Scorpion Tube power Supply Build Thread

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Scorpion Tube power Supply Build Thread

Post by Joe Malone »

Scorpion Tube power Supply Build Thread

DANGER HIGH VOLTAGE EVERYWHERE ON THIS PCB. ONLY QUALIFIED TECHNICIAN SHOULD WIRE THIS POWER SUPPLY
150v or 300v High voltage out is set by J1. Centre 2 pins 2-3 linked for 300v and outside 2 pairs 1-2 & 3-4 linked for 150v.
Also for 150v only one 150v zener is fitted the the other is replaced with a wire link.
If you want the high volts rails to sag like vintage gear do not fit any 150v zeners.


Scorpion 30w wattage calc
300v high voltage setting = 21 x Filament current + 320 × HV1 + HV2 current = 30W or less.
150v high voltage setting = 21 x Filament current + 160 x HV1 + HV2 current = 30W or less

Build map for top of scorpion pcb
http://jlmaudio.com/builds/maps/ScorpionPCB.html

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Build map for bottom of scorpion pcb
http://jlmaudio.com/builds/maps/ScorpionReg.html

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Regulator and FET TO220 mount with metal tab away from pcb and are covered by silicon thermal tubes before mounting to case.
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downbeatstudio
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Re: Scorpion Tube power Supply Build Thread

Post by downbeatstudio »

Hi there,
Fully built this power supply and it’s putting out proper voltage, but the power transformer is getting super hot. Specifically the one near the mains voltage input. It almost looks like then plastic casing has softened or melted.

I’m running a two channel Gates SA-70 tube preamp which leverages two 6J7 and two 6C5 tubes.


I’m running the supply external with a 5 pin XLR to the main preamp unit. I attached some pictures as well.
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downbeatstudio
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Re: Scorpion Tube power Supply Build Thread

Post by downbeatstudio »

Also here is the preamp schematic.
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Re: Scorpion Tube power Supply Build Thread

Post by Joe Malone »

downbeatstudio wrote:
Fri Apr 29, 2022 3:51 am
Hi there,
Fully built this power supply and it’s putting out proper voltage, but the power transformer is getting super hot. Specifically the one near the mains voltage input. It almost looks like then plastic casing has softened or melted.

I’m running a two channel Gates SA-70 tube preamp which leverages two 6J7 and two 6C5 tubes.


I’m running the supply external with a 5 pin XLR to the main preamp unit. I attached some pictures as well.
(21 x 1.2A) + (320 x 0.05A) = 42W from 30W transformer = meltdown.

You would need to use a Scorpion per SA-70 preamp which would use 21W and leave some wattage for phantom power and a bit spare which would be perfect.

Warning the melted transformer is now highly dangerous and should be replaced before powering up again with one mic pre.

Also the thin metal box will not spread the heat enough to cool the filament regulator properly. Ideally a 3 to 6mm thick bottom plate the internal size of that box would be enough cooling for 2 x Scorpions.
Joe :-)
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downbeatstudio
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Re: Scorpion Tube power Supply Build Thread

Post by downbeatstudio »

Hey Joe,
Thanks for following up and providing clarity. I should have done my math up front. :oops:

Do you sell single replacement transformers? or know of a good place to source them in the US?

I'll build out a different power supply for this preamp.

Thanks!

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Re: Scorpion Tube power Supply Build Thread

Post by Joe Malone »

downbeatstudio wrote:
Fri Apr 29, 2022 1:36 pm
Hey Joe,
Thanks for following up and providing clarity. I should have done my math up front. :oops:

Do you sell single replacement transformers? or know of a good place to source them in the US?

I'll build out a different power supply for this preamp.

Thanks!
Yes we have the transformers for $50AUD + shipping but you could also use a standard 50VA or 80VA 2 x 15vac toroid transformer wired in the melted ones place which would make that power supply work as-is. But I still think you will need more heatsinking with a thick bottom plate.

Drop me an email if you want to order a transformer.
Joe :-)
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downbeatstudio
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Re: Scorpion Tube power Supply Build Thread

Post by downbeatstudio »

Hey Joe,
Thanks for the reply. Really appreciate the help. I just want to summarize to validate my understanding.

I can swap in a toroidal 50va or 80va 2x15AC for the current melted transformer, mount the entire supply PCB in a thicker enclosure to dissipate the heat better and it should be good to power both preamp channels and 48V phantom?

Thanks so much for the guidance.

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Re: Scorpion Tube power Supply Build Thread

Post by Joe Malone »

downbeatstudio wrote:
Sat Apr 30, 2022 12:08 am
Hey Joe,
Thanks for the reply. Really appreciate the help. I just want to summarize to validate my understanding.

I can swap in a toroidal 50va or 80va 2x15AC for the current melted transformer, mount the entire supply PCB in a thicker enclosure to dissipate the heat better and it should be good to power both preamp channels and 48V phantom?

Thanks so much for the guidance.
Yes correct let me know which transformers you are looking at using so I can check it will work and I can let you know where each coloured wire should go to the pcb
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downbeatstudio
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Re: Scorpion Tube power Supply Build Thread

Post by downbeatstudio »

Thanks Joe!
I'm looking at this Triad: https://www.mouser.com/ProductDetail/553-VPT30-1670

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Re: Scorpion Tube power Supply Build Thread

Post by Joe Malone »

downbeatstudio wrote:
Sun May 01, 2022 11:23 am
Thanks Joe!
I'm looking at this Triad: https://www.mouser.com/ProductDetail/553-VPT30-1670
Yes that will work but I would probably go to the next size up like 80VA for cooler running transformer. The colour code winding diagram on the spec sheet layout perfectly on to the existing pcb transformer.
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downbeatstudio
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Re: Scorpion Tube power Supply Build Thread

Post by downbeatstudio »

Hi Joe,
Got the new transformer and installed everything in a new enclosure. Now I’m experiencing an issue with the filament voltage. When not under load it holds steady at 6.3vdc. Once it’s under even a small load (ie single tube or even just a indicator bulb) it will slowly drop down to 0vdc.

All other voltages hold steady.

Is it possible one of the regulators or FETs got damaged previously? Upon inspection of the board nothing looks burnt or damaged. No bad smells.
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Re: Scorpion Tube power Supply Build Thread

Post by Joe Malone »

downbeatstudio wrote:
Sat May 07, 2022 2:44 pm
Hi Joe,
Got the new transformer and installed everything in a new enclosure. Now I’m experiencing an issue with the filament voltage. When not under load it holds steady at 6.3vdc. Once it’s under even a small load (ie single tube or even just a indicator bulb) it will slowly drop down to 0vdc.

All other voltages hold steady.

Is it possible one of the regulators or FETs got damaged previously? Upon inspection of the board nothing looks burnt or damaged. No bad smells.
From the photo, there is no bolt clamping down the 48v and 6.3v reg to the bottom of the case on the end the transformer was removed. The 2 blue transformer center bolts are very important to clamp the regs in their silicon tubes tight to the bottom panel or heatsink very tightly. So you would need to fit a bolt in the large hole on the pcb. Also, I cannot see the thick aluminum bottom panel I mentioned. So just sounds like the reg is overheating and shutting down to protect itself. That painted thin black steel bottom panel doesn't offer anything much in the way of heatsinking.
Joe :-)
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downbeatstudio
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Re: Scorpion Tube power Supply Build Thread

Post by downbeatstudio »

Thanks Joe.
The bottom part of that enclosure it 4mm steel, so I assumed that would be enough to dissipate the heat. I'll try to bolting down that side. The drop in voltage happens almost immediately upon startup, within 10 secs. I'll add a bolt, test and trying replacing the regulator if that doesn't work.

Thanks again for all the help!

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Re: Scorpion Tube power Supply Build Thread

Post by Joe Malone »

downbeatstudio wrote:
Mon May 09, 2022 1:51 am
Thanks Joe.
The bottom part of that enclosure it 4mm steel, so I assumed that would be enough to dissipate the heat. I'll try to bolting down that side. The drop in voltage happens almost immediately upon startup, within 10 secs. I'll add a bolt, test and trying replacing the regulator if that doesn't work.

Thanks again for all the help!
If the panel is 4mm steel then should work but would be best to sand off the paint where the regs touch and needs clamping down that centre bolt. If the reg drops like you said even with a small load after bolting down then the reg is probably damaged. If you have to replace the LM317 I would fit a LM350 in the same TO220 package as it will replace the LM317 exactly but because of its higher 3A limit it will not go into temp protection as easily.
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Holger
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Re: Scorpion Tube power Supply Build Thread

Post by Holger »

The Scorpion works wonderful in my 1 Ru mic pre.

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