trinityamps.com

Now that my sIII (a modified W**** TMB with Trinity/Heyboer RS Clone and PT, tube rectifier, JJ can cap) is up, working and sounding "good", I looked at voltages and they appear high.

B+ 356.6 (@ 1st can cap lug) goes to OT
B++ 332.6 (@ 2nd can cap lug) goes to the board & power tube cathodes
B+++ 331.7 (after 1st board-mounted cap) goes to power tube grids & PI plates
B++++ 314.7 (after 2nd board-mounted cap) goes to preamp tube plates

V1 (GT-12AX7-M)
P1 184
P3 1.1
P6 181
P8 1.2

V2 (GT-12AX7)
P1 216
P3 1.9
P6 315
P8 216

V3 (PI-GT12AX7)
P1 254
P2 60.6
P3 88
P6 250
P7 59
P8 88

V4 (JJ-EL84)
P3 9.4
P7 346
P8 276

V5 (JJ-EL84)
P3 9.4
P7 345.6
P8 276

V6 (6CA4)
P1 301.4
P3 356.7
P7 301.1

I do notice that I have "plenty" of headroom, but I have to turn up volume levels past 7-8 to get the distortion that I want. I assumed that most players get that distortion at around 4-5 (from postings here and on 18watt.com). So, how do I get my voltages down to a more reasonable level? I assume that I need start at B+, but there's obviously no resistor before the 1st can cap lug... What do I do? My house voltage is around 120V (119V last I chacked). Cap & resistor values on the board are fairly "stock" other than the hot rodding of the 2KR & .22mF cap that I switch-in on the preamp (from the sIII hot rodding post)...

Thanks,
dgately

B+ should be about 350. You're not far off. They do seem a bit high though.

On the sIII, you can get clean on the sIII channel almost to 5-6 - again, not far off. Try turning the Vol Up and the Master Vol down i.e. drive the pre-amp harder.

Do you have the 1K5 resistor installed across the can cap and are you taking the power to the board after that?

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

OK, sounds lke my B+ is reasonable. I'll try the Vol & MV changes (I've been tryiong to drive the power tubes:-)

Yes, I have the 1.5K (cement block 5W) across the can cap and the power goes from there to the board. Should I start to increase that resistor's value (2.5K)?

BTW: I used the amp last night in a practie session and it sounds great! I just had to use a distortion box for some solos. Kind of would like to get there without a distortion box if I could...

Thanks,
dgately

Yes, you can increase that to 2K5 max. Try 2K2. What values are you using as the dropping resistors from the 16 uF caps.

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

--Stephen said:
----Yes, you can increase that to 2K5 max.
----Try 2K2.
----What values are you using as the dropping
----resistors from the 16 uF caps?

Thanks Stephen!


BTW: HTML is not working in these post replies So, I'm not able to quote your post, add lists, etc...


OK, I'm @ work, so I'll try the 2K2 later...

I have:
• a 100R 2W on the board before the 1st 16 uF cap
- it goes to the P9s of V4 & V5
- V is 332.8V before the resistor and 276V at P9's of V4 & V5
• a 8K2 3W in series before the 16 uF cap's +
- V is 332.8V before the resistor and 331.7V @ the junction
- Not much drop for a 8K2 resistor, correct?
• 2 91K .5Ws after the 1st 16 uF cap
- they go to P1 & P6 of V3 (PI)
- 331.7V before the resistors
- 254.2V @P1 of V3
- 250V @P6 of V3
• a 2K2 2W in series before the 2nd 16 uF cap's +
- where the junction of the resistor and 16 uF cap
go to P6 of V2 (with a 100K to P1 of V2)
- 331.7V before the resistor
- 314.7 @ the junction
- 314.7V @ P6 of V2, 216.5 @ P1 ov V2
• 2 91K .5Ws after the 2nd 16 uF cap's +
- which go to P1 & P6 of V1
- 314.7V befoie the resistors
- 184.3V @ P1 of V1, 180.7 @ P6 of V1

I did not have 100Ks on hand when I was doing the build, but I did have some 91-92K .5Ws (precision resistors) that I used in place of the 100K's from the schematic and layout. I might have changed those out but am @ work and don't have the board in front of me. Could this be a problem if I left those at 91K?

Thanks again for all your help!
dgately

Now I know why my voltages seemed too high...

I had swapped the 100 & 8K2 R's on the board where the high voltage DC enters the board! Have only tried the amp at low volume (it's late) with an attentuator hooked up, but it seems to distort at a lower volume now!

Here are my voltages:

V1 (GT12AX7M)
P1: 149.6 - Normal Channel
P3: .90
P6: 147.1 - TMB Channel
P8: .922

V2 (GT12AX7)
P1: 174.0
P3: 1.544
P6: 253.2
P8: 174.3

V3 (PI) (GT12AX7)
P1: 204.3
P2: 48.4
P3: 70.8
P6: 201.7
P7: 48.1
P8: 70.8

V4 JJ EL84
P3: 11.15
P7: 335.7
P8: 324

V5 JJ EL84
P3: 11.15
P7: 335.5
P8: 324.2

V6 Recto EZ81
P1: 296.5 VAC
P3: 348.2 VDC
P7: 296.5 VAC

Thanks again for the advice,
dgately

Good news. These things happen. At least your amp is working and you found a way to clean it up LOL! The voltages now seem a tad low but test it out. Hope you like it.

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