breaker keeps popping on power amp - solutions?

Archived from groups: rec.audio.pro (More info?)

I've aquired a rather old solid state power amp (from 1971) that I'm
trying to get fired up.

Every time I turn it on, the power light glows for a second, the VU
meter twitches, and then I can hear the breaker pop and the whole thing
dies.

Turning the amp off, pushing the breaker button, and turning it on
again repeats the process - a fleeting second of glorious power, and
then death.

I'm not a genius when it comes to surgery on my gear, but I know some
basics. I inspected everything inside and didn't see anything obviously
out of place.

Any idea about starting points for figuring this out?

TIA

JT

Archived from groups: rec.audio.pro (More info?)

On Thu, 19 Aug 2004 21:31:38 GMT, j t <jt.REMOVETHIS@tydirium.net>
wrote:

>
>
>I've aquired a rather old solid state power amp (from 1971) that I'm
>trying to get fired up.
>
>Every time I turn it on, the power light glows for a second, the VU
>meter twitches, and then I can hear the breaker pop and the whole thing
>dies.
>
>Turning the amp off, pushing the breaker button, and turning it on
>again repeats the process - a fleeting second of glorious power, and
>then death.
>
>I'm not a genius when it comes to surgery on my gear, but I know some
>basics. I inspected everything inside and didn't see anything obviously
>out of place.
>
>Any idea about starting points for figuring this out?
>
>TIA

Check the power supply.


>
>JT

Rick Ruskin
Lion Dog Music - Seattle WA
http://liondogmusic.com

Archived from groups: rec.audio.pro (More info?)

The most-likely problems are a short in the power transformer or the rest of
power supply, or shorted output transistor(s).

Replacing all the elelctrolytic caps is a good idea, just on general principles.
However, electrolytics rarely short out. New capacitors is unlikely to fix the
problem.

Do you have an ohmeter? Can you get the service manual?

Archived from groups: rec.audio.pro (More info?)

Thanks for all the advice.

Basically, I got this thing for almost-free, and figured that getting
it running would be a good excersize for my electronics and gear maint.
skills. I've got MUCH better gear in my 'real' rig - but this dinosaur
seemed like a good place to brush up on some basics.

thanks

JT

Archived from groups: rec.audio.pro (More info?)

Rob Reedijk <reedijk@hera.med.utoronto.ca> wrote in news:cg5obv$j1j$1
@news1.chem.utoronto.ca:

> George <g.p.gleason@worldnet.att.net> wrote:
>>
>>>
>>> On some amps it can be worthwhile to fire them up on a variac and
>>> look at where the current is going. But anything from 1971 is going
>>> to have so many bad capacitors that it might be worth shotgunning all
>>> the electrolytics before touching anything else.
>>> --scott
>
>> I would shotgun the amp as well
>> a deerslayer will be much more satisfying than buckshot
>
> I think you all are a bit quick to toss away a good thing. I just
> picked up an old Dynaco SCA 80Q at a garage sale last weekend. It
> didn't sound all that great. An SCA 80Q is a PAT4 preamp packaged
> together with an ST 80 amp with a little bit of fake quad thrown
> in. I bypassed the entire preamp section, thereby converting it
> into an ST80 and it sounds pretty good, when kept at moderate levels.
>
> I don't believe it has seen any re-capping. Personally, I think there
> is a madness out there to re-cap everything in sight, often
unnecessarily.
>
> Rob R.
>

Rob,

I have a tendency to agree with you. I just had 2 pieces on the bench
both built prior to 1967 and all of the caps in them were fine. OTOH I
had the caps go south in my 3 year old computer. It would not boot so I
replaced them and all was fine.

r

--
Nothing beats the bandwidth of a station wagon filled with DLT tapes.