Ampeg SVT-DI Tube Direct Injection re-wire for European voltages?

[boroman]

My friend just bought two of them from U.S. and brought to me today, wow. I must say that I hated DI-s but this one sounds killer. The problem is, it's US model wired for 120V. It has universal transformer and fuse holder indicates that it could be run either 120 or 240V. I worked on SVT-CLs and VRs and re-jumpered them for European voltages but there were clear AC board schematics for it. I can't find SVT-DI AC board schem anywhere. Does anyone of you could help me with these?

Here's the shot of the guts. As you see, 3 wires from PT are free, so they might do the trick, but schematic shows only the audio path...

[vintagekiki]

https://www.talkbass.com/threads/ampeg-svtdi-schematic.1395577/

https://www.talkbass.com/attachments/ampeg-svtdi-schematic-pdf.3368750/

[boroman]

https://www.talkbass.com/threads/ampeg-svtdi-schematic.1395577/
https://www.talkbass.com/attachments/ampeg-svtdi-schematic-pdf.3368750/

Thanks, I have that schematic. It's only preamp. No PT/HV wiring there unfortunately

[vintagekiki]

Using an Ohm meter (200 Ohm range) measure the resistance of the primary winding at the ends of the main cable.
Connect one end of the Ohm meter to the neutral pin of the main cable, and with the other end of the instrument measure the resistance of the other primary windings.
The winding with the highest resistance is the 230VAC winding.

[J M Fahey]

Just in case post a couple closeup pictures showing transformer, any labels on/around it, its connection to a PCB

Verbal descriptions are always incomplete and leave vital details out.
And for safety evenn if you *think* you got the 240V connection right, plug it into mains through a lightbulb limiter with a small bulb, think 15W (sewing machine or bar cabinet lamp) to 25W (fridge lamp).

Plugging a 240V device into 120V mains is fail safe, worst case itīs anemic; the opposite creates expensive fireworks so be doubly careful.

[nevetslab]

It seems to me we have (had?) a few of these in our Audio Dept, I do recall seeing them in the cabinets where the good stuff is kept, and never did take one over to the shop to have a look at it. So, now looking at the one photo we have here,.....I know there's a tube inside (12AX7?), but.....where is it? I don't see anything on that one PCB, which does have a right-angle PCB between the Output Xfmr and the Power Supply caps to run the tube's HT. Do I guess the tube is removed, and plugs in horizontally into that vertical board to occupy the space between the DC Heater Supply parts and the HT supply parts?

[Enzo]

If you look just below the yellow light bulb, you can just see a socket peeking out. And the yellow light shining on the tube makes fun eye candy. Yes, a 12A?7 plugs into that ssocket and fills the valley between filter caps. It points towards the transformer. You can see the illuminated tube through the vent in the cover.

[Enzo]

Here: 587PWA_0.pdf

[nevetslab]

I wonder if this power xfmr is not a split primary. On their other xfmrs, BRN and BRN/WHT are the lower primary wires. If you wired the two primaries in series (join WHT with BRN), BRN/WHT would be 0V, BLU would be 220V & BLK would be 240. I'd guess the BLU wire is a 100V tap on the BLK/WHT primary. If it is a split primary, The BLK & BRN would be joined, as would the WHT & BRN/WHT for 120V use.

Typical color code seen on the SVT-CL Power Xfmrs as seen below:

Ampeg SVT-CL Power & Heater Xfmrs.pdf