Sansui 881 - Volume Problem

[SAMs978]

Hello everyone,

I recently purchased a Sansui 881 from the flea market. When I got it home, the first problem I noticed was that some of the front lights were out. Next, I tested the unit with speakers and did not find any noticeable problems. All channels seemed to be loud and clear. AM FM came in perfect and all other inputs worked. Since everything seemed to be working correctly, I decided to replace the front bulbs with LEDs.

The unit looked and sounded perfect for about two weeks and then I began having problems. First one of the LED lights started to appear dimmer than the rest. Then, the sound stopped working on all channels.

I took the unit apart again and cleaned all the connections, knobs and buttons. I noticed that 3 fuses were blown and replaced those next.

I tested the unit again and was able to get the unit to produce some sound using the AUX input. The sound only worked when I turned the volume almost all the way up. The sound is some what clear, but also has some static.

This is one of my first restorations and I’m not really sure where to go from here. I apologize if this may have been answered before, but if anyone has any advice it would be greatly appreciated.

 

[ConradH]

881 is getting on it years and would need service regardless. Tell me more about the LED conversion- resistors used and such. Blown fuses is not a sign of something minor. Do you have a DVM or scope? What's your background?

 

[SAMs978]

Thanks for the quick reply. I only replaced the 5 front fuse lamps with LEDs and did not use a resistor, as I thought they were designed to be an exact replacement.

I have a DVM, but have only used it sparingly. I certainly do not have a broad background in electronics. I have read a lot on here and watched a lot of videos for reference. I started getting into restoring vintage electronics a few months ago and this was one of my first attempts with a receiver. Hoping I didn’t do too much damage.

 

[ConradH]

There are LED assemblies that include a resistor and might be a drop-in replacement. Plain LEDs need a current limiting resistor. Can you post a link to what you used? Did the fuses you installed remain good during testing? It might be time to build a dim bulb tester before proceeding!

 

[SAMs978]

The link where I ordered them is followed:
https://m.ebay.com/itm/7-Warm-White...438422?hash=item3f652dc696:g:XzwAAOSwuhhXUepS

The tester is a great idea. I just read about it and it seems like it will be really useful.

The new fuses did remain good.

 

[ConradH]

The lamps should be OK. The originals are 7V, so something else has likely just decided to get old and fail. The usual step is to check power supply voltage to be sure those are OK, then try to narrow things down to either the power amp, or stuff behind the power amp (pre and tone). At that point, do power-off checks with the DVM on all resistors and semiconductors in a given section. Be sure you know how to test a transistor using the DVM "diode check" function.