Bush TR82 help/advice - UK Vintage Radio Repair and Restoration Discussion Forum

glasstransistor · 10th Aug 2022, 9:35 am

Hi all,
I have recently taken some time to wake up my TR82 collection, all good fun and they all responded well, except one that needs a bit more than a clean up. It's a lowish serial number TR82C that is nice and clean, but after a check over I found the fault in the picture attached.... It seems the folded brass LW/Osc trimmers (hope this is the right terminology) have strangely broken up over time? Please excuse the 'blobs' of solder just wanted to see if strengthening them would help it's weakish LW performance it did somewhat, but it has the faults of the dial being out to what is being received and is quite unstable (bouts of above set volume aggressive white noise) on both lw and mw. I have over the years always had great luck with these sets so this will be the first one I'm going to give a proper look at with a friend a little more electronically set up than me (bench/sig gen)but am looking forward to this and learning from it for the future so I can self help without bothering people

this leads me to asking if anyone could help if anyone has had this before and if anyone has a scrap A177 chassis I would gladly buy the spare 'trimmers' as per the photo, should anyone have them before buying in the rest of the components needed after testing, Thanks for your time and consideration. Hope this wasn't too much of a ramble, and hope my descriptions weren't too amateur compared the knowledge and experience on here.
Kind Regards,
Neil.

G6ONEDave · 10th Aug 2022, 10:26 am

Hi Neil,
If you mean that triple ceramic and brass strip section, it's actually a group of three pre-set capacitors. You might be able to repair them or otherwise replace them. You would probably need to look at the circuit diagram for their value in picofarads, which will be needed to get the correct replacement.

Dave

David G4EBT · 10th Aug 2022, 1:31 pm

The two banks of three trimmers, each of which are 3 - 30pF, are ceramic/silver mica compression trimmers, approximately 10mm x 18mm. While similar trimmers are individually available surplus NOS, unfortunately, each bank of three in the TR82 is specific to the TR82, built onto the mounting bracket as a combined unit, so ideally, you do need what you've asked for - a group of three from a TR82.

Don't know if you've seen the thread at this link. You could send a PM to Dave to see if he can help:

https://www.vintage-radio.net/forum/....php?p=1472116

Hopefully Dave or some other forum member will be able to help.

If not, as a last resort you could perhaps replace them with individual ones, hard wired, such as these, which are 4 -30pf and a similar physical size, but are for PCB mounting:

https://www.ebay.co.uk/itm/112020434935

Hope that might help a bit.

Good luck in your quest.

paulsherwin · 10th Aug 2022, 2:00 pm

Are you sure these aren't working? It's very unusual for compression trimmers to fail in the way you describe.

AC/HL · 10th Aug 2022, 4:50 pm

Difficult to make out, but it looks a bit like brass rot. They're not compression on either of my examples, but rotary ceramic as Dave says. You can have the one off my scrapper for the postage if you want it. PM your address.

dave_n_t · 10th Aug 2022, 10:14 pm

Quote:

Originally Posted by David G4EBT

Hopefully Dave or some other forum member will be able to help.

Good luck in your quest.

Neil's been in touch, and yes, I've got one bank of 3 trimmers which will be dispatched tomorrow (together with a couple of other bits).

dave

David G4EBT · 11th Aug 2022, 12:33 am

That’s great news Dave!

glasstransistor · 11th Aug 2022, 9:29 am

Good Morning all,
Thanks so much for getting back with advice and the offer of a spare bank of trimmers. Have sorted a replacement with dave_n_t and a couple of other bits to tidy up my other sets, looking forward to getting it installed and eventually getting some R4/music out of the set again

Totally agree with the rot causing the fractures on the existing trimmer, 2 out of the 3 were a bit green and the cracks were visible under the corrosion, they weren't caused by a rough clean up no signs of it being got at with tool gouges and even the factory paint was intact, I'll never know but could it may have lived in a humid environment causing the brass fail? Bit of a mystery. Thanks again to everyone.
Kind Regards,
Neil.

10th Aug 2022, 9:35 am	#1
glasstransistor Triode Join Date: Jan 2016 Location: Bristol, UK. Posts: 10	Bush TR82 help/advice Hi all, I have recently taken some time to wake up my TR82 collection, all good fun and they all responded well, except one that needs a bit more than a clean up. It's a lowish serial number TR82C that is nice and clean, but after a check over I found the fault in the picture attached.... It seems the folded brass LW/Osc trimmers (hope this is the right terminology) have strangely broken up over time? Please excuse the 'blobs' of solder just wanted to see if strengthening them would help it's weakish LW performance it did somewhat, but it has the faults of the dial being out to what is being received and is quite unstable (bouts of above set volume aggressive white noise) on both lw and mw. I have over the years always had great luck with these sets so this will be the first one I'm going to give a proper look at with a friend a little more electronically set up than me (bench/sig gen)but am looking forward to this and learning from it for the future so I can self help without bothering people this leads me to asking if anyone could help if anyone has had this before and if anyone has a scrap A177 chassis I would gladly buy the spare 'trimmers' as per the photo, should anyone have them before buying in the rest of the components needed after testing, Thanks for your time and consideration. Hope this wasn't too much of a ramble, and hope my descriptions weren't too amateur compared the knowledge and experience on here. Kind Regards, Neil. Attached Thumbnails

10th Aug 2022, 10:26 am	#2
G6ONEDave Octode Join Date: Dec 2019 Location: Owston Ferry, North Lincolnshire, UK. Posts: 1,701	Re: Bush TR82 help/advice Hi Neil, If you mean that triple ceramic and brass strip section, it's actually a group of three pre-set capacitors. You might be able to repair them or otherwise replace them. You would probably need to look at the circuit diagram for their value in picofarads, which will be needed to get the correct replacement. Dave __________________ Quote "All is hyperthetical, until it isn't!" (President Laura Roslin, Battlestar Galactica)

10th Aug 2022, 1:31 pm	#3
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,761	Re: Bush TR82 help/advice The two banks of three trimmers, each of which are 3 - 30pF, are ceramic/silver mica compression trimmers, approximately 10mm x 18mm. While similar trimmers are individually available surplus NOS, unfortunately, each bank of three in the TR82 is specific to the TR82, built onto the mounting bracket as a combined unit, so ideally, you do need what you've asked for - a group of three from a TR82. Don't know if you've seen the thread at this link. You could send a PM to Dave to see if he can help: https://www.vintage-radio.net/forum/....php?p=1472116 Hopefully Dave or some other forum member will be able to help. If not, as a last resort you could perhaps replace them with individual ones, hard wired, such as these, which are 4 -30pf and a similar physical size, but are for PCB mounting: https://www.ebay.co.uk/itm/112020434935 Hope that might help a bit. Good luck in your quest. __________________ David. BVWS Member. G-QRP Club member 1339.

10th Aug 2022, 2:00 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Bush TR82 help/advice Are you sure these aren't working? It's very unusual for compression trimmers to fail in the way you describe.

10th Aug 2022, 4:50 pm	#5
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Bush TR82 help/advice Difficult to make out, but it looks a bit like brass rot. They're not compression on either of my examples, but rotary ceramic as Dave says. You can have the one off my scrapper for the postage if you want it. PM your address.

11th Aug 2022, 12:33 am	#7
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,761	Re: Bush TR82 help/advice That’s great news Dave! __________________ David. BVWS Member. G-QRP Club member 1339.

11th Aug 2022, 9:29 am	#8
glasstransistor Triode Join Date: Jan 2016 Location: Bristol, UK. Posts: 10	Re: Bush TR82 help/advice Good Morning all, Thanks so much for getting back with advice and the offer of a spare bank of trimmers. Have sorted a replacement with dave_n_t and a couple of other bits to tidy up my other sets, looking forward to getting it installed and eventually getting some R4/music out of the set again Totally agree with the rot causing the fractures on the existing trimmer, 2 out of the 3 were a bit green and the cracks were visible under the corrosion, they weren't caused by a rough clean up no signs of it being got at with tool gouges and even the factory paint was intact, I'll never know but could it may have lived in a humid environment causing the brass fail? Bit of a mystery. Thanks again to everyone. Kind Regards, Neil.