Beocord 1200 belt change and repair

Do you have a Bang and Olufsen BeoCord 1200 reel to reel tape recorder with a faulty take up reel? Maybe it’s spilling tape or judders on playback? This post may help fix the fault with a fairly simple belt change.

I’ve always admired Jacob Jensen’s designs for Bang and Olufsen. His use of the slide rule, echoed in the Beolit 400 / 600 series transistor radio and the Beomaster 1200 amplifier, with the clean lines are iconic. When a colleague Tony mentioned retro B&O and said he had a Beocord 1200 that needed servicing I could not resist the opportunity to see one in action. It proved a challenge to get working but well worth the effort to repair.

The Beocord 1200 has an interesting history. David Bowie, among other 60s musicians, made use of the 1200’s sound on sound function that allowed over dubs to build multiple layers of sound and one or two hits without the need for an expensive studio. As a 70s student I could only afford the cheaper Akai 4000D which, although sounding reasonable, had far less features and no slider controls for easy fading.

This example arrived well packed weighing nearly19Kg. But it’s a heavy beast and a few things had come loose in transit.

First look inside

Removing the 4 slotted screws from the base revealed two pieces of paxolin floating inside. These had become detached from the base and sat below one of the main amplifier boards, see below.

Beocord 1200 inside view

Sometime in its life it had suffered an impact and glue fixing the two boards had detached from the base cover. It was a simple matter to glue them back using PVA. The smaller board has a copper side that faces outwards to make contact with the metal finger pad, I guess as a screen to reduce radio frequency interference. There was no obvious copper screen on the larger piece of paxolin but it prevented anything touching the PCB through the base cover grille.

A single phase AC motor in the centre uses a large cylinder 8uF capacitor to run. Also visible is the bottom of the capstan under the clear plastic cover with the belt driving the take up reel clutch – more about that belt later.

An impact had left another injury which had resulted in a bent PCB board and bracket. This was not just cosmetic – the bent bracket pulled down the edge of the amplifier circuit board which caused one of the slide switches to jamb and would not engage in record mode.

Straightened bracket

Bent PCB bracket

Circuit board and bent bracket

I removed the bracket and using a bench vice corrected the angles so the PCB was held in the right position.

Take up reel belt change

With the base back in place, powering the Beocord up revealed further problems. The take up reel failed to turn properly causing tape to spill when engaging play mode. The tape counter also failed to move. Fast forward and reverse seemed to work well, but these modes were driven by idler rollers not the dreaded belts.

The take up reel drive belt was in place and looked okay so needed a closer inspection to fix the spilling tape on play. Taking the top plate off revealed no clues for the take up problem with the break cord in place. But there was no tape counter belt so that also needed a new one, see how to change the tape counter belt later.

Getting the take up belt off from beneath simply required removal of the three slotted screws holding on the clear plastic cover as shown below. Care is needed to avoid getting grease on the belt from the bottom bearing. I lifted the belt clear from the take up pulley then pushed a loop back through the plastic slot while lifting over the grease. Needs two steady hands.

Take up drive belt

When free the belt showed an obvious stretch from years left in the same position on the smaller drive pulley, see below, the right belt compared with a replacement belt on the left. It could explain the tape spill. My replacement sourced from Italy was a little smaller at 2.5mm thick instead of 3mm.Both had similar diameters at around 100mm for the new and over 105mm for old. I should have found a cone or funnel to check diameters more accurately.

Old and new take up reel belts

Replacing the take up belt seemed to cure the problem. There was still a slight delay in take up when engaging play – see video. This may be normal for a machine this age, I remember the Akai 4000D behaving in a similar way.

Tape counter belt

As there was no original tape counter belt to compare I used one of the main motor drive belts that are slightly thinner and larger diameter to the take up belt. But how is it fitted? It looks easy to slip it over the top platter but there’s a few obstacles in the way. First you need to remove the thin break cord that is attached with screw at the top and spring below.

Beocord 1200 Inside Top Plate removed

Next you need to turn it on one side and using a hex head allen key undo the two grub screws that hold the take up reel pulley in place. Notice there are two grub screws at 90 degrees. You can then lift the top platter clear to loop the new belt over onto the pulley beneath the reel platter. You may be lucky and manage this manoeuvre without lifting the platter but as there’s also a break pad hiding under the platter I found it easier to see what I was doing to save damaging the belt. Keep the belt under tension while pulling the belt over the tape counter pulley. Three hands would help! B&O probably had a jig to help.

When the belt in engaged, hold the platter in place while tightening the take up pulley. Finally replace the break cord and the tape counter should tick again.

Finished Beocord 1200

Some shots of the reassembled tape recorder with and without cover.

BeoCord 1200 assembled

BeoCord 1200 with cover