ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I've been working on the Beocord 900 today, replaced caps and some trimmers. Belt looked a bit old, so swapped that out too.
I get power, and as soon as I turn it on, the motor starts turning - I don't know if that is normal behaviour. If I press Play, it runs, tape appears to work as it should, Reverse << works, but FFW >> not so much. It pretends to try then stops. I suspect this is a mechanism issue rather than anything electronics. Any ideas what it could be?
Also, there are a lot of trimmers that I don't know how to adjust, and therefore I am reluctant to replace them without the info to set them. My sheet inside the machine says R103 should be set to 32V - but no matter what I can only get 24-26V Max out of it, and I should stress I tried that adjustment prior to installing the new trim pot too. <edit> I got a bit confused here. Checking the schematic it should be trimming for 24 out</edit>
I really hope I am able to get this going as it is in excellent condition, and everything points to this being fixable through relatively minor effort.
Thanks for any advice!
Some further info:
I tried a shorter belt, that seems to have made the rev/ffw work better.
I rehooked up the VU meters, but they don't seem to move.
R99 the 270 ohm 3W resistor gets HOT. In fact I replaced it with a 5W, as the original had burnt out. Edit:no wonder really, it is dropping 20v to supply the on lamp with 12v! /edit I touched it after I had the unit on for a short time and it is very hot to touch.
That's as far as I have got today. Unplugged, and going to leave if for now.
Update time:
I hooked up some headphones to the output jack - don't ask how! - and I could hear music from the tape I put in. So I hooked it up to my Panasonic boombox and indeed it is working! Unfortunately I don't know how well. The only tapes I have are a very used James Last and it sounds a bit...wonky, a CD I recorded on a cheap Chinese tape on the Panasonic, definitely not studio quality. I haven't tried recording to it yet, that will be the next thing to do.
Another update:
Well it has been a bit of a challenge to figure this thing out, but it seems to be (deceptively?) simple. Not having a full service manual is a bit of a disadvantage, but the schematic that is included in the machine actually seems to have most of the information required to get it (mostly) up and running. What is missing though is some detail on HOW to use that info, make the measurements, etc. An owner's manual would help too.
I thought my VU meters were bung, until I found they only work on Record mode. I couldn't quite get the right measurements on the trim pots with the multimeter, so I ran a 1khz signal, pushed the Volume sliders to max and adjusted until they were pegged at the highest marker. Seems to be relatively OK. Intial test recordings show that if the meters swing too much into the red, it is too loud and will be heavily distorted.
I noticed a drop in audio in left channel about every 2 seconds:
and then the channel got good, then dropped out completely:
I half suspected the dodgy way I hooked up the wires into the input jack (I don't have a DIN plug I can hook up), so I redid it and things look a lot better.
Below is a 1khz tone - there's a bit of wow wow to it, but as this was imported to the computer using the Panasonic it is unclear whether it is a problem in the 900 or the Panasonic, or a bit of both (or even the cheap Chinese tape I am using).
And this is some audio, absent of drops every 2 seconds, and nicely in bounds - no noticeable distortion or clipping.
So far so good. I am pretty happy that the major functions are working as they should, I just need to work out if there is a bit of wow in that and if so, how to fix it. I might need to source a better belt than I have - it could be that it is a bit thin and stretchy. Other than that I am out of ideas, as the motor sounds good - seems even and is very quiet.
Todays job was to try and work out what is going on with the tape mechanism. I started by going to the local electronics shop and getting a 5pin DIN plug, some cable and a 3.5mm plug to make an input cable - curiously the pins are opposite sides to the cable I already bought to connect my phone to the BM2000, but that cable works nicely as an output cable.
So, to do away with any other wow getting introduced from another machine, I recorded onto the BC900 from my phone, then played that back and recorded on my Olympus voice recorder. Worked well, but I kind of wish I had made a cable with 2 3.5mm plugs at one end so I could just have everything set up ready to go. Live and learn.
What I found was that too loose a belt and the fast forward/rewind don't work, too tight and wow is exaggerated. I found one belt that had quite good wow but I changed it and dropped it in the others and... Anyway, I found another with the same length but way worse wow. What is going on?
I'll tell you what I think: these belts are just some cheap Chinese belts and I have noticed on this belt that it is much thinner on one end than the other. I'd guess it goes from 1mm down to 0.6mm. That can't be good. And it isn't. And I think that is the difference with the belt that had minimal wow - it was more consistent. That and it think the rubber is too stretchy. So now the search is on to get a decent belt (or 3) and hopefully that will sort this out.
Finally, as I suspected, the tape I was using was fairly creased at regular intervals - and that seems to be what was causing the dropouts every 2 seconds. And making a proper input cable resolved a lot of other inconsistency issues I was having.
I'm off overseas next week, so I doubt it will get finished before that, but it looks quite promising and I'm quite please with how things are turning out.
Standard belts...Cheap chinese toy belts...Cheap Ebay belts ...No consistent thickness, no consistent elasticity, no good in any B&O.In the best of cases they leave no permanent damage. - But some do.
The cable issue is because different pins are used for recording and playing back.
And always use a new tape when calibrating.
But it doesn't look THAT bad already.
Martin
Dillen:But it doesn't look THAT bad already.
It sounds pretty crook though. You don't happen to know the size of the belt that is supposed to be there?
edit:
This is from the cleanest tone I could get. 1khz:
You can see it bounces around a bit. I found a place online that sells quality (I hope!) belts around $5 each. I measure 260mm belt path, so I ordered 3 different sizes under that.
5 dollars?Eh.. even the cheapest ones on Ebay aren' that cheap.
?? I thought that was pretty much about right. If I could type in "Beocord 900 Belt" and get a result that was the exact perfect thing and it was $20, even $30 I'd probably get it. But absent any results and other info about the exact size to get I have make do. Even places that specialise in tape belts don't seem to have anything listed. If you've got a source, I'm all ears.
Proof will be in the pudding, as it were. When they come I'll have an idea about whether they are any good or not, and what size I should be using.
As an aside, the wow, while noticeable, is not as bad as when the belt went on my boom box as a kid. No money meant I used what I had. What I had was rubber bands. Rubber bands are an awful substitute, too much stretch and they turn to ooze and make a sticky mess exacerbating the situation. Good times. I got so used to it it took me ages to adjust when I did finally manage to get a proper belt for it!
I made a few some years ago, but they are all used or sold long ago.Making these belts, in small numbers as I do, can be quite costly.Most belts I make are for my own use, and the rest is sold without profit worth speaking of.Based on this, I would not expect to get a custom belt for anything less than 15-20 euros (plus profit and VAT if from a business seller).
Oh you made them? Yeah that would make it an expensive exercise. I've got a similar issue with my plastics at the moment, I've done a ton of work on the CAD models, but getting them printed, at anything resembling a reasonable price is...hard. That'll be a new topic if and when anything happens out of it.
Anyway, I'll see what the belts are like when they come in the post, should get here a day before I leave at the latest, maybe Friday if I am lucky. I probably have a good chance to pick something up OS failing that, so will look around. Will look around for 3D printer services while I am there...
Yes, I made them, just as I have made many other belts that couldn't be found anywhere in a decent fit and quality.You'd be surprised how much useless junk is sold on Ebay etc. as "perfect replacements" for B&O.I see a lot of it, when the things arrive here for repairs afterwards.A few months ago I posted this. https://archivedforum2.beoworld.org/forums/t/38090.aspxI can't be bothered updating the thread, and it would end up quite repetitive anyways, but I just had a Beogram 1000 in two days ago together withno less than three replacement belts, all very different, sold by different suppliers. None were correct, and one of them couldn't even be fitted due to being far too small.
I have also made many other B&O parts that just couldn't be found anywhere, or only in buy-and-throw-away-condition.Some can be seen here: https://beoparts.com/category/reproduction-parts/I don't 3D-print.
Yeah, I have figured already that getting the belt right will be critical to this working well again.
I am getting them from a very well known and (I believe) reputable supplier. It's more that I am flying blind in terms of sizing. Schematic doesn't even list a part number, but I can know every transistor, capacitor, etc.
Back to the BC900..
I found that amongst the bag of extras I was given, is another cover for the VU meters - this is a piece of plastic and there is also what I believe is the original metal cover that has Left and Right printed on it. Currently fitted one is blank. Odd. So I'm gluing that up and returning it to "normal".
New belts finally arrived today. Miles ahead quality wise, and I took a punt and went for 1.2mm instead of 1mm and it seems about right:
So here is the reult, 1khz test tone, top 2 are from today, bottom 2 are my previous best:
It's not perfect but it is much better, and sounds better. With these belts, I feel almost like I could go a size up. I'll take not of the dimensions as I may have luck finding something when I'm away. I'm not sure if there will be any benefit though, but at this point I'm happy enough. Anyway, next test will be to record a full song and see what it sounds like.
Put it back together as anything else needs doing can be done in the case. I think it looks pretty good, works pretty good, and there are just a couple of marks on it from 40 odd years. I'll almost be sad to see it go.