It looks as if someone has been in there before, some very dodgy looking joints there. The 4th and 5th crystals don't look to be fully seated in their sockets either. Apart from that I like the way that each section has its own pcb, makes it easier to a full recap etc board by board. ![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif.pagespeed.ce._JElyJQqdB.gif)
I found out what the capacitor and resistor with loose ends were for. The capacitor is OK to be there, it is connected across the loop antenna jack (I do not have the loop antenna). I do not know why it was disconnected, it may have popped off. I re-soldered it.
The resistor too is OK to be there, it is an optional mod the user can install at those terminals to control the AVC time constant. The SPR-4 comes with no resistor or wire connected across those terminals. The user was experimenting with a 3.2 Megohm value which is a valid value in the range indicated in the manual. They obviously didn't keep it connected. I will remove it for now and experiment with that later.
For today I replaced three electrolytics and one tantalum on the audio board. All went well. The wires you see next to the old caps were what the assemblers used as tie wraps, back in the day. I will replace some of them to keep it vintage.
Next board - please step up to the soldering station.
![Tweak :-/O](https://www.eevblog.com/forum/Smileys/default/smiliey_cal.gif.pagespeed.ce.yYMcAvxBJk.gif)
Interesting noise blanker you got there ![Wink ;)](https://www.eevblog.com/forum/Smileys/default/xwink.gif.pagespeed.ic.cldandycH0.png)
Yea, that board is rare and I do not have it.
![Sad :(](https://www.eevblog.com/forum/Smileys/default/xsad.gif.pagespeed.ic.L3FGyzQrjB.png)
Looks pretty good inside. The thing will be easy to debug at least as each bit of the signal chain is separate.
Yes it's old school and pretty open to troubleshoot.