UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

PaulDarzi · 1st Dec 2022, 10:40 am

Hi Martin (and everyone),

Your comments about off-load voltage from wall warts - especially the olde linear types are well made. As a newbie to this forum and the whole repair/restoration of vintage radios I'm finding it's a new world compared to my previous experience, which has mostly been on the design, test, and implementation of new (much higher frequency, with great test kit to hand too) circuits - looking at old radios I'm finding needs new skills.

Back to topic, I've rummaged through all my wall warts and found a couple of otherwise OK switchers but these sadly are noisy on AM bands. So I've looked at old linears and tried to aquire a new linear wall wart or two, only to find as you mentioned thei regulation is rarely very good, and two in particular (same design it seems, although branded and cased differently on the outside) not only have poor regulation but are also somewhat noisey too.

Am hoping to add some regulation to the unregulated wall warts - if anyone has a favoured circuit or approach I'd love to hear about it, otherwise I'll try either LM78xx or LM317 based design using the appropiate application notes as a starting point and see how that looks in practice.

1st Dec 2022, 10:40 am	#14
PaulDarzi Tetrode Join Date: Nov 2022 Location: Near Worcestershire/Gloucestershire border (in WR), UK. Posts: 70	Re: Question about Roberts "Wall Warts" Hi Martin (and everyone), Your comments about off-load voltage from wall warts - especially the olde linear types are well made. As a newbie to this forum and the whole repair/restoration of vintage radios I'm finding it's a new world compared to my previous experience, which has mostly been on the design, test, and implementation of new (much higher frequency, with great test kit to hand too) circuits - looking at old radios I'm finding needs new skills. Back to topic, I've rummaged through all my wall warts and found a couple of otherwise OK switchers but these sadly are noisy on AM bands. So I've looked at old linears and tried to aquire a new linear wall wart or two, only to find as you mentioned thei regulation is rarely very good, and two in particular (same design it seems, although branded and cased differently on the outside) not only have poor regulation but are also somewhat noisey too. Am hoping to add some regulation to the unregulated wall warts - if anyone has a favoured circuit or approach I'd love to hear about it, otherwise I'll try either LM78xx or LM317 based design using the appropiate application notes as a starting point and see how that looks in practice.