SA212 troubleshouting

HIWATT amps from the Hylight Electronics era

Moderator: Mods

User avatar
jujub
Posts: 23
Joined: Thu Jan 31, 2013 12:23 pm
Location: France

SA212 troubleshouting

Postby jujub » Sat Aug 20, 2016 2:50 pm

HI everyone

Was playing with my amp à low volume.... hten it sudenly fade the now there no more sound of it.

tube are lighting... tranny are not hot..

Hope it not the patridge :?

what can I do ?

User avatar
mhuss
Site Admin
Posts: 1354
Joined: Thu Nov 15, 2007 5:40 am

Re: SA212 troubleshouting

Postby mhuss » Sun Aug 21, 2016 2:39 pm

Did you check the HT fuse? That fuse only interrupts the high voltage, the tubes and indicator will still light if it is blown.
http://hiwatt.org/tech.html

On very rare occasions, this fuse will fail due to age & vibration, but it most often indicates a bad output tube (EL34). If the fuse is blown, replace it, but watch the EL34s when you turn it on again. One may be red-plating (the tube structure itself starts glowing a dull red, different from the bright orange heaters). This condition somestimes causes extra hum from the speakers, but otherwise there's no audible indication.

If a tube did red-plate for a while, it may be permanently damaged, i.e., the HT fuse will blow again quickly.

In any case, I suggest you remove the chassis and inspect the output tube sockets for any sign of overheating or charring. There is a small resistor connected to the socket that typically burns/turns black when an output fails catastrophically.

User avatar
jujub
Posts: 23
Joined: Thu Jan 31, 2013 12:23 pm
Location: France

Re: SA212 troubleshouting

Postby jujub » Sun Aug 21, 2016 7:13 pm

thanks !

Ht fuse is ok, therefor tube are red plating ( mullards XF2 :( ) ...

my be a problem with the bias...bias cap is original... :oops:

User avatar
mhuss
Site Admin
Posts: 1354
Joined: Thu Nov 15, 2007 5:40 am

Re: SA212 troubleshouting

Postby mhuss » Tue Aug 23, 2016 1:02 am

Are you sure the fuse is OK? Sometimes (particularly with vibration failure) the fuse looks perfectly fine, but measures open.

User avatar
jujub
Posts: 23
Joined: Thu Jan 31, 2013 12:23 pm
Location: France

Re: SA212 troubleshouting

Postby jujub » Tue Aug 23, 2016 4:16 am

Fuse have been tested ok

Could it be a préam tube? PI?

User avatar
jujub
Posts: 23
Joined: Thu Jan 31, 2013 12:23 pm
Location: France

Re: SA212 troubleshouting

Postby jujub » Wed Aug 24, 2016 7:12 am

:D

Amp is working again !

There was just a broken wire :?: :?: :?: ... the HT1 connexion to the output tranny. HERE


Image

I wonder how this happen

Thanks. :D

User avatar
mhuss
Site Admin
Posts: 1354
Joined: Thu Nov 15, 2007 5:40 am

Re: SA212 troubleshouting

Postby mhuss » Sat Aug 27, 2016 3:56 am

I'm glad you found it, and that it was a simple fix. :D


Return to “Hylight era Amps”

Who is online

Users browsing this forum: No registered users and 1 guest