Hacker Hunter VHF RP38 Refurbishment

[ajgriff]

INTRODUCTION

I’ve restored a few 1970s transistor radios over the years all of which were bought cheaply at boot sales and the like. However I’ve always hankered after a Hacker Hunter but hadn’t found one at the right price and condition until now. I bought this one online and it duly arrived safely in the post a few days ago. It’s a latish RP38 so doesn’t have the DC socket of the RP38A but does have an Elac speaker and it’s mostly complete.

An edited selection of the vendor’s photos can be seen below. Overall the cosmetic condition is reasonable but some work will be required to bring the set back to an acceptable standard. The flimsy aluminium grille is quite badly dented, the feet are missing and the damage to the top left corner might be tricky to repair invisibly. The description of the radio was brief but it stated that medium wave didn’t work although it worked fine for me, along with VHF and long wave, during a brief test using a bench supply. It was also mentioned that the tone control didn’t work because of a “broken knob”. In reality the remains of the knob is locked solid so that the shaft doesn’t turn in either direction.

My intention is to document the refurbishment as and when real life allows. I know that there are a number of Hunter owners amongst our community so any comments/advice along the way would be very welcome.

Alan

[ajgriff]

DISMANTLING

Hackers are renowned for ease of servicing and dismantling the Hunter proved to be a relatively straightforward task although I did refer to the service manual as well taking a quick look at a couple of YouTube videos. The volume and tuning knobs were stubborn but succumbed to the old trick of wrapping a thin strip of rag around the spindles followed by a hefty tug. Also my small BA socket set made things easier than using pliers or a spanner to undo the various nuts holding the case together. The tear down revealed the following additional issues:

1. TONE CONTROL − This was locked solid. My guess is that something heavy got dropped on the radio and caused damage to the corner of the case as well as breaking the tone control knob. In an attempt to repair the knob someone used too much super glue which ran down the shaft with inevitable consequences. I had to break away the remains of the knob in order to release the dial plate. The potentiometer was clearly beyond redemption so I hacksawed the shaft so that the mounting bracket could be reused (see third photo). The pot will have to be replaced and a new knob acquired.

2. AERIAL − The top rod of the aerial pulls out of the tube below when the aerial is extended. This should be an easy fix once the aerial is dismantled. However I’m scratching my head with regard to the second fault whereby the bottom tube has split. This is something I’ve not come across before and I’m struggling to decide on the best away of affecting a repair which at least stops the split from spreading upwards. Please see first two photos.

3. SPEAKER CLOTHS − The black cloths behind each grille (back & front) are badly discoloured with age and are starting to disintegrate. Fortunately I’ve got some suitable replacement speaker cloth in stock.

4. REAR GRILLE − This had clearly come away at some time in the past and had been enthusiastically reattached with rather too much glue which has contaminated the surrounding leatherette. I suspect this will be difficult to remove completely without damaging the material. See fourth photo.

5. CASE − Some of the glue holding the teak panels together has dried out and there is a gap forming between one of the side panels and the base. Again this should be an easy fix.

In the next instalment I hope to report on progress with the repairs.

Alan

[ajgriff]

TONE CONTROL REPAIR

The damaged pot was a miniature type with an ⅛” shaft and flat so it proved difficult to source an exact replacement. Nothing in the spares box was suitable and most modern types have 6mm shafts with splines. New knobs seem to be similarly configured. After much googling I found a pot (6mm splined) that I thought would fit plus a knob which should look the part.

The first photo is the new control in place despite being a bit of a tight squeeze. Fortunately the 6mm shaft clears the hole in the tuning dial plate. The second shot is a trial fitting of the chosen knob which will acquire a black indicator line in due course like the original. It’s also been shortened by a couple millimetres to ensure a snug fit on the shaft without fouling the dial plate

Interestingly the old pot was not wired as shown in the RP38 manual (third image) and there is no C24. The pot was connected as a simple variable resistor in series with C40 in an arrangement similar to the Roberts R505 for example (fourth image). Presumably the design was modified at some point during the production run. In any event I’ve decided to stick to the original configuration.

I should confess that the new pot has a value of 100K log rather than 50K log as I couldn’t find a supplier with a 50K or 47K pot of the right dimensions in stock. This should make little difference in practice.

Alan

[ajgriff]

AERIAL REPAIR

First I cut through the swage and removed the aerial’s bottom plug from the split tube. Having contemplated various bizarre methods of bandaging the lower part of the tube I opted to try soldering. The chrome plating was filed away from either side of the split edges to reveal the brass underneath. Using a small g-cramp I was able squeeze up the splayed edges of the split so that they met nicely with just a tiny gap between them. A trial fitting of the upper part of the aerial demonstrated that everything slid freely. The recommended temperature for soldering brass is 380°C so I figured that a N°7 Weller TCP tip (370°C) should just about be adequate. The outcome is pictured in the first photo after a bit of cleaning and tidying up with a file. Peering inside the tube the solder looks to have wicked into the gap and the upper part of the aerial still slides freely. The repaired tube will of course be inside the radio and in any case the aerial’s black plastic tube will conceal the repair.

Having sorted the split my attention turned to the detached top rod. To fix this I had to cut the swage above the knuckle, unscrew the top cap and dismantle the top seven sections of the aerial as pictured in the second photo. This revealed that the copper bearing shells (pairs) are the sort that fit into slots at the base of the tubular sections. The top section however is just a solid rod and is fitted with a single shell which is meant to be an interference fit with grooves turned into the lower end of the rod. This ‘joint’ had failed allowing the rod to pull from the uppermost tube. A dab of solder secured the shell in the correct position and should result in a lasting repair. I now had an aerial which could be reassembled (see third and fourth photos).

Because the bottom tube has been shortened by about ¼” the aerial will no longer sit in the hole next to the audio board and still protrude sufficiently above the dial plate. I’ve therefore glued a small chock of wood in the hole and added a rubber block with an appropriate aperture to prevent lateral movement. This was cut from a piece of scrap rubber which just happened to have a hole of the right size (last photo). Something similar could easily have been fashioned from an off-cut of timber.

[ajgriff]

DAMAGED CORNER REPAIR

The third photo attached to post #1 shows the damage to the front corner of the set. For the repair I needed a small piece of matching leathercloth. Obligingly Hacker folded over plenty of excess material at the top & bottom of the panels so it was easy to lift a piece from behind the damaged area. After a bit of careful slicing with a craft knife I was able to tidy up the torn cloth and glue in two patches using PVA adhesive. The slight indentation in the corner of the plywood was effectively filled with extra glue.

The first two photos below show the patches glued in place and the third shows the rear of the panel where the donor material was removed. This area will of course be completely concealed once the radio is reassembled. The last shot depicts a trial fitting of the front panel before I tidied up the scars on the adjacent teak.

Overall I’m reasonably happy with the repair. Although the joins aren’t totally invisible from all angles they’re pretty hard to spot without close examination. This is helped by the fact that I was able to match the direction of the grain in the cloth as the material came from an area close to the damage.

Alan

[Mr 1936]

Hi

Thanks for these very detailed posts of how you tackled the various jobs.

[Sideband]

When I refurbished my Hacker VHF Herald, I used Meltonian shoe cream of a similar blue colour to polish and bring up the colour.

[Edward Huggins]

I note that his version has an ELAC drive unit with a rather small magnet. Regarding the front grille dents, if you can't remove it to flatten it (with a bread roller) try using a strong adhesive tape to pull them out.

[ajgriff]

I believe that the small magnet Elac was fitted to most Hunters (38 & 38A) after Hacker's early flirtation with Fane and Goodmans speakers. Mine has a grey painted frame whereas later Hunters had an Elac with a gold coloured frame like the magnet.

The leathercloth and grille will feature in subsequent posts.

Alan

[ajgriff]

BASE PANEL AND FEET

The second photo attached to post #1 shows how the bottom of the case had suffered once the feet had disappeared. However the first task was to secure the joints to the side panels as they were starting to fail. Having brushed some PVA wood glue into the joints I used a sash cramp to secure the panels in position while the glue set (see first photo below).

I decided early on that the teak panels would have an oiled finish. What I failed to appreciate was that Hacker originally used a lacquer finish which must have been applied in several thin coats. This meant that the lacquer had really soaked into the grain of the timber and was an absolute pig to remove. Removal was essential of course as it’s pointless oiling a lacquered or varnished surface. I had to apply several coats of paint stripper followed up by rubbing down with a fine grade of wet & dry, lubricated with white spirit, in order to get back to bare wood. Finally I was able to apply multiple coats of teak oil to achieve the finish I was looking for.

As for the feet it appears from looking at the web that Hunters often lose feet or they get broken so I opted for some more substantial alternatives. They are about a centimetre in depth and are securely screwed in place using the existing holes. The remaining photos attached to this post show the oiled finish of the base panel and the new feet. The teak, if that’s what it is, has a distinctly reddish tinge on this set.

Alan

[ajgriff]

REAR GRILLE AND BACK PANEL OUTER

As already mentioned the plastic rear grille had been glued down by a previous owner. Fortunately it came away easily revealing that all five fixing lugs were broken. However, as predicted earlier, I wasn’t able to completely remove the excess glue residue despite trying a variety of solvents (first photo). I even tested acetone on an obtrusive area and it started to dissolve the surface of the leathercloth. Nonetheless the entire panel was scrubbed with a toothbrush dipped in a strong solution of soda crystals to remove the engrained dirt etc. I finished off with silicone free furniture polish (spray) which has disguised the glue residue quite well. Overall the leathercloth has come up like new.

The speaker cloth behind the grille was in a sorry state as shown in the second photo. Having cut a new piece of cloth, using the original as a template, I glued it in place with PVA (see third photo). The masking tape held it taught while the glue set but subsequently it was steamed for good measure.

Finally the grille was fixed in position using super glue. I only used a small amount in the vicinity of the broken lugs having matched them up to the corresponding remains on the grille itself. All that was then required was firm finger pressure until the glue set. The grille is now nicely centred in the middle of the panel as shown in the fourth photo.

Alan

[Kentode]

It's looking really good so far Alan! I hope you have as much success with the grill. I'd be putting it face down on a hard flat surface, ideally an old surface plate, and gently hammering the dents until they were as flat as you can get them.

Then you can put shim steel pieces, a few thou' thick either side of any troublesome dents to allow them to be flexed past the point of flatness by the hammer, allowing them to spring back to a uniform flatness.

Hope that all makes sense?

[ajgriff]

Thanks Ken. I'll certainly bear your tips in mind and they do make perfect sense. One of the challenges with this grille are the mouldings and fixing tags around the sides, unlike some Roberts' grilles which are simply flat sheets of aluminium.

Alan

[ajgriff]

Since there have been a couple of helpful comments about the grille I’ve attached a photo of the state of play so far. Making progress with the mesh itself but I’m concerned about the top and bottom pressings which have not been touched yet. I’ll report more fully on the grille in a subsequent post. Trouble is any flaws are likely to be very obvious and I’m not surprised that the grille was redesigned a couple of times during the later RP38A’s production run.

Alan

[ajgriff]

BACK PANEL INNER

The main problem with the rear panel was that it didn’t locate properly in the slot in the teak base. I didn’t realise this until I was working on the rear grille. The main cause of the issue was wear on the lip of the groove although it didn’t help that one of the hinge plates had originally been fitted at a slight angle and didn’t protrude sufficiently beyond the panel’s bottom edge. See first two photos.

It seemed to me that trying to repair the damaged lip neatly in both places would be quite tricky so I took the easy way out and moved the two hinge plates inwards by about half an inch such that they now sit in undamaged sections of the groove. It was difficult to get the short screws to tighten firmly in the thin panel so I cut a small section of the quite thick lining material away so that the plate screws could be tightened up more securely. Even though there’s now a redundant screw hole either side the hinge plates everything still looks reasonably tidy as I hope the third and fourth photos illustrate.

Inevitably both foam/sponge battery buffers had long since rotted away. Having found a spare piece of foam I set about cutting some new circular buffers. The sticky residue (now removed with meths) left a mark one inch across which happens to be about the diameter of a two pence piece. Trying to cut round the coin with scissors just didn’t produce acceptable looking foam discs. Not having a suitable tool to perform this apparently simple task I came up with the rather odd arrangement shown in the last photo. Once the foam was firmly clamped between a piece of scrap plywood and the coin it was easy to run a craft knife around the coin. The buffers were glued in place with the usual PVA. The outcome can be seen in the photos. Sorry the sponge is the wrong colour!

Just to mention that I’ve also been cleaning up the worst of the rust on various bits of hardware using wire wool as the refurbishment progresses.

Alan

[ajgriff]

GRILLE RESTORATION

The first attachment is a crop of the first photo in post #1. It shows the dented aluminium mesh well enough but the corrosion affecting the top and bottom pressings isn’t so obvious. The second photo below shows this more clearly along with quite a few other blemishes. This was taken after I’d done some work to flatten the mesh part of the grille.

My weapons of choice for removing the dents in the aluminium mesh are shown in the third photo in the form of a granite coaster and two wallpaper edge rollers. If the grille were a flat sheet rather than a complex pressing (fourth photo) I’d have been able to use a hardwood, granite or marble chopping board but I would still have employed the edge rollers rather than something like a rolling pin because of the concentrated pressure that can be applied. The hard plastic roller is more effective but was used on the inner surface only. The wooden version was reserved for the surface that shows because its smoother, more rounded, edges were less likely to bruise the soft metal. By doing multiple sweeps in different directions the mesh has been persuaded back in to adopting its original flat form.

To remove the corrosion on the highly polished top and bottom rails I used medium grade cerium oxide powder applied with a moist cloth. There was plenty of elbow grease involved in getting back to the original shiny finish but ordinary metal polishes are just not up to the task. Most of the little dents and ripples were impossible to remove because of the shape of the pressings and I never use even a light hammer on aluminium as it’s so easy to cause unsightly bruising. The black of the Hacker stamp was refreshed with a Motolow paint pen.

For me this has been one of the most important elements of the refurbishment simply because the front grille is very much the ‘face’ of the radio. I knew from the advert that achieving an acceptable outcome wasn’t going to be an easy task but have done my best and the result is pictured in the last attachment.

Alan

[Kentode]

That's excellent work Alan. You'll never get it back to original but considering it's age you've got a vintage radio in almost new condition.

It's got to sound better now that the grille's been done...