Old Amp Resurrection

[B1ng]

Morning all,

I was hoping for some help and/or advice with regards to bringing an old amp back to life. The unit in question is a Technics SU-X120, acquired from my Dad. The unit worked wonderfully when last used a year or two ago, but has since been in storage (moisture and dust free). I am hoping to use it as a basic and budget HiFi/AV system to improve on my TV speakers, as he has since upgraded.

The problem in question is the volume. When connected to a suitable source, such as the matching CD separate (SL-PJ28A) or my phone via a suitable Aux cable, the audio is only just audible with the unit indicating maximum volume. The sound is similar to headphones playing loudly on the desk next to you. The speakers used are matching Technics SB-CS55 8 ohm 60W units.

Is it possible that I can tinker and fix this? Has something failed, and would require replacement?

Many Thanks for any tips in advance.

 

[lucid]

Unless it's a really bad case of oxidisation on the volume pot (which normally makes a loud rustling sound when the knob is turned) then the most likely cause is the big electrolytic capacitors have failed.

They're like a wet cell rechargeable battery in how they work. Over time they dry out and no longer hold charge or pass current.

Electrolytics aren't difficult to replace so long as you can solder and are comfortable stripping down the amp. The challenge is specing a replacement part... and the cost. Go for the same or better makes. Stick with the same microFarad rating. You can go higher on the voltage if needed.

 

[Sinopa]

Could it be simply the links missing from the Ext in and out sockets at the rear?

 

[B1ng]

Could it be simply the links missing from the Ext in and out sockets at the rear?

Right on the money! The amp needs either links in place, or to connect up the Graphic Equalizer. The system now works beautifully.

In some ways I am disappointed, as I was hoping for a mini electronics project fault-finding and replacing components. Many thanks for the advice!

 

[And]

Scratchy pots. That sounds like the 20-year-old harmon-kardon amp I use with my decks. In the case of my amp it's the balance and volume pots.

Unless it's a really bad case of oxidisation on the volume pot (which normally makes a loud rustling sound when the knob is turned) then the most likely cause is the big electrolytic capacitors have failed.

They're like a wet cell rechargeable battery in how they work. Over time they dry out and no longer hold charge or pass current.

Electrolytics aren't difficult to replace so long as you can solder and are comfortable stripping down the amp. The challenge is specing a replacement part... and the cost. Go for the same or better makes. Stick with the same microFarad rating. You can go higher on the voltage if needed.

 

[lucid]

Yeah, it happens. I have a Creek 4040s2 here that I rebuilt because of that. The pots needed stripping and cleaning. Works good as new now