trinityamps.com

Nice job!
Is it working at all? Have you tried it with guitar and speakers?
Don't think it would hurt anything.
Stew

It has sound, clean with very little hum etc, it just has no crunch or bite,

I think I'm missing something obvious but I've checked and double checked everything,


Cheers

Dave

Do you have a wire connecting pin 1 and pin7?

Yes it just looks a bit funny on the picture

Well I'm stumped...What tubes are you using in the preamp?

Mullard, JJ & sovtek 12ax7s,

yeah this problem surpassed my very basic knowledge a week ago

thanks for your efforts, if you have any more ideas I'm prepared to try anything right now.

Thanks

Dave

Ok, our voltages are not that bad . On V2, is pin 1 connected to pin 7? Hard to tell in the picture.
What it is the B+ voltage for the amp? If it's low, then these will be low as well.
Measure the resistance of the 2.2K 2W resistor feeding the turret connected to pin 6. If the voltage here is low, it will cause the whole tube to run low.

And confirm the resistance of the cathode resistor of ppin 8 going to ground.

_________________
Stephen
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Alright the V2 1-7 pin is connected, it had a hard life during fitting and isn't quite straight.
The B+ is 364 tubes fitted,
pin 6 resistor is 2.16k
pin 8 resistor is 58k

cheers

Dave

Have you made any headway?
Stew

I'm afraid not, I refitted the board, reflowed almost all the solder joints, the numbers are exactly the same.
I'll reserve judgement on the sound until it is fitted in the cab.

Thanks for checking in, Im grateful for the help

cheers

I just went over what we've done so far.. If you look at the layout here
viewtopic.php?f=12&t=689
You can see that the B+ and the plate voltages on the o/p tubes (pin 7) are the same. On your amp you say the B+ is 364 but the plate voltage is 354. A 10 volt drop across the o/p tranny! I don't know what thats saying but it seems strange.
Stew

I just rechecked my voltages and you are right, I'm 10/12 volts adrift from the output of the trannie.
I'd really like to start playing thru this amp but I don't want to damage it.

Ya I was doing a little reading over on 18watt.com and 5 volts across each half is not uncommon but 10-12 is a little off. I wounder if you could measure the winding resistance from the plate to ct of the tranny (both halfs). Should be anything from a few 10s of ohms to a few hundred ohms. Then we can figure the current flowing in the tranny and o/p tubes.
My thinking is that all the voltages in your amp are a little low. Also your screen voltages are quite a bit lower than the plates. 5 v lower is normal.
Maybe you could measure the voltage drops across the screen resistor and across the various "dropping" resistors in the supply rail.
Stew

Do you mind explaining what I need to do in more simple terms, this problem surpassed my basic knowledge weeks ago.

Ct to pin7 on V5 is 352ohm, ct to pin7 on v4 is 287ohm

106ohm for the resistor going to pin9 on V4/5

Cheers

Dave

Oh sorry!
Let's measure the voltage each side of the power resistor sitting across the can capacitor (1k5 2or5watt). Both sides of the 100ohm on the card, both sides of the 8k2 (near the power supply end). Now near the center of the board, both sides of the 2k2.
Now power off, let the caps discharge or discharge them youself. And measure the resistance from each pin 7(o/p tubes) to the center tap of the o/p tranny which is where the B+ is connected.
All voltages measured at DC with reference to ground
Stew

Ok I'm with you now, across the 1k5 we have stby side 364 & 335 board side.
Following the wire to the 100R 334, other side to pin9 333.5. After the 8k2 it's 276. The 2k2 shows 275 & 262 the other side.
Resistance on the trannie CT, V5 pin7 is 352 ohm, V4 pin7 is 287ohm.

Cheers

Dave

Thanks...I'll need to do some math now. But on first look I see no glaring issues.
Stew

Hi Dave.
I did some calculations and everything looks normal except that V2 issue. If you've checked all the connections at and around V2, all the resistor values and tried changing the 12ax7 at v2.....well...I don't know what's up.
You might try emailing Stephen and pointing him at this thread. Sorry you are having trouble. BTW I checked my docs for my Trinity plexi18 build and I do have 180v on those pins!
Stew

I just noticed something odd, when I plug into the TMB channel with the volume set to zero and high volume on the normal channel I hear sound, not loud but it's there. Is this normal or could this be related to my problem?

Cheers

Dave

Is it there with the TMB gain turned down too?
Probably a little "cross talk" is normal. But it should be quite aways down.
Stew