reburbishing an AMP

[Maverick]

Hi,

I need some advice about getting our old family AMP fixed.

Its a Sansui AU-101 Solid State Stereo Amplifier -pretty good in its day.

I dont know jack about Amplifiers or what could be the problem, so I'd like some suggestions about who/ where I should get it looked at/ fixed in Wellington.

I dont want to get ripped off, and I want someone with good service. Hifi experts probably. If you have any experience with people who fix stereo systems/ amps etc please let me know.

Cheers,

Mav

[Gremlin]

You don't mention whats actually wrong with it ?

If its just not working you may well have just blown an input or output fuse, a quick trip to DSE to get a replacment for 0.20c and you could be up and running again. Use a multimeter to test any fuses you find inside the AMP.

[Maverick]

Thanks for the response Gremlin.

Yes I have checked the fuses, and this evening went systematically over what the problems were.

The Amp actually works fine through headphones, using the AUX inputs. Infact it sounds damn fine, just using my sony discman and sony MDR-CD370 cans.

Turns out the speakers have a noise issue....which added to me thinking it was the amp. Plugged in my old Sony minisystem speakers and the amp works fine.

But with the Amp, the 'Tape' inputs only appear to work on one channel (although that one channel sounds great). The other channel IS infact working, but is VERY quiet.

'Phono' inputs sound really bad. But the manual says that the input sensitivity on the phono input is only 3mV cf. 200mV for the AUX and TAPE inputs. I'm a complete noob with stereo equipment, but I think that perhaps my discman is inputting too much signal for the phono.

It also states that the TAPE input requires a tapedeck with a pre-amp -which might explain the strange TAPE input behaviour.

I am beginning to think the amp is in fact fine, and I need to turn my attention to the speakers, either fixing them or buying another set.

I am now using it as a headphone amp hooked up to my PC.

Cheers,

Mav

[I.R]

Originally posted by Gremlin
0.20c and you could be up and running again.

WOW!!!!!! 0.20c!!!!!! SO I'd need to get about 25 of these fuses so I could make a purchase with cash?!?!??!?!?! :p

[ktulu]

Don't use the phono input for anything but a turntable.

As for the tape inputs... most tapedecks/CD's/DVD's/Videos have a preamp, so that shouldn't be the problem. It sounds like it's either one of your leads that is stuffed (but I'd say you'd already have tried that) or the connections inside your input plug is stuffed.

[Deviant]

Sounds like it's all working fine apart from "But with the Amp, the 'Tape' inputs only appear to work on one channel (although that one channel sounds great). The other channel IS infact working, but is VERY quiet."

This is probably the 1st stage or preamp, inside the amp, and a simple transistor/fet change will fix it. Quick, easy and cheap.

New speakers sound like an idea though.

[Maverick]

Originally posted by Deviant

This is probably the 1st stage or preamp, inside the amp, and a simple transistor/fet change will fix it. Quick, easy and cheap.


thanks Deviant. I figured someone with some elec knowledge was in this group:)

As for the speakers, they are an English kitset (Richard Allan) that my Dad built many a year ago, before being moved to the Garage when my mum bought a Sony mini system on sale:rolleyes:
They were loaned to a guy back home in New Plymouth, who probably abused them, and now they are suffering from this static/ noise/ hum issue.

Would replacing the cones in the speakers fix the problem?

they consist of two speakers, approx 7" and 4 3/4" units.

[_N_]

you can do the following:
pull out your speakers, and get some car audio ones for cheap, chuck them into the same box, the sound won't be optimal etc cause probably the speaker won't be made for that enclosure.
or you can sell the speakers in the box etc,
and just get new ones,

>>static/ noise/ hum issue
this does not mean that your speakers are screwed, it could be some weak joint along the way, or bad DC V on your amp,
so, before doing anything to them, try them on another amp,
I abuse my 10" sub heaps, and it's still going good.

another thing, if it's an old piece of equipment, it will pay to go over all of the solder joints with a soldering iron just to remelt them, and everynow and then, add more new solder, or remove the old solder and put some new on.


you'll probably be best off if someone could take a look at them for free, like a friend who knows something about them, cause he is not out there to rip you off.

if you take it into a shop, there is a chance that they will screw it up even more on purpose, and make you buy a new one from them... :) :rolleyes:

[Deviant]

I'm no speaker expert, but older speakers, even the parts for them were manufactured with older technology. It could be the coils insulation is breaking down. This is common with some varnished wire where the varnish becomes brittle with age and chips off, which then shorts with other loops in the coils. In case you didn't know, the old coils in speakers were wound with varnished wire. This definately causes crackling etc.

If this is happening, there is nothing you can do easily. Some places will rewind the coils with new wire which would probably fix them. Cheaper than new speakers, and at least you keep all the original stuff together.

You can easilly inspect the cones to see if they have deterorated, look for small tears or rips, and make sure the cone is stiff, and the cone flexes easilly where it should around the edges.

[Maverick]

Just an Update...

I have pulled open the speakers, and the webbing (? dont know what else to call it) around the outside of the cones, connecting them to the speaker housing/frame has perished. Just disintegrates in your fingers.
Found out you can get them repaired for about $90 each.

Just dont know if I am being ripped off. Aparently the person we got the quote from sends them away, so I would be keen to know if anyone here knows of anyone that repairs speakers???

Also, the old amp's other input (AUX) just decided to spit the dummy, and only supply me with one channel loud and the other is very quiet (like the TAPE inputs noted above). So I am definately going to have to put this in to get looked at. Hopefully, like Deviant mentioned it will be a cheap, quick fix.