Hum from an old technics amp

[gordy]

As per the title, my 20yr old technics amp makes the speakers hum, even if nothing is plugged in to the input, after reading a few threads on here i have come the the conclusion that it,s knackered! ok more in-depth, the caps are knackered, what/where are they and how do i change them. i have used a soldering iron on car electrics, but not on anything electronic. cost is an issue as it,s an old amp and not worth much. so should i.

A-- just leave it, it still works.

B--give it to someone who knows what they are doing, and hope they take pity on me and don't charge a lot.

C-- have a go myself, because i like the smell of burning, and anyway being an ex royal engineer i like blowing stuff up!!

suggestions please, brainstorming here so funny or wacky is good. :),

gordy

[istari_knight]

Service manual shows it to be a basic STK power amp with an opamp front end... Is the hum 50hz would you say ? If so then replacing the two power supply capacitors could fix the problem yes. They are 4700uF/42v but I would replace them with 4700uF/50v parts.

On this model you'll have to remove the top cover, unscrew the PCB & flip it over to work on it [there is no bottom access.] Its a very easy job but be sure to note the capacitor polarity before removing them... Take a photo or something. IME silkscreen's cannot be trusted :rolleyes:

[gordy]

Thanks for the response mr knight,
Yes the frequency of the hum is about 50htz (about the same as the hum from a knackered strip light so i guess about 50htz), not a lot of time off at the moment but it can wait, so i had better dig out my old soldering iron, would a 40watt soldering iron be ok or would it be a bit too much. also for the cap's is there any particular makes to go for or avoid, and any recommended places to buy from. I know I know, so many questions already. but the help is appreciated..

gordy

[istari_knight]

40w should be okay for the minor work you're doing... Just be careful not to lift the tracks. For easier removal I would recommend getting yourself a cheap desolder pump.

These are the best value I can find & would suite your needs perfectly, you'll just need to make sure they're not too tall http://www.ebay.co.uk/itm/2X-6800UF-50v-105c-Panasonic-can-capacitors-/231065317954?pt=UK_BOI_Electrical_Components_Suppl ies_ET&hash=item35cc90f242

[gordy]

Cheers James, that was quick, i shall get them ordered and give it a go when i get a spare moment. i did google caps but the different makes and prices just confused me.

[gordy]

Well good news, well for me anyway,:) I took the lid off and it was a bit dusty, so i got the hoover and a paintbrush into it and it got a damn clean and inspection, I know what i was looking at of course, HAH:lol:, but i did notice the connectors from the front board to the bottom/main pcb were a simple slot and blade type and they were not sitting in square or fully, so i gave them a wiggle and pushed them in fully plugged it back into the system and hey presto, no more hum, happy days, listening to it now and its all good. cheers gordy.

[istari_knight]

Bonus :thumbsup: