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 have a BeoGram 3500.
Is it right that the light stays on on dim all the time. It lights up fully for a few seconds when you press play then does to dim again.
Keith.
No, it should go off completely.
Martin
Any help please?
Wrong value lamp, or leaking driver transistor or wire?
blah-blah and photographs as needed
The lamp is the one fitted form new, I have checked all the wires and all OK.
The leaking driver transistor, need help to point that one out.
TR3 (a BC337) but it's not guaranteed to be the cause.There could be other reasons.
The BeoGram works really well, nothing is over heating and it's been like this for over a month.
At the bulb the volts are 11.95 when dim and when you press cue the light comes on full and the volts read 11.98.
I have disconnected the bulb for over a week now, with no ill affects on playing records.
Should I leave it like this?
And you did measure with bulb on circuit? Bulb is a collector load in circuit.
Basically it is very simple. NPN transistor is driven from near by big IC pin 16 through R7 and stabiled with C4, thats it. High/Low only.
Yes I did measure the bulb on circuit.
Maybe you should check pin 16 (end of R7) is functioning correctly.
How do I check that?
A voltmeter from ground to the IC pin.Read the voltage when the lamp is supposed to go and off and let us know.
Sorry for being a bit thick, but is it on the control board?
it is big one in middle, but 16 is under shield, so you can measure onR7 more easily
And where is R7 on the board.
R7 is the resistor sitting two components left off TR3, is my guess.
Found R7. and the volts are 0.578 when NOT lit and 0.711 when lit from the R7 side.
The other side is 0.059 when NOT lit and 2.635 volts when lit.
Hope this is right.
Found R7. and the volts are 0.578 when NOT lit and 0.711 when lit from the R7 side of the resistor.
And from the other side of the resistor is 0.059 when NOT lit and 2.635 volts when lit.
Hope this makes sence?
0,578 sounds a little bit too high, I think IC is functioning ok. So maybe tr3 is not ok?
So how do I check TR3
Well... I'm not very good with tr's, but if you measure voltage between collector and emitter, it should be near zero when lid, and near 12V when dark. C4 is connected from base to ground, but I cant see any possible cause there. Anyway is possibly 0,578V enough to keep tr partially open, so bulb light dimly.
And because there simply is not anything but TR3.... I suspect it.
Can I get hold of a TR3 and replace it?
It is quite common and so expencive that changing it is not problem. Only nasty thing is location, have to remove mainboard....
Is removing the board a hard job, and are there any instructions on how to do this?
Where can I get hold of a TR3.
There is that solenoid thing and some adjustments by moving mainboard, so testing is good idea.
I guess any local component supplier can supply these.
Don't get me wrong, I have a huge respect for DIY'ers but from reading your posts, I feel temptedto say that this is not a repair job for you.Removing and reinstalling the board is not particularly easy.Soldering on a board of this type is not something I would advice for beginners.Bring it in for service, it shouldn't be too costly a repair.Maybe another Beoworlder near you can help you.
I live in the UK. The last time I was looking for help, someone put me on to a chap that was an X B&O service engineer, It cost me an arm and a leg. They charged me £80 just to look at it.
Yes, Martin is right in that, this job needs considerable amount of disassembling, so one have to be sure it is within ones limits. Better look than be sorry.
Many thanks to you two for all your help.
I will watch Ebay and see if I can find an old unit some time.
For now I will pull plug out and leave the light off.
P.S. It still sounds great even without the light.
Yes, it is great player and light doesnt affect that.
This site is a great resource if you are interested about fixing this old stuff. Maybe finding something from ebay to start with? Your BG is not the best one for that, not most difficulty but not easies either.
Cheers