[sdiy] aging transformer replacement

[Roy J. Tellason]

On Thursday 10 June 2004 04:47 pm, jhno wrote:

> is it straightforward to replace power transformers in aging synths?

The toughest part there is going to be getting accurate specs,  or guessing 
close enough...

> several of my devices start to hum/buzz acoustically after being powered up
> for a while - typically 0.5 - 2 hours, say. it is the transformers, of
> course. i imagine they are just getting old.
>
> the main offenders are:
> eventide h3000
> orig. nord lead
> roland jx10
> prophet 5 r3
>
> some of the power supplies are more elaborate than others. if i measure
> each winding utilized and find a transformer (or multiple units) that give
> the same voltages with plenty of volt-amps to spare, is it safe to attempt
> the replacement?

Probably.  But I'd be inclined to be *sure* that it was the transformers,  
first.  Take a rod,  non-metal,  and see if you can "probe" for that 
vibration somewhere.  If it _is_ the transformers,  then maybe the 
application of some silicone rubber would fix the problem.

> or, is there some other way to cure the hum? it can be quite distracting.

See above.  Another,  more likely cause,  is aging electrolytic caps,  
particularly those large ones in the power supplies.  These seem to be quite 
a common problem in a lot of equipment.

> as an aside, i have bought a few 110 to 110 transformers for isolation and
> power conditioning purposes. these have buzzed louder than anything. very
> industrial.

Oh really?  I can't imagine why that would be,  unless there was some defect 
in the construction of them.  Again,  perhaps a bit of silicone rubber would 
fix that.

I can understand isolation,  but power conditioning?  What is it that you 
expect that you're getting in that regard?