trinityamps.com

Hey guys!
So I just completed my tc15 kit. This was my first amp build, and I'd never done anything this complex electronically before.
I quite enjoyed the process and I'm thinking I want to build another amp already

The amp fired up just fine first try, but I noticed that the v4/5 screen voltages were way low, as well as the cathode voltages. I tested around for a bit, and realized that my 22k resistor supplying the screens was probably dead, or I had a bad solder joint. I removed the resistor, and sure enough, the resistance was over the 2M ohm limit on my multimeter. I threw in another 22k resistor I had laying around, and all was well. I know it's probably only 1/2W, but it's just temporary until I can find/order another 2W 22k.

I'm running the amp through a Celestion Greenback in an open back cab. The amp sounds great, but I have a few uncertainties.
- When I turn up either of the channel volumes past 9:00 , I get a fair bit of hiss. This is with the master volume bypassed, so by this point, the guitar is way louder than the hiss. I'm assuming this is just due to the carbon comp resistors?

- There is quite a volume difference between the two channels. The ef86 channel at 9:00 volume is a fair bit louder than the top boost channel on full. Is this normal? As it is, I think the volume difference would be too large to switch channels using an a/b pedal mid-song.

- With the vrm turned down past half, my channel 2 volume pot gets a bit scratchy. With the vrm on low, I measured 0.38vdc at the volume pot. All other pots have no dc voltage and are not scratchy.

Here are my voltages:
B+ - 373

V1
1 - 114v
3 - 1.40
6 - 114
8 - 1.40

V2
1 - 156
3 - 1.35
6 - 270
8 - 159

V3
1 - 237
2 - 24
3 - 64
6 - 240
7 - 24
8 - 64

V4
3 - 7.5
7 - 368
9 - 230

V5
3 - 7.5
7 - 367
9 - 230

V6
8 - 284 (in standby)

V7
1 - 70
3 - 1.78v
6 - 100
8 - 1.78

Nice job, looks great! I had the same problem with the scratchy pot on the EF86. Did you add the 1M resistor to ground on pin 9?

Thanks! I left the 1M resistors to ground at the input jacks instead of the relocation to the input tube pins.

The amp has a home!

I just finished the cabinet that I had in the works for the tc15. I have to say, it turned out better than I expected.
The structural design is somewhat based on an old Traynor YRM Reverb Master I've got, so the bottom panel can be removed with four screws to allow access to the guts without having to remove the chassis from the cabinet.

Did ypu put a .1 DC blocking cap in the EF86 channel? Needs to be the same as the other channel to block DC at low VRM settings. And do recommend the 1M get moved as well.

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

Yep, I did put the .1uf in for both channels' input tubes. That only would be blocking dcv to the guitar itself though, right? It's actually the top boost channel volume on the amp itself that is scratchy.
I'll try relocating the 1M resistors tonight.

Okay, so I relocated the 1M input resistors to the input tube pins, but nothing changed. The ch2 non-ef86 volume pot is still scratchy and has 0.36vdc with the vrm turned all the way down, and about 0.16vdc with the vrm at half. I also have a quiet 60hz hum in that channel, but I'm planning on swapping some tubes around to see if it's just a noisey tube. All of my ground connections have been double/triple checked.
I figured out that the volume level difference between the two channels is affected by the vrm. At lower vrm settings, the ef86 channel overpowers channel 2, but they even out at higher vrm settings, so it's all good.