Hacker mini herald fault

Dear all, 

Im looking for some advice regarding my hacker mini herald. Was working but was very hissy and poor reception. Some capacitors had been changed in the amp section before I purchased. The remaining capacitors were all out of value so I recapped. When it turns on nothing, now completely dead. I double checked my work, capacitor polarity etc against schematic and all ok. One of the af117s had also been changed for an equivalent before purchasing. I've checked and changed the remaining 117s with Russian soviet equivalents still nothing. Checked all general wiring and reflowed the solder connections. Next stop I'll have a poke with the audio probe, but just looking for any further assistance.

Many thanks 

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Hi James,

did you read this: AF117 and Tin Whiskers

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Hi thanks for the reply. Yes a good article, I have already changed out the offending Af117s however set is completely silent. I get a sound from the speaker when I turn it on and off, it sounds like the amp activating but that's all. Become a real head scratcher this one. 

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Hi James.

One recommendation, based upon faults I experienced with the bigger sibling Hacker Herald RP30, is that you check whether there is audio at the three pin plug (PL1 in the schematic) that connects power and audio from the tuner module to the audio module below the speaker. You will then be able to determine whether the tuner module or amplifier module is at fault. Note that battery power initially goes to the tuner module, so you should be able to check for both audio and power at the pins of that plug once it is removed.

Reasoning for this reommendation is as follows:
My experience with the Herald RP30, which appears to be of the same vintage, had similar symptoms and problems over the years because of two issues. Also, we bought this radio new, so I well know its provenance and vicissitudes! The AF117 failure occurred in later years and was simple to fix with a substitute transistor of the same type that I found amongst my old salvaged stock.  The other problem that manifested itself in the sixties when we used the radio daily had to do with the 5-pin plug and socket arrangement that connects the power and audio from the tuner module to the separate amplifier module below the speaker. (Note that the RP17 model uses a 3-pin plug whereas the RP30 uses a 5-pin one to include bass and treble tone control connections.) One assumes that the modular audio amplifier made for easier servicing as well as placement in the cabinet, but the choice of that particular plug and socket arrangement led to intermittent audio problems (complete drop-out) on a regular basis. The ‘socket’ is composed of free standing sleeve type female connectors that are soldered individually to the amplifier pc board and are all subject to considerable stress from the insertion of the plug and subsequent flexing of the pc board. Over the years, loosening from vibration and slight corrosion may also contribute to connection reliability at this juncture. Worse, I found that one or two of these sleeve type socket connectors could fracture the joint at the copper trace lands where they were soldered on the underside of the pc board leading to intermittent open circuits and complete loss of audio other than the typical power click as the volume control was switched on.

I hope the above suggestion may help because these Hacker radios are well worth the effort to get operating as selectivity and audio fidelity are well above par and contributed to quality radios in their time.

Kind regards

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Hi Stan, 

Thanks for your post, it was informative and very helpful. I poked there with the audio tracer and found audio at that pin and then no further. Bridged it with probe and audio immediately came back. Had a good look with a magnifying glass and could actually see where the solder had separated from the pin base. Desoldered the pin, cleaned with alcohol and resoldered with a larger tip at 350° and got a good flow on the pin. Been absolutely great since then and really benefitted from the recap and new transistors. Sound very clean and full. Many thanks for your assistance it really was a great help 👍

Kind regards 

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Hi James.

Very glad to hear that my suggestion helped solve your head scratcher! Intermittent failures and fractured joints can be so difficult to pin down, and so frustrating, too. Enjoy that radio to the full, now!  

And in thanking me for my assistance, we should also thank the staff and volunteers at RMorg who make this forum so useful and informative for the rest of us. 

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