Beocenter 4000 (early type)

23rd December 2009

In all cases where the cassette section gives odd results that cannot be easily explained it is a good idea to check the various relay contacts in the signal sections. Removing the relays one by one and checking the resistance of each pole with a meter, powering the coil where necessary with a bench power supply or battery, is one method. In one recent case the recorder would play a cassette normally but recordings with Dolby NR sounded odd as the signal was not being encoded on one channel, a single dirty contact being the cause. With care, the relays can be dismantled and cleaned which is fortunate as they are not easy to substitute with modern types. [Beocenter 4000]

Beomaster 900

20th October 2009

This receiver gave no results and was getting hot because one of the AD139 output transistors was short circuit. After replacing this the set worked but there was a hum in the background and the regulated supply to the amplifier was high at 27V (it should be 22V). The SP1446 regulator transistor had also been damaged, replacing this removed the hum and allowed the output voltage to be set up correctly.

The original transistors used in the Beomaster 900 are becoming difficult to find but the AD139 can be replaced by an AD162 (providing both transistors in the affected channel are replaced) and the SP1446 by and AD149, both of which are still widely available. [Beomaster 900K, Beomaster 900M]

Beovox RL 140

17th August 2009

Although rotten foam roll edges is not a common RL problem some RL140s are now being encountered with woofers whose roll edges have failed. As an alternative to repairing the originals (which were not of outstanding quality to start with) the Visaton WS 17 E (8 ohm version) makes a good substitute (www.visaton.de). These are moderately priced and fit into the cabinets without modification, although it was found to be necessary to cut the positive spade terminal in half along its length so that the wiring connectors would fit. Best of all the Visaton drivers have elastic rubber roll edges so they won’t rot away again. [Beovox RL 140]

Beovision LX 2802

13th August 2009

This set suffered from EW distortion (e.g. an hourglass-shaped picture) when cold that could be cleared by a sharp tap on the rear cover near the timebase / power supply panel (PCB 4). Clearly a dry joint was to blame but where? Everything looked sound but when the iron was touched on the pins of 4C43 the solder fell away, indicating that a good contact had not been being made. Resoldering cleared the fault. [Beovision LX 2802]

Beocord 8802 V

10th August 2009

This V2000 VCR would play OK for a few minutes, then the picture would be lost and the mechanism would return to “stop” mode. It could be seen that the head drum would slow just before this happened so the drum servo was investigated. No faults could be found on the drum servo module and the motor itself tested OK, it was also noted that the +12V supply was steady throughout. The defective component was found to be a small relay fitted to the underside of the mechanism near the loading motor, amongst other things this provides a +12V “motor on” signal for the drum servo. There are two other similar relays located nearby too, one controls the loading motor direction and the other the pinch roller solenoid. All three showed high and erratic contact resistance so they were all replaced with modern alternatives. No further trouble was experienced after doing this. [Beocord 8802 V]

Beocord 8004

29th July 2009

This recorder worked normally except that the motor continued to run even in standby mode. The motor is powered from the switched -15V supply and this was present all the time, however the switched +15V supply, which is controlled by the same circuit, behaved correctly. The cause of the fault was 4TR9 (BC547B) which had a base to collector leak. It is important to resolve faults like this and avoid needless wear as the motors used in these models are expensive and difficult to obtain. A similar circuit is used in all the Beocord 6000, 6002, 8000, 8002 and 9000. [Beocord 8004]

Beocord VHS 80 & VHS 90

8th July 2009

Poor performance from the remote control receiver has traditionally been cured in these models by adding a 1nF capacitor across the collector and emitter of Q924. Recently this has not proved effective however and in some cases it has proved necessary to replace C954 (4.7uF) as well. [Beocord VHS 80, Beocord VHS 90]

Help to save AM/FM radio in the UK

1st July 2009

Following the “Digital Britian” report, AM/FM radio is under threat in the UK. You can help to protect its future by signing this petition:

http://petitions.number10.gov.uk/AM-FM-Radio/

A worthy cause if ever there was one!

Beomaster 3000-2

19th May 2009

This receiver would not stay on tune, the stations drifted erratically about and sometimes disappeared all together. At first the frequently troublesome selector switches were blamed but cleaning them made no difference. A meter showed that the tuning voltage was steady in any case so the tuner front-end was investigated. The tuner unit proved to be extremely sensitive to tapping about with an insulated tool so poor soldering between the case and PCB was first suspected. This proved not to be the cause, the real culprit being the oscillator trimmer (40). The screw was loose and making poor contact with the body of the component. On removing the complete trimmer from the board it was possible to unscrew the threaded part completely through the bottom, this revealed that the two sprung contact fingers inside had relaxed and become stuck in old grease, re-tensioning and cleaning restored stable operation once the trimmer had been refitted and realigned. [Beomaster 3000-2]

Beovision L 2502

12th March 2009

This set displayed bent verticals at the top of the picture when used with a digital receiver connected through the DIN/AV socket, normal UHF reception was unaffected. The slightest adjustment of the line hold control cured the problem completely. As the components used for the line hold and line phase controls are of poor quality replacements of a better type were fitted and set up correctly, this should make for a lasting repair.

These controls are also amongst the things to suspect if the line output transistor fails frequently. [Beovision L 2502]