No sound marshall pa20

[Andrito222]

Hello everyone,
I am new to the forum, and I wanted to ask a question, I'm not much of a tech guy" but I can work out simple stuff,
Anyway I have been playing my little marshall pa20 from 1973 and the other day when I turned it on, there was no sound, shortly it blew the 1amp fuse inside, i swapped the fuse and turned it on, this time didn't blow but still no sound, I changed the el84 power tubes and no luck still.
That's how far I am into it, as I said I'm quite ignorant when it comes to electronics I am planning on learning lots more, any ideas what this could be in hand wired amp?
it's a beautiful little amp that I am using a lot as its so sweet sounding,
Thanks and I appreciate the feedback

[M Fowler]

Well this amp does not have a tube rectifier so we can eliminate that idea.

Next the power tubes and then the preamp tubes.

Speaker connection is still good?

Otherwise a tech will need to open it up to see what component died.

Mark

[xtian]

Please observe if the filament in each tube is lighting up.

[Reeltarded]

Haaaaaaay.. Have you tried hitting it?

Haaaaaaay...

Fonzie

[M Fowler]

Reeltarded wrote

Haaaaaaay.. Have you tried hitting it?

Always have a Louisville slugger handy when diagnosing.

Mark

[Reeltarded]

Haaaaaaaay..

[Phil_S]

I would not attempt to power it up again until it's looked at, unless you find one of the simple things above is out of order. Let's avoid doing any additional damage. Maybe it's simple and maybe not. Maybe something that will not create further damage on power up, but why take that risk?

[M Fowler]

Give us your location and perhaps one of us fine people can take a look at your amp.

Mark

[Lindz]

Only the Fonz can actually pull off hitting things to make them work..

[Reeltarded]

.. he is the Anti-Chuck Norris

[gingertube]

And you guys thought that PM stood for Preventative Maintenance.

We Engineer types know it stands for Percussive Maintenance - its been known to work on all manner of circuits, of-course there is usually a better way!!!

Still worth a try when all else fails, along with RTFM (Read The F..g Manual).

Cheers,
Ian

[Andrito222]

Thanks very much for the replies, I'm gonna do a tube check in the next couple of days when I pickup some new ones,
Thanks for the offer to look at it for me but unfortunately I live on the other side of pacific so that would be hard,
I'm gonna take the amp to a local tech anyway I think it's the best thing anyway, I'll keep those schematics and take them to the tech.

[statorvane]

Whatever caused the fuse to short - it's no longer shorting because something downstream is open circuit - possibly the OT. Those amps are notorious for blown transformers. Well, the reissues anyway. I see yours is a vintage amp.

I suppose a quick check (other than observing the filaments) would be to see if you still have continuity through your OT Pri and Sec windings. Then proceed to check your voltages, starting w/B+.