Sansui 4000: Persistent clicking/pulsating sound on F-1169 board (Jumpered version)

[jpreza]

Hello everyone,
I’m currently troubleshooting a Sansui 4000 receiver and have hit a wall trying to track down a persistent audio symptom on the F-1169 equalizer board.
My unit is running the version of the F-1169 board that features the two jumper cables on the back.

The Symptoms

• Upon power-up, the receiver immediately makes a clicking and thumping sound (which replaced an initial "helicoptering" sound).
• This pulsating noise happens right away and is present across AM, FM, and AUX inputs.

Work Completed So Far

• Transistors: Replaced the four original 2SC871 transistors with brand-new KSC1845s. I have strictly verified and double-checked the pinout orientation.
• Capacitors: Replaced the two 10uF 25V electrolytic capacitors with new 10uF 50V caps. (Note: The remaining electrolytics on this board are four pairs of 10uF 50V, 100uF 6.3V, and 47uF 10V and these have also been replaced with high quality Nichicon caps).
• Result: Despite these replacements, the rapid clicking and pulsating sound remains entirely unchanged.

My Questions

1. Because the noise is persisting across all inputs (tuner and auxiliary), could a leaky capacitor elsewhere on this jumpered board version be driving the circuit into oscillation?
2. Has anyone experienced this specific pulsing behavior with the jumpered F-1169 variation? Should I suspect a breakdown in the jumper wires themselves, or look closer at the remaining low-voltage electrolytic caps (like the 6.3V or 10V ones)?

Any guidance or voltage checkpoints you could recommend for this board would be greatly appreciated. Thanks in advance!

 

[Bruno Primas]

Do you hear the sound using the tape monitor?

There are also two 1.5uf tantalum caps that really need to be replaced. I used Kemet films.

 

[jpreza]

Do you hear the sound using the tape monitor?

There are also two 1.5uf tantalum caps that really need to be replaced. I used Kemet films.

Very faint....even then I hear a clicking sound every 1-2 seconds. I don't have any film caps right now, but I have 2.2uF electrolytic caps that I can use in the meantime to see if that's the issue

 

[Bruno Primas]

Not sure if you have this, but it can't hurt.

 

[jpreza]

thanks! yup I've been staring at these two pages all evening. Replaced TR 601, TR 602, TR 603, TR604 (which should really be Q but I digress) with KSC1845s. Since the KSC1845 is an ECB transistor on the flat side, they are installed 180 degrees from the above diagram. I've replaced C603/4, C605/6, C607/8, and C611/2.

 

[PE9ZZ]

Check power line Ⓕ. Any noise on this line (C005 on the power board F-1187 is suspect) will appear in your audio. TAPE MON bypasses the F-1169 board and thus is not affected.