was on the way out - it has been tracking well and with no signs of distortion. However, it looks like it might be suffering some cantilever damage now!

Re: Beogram 8002 - no damped lowering of the arm

Peter — Sat, 09 Apr 2011 09:23:59 GMT

You would appear to have picked the wrong cartridge! I believe you sent one back to Lee - I imagine that was the one Axel had just rebuilt!

Re: Beogram 8002 - no damped lowering of the arm

Cleviebaby — Sat, 09 Apr 2011 09:11:06 GMT

Peter :

Cleve's deck has had the capacitors changed in the past. It has been serviced both by B&O and TJ.

Peter,

I know from previous threads and from email correspondence with you when I bought the deck that it had been serviced regularly and most recently by TJ - it was one of the reasons why I bought it. However, I guess that service was a couple of years ago now and the ageing process applies to turntables as much as to humans. It is one of the downsides of running old equipment and you have to factor in these things when you decide to go down that road.

I fully take on board Soren's advice about practicing your skills on a bit of old electronics, but I don't think playing with a BG 8002 is the best starting point for a complete electronics novice like me.

Thanks to everyone for their advice - at least I now know what is probably wrong. I think, given Martin's comments, it would certainly make sense not to completely wreck the MMC2 by using the deck until I've sorted the problem. As a sufferer from the Beovirus, the 8002 isn't my only deck, so I can still play records.

Cleve

Re: Beogram 8002 - no damped lowering of the arm

Peter — Sat, 09 Apr 2011 02:45:33 GMT

Cleve's deck has had the capacitors changed in the past. It has been serviced both by B&O and TJ.

Re: Beogram 8002 - no damped lowering of the arm

chartz — Sat, 09 Apr 2011 01:42:21 GMT

Hi,

How are you Martin?

Well even after a full refurbishment of the circuit (yes, even that cap inside the processor box!) the damping problem was never solved. The RC network you refer to was also envisaged. Raising the 1μF cap to 2.2μF restored correct lowering (a bit too long even, I'd say one sec) but the muting relay never triggered.

Any ideas?

Re: Beogram 8002 - no damped lowering of the arm

Dillen — Sat, 09 Apr 2011 01:21:17 GMT

It's hard to say if the tonearm is actually lowering too fast without actually seeing it.
The damping is electronically controlled, it's more or less all down to simple RC-circuits and it can
be adjusted by changing component values.

Has the old capacitors been replaced ?

The low riding of the cartridge points toward a soon failing cantilever suspension, not uncommon unfortunately.

Martin

Re: Beogram 8002 - no damped lowering of the arm

Søren Mexico — Sat, 09 Apr 2011 01:07:31 GMT

Cleviebaby:
Is there a 'Soldering for Dummies' book?

There is a lot on the net, just google it, read the theory, but more important, get an iron and solder and find an old radio or something to train on.

Its simple when you get the hang of it and very fast you will crave for difficault jobs

I use these tools