Beomaster 5000

24th January 2012

If the computer control system of this receiver appears to behave oddly the first thing to do is to replace 4C59 (33uF / 16V) in the reset circuit. 33uF isn’t a common value but 47uF can be used instead. [Beomaster 5000]

BeoVision 7-32

30th December 2011

If the DVD “eject” key doesn’t work or is insensitive it is worthwhile checking that the foam rubber pad on the back of the key itself is correctly placed on the raised square section in the middle. If it is not the key may not operate the peizo-electric sensor above it correctly. [BeoVision 7-32, BeoVision 7-40, BeoVision 7-55]

Beomaster 1100

27th November 2011

If problems are experienced in accurately setting the output bias current to its correct figure of 25mA (e.g. 10mV across 2R158, 2R159, 2R258 or 2R259) because the range of the control is restricted or compressed then adding a 470R resistor in parallel with 2R155 and 2R255 should help. Also ensure that there is plenty of heat sink compound around 2IC101 and 2IC201 so that they are adequately coupled to the output transistors, this is necessary for stability. [Beomaster 1100]

Beocenter 7700

19th November 2011

No recording on the left channel was the fault so the relays 11RL1 and 11RL2 were replaced. This made no difference and ‘scope checks revealed that no signal was reaching PCB 11 at P5 (pin 1). The cause of the trouble was the recording level control, a dose of cleaning spray cleared the fault completely. [Beocenter 7700]

Beomaster 5500

7th November 2011

Instability in the amplifier sections at high volume levels, evidenced by whistling noises from the loudspeakers when adjusting the volume, were as a result of noise spikes on the +8V supply. The cause was 2C14 (10uF 16V), which was open circuit. The Beomaster 5500 seems particularly prone to these sorts of problems (see an earlier entry concerning noise on the -12V supply) but the tones produced are sometimes above the normal range of hearing, however if 2R231 and 2R431 (4R7 1/2W) appear to have been overheating this indicates that something is amiss. An oscilloscope check at the loudspeaker output with no sources connected will reveal if there is a problem, ensure this test is done at all settings of the volume control. [Beomaster 5500]

Beovision 3400

7th November 2011

The NS raster correction circuit of this set can be made more reliable by replacing the capacitor 12C1 (located on the sub-panel at the top right hand side where the degaussing coils plug in). Only use a 47nF 630V polycarbonate type. At the same time ensure that transistor 5TR6 in the blue horizontal amplitude anti-modulator circuit has a 22R 1/2W resistor between its emitter terminal and the chassis. [Beovision 3400 K, Beovision 3400 SJ]

Beovision MX 5500

29th September 2011

A good picture but no sound was the complaint with this set, although a heavy “crack” could sometimes be heard from the loudspeakers when switching on and off. It was soon found that the split 20V supplies to the audio output integrated circuits IC3 and IC4 was imbalanced, rather than using a centre tapped winding the circuit uses some extra circuitry to create a mid point. The cause of all this was 10C96 (100uF), which had leaked its contents over the surrounding components. A thorough clean and some repairs to the PCB tracks beneath, along with a replacement capacitor, were required to restore normal functioning. It is also well work checking the soldering of IC3 and IC4 whenever one of these models is serviced.

Other sets which use this chassis include the MX 3500, the LX 4500 and the LX 5500. [Beovision MX 5500]

Beocord VX 5000

11th July 2011

Now that these models are over twenty years old the lithium back up batteries are beginning to fail. The symptoms include loss of timer and tuning memories and a machine that is stuck in standby and cannot be started using any of the keys. In the latter case the problem can be cleared by applying the mains power for about 15 seconds, briefly interrupting it and then applying it again, the machine should then function normally. The battery is located behind the deck, near to the capstan motor. New batteries are still available (e.g. RS Components 702-0812) but in an emergency two normal alkaline AAA-sized cells can be fitted instead. [Beocord VX 5000]

Beogram 8000

20th June 2011

When “Turn” was pressed the platter would rotate normally but when “Play” was selected the arm moved only briefly and then stopped, the cueing buttons being inoperative. Conditions around the microprocessor 2IC1 proved to be normal so the analogue tracking servo was investigated instead. Measurements showed that the cueing function was engaged and attempting to drive the arm in both directions at once, the faulty component being 3IL1, the bulb inside the cueing button assembly. Interesting, the bulb still had continuity but was producing only a much reduced light output, possibly due to an impaired vacuum. If the correct 18V 30mA lamp is not available a 12V 30mA lamp can be used instead if a suitable series resistor is added. [Beogram 8000]

Beocenter 3500

23rd May 2011

Overheating of the output transistors of either channel should draw attention to resistors 480 and 559 (1.8k) as they are often found to be high in value. The bias current presets 481 and 561 (250R, replace with 220R or 470R with an extra 470R resistor in parallel) also drift so ideally all these parts should be replaced together, along with resistors 482 and 560 (560R) if they are out of tolerance. 20mA of quiescent current, measured at the collector of the upper 2N3055 output transistor, is a good setting to aim for, repeat the adjustment after 30 minutes operation as the current may drift upwards from its “cold” value. The Beomaster 3000 and Beomaster 3000-2 use the same circuit. [Beocenter 3500, Beomaster 3000, Beomaster 3000-2]

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