trinityamps.com

I won't post more than a few pics, as snowy already did a fantastic pictorial AND his work looks a bit better than mine! I went a little bit out of sequence from the instructions, as I'm waiting for my IEC connector to show up today (OUT FOR DELIVERY, WHOO- HOO! ) I figured it was a good idea to not install the transformers or anything else not easily removed in case of any "metalworking" that may be needed to fit the IEC nicely.
Tag board assembled:
[img]
[/img]
Pots are wired except for the flying leads. Really, all I have left to do is install/wire the transformers, do the heater wires and mount/wire the board. Should be testing today. This is a 3 day build!
My sincerest thanks to Stephen for a well thought out package/kit. I am soked to hear this little brute!
Thanx Again,
Gene

Good progress. Take your time!

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

Stephen,
I assure that I am not rushing, but I am currently off work so can devote full time to this project. Each session is started by going over and re-checking the previous session's work.

So,,,,
Mains (wall) power is 122 VAC, no tubes installed
Heater:
3.55 VAC from each leg to ground
7.10 VAC across the legs

Transformer secondary:
330 VAC each leg to ground
660 VAC across the legs

DC voltage at first 50 uf filter cap:
448 VDC

Filter caps are getting warm, but not hot. I realize that my wall voltage is a bit high, by about 6%, but the heater voltage is more than 12% above expected. I suspect that I'm within the ballpark but would appreciate some guidance or assurance before continuing.
Thank You,
Gene

That's Ok to get you going, we can drop the heater voltage a bit later once all the tubes are in and running.

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

WOW!
Thanks for such a quick reply. While I certainly realize that eagerness on my part should not be considered an emergency on your part, I'm truly appreciative AND impressed. I'll continue fire up and post my results.
Thanx Again,
Gene

Well....
At this point, voltage on second cap is at 427 VDC but does not increase with turning of the VRM pot. While tubes were still warmed up, I did confirm that the amp was passing signal, albeit at a fairly low level, as I would expect with the VRM set to minimum. I also confirmed that all volume and tone pots functioned as expected. I have checked all connections twice and all is well there. I don't know how to test the MOSFET? Is there a couple jumpers that could be installed in place of the MOSFET and pot to effectively "bypass" the VRM function for the time being? In case the MOSFET took a dump or.....
Thanx,
Gene

That voltage is about rights or max voltage. When We did the voltages on the layout,we set the VRM to 400. Does the VRM make any change when turned? Is the Zener diode in the correct way and are the wires to the control pot correct?
Can you take a picture of the VRM part of the the board?

Bypass the VRM: Pull the 100R off the board at the MOSFET side, and jump that lifted end to the positive end of the first 50uf power supply cap.

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

I had the terminal 2 & 3 wires reversed at the pot. Fixed that and now with the pot at "idle" I get 457 VDC and as I turn the pot clockwise the voltage "drops" to about 430 VDC.The picture I'm attaching could not be gotten any clearer. If you look at the pic in my first post of this thread, it is clearer. The black band of the Zener is attached to the 100K resistor and the other end is to the junction of the 5R & positive of the first filter cap. Is there a chance that the pin-out order of this MOSFET is different than on the on the layout. Being an idiot, I simply went by the layout for orientation rather than actually looking at the MOSFET for G, D & S markings.
Thanks,
Gene

So, being that there's no smoke, funny noises through the speakers (this amp is silent , even when cranked, no hum, no hiss,no...) so I felt safe to at least take some measurements. And somehow, I forgot the info about MOSFET testing! Will test that soon. The following readings were taken with tubes installed and fully warmed up. Wall/mains in the evening 124.2 VAC. They were also taken at each point withVRM pot at minimum and at maximum and the readings noted as such:

Caps & Junctions Taken At Positive-Min/Max
500uf #1) 48.3-VDC min/425-VDC max
500uf #2) 459-VDC min/432-VDC max
Junction of 1000uf & 750ohm) 2.86-VDC min/30.5-VDC max
33uf #1) 48-VDC min/422-VDC max
33uf #2) 43.8-VDC/353-VDC max
Junction .022uf, .01uf & 56K) 32.5-VDC min/199.4-VDC max

12AX7-Min/Max
#1) 34.2-VDC min/194.8-VDC max
#2) -0.795-VDC min/1.1-VDC max
#3) 115.1-mvDC min/1.956-VDC max
#4) 3.53-VAC min/3.51-VAC max
#5) 3.53-VAC min/3.51-VAC max
#6) 32.8-VDC min/201.6-VDC max
#7) -0.692-VDC min/0.004 mvdc max
#8) 137-mvDC min/1.911-VDC max
#9) 3.53-VAC min/3.51-VAC max

6V6-Min/Max
#1) 0.1-mvDC min/0.1-mvDC max
#2) 3.53-VAC min/3.51-VAC max
#3)48.4-VDC min/422-VDC max
#4) 48-VDC min/421-VDC max
#5) 0.8-mvDC min/25.2-mvDC max
#6) 0.8-mvDC min/24.4-mvDC max
#7) 3.53-VAC min/3.51-VAC max
#8) 2.872-VDC min/30.59-VDC max

It seems odd that the readings we were expecting on positive of the #2 cap are opposite and the kinds of readings expected on #2 cap are actually occurring on #1 cap. The fact that voltages are changing leads me to think that the MOSFET is indeed working, just giving backward readings on cap #2????? The amp and VRM appear to work and function (except for the measurements) as expected, although I have not yet plugged a guitar into it to avoid stressing it in case something is really out of whack. The mains voltage in Las Vegas can typically fluctuate between 120-VAC and as high as 125 VAC.
Please let me know your thoughts.
Thanks Again,
Gene

Cap 2 is in fact the first cap in the schematic before the VRM. So when you lower the voltage for the rest of the amp, it can go up as there is no load on it. Voltages look OK and yes, the VRM is working.
Time to play!

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

To reduce heater voltages, see viewtopic.php?f=12&t=3598&p=28370#p28370

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

Stephen,
Just a few questions:
A-Do you have a part number/brand or cross reference able number for these diodes?
B-Would it be best to locate them between the transformer and terminal strip (effectively reducing the voltage to the LED as well) or better to locate them after the strip to just reduce the heater voltage?
C-What voltages should I be looking for with a 6L6 and where? I have a pair of new Sovtek 5881/6L6WGC. I know you recommend a Winged "C", but I have these on hand.

I did try installing one and it sounded pretty OK but then I got a lightning flash in the tube and removed it. I suspect the tube is faulty right out of the box.

So far the amp sounds great for what it is, although I'm a bit underwhelmed/disappointed, as I expected to see a tad more available gain/overdrive capabilities. Running everything floored in Tude/Fat modes gets me close, but not quite to what I'm shooting for.
Thank You,
Gene

????????,
I just noticed that these Sovtek 5881/6L6WGC tubes have no pin #1 or pin #6! Is this common for 6L6 tubes? Or is this an incompatibility issue? How does it reference ground and how would it access the master volume?
Thanx,
Gene

Those pins are not required for 6L6. No, I don't think it's common!

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

A-Do you have a part number/brand or cross reference able number for these diodes?

1N5401


B-Would it be best to locate them between the transformer and terminal strip (effectively reducing the voltage to the LED as well) or better to locate them after the strip to just reduce the heater voltage?

Between the transformer and terminal strip.

C-What voltages should I be looking for with a 6L6 and where? I have a pair of new Sovtek 5881/6L6WGC. I know you recommend a Winged "C", but I have these on hand.

400 V with VRM on max, rest as published on the layout/schematic.

So far the amp sounds great for what it is, although I'm a bit underwhelmed/disappointed, as I expected to see a tad more available gain/overdrive capabilities. Running everything floored in Tude/Fat modes gets me close, but not quite to what I'm shooting for.

Try a higher gain 12AX7 like a Chinese version. It does take pedals well tho. The gain seems sufficient for most people, so maybe check the switching? Maybe you need to add a second 12AX7 gain stage?

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

Stephen,
All appears to function correctly with the supplied 6V6 power tube, but I'm having a problem attempting to run a 6L6. I'll recap my understanding of schematic/layout, please correct me if I'm wrong:
A-In 6V6 mode, pin #8 sees 750R to ground.
B-In 6L6 mode pin #8 sees 570R in parallel (via DPDT toggle switch) to that 750R for a total resistance of about 323R to ground.
C-The flipping of this switch is all that is required to swap from 6V6 to 6L6 use?
D-Swapping to the different impedance tap of the output transformer is NOT required for 6L6 use and is only needed for EL34, etc.

With amp off/unplugged/tubes removed/caps drained, I confirmed the operation & orientation of DPDT switch and resistors from ground junction of 570R & 750R resistors to power tube pin #8. coincidentally, I got the same reading from pin #1 to pin #8. This confirms good connection/continuity. Upon installing the first 6L6, there was a dramatic change (for the better) in the character of the amp in both volume and sound. After playing through the amp for a minute or 2, I saw, what seemed to be a couple of lightning type flashes in the 6L6 so I turned it off immediately. These flashes did not cause any audible sounds, but a few second after occurring, the sound dropped out and then came back just before turing the amp off. At that point, I conjectured a faulty tube, but checked all connections and compared schematic and layout to the amp. All looked correct. I put the 6V6 back in, tested all points confirming that voltages all matched my initial tests. I played through the amp, cranked, for 45 minutes or more and checked for any heating issues. I was surprised that the first 2 filter caps did not seem to get as warm to the touch as they did when testing with no tubes? All seemed well so I decided to install the other new 5881/6L6, and it sounded great, for a minute or 2, and although I noticed (watching carefully/closely) no lightning/flashing, sound cut out and then came back with some odd sounds in between. This sounded somewhat similar to what you would expect to hear if someone unplugged the power cord and then plugged it back in. I'm not sure where to start searching or what kind of problem to search for. I have already checked layout & schematic and have checked continuity throughout. I will post all power tube pin readings with a 6L6 installed, but suspect that both of the tubes I have may have gotten fried by whatever the issue is. There has been no fuse blowing. FWIW, I don't use pedals, so gain is an important part of the picture for me.
Thank You,
Gene

Pins on 6L6 min/max on VRM:
#1) 0.0-VDC min/0.0-VDC
#2) 3.49-VAC min/3.42-VAC max
#3) 46.4-VDC min/388-VDC max
#4) 46.2-VDC min/387-VDC max
#5) 0.2-mvDC min/1.1-mvDC max
#6) 0.1-mvDC min/0.1-mvDC max
#7) 3.49-VAC min/3.43-VAC max
#8) 2.75-VDC min/27.25-VDC max

Main caps +positive:
C11) 2.749-VDC min/27.15-VDC max
C12) 47.6-VDC min/395-VDC max
C13) 450-VDC min/407-VDC max
Thanx,
Gene

Everything you listed on the theory is correct. If it works in 6v6 mode, flipping the switch to the 6l6 cathode pair should be a no brainer. I cant think what might be the issue. This is a new symptom.

For gain, you can increase the cathode cap in that position up to 25 uf max. from .5 or decrease the cathode resistor in the tude mode to suit.

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

Well,
I played for 10-15 minutes with the 6L6 and starting with the power level low and gradually increased level until wide open.All was well and working fine until within less than a minute of being cranked, the amp cut out completely, did not come back and had a low hum through the speakers and I smelled that tell-tale electrical burning smell and turned it off promptly , unplugged, quickly discharged all caps and started feeling for heat, looking for burn marks/source of smell. There was no visible smoke and the fuse did not open. All three resistors surrounding the octal socket were pretty hot as well as the resistor across the to +'s of the two 33uf caps. Transformers were not hot. Removed the 6L6 and put the 6V6 back in and amp performed as it had previously with that power tube. After some time of letting the smell clear, there was not even a hint of the burning smell in the amp chassis, but the 6L6 (which I intentionally had moved to the other side of the room) stilled smelled strongly of that electrical burning odor. something is just not right when fully cranked with the 6L6, but I have no issue when cranked with the 6V6. Not sure where to start my search. Possibly 2 bad, matched tubes right out of the box? Seems kinda far fetched. At this stage, increasing gain, especially in 6L6 mode does not seem like a wise move. Your thoughts, comments and advice are welcomed.
Thanks,
Gene