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Old 6th Dec 2018, 10:29 pm   #1
martin.m
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Default Hacker VHF Herald RP37 repair

This is my first Hacker repair. I bought the radio untested and after a quick visual examination I switched on then connected the batteries. There was a "plop" from the speaker but no sound. A meter in series with the supply registered a current of 0.5 amps (my present multimeter has seen better days and only works on the 10 amp range). Time to switch off. Repeating the test with the speaker unplugged gave a reading of around 20mA. Out came the audio panel and a few cold checks revealed that a 400uF 10v cap in series with the speaker was short circuit. A replacement 470uF 25v was fitted and this restored sound but the radio burst into positive feedback when the Bass control was advanced. I decided to change the other electrolytics on the panel apart from a blue Philips 125uF and this cleared the instability. I will set up the quiescent current and mid point voltage when I get a new multimeter.

Next problem was the volume control. Not the usual crackling but the sound went off completely if the volume was altered even slightly. I removed and dismantled the control which was full of oily black gunge. Cleaning and careful bending of the rotor contacts followed by a little lubrication cleared the intermittent sound.

I noticed that the frequency coverage wasn't quite right. I couldn't tune in Radio 2 on 88.5 MHz, the local station BBC Tees on 95 MHz appeared at 93 on the tuning scale, while at the top end it was possible to receive BBC Radio York on 104.3 MHz. The set is only supposed to go up to 101 MHZ. There is a brass tuning slug visible on the screened tuner module marked "osc". I don't usually like disturbing any alignment controls but as an experiment switched off and rotated the slug exactly one turn clockwise. This enabled Radio 2 to be tuned in and BBC Tees (95 MHz) appeared at 94.5 on the tuning scale. Classic FM could still be received around the 100 mark so I decided to leave well alone until I know what I'm doing. Perhaps someone had tweaked the control to extend the frequency coverage.

Cosmetically the Herald was in fair condition and responded well to a clean and polish. Unfortunately the gold coloured metal surrounds on the control knobs have suffered a little corrosion probably due to damp and the rear plastic grill is missing.

This model looks very smart in red with gold trim and has a lovely sound. I would like to get one with the Elac speaker eventually.
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Last edited by martin.m; 6th Dec 2018 at 10:31 pm. Reason: spelling
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Old 7th Dec 2018, 12:13 pm   #2
SteveCG
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Default Re: Hacker VHF Herald RP37A repair

martin.m, it is always good to see a working Hacker !

Looking at the pictures I see quite a few 'lockfit' packaged transistors, both on the audio panel and the IF panel. Although these are silicon devices, experience has shown that because of this particular packaging they can and do develop faults like low gain and/or noise. So should your set develop such faults - which I hope it does not - bear this point in mind.
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Old 7th Dec 2018, 1:14 pm   #3
martin.m
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Default Re: Hacker VHF Herald RP37A repair

Thank you Steve. I always thought of those transistors as being reliable but have read that other members have had problems with them. I had never seen or heard of Hacker radios before joining this forum. Perhaps only the wealthy could afford to buy them! Here is a better picture as the flash photography has obliterated the tuning scale on the first one. Next one to fix is a blue Sovereign ll RP25.

Regards
Martin
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Old 7th Dec 2018, 1:31 pm   #4
paulsherwin
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Default Re: Hacker VHF Herald RP37A repair

It could well have had the oscillator tweaked to provide a more useful tuning range so there may not be a fault present.

Lockfits are anything but reliable and getting worse as they age, but they are cheap and easy to replace in Hackers if need be.

You are right, Hackers were expensive when new.
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Old 7th Dec 2018, 3:27 pm   #5
SteveCG
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Default Re: Hacker VHF Herald RP37A repair

Interesting to see that your tuning scale has the Brighton and Sheffield local radio stations down at their original frequencies.
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Old 7th Dec 2018, 3:34 pm   #6
mhennessy
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Default Re: Hacker VHF Herald RP37A repair

What's interesting about this set is the fact it has the early tuner in the aluminium box, yet it is described as an A model.

The change from RP37 to RP37A was caused by the change in tuner. Which suggests that perhaps this set is a mixture of two different sets. It's possible that the scale was taken from a later set, perhaps?

Another indicator is the loudspeaker. I'm not exactly sure when the move away from the Goodmans unit happened, and know that it wasn't timed with the change to the A model by any means, but by and large, non-A models come with a Goodmans speaker, and A models come with either Celestion or Elac.

Either way, it looks like a lovely set. I have a couple of red examples, but they are all rather tired and look as if they will be difficult to restore. I've no idea where to find gold paint to restore the scale where the foam attacks it.

All the best,

Mark
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Old 7th Dec 2018, 6:01 pm   #7
Andrewausfa
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Default Re: Hacker VHF Herald RP37A repair

Mark,

There is a Japanese art pen manufacturer called Shachihata who did a range of 'paint' marker pens, you know the sort with a Xylene or Toluene or similiarly smelly carrier. In particular they did a very good Gold. The thing with this paint was they used a really very fine pigment very similiar to screening ink and if you decanted it from the pen by pressing down on the nib a few times, you could thin it and paint very fine detail with non of the metallic 'flakes' in you'd see in other paints. Unfortunately mine dried up years ago. Anyway, a long story to suggest that option might be worth a look.

Andrew
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Old 7th Dec 2018, 6:41 pm   #8
mhennessy
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Default Re: Hacker VHF Herald RP37A repair

Hi Andrew,

That's interesting - do you mean something like this? http://www.artlineworld.com/products.../ek_900xf.html

I will investigate further when time permits, but in the meantime, thank you for the tip

Cheers,

Mark
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Old 7th Dec 2018, 7:46 pm   #9
martin.m
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Default Re: Hacker VHF Herald RP37A repair

Quote:
Originally Posted by mhennessy View Post
What's interesting about this set is the fact it has the early tuner in the aluminium box, yet it is described as an A model.

All the best,

Mark
I have just had a closer look and it IS indeed an RP37 . My eyesight is not getting any better with age! This radio also has problems with the gold coloured paint at the edges of the tuning scale. I'm not an "arty" type of person and would probably make it worse by trying to touch it up.

Regards
Martin
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