[SonicTrance]

Weirdly enough, putting the those 2 in the correct places, instantly improved the bias gap.



Yes, to ground. I have not tried across yet. Since the resistance values were on point

Im sure its getting confusing for most. Since there arent particular resources consolidated enough for people to be able to troubleshoot on their own. And most senior members are super busy to be able to help. I can move this over to PM's if it helps?

That is kind of strange.

No reason for PMs. Its good to keep the thread alive. Just think we should be as accurate as we can when we post. Im glad the amp is working, finally!
Now you can go back to work on your own amp.

 

[bloodhawk]

That is kind of strange.

No reason for PMs. Its good to keep the thread alive. Just think we should be as accurate as we can when we post. Im glad the amp is working, finally!
Now you can go back to work on your own amp.

Yeah, next on the agenda is adding better quality sockets, along with swapping out the transformer and output wiring!

Before that though i need to swap out the pot and the busted left channel ammeter in his amp. At least for now the gap in voltages has dropped down all the way from being 5-7V apart to 1.3-3V at the most.

 

[baronbeehive]

Im glad the amp is working, finally!

+1

I can also volunteer to do a full write of these things, with pictures and warning, if anyone is willing enough to guide me and explain things.

That's quite a good idea, I get tired of repeating warnings all the time. Also it takes a while to familiarize yourself with the insides of the amp and a quick guide would help. See what Maxx thinks.

Before that though i need to swap out the pot and the busted left channel ammeter in his amp. At least for now the gap in voltages has dropped down all the way from being 5-7V apart to 1.3-3V at the most.

So did you take voltages, if you took them on both sides of the reference points it would help to pinpoint issues.

 

[bloodhawk]

So did you take voltages, if you took them on both sides of the reference points it would help to pinpoint issues.

Yeap, new voltages are 80V / 79.8V / 79V / 79.8V / 77.8V / 78V / 79.6V / 80V

For now hes super happy with the amp , i have 2 new ammeters coming in along with a new pot and new better quality tube sockets. Ill be replacing those in a week or 2, plus the heater wiring coming from the transformers. I really feel that those need to be better.

 

[baronbeehive]

Yeap, new voltages are 80V / 79.8V / 79V / 79.8V / 77.8V / 78V / 79.6V / 80V

For now hes super happy with the amp , i have 2 new ammeters coming in along with a new pot and new better quality tube sockets. Ill be replacing those in a week or 2, plus the heater wiring coming from the transformers. I really feel that those need to be better.

That's looking good bloodhawk!!

What pot are you going to use? Did you check if it would fit?

 

[bloodhawk]

That's looking good bloodhawk!!

What pot are you going to use? Did you check if it would fit?

Its the same Pot, just pretested to make sure that there is not channel imbalance. However for my own amp im getting a TKD 4CP-2500, that ill mount on a custom PCB. I wanted to go with a stepped attenuator, but i really prefer granular control.

 

[SonicTrance]

Which resistors are you referring to? Only 300R resistors I can think of are the grid resistors and the 470R are ground references for the grids. Got nothing to do with bias?

Sorry, my mistake. There's no 470R resistor that I'm aware of? The ground (B-) reference resistors is of course 470K. So you only had 300R to B- instead of 470K. That must be what messed up the bias. The actual grid resistor should not affect the bias at all.

 

[bloodhawk]

Sorry, my mistake. There's no 470R resistor that I'm aware of? The ground (B-) reference resistors is of course 470K. So you only had 300R to B- instead of 470K. That must be what messed up the bias. The actual grid resistor should not affect the bias at all.

These are the ones im referring to - https://imgur.com/a/JHfT2

He had the 2 on the far left swapped around.

 

[SonicTrance]

These are the ones im referring to - https://imgur.com/a/JHfT2

He had the 2 on the far left swapped around.

The ones you circled are not the same type. Look at this pic from first page:

The resistors circled in yellow are 300R grid resistors. The 470K's are not circled but are the other ones right above the tubes.

 

[bloodhawk]

The ones you circled are not the same type. Look at this pic from first page:

The resistors circled in yellow are 300R grid resistors. The 470K's are not circled but are the other ones right above the tubes.

Whoops yeap my bad. Dunno why i always mistake the layout as mirrored/symmetrical.

But the ones of the far left top of the tube were in swapped positions.

 

[Maxx134]

Asa the relays kicked in there was a pop and bye bye Zener. All because of a brittle B- Base wire.

Yeah but its interesting to see the board is now black..
Ha maybe they don't want it traced ha.

plug in headphone hear nothing at all, any help is much appreciated, thanks anyway!

You are only one left with Problem.
I am pretty sure the protection circuit kicked in.
This means you need to re-check everything that you did before.
What did you replace?

Yeah, next on the agenda is adding better quality .....along with swapping out the transformer ....

NO,
nobody mentioned anything about a transformer here...
There are no output Transformers,
And these transformers as PSU only and are specific.
SonicTrance posted a schematic of it.
They cost about $80 US from Little dot and take almost a month in shipping.
You don't want to mess with them.
You can upgrade your PSU other ways if you like but all most noticable upgrades would be the ones mentioned already,
And the driver bias setting(depending on tube) that hasn't been settled on.

That's quite a good idea, I get tired of repeating warnings all the time. Also it takes a while to familiarize yourself with the insides of the amp and a quick guide would help. See what Maxx thinks.

Sure as I have way less time now,
Whoever feels they like to contribute I would paste it in first page.


Baronbeehive I see your doing a nice work in finding out best bias points, just remember there are many points that will sound good .
Your going to have to get a bunch of reaistors to test your bias points with listening.

 

[bloodhawk]

NO,
nobody mentioned anything about a transformer here...
There are no output Transformers,
And these transformers as PSU only and are specific.
SonicTrance posted a schematic of it.
They cost about $80 US from Little dot and take almost a month in shipping.
You don't want to mess with them.
You can upgrade your PSU other ways if you like but all most noticable upgrades would be the ones mentioned already,
And the driver bias setting(depending on tube) that hasn't been settled on.

Wiring coming from and going to the transformer. Not the transformer itself. I actually checked with LD a while back and they said they can ship replacement transformer through DHL which take about 3 days to get here and costs under $20 (for shipping).

 

[baronbeehive]

Yeah but its interesting to see the board is now black..
Ha maybe they don't want it traced ha.

No.... it's so you can't tell if it's burnt lol.

Wiring coming from and going to the transformer. Not the transformer itself. I actually checked with LD a while back and they said they can ship replacement transformer through DHL which take about 3 days to get here and costs under $20 (for shipping).

Looks like Maxx got a bum deal there!

Baronbeehive I see your doing a nice work in finding out best bias points, just remember there are many points that will sound good .
Your going to have to get a bunch of reaistors to test your bias points with listening.

Well just trying to catch up on what you and Sonic did a year or two ago, when most of that stuff went over my head!

I've put my order in for the parts for the CCS mod and the driver bias tweaks. The load lines and operating points are pretty much as I put in the last graph, I will reuse the 1.5K cathode R, try a 1K like you did but with different load lines, and a 390R that I have in atm, like Sonic, but again with different load lines. That should give a reasonable spread as you can see in the graph.

I'm hoping to hear differences now that I'm reacquainted with the sound of the amp after some time.

Edit: Probably won't be using your 1 ear trick though.

BTW how much extra B+ did you get with a 1K 3K3 R?

 

[Maxx134]

BTW how much extra B+ did you get with a 1K 3K3 R?

This is an important aspect as the driver tubes are essentially staved for B+ so I strongly recommend to swap out your 3k3 to the 1k ohm that both me and I believe Sonic using.

Also interesting to note is that on my stock unit it was already droped to 2k2 and when I asked "Little Dot" US rep,
it took a while, but my response was "for stability" ,
Which now we know is not really the case at all but instead to give slightly more B+

The actual PSU voltage at the anode Resistors is dependent upon the driver tube plate resistance, or to view another way, it is the load the tube imposes onto the PSU which is not regulated in any way, will vary.

As I stated before,
The fact that you already upgraded your driver stage by replacing the tiny 33uf with some nice decoupling film caps will offset any changes to the 3k3 Resistor which is performing the function of a RCRC filter for PSU.
The stock 33uf electrolytic was the last "C" of the RCRC circuit and the 3k3 is the second "R".
The first "RC" is located in the driver PSU.
Very old school design bu hey it is clean and works.

 

[Maxx134]

Forgot to add the voltage varied in my testing about 15v,
So not a huge increase, but did make a difference sonically as changes to the B+ affect the bias points