Pioneer SX-800 Resistor replacement - composite vs carbon opinion

[MossFit]

Hi all,

I'm refurbishing a Pioneer SX-800 tube receiver. I've done this for several receivers, but this unit seems to have a sizeable number of "composition" resistors.
I'm assuming this is a carbon-composition instead of the plain carbon film resistor. (Correct me if wrong)

I've read that these can deteriorate faster over time than regular carbon ones. In the past I've left most all resistors alone except where there's evidence of overheating or deterioration.

Should I look at replacing these?

Of course I will be replacing all the electrolytics, paper capacitors, germanium rectifiers but wanted an opinion on the composites.

Thanks in advance.

shaun

 

[gadget73]

If they are still on value i wouldn't be too worried but if they are out, change them. Many will measure in circuit with no fuss.

 

[MossFit]

If they are still on value i wouldn't be too worried but if they are out, change them. Many will measure in circuit with no fuss.

Thanks for the reply.
What about the older germanium diodes (non-glass)? Also, there's a power rectifier wafer (a bridge rectifier according to schem, with 4 connectors).
These may check ok, but do they age out?

 

[gadget73]

About the only place I'd expect germanium diodes is in the receiver circuits, and I would leave them be unless they aren't working. They handle very low voltages and current and rarely go bad.

If you're looking at silicon in the power supply those also tend to be very reliable but you can change them if you want. Selenium is a higher priority. That bridge may be selenium, hard to say, I'm not specifically familiar with this unit.

 

[MossFit]

So if the bridge is selenium, and working, leave it alone?

 

[gadget73]

I'd probably go for changing the selenium bridge. Often those are powering tube heaters and a bias supply, and they aren't super awesome in higher current situations like that. You may need to add some extra resistance to bring the voltage back down if you do this, so if the schematic doesn't have voltages, see what it measures now before you change anything.

If its silicon I wouldn't worry so much.