Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on February 15, 2014, 02:01:24 pm

Title: ZENER diode 5378 for GZ34 ?
Post by: Colas LeGrippa on February 15, 2014, 02:01:24 pm

I am missing 1n 4007 diodes, can I put zener like 5378 between HV a/c and GZ34 ?

Thanks

Colas

Title: Re: ZENER diode 5378 for GZ34 ?
Post by: sluckey on February 15, 2014, 02:42:55 pm

Quote from: Colas LeGrippa on February 15, 2014, 02:01:24 pm

I am missing 1n 4007 diodes, can I put zener like 5378 between HV a/c and GZ34 ?

Thanks

Colas

No. Just connect the PT leads directly to the tube socket.

Title: Re: ZENER diode 5378 for GZ34 ?
Post by: Colas LeGrippa on February 16, 2014, 04:13:37 pm

many techs use diodes between PT and rectifier for some reasons i don't understand quite well , it is supposed to increase rectifiers life and keep them from arcing, but a rectifier is a rectifier, why rectifying ( and not recti-frying just like i wrote before hey hey ) the voltage before it is rectified by the so well called rectifier ?

Colas

Title: Re: ZENER diode 5378 for GZ34 ?
Post by: sluckey on February 16, 2014, 04:28:22 pm

Quote

many techs use diodes between PT and rectifier

That's right. But none of them use a 100V zener.

Title: Re: ZENER diode 5378 for GZ34 ?
Post by: Colas LeGrippa on February 16, 2014, 05:36:28 pm

good point. Now, is it better to use one like the 1n4007 or not at all, does it change the tone, does it change from a certain maner a recto amp to a SS one ?

Title: Re: ZENER diode 5378 for GZ34 ?
Post by: John on February 16, 2014, 07:41:52 pm

For most amps, I think the 1N4007s are fine. Doug also sells heavier duty ones. Still cheap. The diodes protect your PT if the rectifier tube shorts out. No change in tone, because the rect. tube is still causing the sag and/or limiting the amount of available current.

At least, I think that's right.

Title: Re: ZENER diode 5378 for GZ34 ?
Post by: Willabe on February 16, 2014, 08:38:32 pm

Quote from: John on February 16, 2014, 07:41:52 pm

For most amps, I think the 1N4007s are fine. Doug also sells heavier duty ones. Still cheap. The diodes protect your PT if the rectifier tube shorts out. No change in tone, because the rect. tube is still causing the sag and/or limiting the amount of available current.

That's right about the PT protection and about the sag.

All the B+ current still has to pass through the rec. tube so you still get the same sag from that rec. tube in what ever amp it's in.


            Brad    :icon_biggrin:

Title: Re: ZENER diode 5378 for GZ34 ?
Post by: tubeswell on February 17, 2014, 12:12:46 am

The fact that its the SS diode that's doing the rectifying doesn't matter in terms of the effect on the operation of the amp. A 1N4007 has a forward voltage drop of 0.6V, which is teensy compared to your average rectifier tube's forward voltage drop.

Title: Re: ZENER diode 5378 for GZ34 ?
Post by: kagliostro on February 17, 2014, 04:09:40 am

If the Tuber rectifier fails shorted, the presence of the in series diodes don't permit to AC to reach your circuit

K