Help understanding ws1 rectifier.

I'm thinking it's a good idea but I don't know if my amp can handle the WS1 with thermistor If it is a healthy choice.
Bl vta st120 (2010?) Kt88 12at7
I trust Roy who says it's OK even without tdr.
Should I not worry and just plug it in?
Should I do the tdr?
Should I do the sds upgrade cap board?

Njrob wrote:I'm thinking it's a good idea but I don't know if my amp can handle the WS1 with thermistor If it is a healthy choice.
Bl vta st120 (2010?) Kt88 12at7
I trust Roy who says it's OK even without tdr.
Should I not worry and just plug it in?
Should I do the tdr?
Should I do the sds upgrade cap board?

Trust Roy !

Thanks, I do. I guess I'm just trying to understand more about this part of the amp. I'm new to this. The can cap is rated for 525v. When i turn on the amp b+ starts at 500 and settles at 390v at the driver board. At 17 seconds, the tubes mv start climbing.  then moments later the amps starts to draw to about 1.5 amps. That seems normal correct? The weber site says not to use ws1 if amp hasn't a standby switch so does that negatively effect the tubes? I'd love to learn all I can about this. I've watched many yt videos and spoke to trusted contacts mostly with answers but limited explanations.  I'd like to learn how ac dc  flows from one thing to another. I'm going to try the ws1T. Thanks!

Njrob wrote:I'm thinking it's a good idea but I don't know if my amp can handle the WS1 with thermistor If it is a healthy choice.
Bl vta st120 (2010?) Kt88 12at7
I trust Roy who says it's OK even without tdr.
Should I not worry and just plug it in?
Should I do the tdr?
Should I do the sds upgrade cap board?

I would think the WZ68 would be the proper option for a ST120. But the WS1 with thermistor will work too. The main differences are current limit and voltage drop. While the thermistor is good for creating a soft start it does nothing to the voltage. WZ68 has a lower current capacity (still plenty enough for the ST120) but has the same voltage drop as a 5AR4.

If your wall voltage runs over 122 then definitely consider the WZ68. Or you could do the yellow sheet mod and use any 5AR4. With higher wall voltage the 17 volt drop is better for the tubes.

For what it’s worth, on my custom built ST120 I used 2 1N4007 diodes in series on each leg of the high voltage secondary (red wires). I also used the TDR. But then I also plugged the amp into either a variac or bucking transformer to lower my higher wall voltage.

Either way you have options. The right answer mostly depends on your wall AC.

If your wall voltage is lower than 122 then the WS1 with thermistor should be fine.

The TDR is a neat option but I ended up taking it out when I rebuilt my amp for sale. I prefer the yellow sheet mod which allows for either solid state or tube rectifiers. TDR is for solid state rectifiers only.

Personally, I recommend the yellow sheet mod regardless of rectifier you end up with. It won’t hurt anything and actually protects tube rectifiers.

Hey thanks for the feedback! Diode mod was in a while back. Variac I keep at 115 as per Roy. The st120 originally came with 5u4 as per the tubes4hifi site.  but my uncle had a 5ar4 in it which I used for a year.  I dont understand yet what current limit and voltage drop actually means here. (The purpose). Will the caps look like a dead short to the transformer because of the instant voltage? With the 5u4 It takes about 17 seconds for the tubes to start drawing, the ws1 says "a few seconds" I realllly don't wanna mess anything up. Also interested in the diodes on primary reds. What's that do?

I still recommend the WZ68 as it has an internal voltage drop and the WS1 doesn't
Weber gives misleading info on the WZ68 because SOME people in hi-fi don't think they should have SAG like a guitar amp, but any sag is very short term and only at very high levels near overdrive.
Both of these products have reliability problems just as tube rectifier do, but the Webers do have much higher current capability than a rectifier tube.

Is the weber higher current capacity better?
Also.
When I turn on the amp, my amp meter shows 2.9 amps quickly then drops to .9 slowly rises to 1.5 amp. Is that normal? Using 5au4 for now
Pretty sure it just would climb from .9 to 1.5/1.6
I had tried an electro harmonix 5u4 for a week returned it cause of tube noise
I put back in the 5au4 awaiting a new 5u4.

yes, higher current capability is better (it's like horsepower, reserve)
yes, all that is normal