Hacker RP38A Bass circuit noise

[Radio Crackles]

Hi guys,

I have just picked up a Hacker Hunter RP38A after reading the many plaudits these sets have received on the forum. I received the set yesterday morning and everything was fine all day as I gleefully played with my new toy. I thought the R707 was good but wow the RP38 sounds superb, or should I say 'sounded', yes, I have a problem.

The radio was on for a straight 16 hours and worked flawlessly on all bands until disaster struck at 1AM. I was listening to talkSPORT. Now I get very poor reception of tS afterdark so I usually listen by streaming the station on a PC and using a short distance FM transmitter to pipe it through the house. So I'm sat there listening to my rebroadcast tS when I decided to switch to MW to check it out for real. I tuned in but with the same rubbish reception I have always gotten at that time of day so I switched back to FM. Immediately something sounded wrong. Ten seconds of frantic knob twiddling confirmed that I had a problem with the bass control.

After previously working fine the bass control now produces considerable noise. It is difficult to describe a noise in words but it is something akin to being near a fast flowing river. With the knob turned all the way down the noise is barely perceptible but is there. As I crank the knob up the noise increases until I have a raging torrent. This behaviour is the same on all bands and wherever the volume control is set - even turned right down.
HELP!

If some kind soul could give a newbie with no radio repair experience and 'very little' electronics experience some pointers it would be greatly appreciated.

Thanks,
David.

[Hunts smoothing bomb]

Hi David, welcome to the forum.

Well, I would suggest squirting some switch cleaner in the bass pot, but it sounds like you have awoken a noisy carbon resistor!
I don't know this set but if you can, try operating the set with back removed and thumping every resistor with a small screwdriver handle, (not too hard!) with the set playing so you can here the noise when the noise coincides with the thumps, you have found the culprit.

Good luck, let us all know how you get on

Cheers
Lee

[Radio Crackles]

Hello Lee,

Thank you for your advice and the warm welcome. You have indirectly solved the problem for me. When I was checking the resistors as you suggested I nudged a bunch of wires and the noise cleared. Please forgive my ignorance the problem was that 'gang-plug type thingy' going to the board with the aerial on - just needed some gentle pressure to snap it in fully and solve the problem.

Ah, lovely full sound again.

It's easy this radio repair game isn't it

Cheers,
David.

[Hunts smoothing bomb]

Excellent news!

Well done on the fix,
It's a good feeling when you diagnose and get something going again isn't it?

Cheers
Lee

[GJR 11L]

Hello David,

The board you refer to is the audio amplifier, and sometimes these can suffer from corrosion to the tracks underneath, particularly in a set that has some evidence of battery leakage into the floor of the cabinet.

The 5-pin connector may simply have been loose, and that may be all that needed doing, but it would do no harm to check the underside of the board in case there's any corrosion there and any sign of electrolyte (yellow 'goo') oozing from the bungs at the ends of any of the electrolytic capacitors on that board.

Those things are easy to replace if they are at all suspect, though on the Hunter's audio board you will need axial ones as everything lies flat in the interests of keeping the profile as shallow as possible for that particular model.

Agreed Hunters are superb-sounding old things, and like most '70s all-silicon Hackers they're generally pretty reliable if they have been looked after.

[Radio Crackles]

Thanks for the additional information John. It does look as if there has been battery leak in there at sometime so I'll take your advice and check that the board is ok.

Cheers,
David.