Sign in   |  Join   |  Help

BG8000 fuse issues

rated by 0 users
Not Answered This post has 0 verified answers | 87 Replies | 1 Follower

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member
ALF posted on Mon, May 1 2017 7:02 AM

greetings all,

a new arrival, a BG8000, which had a partial re-cap job done by the previous owner.

I noticed C24 was put in the wrong way as its positive should connect to the F1 ?!

anyhow, I corrected that, completed the re-cap job incl C27 - see pictures - and now F1 is constantly blowing

even with my DBT ?

I checked D16 to D19, all measured ok.

did I overlook something ? any ideas or suggestions are most appreciated :-))

cheers

ALF


All Replies

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member
ALF replied on Sun, Jul 16 2017 7:18 AM

The question is, is this optical device really faulty or is there still a different devil to uncover ?

ALF

Dillen
Top 10 Contributor
Copenhagen / Denmark
12,656 Posts
ONLINE
Founder
Moderator
Dillen replied on Sun, Jul 16 2017 7:24 AM

That's the right way. Stop guessing and measure!
Are pulses output from the two receivers when the threaded shaft rotates? 

Martin 

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member

same procedure as before,

signal taken from P2-Pin6

first pic is a bit out of focus, sorry- just carriage moving right across

second pic is with the slow moving carriage, play pressed after carriage has been stopped with >>


ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member

second pic from P2-Pin6, showing a very similar signal as the one from P2-Pin4

ALF


Dillen
Top 10 Contributor
Copenhagen / Denmark
12,656 Posts
ONLINE
Founder
Moderator
Dillen replied on Sun, Jul 16 2017 9:54 PM

Difficult to tell, but if that is 100mV amplitude, the sender IR is not emitting light.
(Those small signals could be caused by ambient light reflecting onto the opto wings on the threaded shaft ). 

Check the power to the IR sender LED.
If power is OK, check its light output with a digital camera.
IR light typically shows as pale blue on a digital camera.
(On some iPhones only the self-facing camera will work for this). 

Martin

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member
ALF replied on Mon, Jul 17 2017 7:04 AM

Thanks Martin,

I assume you are talking about the single optical device in the fixture of three, not the two next to eachother (wings you called them)?!

Its voltage is 4.98V, the other two next to eachother are getting about 14V

I could not see any pale blue traces on my digi camera,  providing I checked the correct element ?!

yes, the signal amplitude was  about 100mV.........! It looks like I will have to replace that single opto element - can you supply that ?

ALF

Dillen
Top 10 Contributor
Copenhagen / Denmark
12,656 Posts
ONLINE
Founder
Moderator
Dillen replied on Mon, Jul 17 2017 7:15 AM

Yes, the bottom element is the IR sender LED.
The wings I refered to are the four interruptors at the end of the threaded shaft. (It was a guess based on the signal and the fact that they rotate).

Martin

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member
ALF replied on Wed, Jul 26 2017 10:23 AM

In the meantime:

I did replace the sender IR diode - and this is what happened:

with only the sub-plater on the carriage now moves to the 30cm drop point but arm does not lower....only a weak attempt to lower can be noticed.

at the lower/drop point I measue at P6-pin18 (signal from 2IC1 pin 24) voltage goes up from about 70mV to 0.67V and very briefly reaches 1.2 V!

same at base of TR18.

at 1IC1-pin7 I measure voltage goes up from about 2mV to 12V

at 1IC1-pin6 I measure voltage  goes down from about 2.2V to 0.76V

looks like the counter is working as the new IR diode delivers a p-p signal of about 18V both for pin4 and 6 at P3.

still a long way ahead !

here is something I absolutely can not understand:

the moment I put the main platter on to the sub platter the carriage goes viral, briefly moves over, not getting anywhere near the 30cm drop point

and returns quickly to its resting position.

leave the main platter off and put a record on to the naked sub platter, the carriage moves in position to drop at the 30cm mark ???

however arm does not lower ?

i begin to wonder if anything is blocking the arm mechnically ? The main platter business I most certainly can not explain nor understand !

any theory on that matter ?

ALF

 

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member
ALF replied on Fri, Jul 28 2017 11:12 AM

Hi John,

thank you for your kind offer to test the main board - I may indeed consider that option, just have to check postsge rates.

not sure whether you saw my last post but it seems the voltages I can measure are pretty similar to yours in respect of the 

arm lowering issue !

now that the am moves into the correct position to lower and seem to be getting the correct signal would  it be fair to suspect a mechanical issue

in the arm assembly itself ?

thanks btw for suggesting the OP240B device which obviously works - I had to settle for the OP240c

ALF

sonavor
Top 25 Contributor
Texas, United States
3,638 Posts
OFFLINE
Gold Member

Hi Alf,

With the Beogram opened up you should be able to watch the solenoid mechanism in the tangential arm assembly slide forward and backward as it is commanded to control the tonearm. Watch it and see if it is moving correctly or sticks. I have one Beogram 8000 myself where the solenoid is sticking occasionally and causes a slight hitch in its lowering operation. So something mechanical with the solenoid will affect the arm lowering.

John

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member
ALF replied on Sat, Jul 29 2017 5:13 AM

Hello John,

thank you for pointing this out.........this table is just so different from the BG4xxx series and lots to learn 😸

You were as usual 'spot on' - knowing where and what to look for certainly helps.

the solenoid was indeed stuck and would have caused some interference with procedure and other signals?!

a non-conductive lubricant-cleaner did the trick and the arm is moving freely up and down thanks to a moving solenoid 🥃....just one for now!

 

This BG8000 has a strange looking tacho disc, more like a Kodak film negative with a plastic-feel ? The whole thing looks like someone tried to cut it out

from a sheet trying to stay on the circle line ??  i wonder if there ever was a replacement in circulation for the original tacho disc that had the peeling-off issue after long-service?

Perhaps it is time to replace that for the metal version that Martin offers ?

I still have the occasional issue with the carriage trying to move towards the drop-down point but when a record is on the platter, but returns after a very short motion straight back to its resting position??

trying 'play' a couple of times Gets it going eventually  - the interesting bit is in that case occasionally the first two digits '33....' can  still appear on the display ?

ALF

sonavor
Top 25 Contributor
Texas, United States
3,638 Posts
OFFLINE
Gold Member

The original Beogram 8000 units had a plastic tacho disk with the black film. Almost everyone I have seen have started to peel. Changing a Beogram 8000 to a metal one (supplied by Martin) is a must do task.

The Beogram 8000 will display 33 on the display if it returned to the park position due to a Pause command. When you press Pause the tonearm lifts and remains over the record for a short amount of time. If Play isn't pressed to resume playing the record the tonearm will return to its park position and wait. Pressing Play again should result in the tonearm returned to the spot where Pause was pressed.

John

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member

yes John,

that is while its working correctly, displaying only the first two digits '33' but not '33.33'.

I am not sure whether the carriage not moving correctly, meaning behaving erratically, towards the drop point is related to that

tachodisc issue ? I have attached a picture of the current tachodisc and contacted Martin via the site"s email (hope it worked)

it seems to work if I give it some minutes rest and then start 'play' again ? looks almost like some old data have to be deleted first or the uP has to be rest?

once the carriage reaches the drop point and the arm is lowered onto the record everything is fine !!

ALF


sonavor
Top 25 Contributor
Texas, United States
3,638 Posts
OFFLINE
Gold Member

The new tacho disc from Martin is more precisely made and will be a good upgrade for sure.

Did you say you re-measured your arm position signal since you replaced that sensor? Are you getting good pulses from that sensor assembly now?

What is the condition of the arm start/stop switch that is mounted to the chassis? Is it operating correctly?

John

ALF
Top 100 Contributor
AUS
968 Posts
OFFLINE
Silver Member
ALF replied on Sun, Jul 30 2017 11:23 AM

Well, I am still hopeful Martin can supply one of these tachodiscs !

yes, I did revisit the sensor signals P3-pin4&6 and the pulses look absolutely fine.

the start/stop switch I will recheck to make sure - so far it has not yet been amongst the suspects.

I am looking at a lenghty wait for that tacho disc - if currently available - and will reinstall the original film-disc

so I can check that on-off switch and table performance.

ALF

Page 5 of 6 (88 items) « First ... < Previous 2 3 4 5 6 Next > | RSS
Beoworld Security Certificate

SSL