High Voltage Non-HRM 100W Build Started

[ampdork]

.015 16PS

[ToneMerc]

I'm in the homestretch, the remaining heaters, preamp board power and OT are wired up.


Not going to touch the string until the FET board is wired up.

V1 JJ83: 156/161
V2 JJ803S 177/191
V3 Sovtek LPS: 256/262V

Plates: 725V
Screens: 351V

SED EL34 seconds, I didn't want to install the Gold Lion KT77's on startup.

Bias:
V4: 27.8
V5: 30.1
V6: 28.2
V7: 24.5

[Structo]

Looking good.

I'll be interesting what you think about the high voltage plates.

[CHIP]

What's the value of those 2 Dale RS-10 resistors on the power tubes?
Are they 1k?

[ToneMerc]

What's the value of those 2 Dale RS-10 resistors on the power tubes?
Are they 1k?

1.5K

TM

[CHIP]

thanks.

[talbany]

TM
The build looks wonderful!!.. Great job.. Just to let you know your voltages look a tad bit low IMO.. I believe this is due to the higher value 50k WW dropper to the PI.. I use a 40K there as well as a 280K bleeder to set up the RC.. Brings everything more in line 220v V1 and 300V on the PI..
I would try it as is first might sound just fine at those voltages but just thought I would mention..

Good Luck!!

Tony

[ToneMerc]

Thanks Tony; I originally had a 25k in there when I was testing voltages with it unloaded, which was fruitless and for grins I then installed the 50K which was the closest value Mouser had in stock at the time. IIRC, the unloaded delta between the two was about 90V or so. I've since gotten values 33k, 37k, 40K & 47K and 820K & 750K bleeders. I ran some numbers and I don't think I'm going to need the bleeder.

I should have my FET board populated tomorrow night. Once that is connected and I see the additional loading, I'm 100% sure that that 50K has to come out. I'm going to go back and install either the 37k or 40K and then tweak the string for around 180/190 and 280-290v in PI for starters.

This power section was a great learning experience and you were a great help as well, in addition to AF . I've been working on this off and on for 2 months, figuring stuff out as I go along, while gathering parts I as go along.

I'm already planning my next high voltage build, 90% PCB based with my own high voltage PT, diferrent style bias supply and maybe a high voltage plate load 100W Marshall style OT.

Also, I have a crazy idea to run pass you too

Mike

[ToneMerc]

Man, I need two bits of hurry up because I'm slow. I finally installed the 3rd relay, FET board and swapped the 50K 10W with a 40K. Now the PI voltage is 285/291. The remaining PA string is about 15V low, but I will fix this when everything is finally buttoned up, RG174 coax might show up today.

TM

[Structo]

Looking good.

Where did you get the orange relay?

Look like Ceriatone relays?

Man, all PEC pots? Spendy!

Do you like having both PI plates at 110K?

I have 110K/ 120K with a 10K trimmer and I have to have it turned all the way one way to get a 6-7v difference.
Thought about changing those to 100K/ 110K to hear the difference.

[ToneMerc]

Tom, they came from a local surplus house, 5V NEC.

PEC- like the pots, don't even mind so much the extra cost, I hate the hassle of not being able to solder the shielded cable end to the backs of them. I wanted to try these in a Dumble style build, I'm going back to CTS and Alpha.

PI control-jury still out, won't know for sure until i make some noise and hear it. If I base it on adjustment alone I don't like the values. Yep, same here, it's bottomed out one way to get the 6V delta, the opposite way I get a as much as a 17V delta.

Mike

[Structo]

Somewhere, maybe on a schematic, it said for increased headroom, increase PI trimmer to 25K from 10K.

I don't really understand that.

#124 had 110K/ 120K with 5K trimmer.

I have 110K/ 120K with 10K trimmer.

I have that same config on my D'lite and I didn't have any trouble dialing in the change.
Weird
Could be a voltage thing.

Found the schematic.
The 101 non HRM ver. 1.4

[ToneMerc]

Yeah, I'm going to wait until I hear it to make final judgement. My RG174 arrived today, so I fire up my soldering iron and I'm out of cardas quad solder. I thought I had another 20' in the drawer. Maybe this is a sign.

Mike

[Bob-I]

I have 110K/ 120K with a 10K trimmer and I have to have it turned all the way one way to get a 6-7v difference.
Thought about changing those to 100K/ 110K to hear the difference.

It's not about DC voltage difference, it's about the AC balance. Check the Ampeg SVT method for balancing the PI, it works.

[Structo]

I know Bob but I have found that if the input side is 4-6v DC higher, I get the desired overtones.