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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 29th Aug 2014, 2:14 pm   #1
ben
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Default TLH85 headset: low cost repair

These headsets, usually found as Tandberg TLH85 but also badged ASC, Cybervox, German Maestro, Sanako and others, are perhaps the most ubiquitous of their kind in education and some pro audio applications. They first appeared in the mid 80s and by now, most of the original ones have suffered some deterioration.

They are generally very robust, made of thick plastic, but there are a couple of areas that wear:
1. The ear cushions
2. The 'bellows', a concertina-style piece of thin rubber located between the headband and the earpieces.

The ear cushions will be covered later ; for now I want to concentrate on the repair of the 'bellows'/ 'folding jacket' (Sanako P/N 1395086; Canford P/N 27-813). These really look awful when they get ragged, and re-doing a whole language lab's worth at just under a fiver each can get costly!

This fix will not allow the headset to self-adjust (over the head of the user) to the same degree as orignally made; however in practice there was only ever a slight amount of movement anyway. Trial and error with the hole mentioned in point 7) will give a good compromise.

You will need:
-length of heat shrink tubing, 13.0 cm diameter.
-scissors.
-soldering iron
-small crosshead screwdriver
-flat blade knife or screwdriver

First, remove the old bellows:
1. Remove ear cushion.
2. Using the knife or flat screwdriver, gently prise up the inner section of the earpiece, separating it from the main unit.
3. Desolder the two wires to the speaker, making note of what goes where. Note that on the mike/connection cable side, the input cables may combine on the same lands. (Pic 1)
4. Remove manufacturer's badge from outside earpiece.
5. Unscrew small black phillips screw to release nylon slider. Pull earpiece away from headband. (Pic 2)
6. Unscrew headband clamp. Separate pieces. Pull off old torn bellows.(pic 3)

Then prepare the piece of heatshrink that will form the new bellows:
7. Cut approx. 10cm of heatshrink tubing (Pic 4). Make holes as shown in pictures for cable to enter and leave and also, at one end, for accommodation of headset clamp stud. Make holes about 1.5 cm from each end and a second hole about 3cm from one end. If the headset is to be used by younger people, make one of the holes 2 cm from the end (Pics 5 and 6).
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Old 29th Aug 2014, 2:16 pm   #2
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Default Re: TLH85 headset: low cost repair

Fitting the new part:
8. Taking the end with one hole, push it over metal headband extension. Make two small cuts of less than 0.5cm in the heatshrink sides to allow a snug fit over the headband padding (pic 7). Push up heatshrink so that hole in heatshrink lines up with that in metal headband (Pic 8).
9. Thread cable through hole, feed it down the inner side of the new bellows and out the upper of the two holes at the botton end. (pic 9).
10. Affix headband clamp, ensuring the little gap goes over the hidden cable. (Pic 10).
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Old 29th Aug 2014, 2:18 pm   #3
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Default Re: TLH85 headset: low cost repair

Fitting (cont'd):
11. Thread on earpiece and pass cable through into recess (pic 11). The nylon slider is usually worn too. I usually just put the philips screw and washer on the inside, and screw it into part of the slider on the other side of the bellows, that is to say on the outer side beneath the manufactuer's badge (Pic 12).

Rest of reassmbly is initial instructions in reverse!

Hope this is useful. There's lots of life left in these headsets and other spare parts are readily available from sources mentiones in Post 1.
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Old 29th Aug 2014, 2:41 pm   #4
Nickthedentist
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Default Re: TLH85 headset: low cost repair

Very clever.

These are fine sounding headphones from what I recall.

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Old 29th Aug 2014, 9:08 pm   #5
dseymo1
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Default Re: TLH85 headset: low cost repair

I look forward to the next instalment (ear cushions), as I have several sets of cans with flat cushions!
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