Repairing (and upgrading) a simple radio from 1983 - Grundig RF100

This time on the workbench, I have a simple and beat up Grundig tabletop radio from the 80s. It is in need of a repair in the power supply and a lot of cleaning. Then I also give it an upgrade by adding a Bluetooth receiver to it, to make it a bit more useful these days and potentially give it again a bit of a new life.
00:00 Introduction + teardown
19:50 Power supply repair
32:59 Alignment (AM)
46:19 Alignment (FM)
51:14 Adding Bluetooth
56:40 Demo + outro
WARNING: Do not attempt to repair electronic equipment if you don't know what you're doing.
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Music by Karl Casey @ White Bat Audio
Noise video footage by Milan Matos
Electrocution logo by Nesdon Booth, The Noun Project

[@Donno308]

Thanks for another interesting video. What a bizarre way to set up the power switch! I've never seen anything like it (although I admit my experience with 1980's radios is limited. That wobulater is cool! Probably the ideal way to do alignments. One day I'll get myself one. I notice Manuel Caldeira uses the same or similar method. Amazing that this was almost an afterthought at the bottom of the Grundig catalogue!

[@retro_tech]

Thanks, Don. I think the only reason for this power switch design is to have the dial bulb dim slowly when you shut off the power instead of just turning off instantly. If you look at the yearly power consumption when leaving this radio plugged in 24/7, you don't get a lot of return on investment with this super useful feature. 😅
Yes, the wobbulator is really fun to work with. I think Manuel uses a modern sweep generator, but indeed, the method is similar.

[@GeorgeChristofi]

I do love a nice wobbulated alignment. Much better than just a peaked one. I do find an analogue scope better for it though even though my Rigol has better specs in theory.

[@retro_tech]

I agree, but I don't have the space on my bench to put two scopes at the moment. And if I reduce the memory depth on my digital scope, it is actually quite responsive in XY mode.

[@migsvensurfing6310]

At 24:00 rewiring the bulb LA1 would solve the issue with noise in the speaker when switched on. As it is ired from the factory it bypasses current around the power supply. A weird decission from Grundig.

[@retro_tech]

Indeed, but that still wouldn't fix the voltages which were low due to transistor T8 being bad. The reason why Grundig wired up the bulb this way is to have it fade out slowly when the radio is switched off (instead of just turning off instantly). Just a gimmick...

[@janmos5178]

Strange? Grundig did not have the Japanese government and the notorious Ministry of Foreign Trade and Industry quietly protecting and subsidizing its corporations. It had to, like many Western companies, cut costs more. They got no concessions or subsidies. Financially not technically, they could not afford many things even then.