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Good morning all. New to the forum but I'm building an OSD for a friend so I figured it's time to sign up. I've built a couple of Trinity 5E3's and a Tramp. I've also serviced and built many amps from scratch, mostly Fender circuits.

Anyway, last night I got the board populated. I noticed an extra .02mfd capacitor. The parts list shows 14 OD caps as well but the amp only uses 13 far as I can tell. I briefly jumped ahead to the pedal circuit but didn't see anything there either. The only .02mfd cap I see goes to one of the grids on V3.

Note - I'm reluctantly trying to self discipline by going through the instructions rather than just going by the schematic/layout.

GW

Heh... this is a good place to develop that self discipline. Pretty close to being my most complicated build to date. Proper layout and lead-dress is critical in a D-Style build and the instructions absolutely make sure that is done right. While Dumble circuits have their roots in Fender-ish designs, they certainly raise the complexity bar quite a bit, especially in the EQ and preamps. While I am pretty comfortable doing a build by layout/schematic and even doing my own custom layouts, this is one build where I stuck to the step-by-step instructions and it paid-off in a working amp right out of the gate.

Also, there's no way you'll figure out the relay boards without the instructions, and even then it can be a little confusing. Probably the biggest source of issues that come up here?

As far as your capacitor goes... I'd have to go back and check the guts of my build.

Yes, the relay board, rock/jazz switches catch people. The foot-switch is fiddly, I would like it to be easier.
Rest is pretty basic, just follow manual as recommended!

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

This build is a little meticulous but not as bad as a Peavey Triumph 60. I recently did a complete service on one, new caps, etc. PCB's stacked like an Oreo cookie.

It's inching along. I should be able to start checking voltages mid week.

GW

Sweeet. Looks like you know what you're doing there! Nice job.

Good progress!

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I think I'll do some experimenting when this is up and running. Zip ties are cheap. I may do an A/B test for noise with some of the leads zip tied together, like the run of the few coax from the controls. Tidy things up in the chassis and see if it makes any difference. A quick clip with the cutters reverses anything. Maybe somebody has already gone this route?

GW

Finished up the amp today. I'll power it up tonight and get some readings and if all is well I'll start on the cab tomorrow. I used 18 gauge solid heater wire on the inside of the pedal through the solder tabs with about an extra 1/2" angled down to the LED's. I carefully opened up the tabs on the switches to accept the larger gauge. The larger wire diameter does a good job of holding the LED's firmly in place.

I also went with a Switchcraft style input jack vs the Cliff. I did have to drill the hole out to accept the isolation washers for the new jack. You have to use a L12A (long) shorting jack.

GW

Amp is up and running, nice and quiet. My voltages are all a bit low though. The heater voltage is good at 6.6vac. My household current measures 121vac. I also need to bump up the bias current for the 6L6GC's.

GW

OSD Voltages
B+1 = 436vdc
B+2 = 429vdc
B+3 = 422vdc
B+4 = 293vdc
B+5 = 284vdc
Bias Current = 36mv

V1
Plate 1 = 190vdc
Plate 2 = 188vdc
Cathode 1 = 1.46vdc
Cathode 2 = 1.48vdc

V2
Plate 1 = 193vdc
Plate 2 = 195vdc
Cathode 1 = 1.55vdc
Cathode 2 = 1.54vdc

V3
Plate 1 = 302vdc
Plate 2 = 300vdc
Grid 1 = 37vdc
Grid 2 = 35vdc
Cathodes = 57vdc

V4 6L6GC
Plate = 433vdc
Screen = 431vdc

V5 6L6GC
Plate = 433vdc
Screen = 431vdc

Finished up the cabinet on this build. The customer wanted more of a rustic look (minus the slivers) with a 15" speaker. I'll give it a polish in a couple of days and should be ready to go. Great sounding versatile amps.

I know I'm late on this thread, but I just started my OSD build and I have to ask. Why did you omit the 150k/2watt bleed resistor from the filter capacitors? I've never known this to be a tone issue and it's a great safety device.

This is an excellent environment in which to hone your self-discipline. This is probably going to end up being my most difficult construction to yet. With a D-style construction, getting the layout and lead-dress correct is very important, and the instructions make sure that it happens correctly every time. Despite the fact that Dumble circuits stem from Fender-like design principles. Why did you leave out the 150k/2watt bleed resistor that was supposed to be in the filter capacitors? To phrazle my knowledge, this has never been a problem with the tone, and it is an excellent preventative measure.

It can draw down the voltage so if voltages are low, you can remove it.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Curious how that 15" speaker sounds!