my stax 717 blows the fuses at the input of the transformer 220v 1.5 fast blow - do i need test slow blow or fast blow 30A fuse?

[Omega_ELS]

Good day, dear gentlemens.

my stax 717 blows the fuses at the input of the transformer 220v 1.5 fast blow.

do i need test slow blow or fast blow 30A fuse?

If I decide to install 30A, is there a safer way to do it, like connect it through an incandescent lamp or something like that?

What is the normal resistance of the windings of this transformer in 717 should be at the input on the socket?

 

When I bought it, it had a 220-volt, 1.5-amp fast-blow fuse installed.

But according to the schematic, I need a 220-volt, 1.5-amp slow-blow fuse.
But I can't find one anywhere yet.

 

By the way, I measured the transformer resistance on the 220V plug that plugs into the outlet—it's only 12.7 ohms.
I'm not sure that's how it should be...

 

any advice is welcome

Edited 2 hours ago by Omega_ELS

[kevin gilmore]

are you sure of the jumpers for the voltage you are using.  if jumpered on 100 or 120v and you put 220 in it, fuse will blow instantly.

but you do need a slow blow fuse.

[Omega_ELS]

14 hours ago, kevin gilmore said:

are you sure of the jumpers for the voltage you are using.  if jumpered on 100 or 120v and you put 220 in it, fuse will blow instantly.

but you do need a slow blow fuse.

Hi Kevin
Thank you for your interest in this topic.

Yes, I set the jumpers to positions 3 and 5.
When I bought it, it had a 220V 1.5A fast-blow fuse.
But after a few months, it failed and blew.

Today, I bought the same one, 1.5A, and even 2A – they both blew instantly.

Since I can't find a slow-blow fuse, I bought several fast-blow fuses, 10-20-30A, and I'm thinking of trying them.

But I'm afraid to do that because I'm not sure it's just the fuse....

By the way, I measured the transformer resistance on the 220V plug that plugs into the outlet—it's only 12.7 ohms.
I'm not sure that's how it should be...

Edited 2 hours ago by Omega_ELS

[spritzer]

If the fuses are blowing, then something is wrong somewhere.  Never use fast blow fuses, let alone 30A.  If the fuse manages to hold and something is shorted, do you want to dump 2.4kW into the amp?  No...  

[kevin gilmore]

you do not have the jumpers in the right position for the voltage you need.

the voltage rating on the fuse is meaningless.

[Omega_ELS]

13 hours ago, spritzer said:

If the fuses are blowing, then something is wrong somewhere.  Never use fast blow fuses, let alone 30A.  If the fuse manages to hold and something is shorted, do you want to dump 2.4kW into the amp?  No...  

Hi Birgir
Thank you for your interest in this topic.
I just can't find a suitable slow-blow fuse =(

Its dimensions should be 6x30 or 6.2x32 or something like that, it should be rated for 250v and 1.5a and be a slow blow..

So I thought I could use a higher-amperage fast-blow fuse for timing tests...

 

1 hour ago, kevin gilmore said:

you do not have the jumpers in the right position for the voltage you need.

the voltage rating on the fuse is meaningless.

 

Hi Kevin, thanks for your comment.

Well in my 220-volt network, the voltage sometimes rises to 230...
So I thought it would be a good idea to put jumpers on 3 and 5...

instead of 2 and 5....

just to have some reserve...
It seemed to me that it's better to have a reserve of -10 volts

than +10..

As far as I understand, the power supply here is unregulated

and exceeding the input voltage is a bad idea...

Edited 2 hours ago by Omega_ELS

[kevin gilmore]

that is not one of the available options.

the options are 100v, 120v and 240v

some people think the 120v option is 115 but it is not.

for 240v the 120v windings are in series.

if you really want the 120v in series with the 100v for 220v, you have to wire remove all the jumpers and wire by hand

 

 

Edited 2 hours ago by kevin gilmore

[Omega_ELS]

I found this drawing...

The jumpers are currently set to 3 and 5...

[Omega_ELS]

9 minutes ago, kevin gilmore said:

that is not one of the available options.

the options are 100v, 120v and 240v

some people think the 120v option is 115 but it is not.

for 240v the 120v windings are in series.

if you really want the 120v in series with the 100v for 220v, you have to wire remove all the jumpers and wire by hand

 

 

Thanks, Kevin.
I'll try switching it to 2 and 5.
And I'll install a 3A or higher fuse.
And I'll test it...

[spritzer]

2 and 5 is what I'd set it to and that is also likely not the cause, fuses blow for a reason so check for any failed parts.  These amps are almost 30 years old at this point so they need to be refurbished.  

[Omega_ELS]

40 minutes ago, spritzer said:

2 and 5 is what I'd set it to and that is also likely not the cause, fuses blow for a reason so check for any failed parts.  These amps are almost 30 years old at this point so they need to be refurbished.  

Yes, Birgir, it looks like you're right...
I installed a 3A fuse - This time he held out and didn't burn...
I installed jumpers on 2 and 5...

and it looks like smoke is coming from one of the diode bridges, D11, at the bottom...
It's not much, but still...
I immediately turned it off
I'll look for a modern replacement...

 

It looks like it's 30 years old and needs replacing...
along with the d12...

It looks like the problem isn't with the slow blow fuse...

 

 

Edited 55 minutes ago by Omega_ELS