BOM Help

[Knotty]

Hello audio brains,

***Please repost to proper section if needed***

I am taking my first dive into a recap or rebuild with a SX-737.

I found a BOM that lists capacitors, transistors and a few parts I'm still working to identify.

My main question is should I replace all of these or just some that may be known trouble makers?

I am torn between spending money on unnecessary replacements and and not wanting to take it all apart later if I missed something I should have replaced the 1st time around.

Thanks in advance,

Knotty

 

[DaveVoorhis]

I am taking my first dive into a recap or rebuild with a SX-737.

I found a BOM that lists capacitors, transistors and a few parts I'm still working to identify.

My main question is should I replace all of these or just some that may be known trouble makers?

In general, if you're seeking to restore a working unit to original factory performance, I'd recommend replacing all electrolytic capacitors -- at least some of them are almost certainly out of spec if not outright failed -- and any other known troublemakers like transistors known to become noisy, thermal paste on power transistors or amplifier modules that dries out, resistors that drift in value, etc. Aside from these, I do not recommend replacing all parts, as it's both unnecessary and subjects you to the risk of replacing an excellent original component with a substandard replacement (or even a knock-off) whilst risking damage to the circuit board(s).

 

[WaynerN]

Does the unit not work?

 

[EastPoint]

Just replace all of them. You can do a full recap and replace all the transistors on all the non-tuner boards, excluding the output transistors, for under $50.

 

[restorer-john]

Throwing a whole bunch of new parts at a vintage receiver is a sure fire way to balls it up completely.

Firstly, ascertain exactly the overall current performance of the unit. What is not working and what issues there are.

Solve any and all issues or problems first.

Then discuss and decide the scope of a restoration. Do not do it the other way around or you will have an expensive paperweight.

Vintage receivers are not cars. They don't need a standard change of fluids, some hoses and spark plugs to keep them going for another 50 years.

 

[restorer-john]

Just replace all of them. You can do a full recap and replace all the transistors on all the non-tuner boards, excluding the output transistors, for under $50

No. This is not good advice.

 

[Knotty]

Thanks for all the fast responses.

The unit works with at least one issue. The protection cycles on and back off. I'm working on learning to set the DC and just recently read on here that the service manual has the adjustments backward. I have cleaned all the pots and waiting on the replacement lamps for the display. Luckily all the small lamps are working so just the fuse lamps need to be done.

Is there a good list of known troublesome parts to replace for sure? I have found a couple here and there in different threads.

Does the 737 have any unobtainiam parts I should be extra careful with?

I'm a fan of the SX-x3x series and have found most of the line. I chose the 737 to really go through first as it's a good mix of fairly complex but not not as daunting and its bigger siblings.