[hcraig244]

check out beolovers blog on this…..may help you understand whats going on

https://beolover.blogspot.com/2022/05/beogram-Replacing-sensor-arm-bulb-with-led.html

[hcraig244]

did you change the tuning indicator lamps in the tuning circuit? if so these must be replaced by lamps of the exact current pull….i had an issue with some i changed on a 4400, Dillen provided the correct lamps and all was well.

Craig

[hcraig244]

hcraig244 wrote:

Also bear in mind that some components can measure up fine when tested, but fail under load…..I’ve had this issue in the past, and replacement parts from suspect suppliers should be avoided…early transistors can still be found as old stock and are a safer bet than ebay

Craig

hehe…..

[hcraig244]

I’ve had a similar problem in the past and with the help of a signal generator and an oscilloscope traced it to a noisy transistor in the pre-amp section as I recall….I’ll take a look at the circuit diagram and see if I can remember which one it was. There will be a post by myself in the archives detailing this im sure 🤔

[hcraig244]

It’s tricky…

You dont need to remove the front panel, thank goodness…..would be a shocking design defect if one did. The lamp is held in a holder that slides into the side of the moving coil meter, the holder has two wires soldered to it to illuminate the lamp therein. the meter also has two wires soldered on to it externally to power the moving coil, cant remember if its a moving coil or moving iron meter…..non the less it has two wires!

The meter is held in place on the front panel by a copper leaf spring which in turn is held in place by a single screw, see below. when this screw is removed the meter will push in from the front of the switch panel and be sort of accessible, the connecting wires are single strand and very unforgiving….the tugging and pulling required to remove the lamp holder in situ with all wires still connected is traumatic and in one case for me I broke a connection to the moving coil and had to replace the whole thing….fortunately Dillen from this site had a used one he let me have ;¬)

My approach of choice now is to snip the four wires that connect to the meter, well inside the unit for ease of re-soldering later, then undo the screw and spring thus allowing the meter to be removed from the underneath of the chassis, the lamp holder can then be slid out and a new lamp inserted and the meter re installed prior to re soldering the snipped wires. This is a very delicate operation, partly due to the frailty of the connections and getting the spring loaded screw back in place is also a challenge best done before soldering the wires back in place. You also need to replace the lamp with one with the correct ratings…Dillen can provide the correct one.

 

• This reply was modified 2 months, 3 weeks ago by hcraig244.

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[hcraig244]

I have found a number of these random intermittent faults have been caused by the switches feeding the logic gates within the control panel, the logic chips are very reliable and seldom, if ever fail….the switches feeding the gates however are very susceptible to fail…typically arc and corrosion, and also bending over time…if a leaf type switch is left stood in one position for a long time it will loose some of its elasticity. The switch that controls the lower current to the magnetic coil is one such switch, if this is not clean and fully functional it could cause the issue you describe, also clean and inspect the control panel switches….have a read of the training notes donated by Solderon in the manuals section of the products area…..they are very informative.

Good luck!

[hcraig244]

When you say it only happens in the first 1/3 of the record does it always happen at the same point each time it occurs?

[hcraig244]

good work….sounds like the red herring thrown up by the DBT is resolved, regarding zapping something if you power up I suspect the offending component will have been zapped sometime ago when the problem first arose, again if you have a variac (very useful for fault finding) try disconnecting the 15v supply from the circuit somewhere around halfway through and power up the 240v slowly monitoring the current pull (put your DVM in series) as you do so…..if the current starts to go up alarmingly the fault is in the part of the circuit connected…..check all components

Good luck

• This reply was modified 3 months, 1 week ago by hcraig244.

[hcraig244]

One other thing…..the circuit diagram shows 22vac from the transormer to the 15vdc rectifier…..your measuring 17.6vac

made a proper bollocks of the images i know ;¬)

• This reply was modified 3 months, 2 weeks ago by hcraig244.
• This reply was modified 3 months, 2 weeks ago by hcraig244.
• This reply was modified 3 months, 2 weeks ago by hcraig244.

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[hcraig244]

you have replaced or proved every component in the circuit, confirmed every track and solder joint all to no avail….the only outstanding item is your transformer….do you have a variac you could power the 15v rectifier from?……you have eliminated every other component in what is a basic power supply circuit….i keep thinking of the fact that the circuit performs correctly on power down….back emf from the transformer, if that’s even possible, could be doing this……there isn’t anything else to check ;¬)

Craig

[hcraig244]

could that brief spike be back emf from the transformer when it shuts down….i have to agree this isnt making much sense, you have changed the smoothing cap and bridge rectifier…cap is in the correct polarity, have you powered up without the DBT on the supply?

Craig

[hcraig244]

Sounds like some progress…..change TR17 out and you should be good to go for the FM issue, dillen from the site always advocates the “half it” approach which is to go half way into the circuit and disconnect/test then work back or forth from that position…..always works for me ;¬)

Craig

[hcraig244]

Hi

just seen your post, this can most likely be repaired, see my post in the forums for Beovox for the procedure

hcraig

[hcraig244]

this?

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[hcraig244]

Not quite sure what your describing here….do you mean the tone arm?….or something else?

Craig

 

[hcraig244]

Also bear in mind that some components can measure up fine when tested, but fail under load…..I’ve had this issue in the past, and replacement parts from suspect suppliers should be avoided…early transistors can still be found as old stock and are a safer bet than ebay

Craig

 

[hcraig244]

if you disconnect all users from the 15v power supply rail and measure the output is the problem still present?

Craig

[hcraig244]

Have you checked for broken traces and dry joints…..it’s got to be something obscure 👀

[hcraig244]

Replace ZF9,1V……..see if that helps, if not then at least you can eliminate it from the problem

Craig

[hcraig244]

Ive had to think hard about this reply so as not to offend anyone who has been good enough to give you the technical advice your currently in receipt of, however it appears said advice is  condemning a valuable deck in a  somewhat  off hand manner. The power supply stabilisers and associated reed relays are a little daunting but they can be repaired/restored…even the relay coils can be rewound….I have no doubt Nick is the man for the job…..given his B&O service engineer background ;¬)

 

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