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Old 16th Aug 2022, 11:44 am   #1
IanNVJ35
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Default Hacker Hunter RP38A tuning dial adjustment

I have always wanted to own one of these since a neighbour had one in the Early 90's and I liked the build and tone.

So I picked up one from Ebay and it arrived today. It is serial No. 13160 and looks clean and not battered. Came with two new batteries as well.

I attach a photo.

The one thing I notice is that the tuning is a bit off, the marker goes out of sight on the left side and is still visible on the right.

Is this an easy adjustment or does it mean taking the cord off?

Apart from that it seems great, however are there any worthwhile preventative jobs I need to do?
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Old 16th Aug 2022, 12:13 pm   #2
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Normally the dial pointer is just a snug slide-fit on the cord and you can nudge it further to the right or further to the left without unmounting the drive cord, in fact you should avoid unstringing the drive cord without a good reason as there is a bit of an art to winding them back on the right way with the right tension, etc.

But first, ascertain whether the dial pointer really is offset - tune to a radio station you definitely know the frequency of and look to see whether the pointer is dead-on that frequency on the dial. If it is, leave well alone.
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Old 16th Aug 2022, 12:58 pm   #3
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Default Re: Hacker Hunter RP38A tuning dial adjustment

That is certainly a good example of an earlier iteration of the design, which has acquired separate tone controls but retains the extruded aluminium speaker fret, so commonly bashed and battered.
As said, establish the frequency / wavelength of a known station and determine whether the pointer is truly offset first. If so, it should be possible to tease it along the drive cord without anything more invasive being required.
As regards further work, if you have the test equipment, it might be worthwhile testing the aged electrolytics.
That said, I have no experience of this iteration of the model - mine being, I think, the very last in the line and having all Philips electrolytics with the transparent blue sleeves which are all sound.
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Old 16th Aug 2022, 2:18 pm   #4
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Thank you kindly. Yes I'll check that, make sure it's actually not correct.
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Old 16th Aug 2022, 2:31 pm   #5
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Hi

Some sets have a subtle mark on the dial at the low frequency/high wavelength end to show where the pointer should sit when the tuning capacitor is fully meshed.

The pointer mechanical adjustment should be done before any electrial alignment

Unfortunately I don't know if the Hacker has this useful feature.
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Old 16th Aug 2022, 2:58 pm   #6
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Agree with previous advice regarding the dial pointer.

As for other maintenance jobs, if it is working well with no apparent issues then I would leave well alone!
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Old 16th Aug 2022, 6:09 pm   #7
IanNVJ35
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Default Re: Hacker Hunter RP38A tuning dial adjustment

I've given it a careful examination.

MW. Excellent apart from a sort of scratchy volume pot noise in the middle.

FM. Starts off reading 0.5 high and ends up 1.0 high. So it can't get 100.9 Classic FM. Also sensitivity seems worse at the highest end with 98.8 sounding a bit distorted.

So moving the pointer won't cure it all sadly. Is there an adjustable pot that may need tweaking?

But it's excellent with good sound and the AM sensitivity has made it a worthwhile purchase.
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Old 17th Aug 2022, 10:06 am   #8
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Every Hacker I've worked on has needed an RF alignment. It's just how they are...

This starts with setting the pointer datum. This is always wrong. From the manual:

Quote:
Check pointer datum position and adjust if necessary so that the pointer coincides with the R/H end of the scale markings when the gang is at maximum (Fully closed).
I interpret that to mean the pointer is just on the verge of disappearing when at the right hand end of the scale. As mentioned, it just slides on the cord.

Doing that usually reduces the errors, so this is worth doing, even if you don't want to do any more. But the next step is to follow the procedure of RF alignment, and this needs to be repeated across all three bands. It is possible to do it with off-air sources, but it's much better to use an RF generator if you have access to one.

The adjustments interact, so it's an iterative process, alternating between the oscillator coil and padding capacitance. Once the oscillator is set, you then have to tweak adjustments for maximum sensitivity, which can be tricky if signals are strong where you live (that's one reason why an RF generator is better). These adjustments are also iterative, but are well worth the effort.

The procedure is detailed in the service manual. Unless it's changed recently, I believe that the only option from Paul's data is for the RP38, not the A model, so I think it's OK to point you towards the Hacker Radio group at groups.io.

Otherwise, aside from cleaning the switchbank and checking the two pre-sets in the audio amplifier, I'd leave it alone. The electrolytic capacitors are generally very reliable, so "innocent until proven guilty" rather than "change on sight". A low frequency rumbling noise that's present even at minimum volume could be caused by T1 on the amplifier board, or by the carbon-comp resistors surrounding it. Otherwise, these sets are very reliable, and obviously very nice to listen to, especially those with the Elac speaker.
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Old 17th Aug 2022, 10:18 am   #9
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Incidentally, you might have seen this thread: https://www.vintage-radio.net/forum/...ad.php?t=81927

Yours is the earliest RP38A that I have on record, so that's a useful data point - thank you.

In theory, yours should have the Elac speaker with a grey painted frame, and no DC input. I can see from the photo that the other details are correct, aside from one: in theory, there should be a black Rexine strip in the handle (though those are often lost by this point). Would you be able to confirm if it is present, or if there are signs that it might once have been (such as glue residue)?
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Old 17th Aug 2022, 11:04 am   #10
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Thank you. That's really helpful. I can easily do the pointer alignment and also clean contacts and switches, but RF alignment is something I have not done - being more mechanical electronics based. Is there may be someone who can do this service and is sympathetic to these sets? Its such a nice example I really don't want to mess it up through inexperience. I have basic test gear but no signal generator. I think joining the hacker group may be a good idea, I'm keen to understand more.

Interesting its an early one! My set has a Hacker aftermarket DC input - very professional but with a rectangular badge, not circular. It has a wood veneer effect in the handle. It has a grey speaker. See attached pics.
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Old 17th Aug 2022, 1:06 pm   #11
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Ah yes - the teak sets have the fake wood insert. Black ones have Rexine. Later sets were just plain aluminium, and the very latest moved to the 3-piece style that Sovereign III and related sets used.

We've seen the occasional DC input added to the RP18 Sovereign, and we think those might have been a dealer-fit option, using parts supplied by Hacker, but we've no documentary evidence to support that yet.

I used to do a lot of servicing of these, but I'm just too busy at the moment. But it's not too difficult. Just be careful not to break the ferrite cores. If you only make small movements, you won't make it too much worse. You just need to know exactly what frequencies Classic FM and Radio 2 are on in your area to get the oscillator about right. Adjust the coil to get R2 right, then the trimmer to get CFM in the right place (and repeat several times). Turn the AFC off during this by shorting out C21 with a test lead
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Old 17th Aug 2022, 1:51 pm   #12
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Default Re: Hacker Hunter RP38A tuning dial adjustment

"We've seen the occasional DC input added to the RP18 Sovereign, and we think those might have been a dealer-fit option, using parts supplied by Hacker, but we've no documentary evidence to support that yet."

Hacker definitely provided a dealer-fitted external power supply socket kit for the RP25 - I think it was available from the early 1970s (1973?), which is when I had one fitted to mine.. It was designed to work with the VP whatever-it-was Hacker power supply (which had adjustable DC output voltages). I assume they would have supplied the same (or similar) kit for the RP18.
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Old 17th Aug 2022, 2:42 pm   #13
IanNVJ35
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Default Re: Hacker Hunter RP38A tuning dial adjustment

Quote:
Originally Posted by mhennessy View Post
Ah yes - the teak sets have the fake wood insert. Black ones have Rexine. Later sets were just plain aluminium, and the very latest moved to the 3-piece style that Sovereign III and related sets used.

We've seen the occasional DC input added to the RP18 Sovereign, and we think those might have been a dealer-fit option, using parts supplied by Hacker, but we've no documentary evidence to support that yet.

I used to do a lot of servicing of these, but I'm just too busy at the moment. But it's not too difficult. Just be careful not to break the ferrite cores. If you only make small movements, you won't make it too much worse. You just need to know exactly what frequencies Classic FM and Radio 2 are on in your area to get the oscillator about right. Adjust the coil to get R2 right, then the trimmer to get CFM in the right place (and repeat several times). Turn the AFC off during this by shorting out C21 with a test lead
Thank you - and I think I can do that.

Would you happen to know if the service manual is online? Just need to know the component locations and amplifier setup instructions.
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