BeoGram

Re: Beogram 4000 - Arm Doesn't Lower

tournedos — Tue, 16 Feb 2010 05:34:36 GMT

alexb1406:

Made the link lead up yesterday and plugged it in, and after I connected a ground lead with a couple of crocodile clips to cure the mains hum (it's missing altogether) it sounded great. Anyone have any idea where this lead originally connected to on the Beogram? Finicky maybe, but I'd like to make it look as original as possible.

There was no separate ground lead - the sleeve of the DIN connector and the outer shield of the cable create the shield ground connection. It connects to the chassis inside the Beogram.

I don't think anyone will overhaul the SP15 if the coils are broken, apparently both Sound-Smith and Axel from schallplattennadeln.de only fix the suspension (and Axel replaces the entire cantilever/stylus). It was indeed the original cartridge, I would just keep it as a display piece as the whole set with the factory test charts is quite rare.

Re: Beogram 4000 - Arm Doesn't Lower

alexb1406 — Tue, 16 Feb 2010 05:25:32 GMT

Well, we're up and running!

Made the link lead up yesterday and plugged it in, and after I connected a ground lead with a couple of crocodile clips to cure the mains hum (it's missing altogether) it sounded great. Anyone have any idea where this lead originally connected to on the Beogram? Finicky maybe, but I'd like to make it look as original as possible.

As predicted the SP15 doesn't work at all. If Soundsmith can do anything with it I may be tempted to let them overhaul it as I believe this would have been the original cartridge fitted to the BG4000. And I have another project on the way that is missing a cartridge and the MMC20E would be a good candidate for it...yes, the temptation was too much - I bought the BG2200 that I had my eye on...EBAY, THOU ART TEMPTATION...

Any psychologists on our forum, can you please set up an ebay rehabilitation program...or more appropriately, a B&O rehabilitation program...

Re: Beogram 4000 - Arm Doesn't Lower

alexb1406 — Sat, 13 Feb 2010 17:48:46 GMT

Thanks Peter, you've confirmed exactly what I thought.

I'm trying to get the bits together to make up the din/rca converter lead. Our local Maplin didn't have a female din plug. I've found one in another store but I can't collect it till Monday.

Re: Beogram 4000 - Arm Doesn't Lower

Peter — Sat, 13 Feb 2010 07:10:05 GMT

Amplifiers of that vintage normally have the RIAA built in as you surmise. My SP15 still performs well so certainly worth a try - very similar to the MMC20EN and hence better specified than the black 20E.

Re: Beogram 4000 - Arm Doesn't Lower

alexb1406 — Sat, 13 Feb 2010 05:14:36 GMT

Thanks Chris, I have with the SP15 the original box that it was supplied in dated 1973, cleaning brush and scales - I haven't fitted these back in the box yet as they were given to me loose but it looks like there are compartments underneath inside the box for these. There is also a graph that looks like it might be the performance chart, I assume for this specific cartridge from the factory.

Coming back to the RIAA, please correct me if I'm wrong but I thought phono inputs were, by definition, designed to have the preamps in the amp. If the preamp was in the turntable then you would have to connect it to an AUX input. My amp, an AKAI AA-1175 (nearly as old as the BG4000) has both phono and aux inputs. I presently have two other turntables connected via a switching box to the phono input. So I presume that there must be a RIAA built into the phono input of my amp...am I right?

Re: Beogram 4000 - Arm Doesn't Lower

Medogsfat — Fri, 12 Feb 2010 20:11:32 GMT

alexb1406:

I haven't actually played it through an amp yet. Am I right to think it will be ok to plug into any phono input, or do I need any other type of preamp? I have two cartridges with it, an SP15 and an MMC20E.

Depends on whether your amp has a RIAA preamp in the the phono input. The Beogram 4000 doesn't have this fitted, Steve at Soundsheavenly & Lee at LifeStyleAV can both supply a preamp kit with all relevant cables to do this.

The SP15 is quite a rarity as it was the 1st in this B&O range of integrated cartridge/stylus design & the chances are it may be goosed due to age as much as anything else - worth keeping though just for the rarity value. The MMC20E will also be quite old but is likely to be the best candidate for a decent performance but, hey ho you won't know until you give them a whirl.

Chris.

Re: Beogram 4000 - Arm Doesn't Lower

alexb1406 — Fri, 12 Feb 2010 19:30:17 GMT

Thanks Geoff for your help so far, and everyone else for that matter, it has been invaluable.

Although I'm not at home at the moment I have sneaked a few minutes away from other duties to browse the forum. I'm being summoned to bed as I write - but I'll leave that one there in case I get moderated...the bug has definitely got hold of me...

I just couldn't recreate the problem before I left home so I decided to box it all up and be wary of it in case it happens again. I'll just have to test it every now and then and see what happens.

All I need to do now is make an adapter lead up to connect the DIN plug to my RCA input. I haven't actually played it through an amp yet. Am I right to think it will be ok to plug into any phono input, or do I need any other type of preamp? I have two cartridges with it, an SP15 and an MMC20E.

Re: Beogram 4000 - Arm Doesn't Lower

geearr — Fri, 12 Feb 2010 18:40:21 GMT

Hi Alex

That is just typical for these machines, you fix one problem and only end up identifying the next one.

Unfortunately, you have reached a point where your BG4000 loses its similarity with my BG6000 - I have no complex switching system to fiddle with, so I can't help you with that one. I am sure that someone on the site does know the nuances of your machine and will follow your progress with interest. I am sure you will end up fixing it - it only takes time.

Best of luck and have fun

Geoff

Re: Beogram 4000 - Arm Doesn't Lower

alexb1406 — Fri, 12 Feb 2010 11:00:36 GMT

Thanks Geoff, photosensor now adjusted and working.

Guess what! I have another problem!

With everything reassembled and no record on the platter, the arm sometimes travels to the very end and then drops onto the empty platter. Sometimes it works ok and returns without dropping, but every so often it will come down. This is after the search light goes past the end of the platter ribs, so is it still searching for the start of a record? Once it goes past the end of the ribs it must think it's found the record. Fortunately I realised what was happening before I replaced the cartridge.

I have looked at all the switches under the arm and they all seem to be operating ok. I can even work them manually and so far I have not been able to recreate the problem. It seems that the end switch may not be working, but the arm looks like it presses it down - in fact when it does work it only has to touch it and the arm instantly reverses.

I've had enough of it for one day. I'm away for the weekend but I plan to return to the task on Monday - refreshed and ready for another battle...!!!

Re: Beogram 4000 - Arm Doesn't Lower

geearr — Fri, 12 Feb 2010 06:55:50 GMT

Well done Alex

I must have missed your follow up post, the one after you reported the readings. It probably came along while I was compiling my replies. Anyhow, at least you have a solenoid that works and an arm that drops when required.

Yes, I would have a look at the adjustment of the photosensor - I had that problem on my unit as well - it was fairly simple to fix.

Geoff

Re: Beogram 4000 - Arm Doesn't Lower

alexb1406 — Fri, 12 Feb 2010 06:29:20 GMT

Hi Geoff,

I think you may have misunderstood me. It now works after refitting 1R28 - hence why I suspect it was a dry solder joint. I now have a range of voltages across 1TR11 and 3v at the base of 0TR4 when the solenoid is activated - 3.37v to be precise, but I don't fully trust the accuracy of my meter so I have rounded off all the figures I provided. Across 1TR11 I have 3.37v, 4.05v, and 5.87v again when the solenoid is activated. When the arm is in the up position the voltages are 0v, 0.73v, and 0.08v.

Of course this is purely academic now and I am only providing these voltage readings in case it may help someone else in the future.

I have however since fixing it discovered another problem for which I may start another thread - that is once lowered, the arm cues across the record very quickly and skates across the surface. Is this likely to be an adjustment of the arm that moves across the photoelectric sensor? I don't want to mess with it until someone can confirm this.

Re: Beogram 4000 - Arm Doesn't Lower

geearr — Fri, 12 Feb 2010 05:06:21 GMT

Hi Alex

Thanks for your voltage measurements, they have cleared a few things up.

Firstly, you have 40v on the collector of 0TR4 and both terminals of the solenoid so you don’t appear to have a power supply issue.

Second, 0TR4 has 6v on the base and 0v on the emitter and is not conducting. Hence there is a good chance that 0TR4 is cooked.

You measure 6v on the three terminals of 1TR11. When the signal is sent to activate the solenoid, 1TR10 should be off, providing the 6v to the base of 1TR11. My guess is that 1TR11 is in the correct state and 1R28 could well be OK. I am assuming that you are measuring to the nearest volt and are not seeing the 0.7v drop that exists across the transistor.

When the arm is being instructed to drop and the solenoid is being activated, the base of 1TR10 should be low and that seems to be the situation from your measurements. My money would be on a faulty 0TR4 at this stage.

Regards

Geoff

Re: Beogram 4000 - Arm Doesn't Lower

geearr — Fri, 12 Feb 2010 05:05:07 GMT

Thanks tournedos

I continue to learn something every day

Regards

Geoff

Re: Beogram 4000 - Arm Doesn't Lower

tournedos — Fri, 12 Feb 2010 04:43:22 GMT

alexb1406:

Now I'm going off to google Wein bridge sine wave oscillators...

You will get better results with Wien bridge (as in Vienna), not Wein or Wine

Good work, enjoy your Beogram! Be warned that there is no escape

Re: Beogram 4000 - Arm Doesn't Lower

alexb1406 — Fri, 12 Feb 2010 04:37:36 GMT

Result! Removed 1R28 only to find the value was fine around 150ohms. Replaced it back into the board and now it works! Must have been a dry solder joint though it looked ok before I removed it.

Just for the record the voltage at the base of 0TR4 when activated is a little over 3v. The voltage at the solenoid is 31v and 34v referenced to ground, so it only needs 3v to work, but it is possible that it needs a higher peak voltage to draw it in.

Now I'm going off to google Wein bridge sine wave oscillators...

Thanks for your help guys! I guess this was a pretty basic fault, but without your help and knowing roughly what voltage readings should be I'd have been p***ing in the wind.

Now onto the next project...I've got my eye on a faulty BG2200 on ebay...not in the same league as the 4000 but...SOMEONE PLEASE STOP ME NOW!!!