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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 12th May 2024, 8:26 pm   #1
Gabe001
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Default Restoration of an HMV 1138 radio

I'm on a bit of a restoration roll, so I returned to my first love, radios.

Posting this here as it's a relatively uncommon set, so hopefully this may help someone in future. I had done a few 1134s for friends and they're attractive sets which are always well received. The 1134 is the better of the two models in my view. More about this later.

Whilst the case of the 1138 is very similar to the more common 1134, there are differences.

1. There is a piano key arrangement to switch bands and turn off, like the bush VHF models

2. There is a tuning knob for AM and one for FM. Each with their own insanely complicated tuning cord arrangement.

3. The tuning dial bulbs are too close to the AM tuning cord, making it susceptible to scorching. Luckily mine was still serviceable. I directed the bulbs away from the cord, but this made the tuning dial a bit dim

4. The backing of the tuning dial is cardboard paper instead of metal, which is a bit 'cheapskate' for an HMV set

Taking the set apart, one of the tuning knobs was broken, otherwise there were no surprises. A lot of dust, which was carefully cleaned. The moving parts were lubricated which made the tuning smoother and sorted the sticky piano keys.

I lost the battle with the on and off switch. This is a double pole single throw switch. No matter how much I worked it, and how much switch cleaner I sprayed, I couldn't get one of the poles to worked reliably. It also wouldn't come apart easily. I ended up converting it to a single pole switch (switched live). It works well this way.

All pots got a squirt of servisol. The selenium rectifier was still good and delivered the required volts. The plessey triple capacitor can also reformed nicely with no discernible leakage.

The hunts capacitors were replaced one at a time, checking that the set works on all bands after each replacement. The mains filter capacitor was also replaced with a suitable type X

AM reception didn't work. It turns out that the anode load resistor to the oscillator valve was open circuit. Replacement restored normal service. A couple of 47k anode load resistors in other sections were also high (>100k), so these were also replaced. I had run out of 47k 1watt resistors, so I used 43k which is still within 10% tolerance range of the original ones.

Finally replaced the mains cord with a 3-core and earthed the chassis.

The em81 magic eye was effectively dead, and was replaced. The el84 looks like it had a hard life but it still works well.

The case was given some love with a polish reviver and retouched, and ended up looking quite nice

The main problem was the broken knob (see picture). More about this in post 2
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Last edited by Gabe001; 12th May 2024 at 8:31 pm.
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Old 12th May 2024, 8:46 pm   #2
Gabe001
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Default Re: Restoration of an HMV 1138 radio

The broken tuning knob required some thought. In the end, I decided to solve the problem with my 3D printer. I 3D printed a sleeve to go round the existing 'stalk' with an extension to fit a grub screw and nut. Dimensions had to be precise. Pictures below. The swear box was full by the time I sorted it, but securing the already tight fitting sleeve to the existing short stalk with epoxy, I'm confident it'll last a century.

Putting it all together, I must admit it's quite a looker.

Performance-wise it's probably similar to the bush VHF 61. On VHF, I get maximum magic eye deflection on classic FM and the BBC stations with the default aerial, which is pretty decent. AM reception is good too, as you would expect from a set with a directional ferrite rod.

Hope this helps someone in future.

Gabriel
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Old 16th May 2024, 11:56 am   #3
AnalogueMan
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Default Re: Restoration of an HMV 1138 radio

Nice work. I've just started on a Pye Fenman 1 which also has 'knob rot' and will be posting a write-up once it's done. For reference and perhaps to help others searching for info on this in the future, David G4EBT has also done some great work on knob repair which involved skimming the existing shaft off the knob, turning up a new one and gluing it on
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Old 17th May 2024, 6:34 am   #4
Gabe001
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Default Re: Restoration of an HMV 1138 radio

Some fascinating posts by David. Thanks for that.

I had the same problem in a KBMR10. Initially tried extending rod with epoxy/milliput, but that wasn't strong enough for the waveband switch, so I sleeved it and glued the sleeve to the existing shaft stub, and it feels solid to this day. The only difference here is the addition of the grub screw. Originally it was push fit with a metal clip, but this was lost. In all honestly, the 3d print extension was a tight enough fit on the shift, and the screw wasn't absolutely necessary, but it was easy enough to implement and gives extra peace of mind.
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