Forums - Print Page

Forums
https://www.decware.com/cgi-bin/yabb22/YaBB.pl
AUDIO FORUMS >> General Discussion and Support >> Firework in 5AR4 sovtec 1503
https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1564794438

Message started by RF on 08/03/19 at 02:07:17

Title: Firework in 5AR4 sovtec 1503
Post by RF on 08/03/19 at 02:07:17

Hi Friends,

I turned on the tori mk IV today and saw fireworks for 30 sec in sovtec 1503 tube... it stopped after that... Any idea what is going on? Never seen this before :-[

Thanks,
RF

Title: Re: Firework in 5AR4 sovtec 1503
Post by will on 08/03/19 at 02:20:32

30 seconds of fireworks! I am surprised the 5AR4 did not short out altogether and blow a fuse. It would seem your rectifier is going! In my experience, when a rectifier fails, it has blown the IEC fuse and not damaged the amp, though maybe I have been lucky. I am thinking I recall seeing that Steve has started using fuses inside some amps as well, I am guessing for double coverage??? Anyway, I would get a new pair, and in the meantime, I would pull the suspect pair you have in, and use spares until the new ones come.

Title: Re: Firework in 5AR4 sovtec 1503
Post by RF on 08/03/19 at 03:52:22

Thanks Will for the feedback. I will swap it out.

It sounds just fine after the flickering.

RF

Title: Re: Firework in 5AR4 sovtec 1503
Post by Steve Deckert on 08/03/19 at 04:03:34

Yes, if a rectifier arcs more than once or twice when it is new, then consider not up to the task. It might work in an amplifier with lower capacitor values like those built in the 1940's. Today that value has gone from 6 ~ 8 uF up to 47 uF. If you rectifier is not new, and one day it just arcs it means it is getting ready to fail.

Steve

Title: Re: Firework in 5AR4 sovtec 1503
Post by RF on 08/03/19 at 07:44:50

Thanks Steve. Swapped a new one.

My understanding is that always change both sides at same time, even when only one is going bad.

What is your favorite one for mk IV?

Thanks,
RF

Title: Re: Firework in 5AR4 sovtec 1503
Post by Rivieraranch on 08/03/19 at 13:58:17

Hey Radiofrequency:

Will, Lon and them have a huge thread on rectifiers in the MKIV. When I had one I used old US Made 5Z3's through an adapter. I never had arcing like you describe with those. That did happen to me with a Valve Art in my Zen; it blew the fuse.

Title: Re: Firework in 5AR4 sovtec 1503
Post by will on 08/03/19 at 19:28:56

If it is a standard, newish Sovtek 5AR4 Mullard GZ34 copy, the spec is for a 60 uF capacitor, so that should be conceptually fine with your MKIV 47 uF rectifier cap. If this is the case, the problem is more likely a bad rectifier. Years ago, I had a single Sovtek 5AR4 go on me, I think in my Torii III. Replaced it and all was well.