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

mikes08 · 27th Jun 2022, 1:25 pm

I reflowed the joints over weekend and no joy so swapped out Tr102 (ZTX304) for a BC546 but was getting some strange voltages (39v instead of 67v across pins 1 and 9 on the board) so swapped back again - voltages normal again. I am looking at two data sheets for the ZTX300 series which show the Emitter and collector transposed so may have fitted the BC546 wrong way round unless the sun got to me over the weekend?

Quiescent all good. Diodes all good.
Does anyone have a definitive configuration - I do tend to go with 'alldatasheet' but it might be wrong?
If that doesn't solve it going to swap out the two power transistors (with genuine RCA spares i have from another 303) as definitely confirmed only right channel affected.

https://alltransistors.com/adv/pdfvi...f&dire=_diodes

https://pdf1.alldatasheet.com/datash...LA/BC546B.html

I could try swapping the boards over and then if the pop stayed in the right channel i know the boards are not at fault.

27th Jun 2022, 1:25 pm	#24
mikes08 Pentode Join Date: Dec 2021 Location: Canterbury, Kent, UK. Posts: 133	Re: Quad 303 pop on switch on I reflowed the joints over weekend and no joy so swapped out Tr102 (ZTX304) for a BC546 but was getting some strange voltages (39v instead of 67v across pins 1 and 9 on the board) so swapped back again - voltages normal again. I am looking at two data sheets for the ZTX300 series which show the Emitter and collector transposed so may have fitted the BC546 wrong way round unless the sun got to me over the weekend? Quiescent all good. Diodes all good. Does anyone have a definitive configuration - I do tend to go with 'alldatasheet' but it might be wrong? If that doesn't solve it going to swap out the two power transistors (with genuine RCA spares i have from another 303) as definitely confirmed only right channel affected. https://alltransistors.com/adv/pdfvi...f&dire=_diodes https://pdf1.alldatasheet.com/datash...LA/BC546B.html I could try swapping the boards over and then if the pop stayed in the right channel i know the boards are not at fault. Last edited by mikes08; 27th Jun 2022 at 1:35 pm.