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 three additional pairs of 10uF 50V, 100uF 6.3V, and 47uF 10V. These have also been replaced with higher voltage Nichicon KL 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!

JP

 

[Hyperion]

From your description the problem is most likely to originate in the power supply, give that a refresh and see if it improves things. Other things to check are local filtering capacitors - these are ones placed ( +ve rail to ground for positive supply, and & -ve rail to ground for negative supply), across power rails to the various stages.

or look closer at the remaining low-voltage electrolytic caps (like the 6.3V or 10V ones)?

Good idea, replace with at least 10V equivalents - I use 16V when I replace those.

 

[jpreza]

It's definitely a problem with the board. I pulled an old F-1169 board I have that I was never able to fix - the right channel is out. Last night, in my desperate attempt to troubleshoot, I pulled this old board and plugged it in. The thumping/clicking goes away and I'm able to listen to FM and AUX with no issues (albeit no right channel).

 

[Hyperion]

I just re-read your 1st post and you say the issue is with the Equalizer Board - and it interferes with the tuner and the Aux input!

I see now that the phono stage gets reconfigured as a gain block, if not being used with a turntable - so the Aux input gets amplified by the Phono Stage in non-RIAA mode.

Replace the remaining original electrolytics on the the F-1169 (if any), and make sure the switches S1a, b, c & e are clean.

 

[jpreza]

I just re-read your 1st post and you say the issue is with the Equalizer Board - and it interferes with the tuner and the Aux input!

I see now that the phono stage gets reconfigured as a gain block, if not being used with a turntable - so the Aux input gets amplified by the Phono Stage in non-RIAA mode.

Replace the remaining original electrolytics on the the F-1169 (if any), and make sure the switches S1a, b, c & e are clean.

All electrolytic caps have been replaced. Also, I replaced the 1.5uF tantalum caps with 2.2uF electrolytic ones as I don't have any film ones at the moment either. Unfortunately, no change, still clicking and thumping away!

 

[Hyperion]

All electrolytic caps have been replaced.

Even in the PSU? - S1a, b, c, & e are clean?

 

[jpreza]

Even in the PSU? - S1a, b, c, & e are clean?

I meant I recapped the Phono/EQ board, both amp boards, and the multiplex board. I haven't touched the PSU but I don't think the PSU would create these issues that I'm seeing. Otherwise, why would the old phono/EQ works (albeit with no right channel) and doesn't produce the thumping/clicking?

 

[Hyperion]

I haven't touched the PSU but I don't think the PSU would create these issues that I'm seeing. Otherwise, why would the old phono/EQ works (albeit with no right channel) and doesn't produce the thumping/clicking?

I really have no idea. I'm just telling you the likely causes. You seem to have replaced most of the F-1169 parts and you say it hasn't made any difference, shouldn't this tell you something?

 

[Bruno Primas]

Could you post a really good picture of the front and back of the board?

 

[jpreza]

I modded the board by removing the jumpers and adding R617 and R618 to mimic the original board that I have to no avail. Still clicking and thumping. Pictures attached.

 

[Bruno Primas]

I would take your multimeter in continuity mode and verify that every solder pad that is connected is supposed to be and vice versa.

 

[Hyperion]

There are a lot of 'suspect' looking solder joints on that board. It seems like half of them have 'blow holes', others look 'pasty' (cold solder joints), or simply 'poisoned' (insufficient flux).

 

[jpreza]

These Sansui boards are notorious for the solder that was used for these joints. In fact, I've retouched almost every solder joint just to make sure but I will double check with my DMM