Philips SBC 521 - UK Vintage Radio Repair and Restoration Discussion Forum

eaglework · 3rd Sep 2017, 5:30 pm

I'm working on an auction buy - parts not working - signal generator Philips SBC 521.
The microprocessor board seems to be working but no RF output from the sig gen board. It uses reed relays to switch inductors into circuit for frequency control and at least one of these is broken.
I was able to get a copy of the service manual via Jac (Forum Member) and the circuit diagram implies the reeds are all SPNO but a number of the ones in this unit measure as SPNC - does anyone know if they are all NO or a mixture on NO and NC types.
Thanks

Jon

karesz* · 3rd Sep 2017, 6:49 pm

Hi Jon,
I assume you knows these thread...
Regards, Karl

eaglework · 4th Sep 2017, 4:04 pm

Hi Karl,
Thanks for the link to the earlier thread - I had seen it a while ago.
I'm looking at this unit as a challenge more than a 'must fix at all costs'.

It looks to me as though the interface between the digital and analogue boards may not be working properly - its a BCD to decimal decoder and it drives the reed relay coils. That does not explain why some of the reeds appear to NC and 2 others NO format.
Regards
Jon

3rd Sep 2017, 5:30 pm	#1
eaglework Pentode Join Date: Jun 2017 Location: Alton, Hampshire, UK. Posts: 160	Philips SBC 521 I'm working on an auction buy - parts not working - signal generator Philips SBC 521. The microprocessor board seems to be working but no RF output from the sig gen board. It uses reed relays to switch inductors into circuit for frequency control and at least one of these is broken. I was able to get a copy of the service manual via Jac (Forum Member) and the circuit diagram implies the reeds are all SPNO but a number of the ones in this unit measure as SPNC - does anyone know if they are all NO or a mixture on NO and NC types. Thanks Jon

3rd Sep 2017, 6:49 pm	#2
karesz* Heptode Join Date: Jun 2010 Location: Zurich, Switzerland Posts: 538	Re: Philips SBC 521 Hi Jon, I assume you knows these thread... Regards, Karl

4th Sep 2017, 4:04 pm	#3
eaglework Pentode Join Date: Jun 2017 Location: Alton, Hampshire, UK. Posts: 160	Re: Philips SBC 521 Hi Karl, Thanks for the link to the earlier thread - I had seen it a while ago. I'm looking at this unit as a challenge more than a 'must fix at all costs'. It looks to me as though the interface between the digital and analogue boards may not be working properly - its a BCD to decimal decoder and it drives the reed relay coils. That does not explain why some of the reeds appear to NC and 2 others NO format. Regards Jon