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How to restore old Boombox?

Wanting to fix my childhood boombox. Thought I'd have a look and found that this could be why my volume control is not working. A crack in this round circuit under the switch. Is there any chance of me saving it? Or does anyone know where I could take it in Brisbane as I've tried a few places and nobody wants to touch it:( I just want to keep it alive, wish I could fix it myself. Any advise would be appreciated, thankyou!

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MitchellMc

Hi @MarcL,

I do want to add an important electrical safety note here. I would strongly discourage opening or inspecting the internals yourself unless you have proper electronics experience. Even when unplugged, audio equipment can retain charge in capacitors and there is a real risk of electric shock or damaging components. This is not something to poke around in casually.

First thing I would check is whether the unit actually powers on at all. If you are not getting any lights, display, motor noise from the cassette, or any other sign of life, then the crack in the volume control board is unlikely to be the root cause on its own. The main exception would be if the volume control also doubles as the power switch, which was very common on older boomboxes where the first click of the knob turns the unit on and the rest of the rotation controls volume. If that is the case, a cracked track in that circular board could absolutely stop the unit from powering up.

In terms of repair, that round board is usually part of a combined potentiometer and switch assembly. Cracks in the PCB can sometimes be repaired with fine jumper wires or conductive paint, but it is not something some modern repair shops want to touch, especially on older consumer electronics. The bigger issue you will likely run into is parts availability, as those volume controls are often model-specific and not something you can buy off the shelf anymore.

If you can identify and source a compatible replacement potentiometer, you may have more luck finding a small electronics repairer willing to fit it for you. Otherwise, your best bet is to search specifically for vintage audio repairers or hobbyist electronics technicians in Brisbane, as they are generally more open to this kind of work.

As much as it hurts to say, the cost of diagnosis and repair can very quickly exceed the value of the unit, which is why many places will turn it away. That said, for something with strong sentimental value, it can still be worth the effort, especially if the fault turns out to be limited to that volume control assembly.

Please let me know if you have any questions.

Mitchell

MarcL

Thanks Mitchell, it does power up. Lights and radio working, one speaker working faint and won't adjust volume. The volume adjust is seperate to power on switch. Cassette tries but not turning and I realise that's a whole other deal to fix but was hoping I can at least get it to working volume with radio untill I get it into someone for new speakers and casstte repair or replacement.. Appreciate the pointers. I attached a photo of the only stamp I could see near the switches not sure if that helps me with the part no though

Noyade

Hi @MarcL and @MitchellMc

"Wanting to fix my childhood boombox."

I guess nostalgia is the big reason, but you can buy 'replica' boomboxes, possibly at a fraction of what it may cost to repair?

Do you have many cassettes left?

These work well with cassettes and you also get Bluetooth = Spotify.

Just a thought.

Cheers.

DIYGnome

Hello @MarcL 👋

You can absolutely repair that cracked circuit trace on the potentiometer, the standard approach requires cleaning back the trace either side of the break and soldering a bridge between the 2 sides, this could be a few mm of wire, a donor length of component wire like an anode/cathode off an LED OR the more expensive adhesive circuit trace repair foil, personally I prefer the short wire jumper for basic repairs.

If that's on 1 part of the potentiometer and there are additional components missing and/or effected a replacement volume control will be required.

You're going to need a few items, like a soldering iron suitable for detailed work, solder and a well ventilated work area, due to environmental policies solder now contains less lead that it previously did, thus it's melting point is slightly higher, a multimeter is handy for checking circuit continuity, I also find a pair of "off the shelf" reading glasses invaluable for fine detailed (close in) work such as this, additional lighting helps equally well 👍

The cassette mechanism likely requires new rubber belts for the drive components OR there is an issue with the small motor.

There are plenty of DIY videos, tutorials and resource material searchable online such as linked below 😉

https://www.chemtronics.com/how-to-pcb-trace-repair-with-a-wire-jumper?srsltid=AfmBOoqBvtd5gpIM2a1xj1dRze7Z9iDyEY545wUSgbxpQr_juphcFgVp

R4addZ

https://www.workshop.bunnings.com.au/discussion/comment/61114#Comment_61114

Hi @MarcL

Ok so some bad news but followed by a possible solution. This is not a PCB repair, the potentiometer is basically made of a carbon coated track (or multiple tracks in your case). As such you can't solder to it and if you attempt to do so, you may destroy the carbon track. This is why the metal tags are riveted to the track so you have something to solder to. A good repair shop should be able to either find a replacement for it or substitute another form factor version but if not, you may be able to use something like this....

https://www.aliexpress.com/item/1005008215166084.html?src=google&pdp_npi=4%40dis!AUD!3.00!3.00!!!!!%40!12000044267054804!ppc!!!&snps=y&snpsid=1&src=google&albch=shopping&acnt=708-803-3821&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=_oDeeeiG&gclsrc=aw.ds&&albagn=888888&&ds_e_adid=&ds_e_matchtype=&ds_e_device=c&ds_e_network=x&ds_e_product_group_id=&ds_e_product_id=en1005008215166084&ds_e_product_merchant_id=5551326180&ds_e_product_country=AU&ds_e_product_language=en&ds_e_product_channel=online&ds_e_product_store_id=&ds_url_v=2&albcp=19366639602&albag=&isSmbAutoCall=false&needSmbHouyi=false&gad_source=1&gad_campaignid=17338734196&gbraid=0AAAAAD6I-hH41MGAZKtcO1_WSuppEvgbX&gclid=CjwKCAiA09jKBhB9EiwAgB8l-M6IOkN3lfnvAxavN8ikHDFGLwpGGLXkAyNk4yw2aUlNjcwbWtZKghoC_BoQAvD_BwE

That is an Ali Express version but you may be able to get the same from somewhere like Altronics or Jaycar.

The good thing is there are spare parts available for the cassette deck and even complete replacement units (they just have ridiculous postage costs because of their location).

https://www.ebay.com.au/sch/i.html?_nkw=sharp+gf6060&_sacat=0&_from=R40&_trksid=p4624852.m570.l1313

AlanM52

Hi @MarcL

I have been doing that stuff from way back in the sixties when everything was valves - before semiconductors.

I have permanent burn marks from being thrown across the bedroom.

Your pot issue is the result of heavy-handedness, not so much turning the volume knob but the sideway forces have stressed and broken the tracks along a common path. The tracks must be cleaned and bridged with soldering iron and solder.

That boombox is low voltage and no possibility of getting shocked by capacitors HOWEVER it will have a power lead with 240V plug one end and smaller 2 pin plug at the other along with AC-DC slide switch. Ensure the switch is on DC and use batteries. Do not use the power lead.

With the PCB tracks repaired pop-in fresh batteries and check the volume control (hopefully) is working.

Come back to proceed...

Cheers

R4addZ

https://www.workshop.bunnings.com.au/discussion/comment/61154#Comment_61154

Hi @MarcL

I took another look at your pictures and zoomed in to 400% and I would't bother trying to repair that Volume control as there appears to be a crack running just about all the way across the base of it. I did a search and found a circuit diagram for the Sharp GF6060 and whilst I can't be 100% sure it is the exact same model I did find the Volume control on it (about the middle of page 2 to the right of the tone control) and it is the same value as the stamp in your picture implies.

https://elektrotanya.com/sharp_gf-6060x_sch.pdf/download.html

It's very hard to read though. You should be able to buy a new part but you will have to be creative in how you mount it and how you wire it in (it would be a near miracle to find the exact replacement part). As it is a Volume control you will probably need a Logarithmic Potentiometer not a linear one and often these days instead of two tracks on one level, they just make tandem ones, so you will have to common up the centre pins.

One last option is try contacting Sharp to see if they can give you a part number and manufacturer, the worst case is they say no.

A search that might give you more info

https://www.google.com/search?q=20K+ohm+dual+track+pcb+mount+potentiometer+common+swipe+contact+logarithmic&sca_esv=b4f6c3afd6a29af1&biw=1920&bih=957&sxsrf=AE3TifOCdtSYMu-bejwS85P12-SMcSbwbQ%3A1767421806939&ei=brdYacLsON6jvr0P6f2B0Aw&ved=0ahUKEwjC2-Gn3-6RAxXeka8BHel-AMoQ4dUDCBE&uact=5&oq=20K+ohm+dual+track+pcb+mount+potentiometer+common+swipe+contact+logarithmic&gs_lp=Egxnd3Mtd2l6LXNlcnAiSzIwSyBvaG0gZHVhbCB0cmFjayBwY2IgbW91bnQgcG90ZW50aW9tZXRlciBjb21tb24gc3dpcGUgY29udGFjdCBsb2dhcml0aG1pY0iNVFC4C1jmTnABeACQAQCYAYUCoAGlFKoBBDItMTK4AQPIAQD4AQGYAgCgAgCYAwCIBgGSBwCgB7YMsgcAuAcAwgcAyAcAgAgA&sclient=gws-wiz-serp

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