ExTech 382270 Schematic (not complete) - Page 1
Forum section: electronics / projects

author: RDC
author_rank: Newbie
timestamp: October 14, 2025, 02:31:47 pm
content: Picked a couple of these up quite awhile back, one with a pretty busted up front panel, and have been meaning to schematic the thing up for far too long. This is not what I personally consider a 100% complete schematic, as I prefer to strip the board, scan it, then rebuild it in software from the schematic to confirm everything connects where it actually does, but I'd like to (eventually) put this one back into service without having to rebuild it from scratch so I didn't get real invasive, but it should be mostly complete.I also have not tossed her back together and tweaked all of the POTs, so the unknowns are marked with a ? in there. There seem to be multiple revisions of this thing also, as both of mine are, one has the Toroidal style transformer and CH3/CH4 Regulators built into the control board, while the one I made the schematic from has the Laminated transformer and the CH3/CH4 Regulators as plug in boards, so expect some differences between these schematics and your boards.If anyone spots anything that looks wrong or what not let me know and I'll tweak the schematics accordingly.A couple of things that I found interesting were how in the manual for Series operation it states (5. The user must physically short the negative terminal of the Master output with the positive terminal of the Slaved output.) but when you press S501 that turns on RL506 and it does that internally.Then for Parallel operation it also states (4. The user must short the two positive terminals. 5. The user must also short the two negative terminals.) Which the thing also seems to do internally, but I don't get how RL507 is turning on the way they have it in there?POWER BOARD - RS1340_2A 2011_4_15DISPLAY BOARD - RS1340_B3 2017_03_8CH3 REGULATOR BOARD - No MarkingsCH4 REGULATOR BOARD - No MarkingsCONTROL BOARD - RS1340_23 170225TOP(NOTE: All TH components have been removed to scan board)BOTTOM(NOTE: All TH components have been removed to scan board)

author: moffy
author_rank: Super Contributor
timestamp: October 14, 2025, 11:49:58 pm
content: Thanks for the effort, I don't have one but it is always nice to have schematics for gear out there, never know when it'll come in handy.

author: jwet
author_rank: Frequent Contributor
timestamp: October 15, 2025, 03:03:47 pm
content: Nice job on these. I didn't see anything that didn't look reasonable. That's a lot of stuff.On the toroid vs. laminated transformers, this is probably just an inline improvement, identified a toroidal supplier that was competitive and went with them. I prefer toroids especially in a lab, less leakage and usually run cooler.On the parallel and series stuff, it could just be model revision differences- safest to have the user do it too if unsure.Good luck. I've struggled through a few repairs on these. The relays that switch the secondaries are a trouble spot, if they got stuck, things will work but will get very hot and eventually burn up and take out power stuff and sometimes drive stuff.

author: RDC
author_rank: Newbie
timestamp: October 15, 2025, 03:53:42 pm
content: Welcome and Thanks.This one wasn't too horrible to muddle thru, I've just been putting off making the thing forever. I'll spend more time on it now here and there cleaning it up. Now the DRB-III scan tool, that one was a bit more 'fun' to pull a schematic out of. Two of the main boards in there are 6 layer, with the third one being a 10 layer and over 850 components on it alone. This is one of the 6 layer boards, just haven't felt like laying it out into sheets yet, but it's all blocked together ready for that to be done.The other 382270 that I have has been on the bench doing this and that jobs is the Torroid style, but still seems to be the same basic layout. It also seems to be the older version with a Green PCB and the Control board marked RS1340_23 081126, so I'm guessing there's almost a good decade between them being this one is marked RS1340_23 170225. That older one also has nice multi-turn trimpots instead of the little 3mm cermet ones this version has. At some point I'll open her up as well and note all the differences or just make a another schematic for it, as it could use a bit of attention as well.