GZ34 sanity check

We all start somewhere
Post Reply
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#1 GZ34 sanity check

Post by Thermionic Idler »

I believe I have this right but just want to "check my working".

For my 300B project, the circuit I'm basing it on has the power supply wired thus:

Image

The power supply on the right uses the 6CJ3 which does NOT have the heater connection tied to the cathode. Therefore the centre tap of the heater supply has been tied to ground. The power supply on the left has an unspecified rectifier valve and also has the centre tap of its heater supply tied to ground (highlighted).

My plan is to use the GZ34 in both power supplies which, although indirectly heated, has the cathode tied to the heater. I believe that because of this, the 5v supply should not be grounded, with the idea being that it follows the changes in voltage at the cathode. Am I right?

Image
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#2 Re: GZ34 sanity check

Post by Cressy Snr »

Don’t whatever you do, ground the centre tap of the rectifier winding. You’ll burn out the mains transformer.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#3 Re: GZ34 sanity check

Post by pre65 »

Cressy Snr wrote: Sun Aug 16, 2020 2:53 pm Don’t whatever you do, ground the centre tap of the rectifier winding. You’ll burn out the mains transformer.
You could take the HT from the 5V centre tap. :)
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#4 Re: GZ34 sanity check

Post by Cressy Snr »

pre65 wrote: Sun Aug 16, 2020 3:01 pm
Cressy Snr wrote: Sun Aug 16, 2020 2:53 pm Don’t whatever you do, ground the centre tap of the rectifier winding. You’ll burn out the mains transformer.
You could take the HT from the 5V centre tap. :)
Exactly :shock: :lol:
Sgt. Baker started talkin’ with a Bullhorn in his hand.
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#5 Re: GZ34 sanity check

Post by Thermionic Idler »

So I'm right in other words :lol:

I was looking at the Olson drawing and suddenly thought - hang on, with a GZ34 that's a short circuit waiting to happen.

To be faiir, it had probably been quickly edited to use a recifier instead of the diodes and doesn't specify any link between the cathode and heater.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
User avatar
izzy wizzy
Old Hand
Posts: 1496
Joined: Fri Nov 02, 2007 7:02 pm
Location: Auckland NZ
Contact:

#6 Re: GZ34 sanity check

Post by izzy wizzy »

The gz34 and 6cj3 are indirectly heated so take the HT off the cathode.

The 6cj3 is a damper and has very high heater cathode rating. Not so gz34.

Ref the gz34 heater to the cathode.

The symmetric reichert has some left overs from the karna and do can be a bit confusing.
User avatar
Nick
Site Admin
Posts: 15708
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#7 Re: GZ34 sanity check

Post by Nick »

Yep, the damper diodes can stand that voltage between the heater and cathode, the indirectly heated normal rectifiers can't, and the directly heated has no cathode. Also make sure when you get the transformer wound that the heater winding is spec'd to run at the voltage you are intending to use it at. You can use a simple toroid with the damper diode and ground the heater supply to protect the transformer. A normal rectifier would need a heater winding that's safe to run at 600v or so above the core.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
izzy wizzy
Old Hand
Posts: 1496
Joined: Fri Nov 02, 2007 7:02 pm
Location: Auckland NZ
Contact:

#8 Re: GZ34 sanity check

Post by izzy wizzy »

Although the sym reichert is a thought experiment, I'm guessing Lynn will have drawn it to use a dual damper for the front end and so could ref the heater to ground (probably). Maybe 6by5. 6cj3 would have been completely ott for 6sn7 front end. In the Karna he ran all 4 6cj3 from the same winding and so ref'd the lot to 0v.
User avatar
Thermionic Idler
Old Hand
Posts: 1018
Joined: Sun Apr 22, 2012 8:22 pm
Location: Southsea

#9 Re: GZ34 sanity check

Post by Thermionic Idler »

Nick wrote: Sun Aug 16, 2020 5:36 pm Yep, the damper diodes can stand that voltage between the heater and cathode, the indirectly heated normal rectifiers can't, and the directly heated has no cathode. Also make sure when you get the transformer wound that the heater winding is spec'd to run at the voltage you are intending to use it at. You can use a simple toroid with the damper diode and ground the heater supply to protect the transformer. A normal rectifier would need a heater winding that's safe to run at 600v or so above the core.
I'm planning on using two off-the-shelf Hammond models, the 375X and 378X rather than custom wind (in an effort to stop costs completely spiralling out of control :lol: ). Both have 5v and 6.3v secondaries and I'm anticipating that the 5v winding was intended for use with rectifiers. The datasheet only mentions primary to secondary maximum potential difference, given as 2500V.
Deck: Garrard 301 - Audio Origami PU7 - NW Analogue DH3S
Phono: Pete Millett LR, Lundahl SUT, AMB σ22 PSU
Linestage: Bruno Putzeys Balanced Pre + Hans Polak relay mod, LCDuino control
Power amps: 300B PP 'Symmetric Reichert'
Speakers: FF225WK Big Mets
User avatar
Nick
Site Admin
Posts: 15708
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#10 Re: GZ34 sanity check

Post by Nick »

Thermionic Idler wrote: Sun Aug 16, 2020 7:16 pm
Nick wrote: Sun Aug 16, 2020 5:36 pm Yep, the damper diodes can stand that voltage between the heater and cathode, the indirectly heated normal rectifiers can't, and the directly heated has no cathode. Also make sure when you get the transformer wound that the heater winding is spec'd to run at the voltage you are intending to use it at. You can use a simple toroid with the damper diode and ground the heater supply to protect the transformer. A normal rectifier would need a heater winding that's safe to run at 600v or so above the core.
I'm planning on using two off-the-shelf Hammond models, the 375X and 378X rather than custom wind (in an effort to stop costs completely spiralling out of control :lol: ). Both have 5v and 6.3v secondaries and I'm anticipating that the 5v winding was intended for use with rectifiers. The datasheet only mentions primary to secondary maximum potential difference, given as 2500V.
That should be fine. Will be on a bobbin unlike a typical toroid.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
Post Reply