Tube DIY Asylum

RE: Maybe schematic is correct & diodes should go in series

1.124.29.149

Johno

In Reply to: RE: If you had to guess ..................... posted by Cut-Throat on October 06, 2023 at 19:04:25

With the Kathode resistors?
Just saying & what's the diode part number?

Cheers

Follow Ups:

Nope !! - Cut-Throat 23:50:30 10/06/23 (2)
Build Instructions are very specific on where to attach diodes. Same terminals as the resistor and Cap. I was not smart enough or lucky enough to come up with an 'accidental' working design. Back then or Now! The 4 diodes are 1N5363B
(Note: This diagram does not show all parts. There are quite a few of these in the build instructions.)
Here are the attach points for Diodes, Caps and Resistors. - All in Parallel.

Edits: 10/06/23 10/07/23
- RE: Ok the diodes are 30V,5W Zeners - Johno 03:32:51 10/07/23 (1)
  So I'm assuming they are a fail safe if for example Rk develops an o/cct or pin 8 on valve base looses continuity with valve pin. According to spec sheet the diode has a max regulated current of 158ma. I'm assuming if this is a EL34 PP amp the valves are each running 50-60ma individually. So across 330 ohm cathode resistor @ say 50ma current you should read around 15-18V across each cathode branch (resistor).But if a open cct in that branch occurred I'm assuming the voltage would go high and the zener would conduct to stabilize the cct in which you would hear distorted sound through that channel. Why the zener popped is unknown to me but I would replace all the parts and check in question the associated solder joints and make sure pin 8 on socket is tight. Best of luck, cheers.
  - RE: Ok the diodes are 30V,5W Zeners - Cut-Throat 06:10:17 10/07/23 (0)
    It is basically an EL34 PP Amp, but you can run a variety of Power Tubes, as it is self biasing. You can use 5881s, KT-66s, E34Ls and KT-90s I have run KT-88s for over 20 years in it.
    The only parts I am replacing is the resistor and the diode and a new set of Power Tubes. I've only got two solder points for these parts. So, I have cleaned off all the solder and will re-solder when I get the diode in place.
    If you're interested there was a review done on this amp over 20 years ago at the below link.
    Here is a picture of my amp which had wood side panels, which came with the kit.
    - http://www.soundstagenetwork.com/revequip/aes_ae25_superamp. (Open in New Window)
    Edits: 10/07/23

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