Help needed with dropping string

[Ed de Jager]

Hi,my voltages are way off and i`m afraid that adjusting the dropping string is a bit above my head so help would be greatly appreciated.
Voltages are:
After 500Ohm resistor:407V,
After 1K:400V,
after 10K:368V,
after 2.2K:362V.
V3-1:306V,
V3-6:279V,
V2-1:230V,
V2-6:279V,
V1-1:228V,
V1-6:227V.
P.T.gives 300-0-300@0,2A and6.3V@6A.

Thanks VERY much in advance,Ed

[Bob-I]

Do you have the 150K load to ground at the end of the string? Your measurements look typical of this load missing.

[Ed de Jager]

Thanks,no i have not.
It was said the dropping resistor was not neccesary with a 300-0-300 PT.
It will be rather difficult to put it in too because i used the original Dlite powerboard which had no dropping resistor.
To put it there i guess i have to dismantle the whole powersection to put in the two missing turrets so i am hoping for an easier solution.

Ed

[Robert]

Just for debugging purposes try the 150K resistor. If it solves your voltage issue, very likely you can figure out a way to mount the resistor to ground without putting it on your PS board, e.g. terminal tree. If it doesn't solve your problem you can consider other possibilities.

[Funkalicousgroove]

Are these voltages with or without tubes in it?

THey don't look too far off, FWIW I don't know where you got those resistor values but they're not right!

Non HRM is (CHOKE OR RESISTOR) 2K2,22K, 1K 0r 2K2

HRM is (Choke or resistor) 3K, 12K or 15K, 10K

If you don't have an FET input you also need to put a 150K-220K to ground at the node of the V2 plates to drop the voltages to the correct range.

[Ed de Jager]

Sorry,the voltages are with the tubes in their sockets.
I`ll try the resistor as you all suggested and see what it does.
Hopefully i will have a bright moment and find a way to connect it too

Ed

[Ed de Jager]

Again sorry i forgot to mention it`s a Dlite.
I got the resistorvalues from an earlier post from Normster.
In that thread it was also mentioned that there was no need for a load resistor.That`s why i did it this way.
Ed

[Funkalicousgroove]

post a pic, there's gotta be somewhere!

[Ed de Jager]

I guess i had my bright moment;it is actually very simple to place the resistor with the 2,2K resistor in the turret and then accross the 22uF cap into the turret of that cap.
I will try a few resistors using alligator clips and see what it does.
BTW does anyone know how many watts the big reddisch-brown resistors are that Marshall used to use?
I have quite a few of them but don`t know if i can use one of them in this position.
Thanks in advance,Ed

[drew]

According to Rocco,

Yes, the dropping string goes; 1K, 22K, 2.2K The middle one is 22K, not 10K

[Bob-I]

Thanks,no i have not.
Normster said the dropping resistor was not neccesary with a 300-0-300 PT.

That may be correct, only your voltages don't show it.

It will be rather difficult to put it in too because i used the original Dlite powerboard which had no dropping resistor.
To put it there i guess i have to dismantle the whole powersection to put in the two missing turrets so i am hoping for an easier solution.

Ed

No you shouldn't need to do that. First test by soldering leads onto a 150K 2 watt resistor and soldering them across the last cap in the string. If that gives you the voltages I'd lift the board and solder the 150K under the board to the turrets of the last filter cap. I've done that before successfully.

I've found that in addition to adjusting the voltages, this resistor changes the feel of the amp. I like it.

[Normster]

I think Ed is referring to the original 6V6 build that I did using Moose's Trainwreck iron. The dropping string on that one used 1k/10k/2k2 with no resistor to ground and the voltages were correct...BUT it also used a 5AR4 rectifier. I would start by upping the 10k to 22k and then add a 470k tail to ground if needed. (Sorry, didn't do the math, but using a 325-0-325 PT only requires a 220k to bring the plates in line. I figured a 300-0-300 would need a higher value.)

[Bob-I]

I.....Sorry, didn't do the math

Math... we don't need no stinking math.... just tweak till it soulds good.

[Ed de Jager]

I was talking about these resistors.Anyone familiar with them?
Sorry for the bad quality of the picture

Ed

[ampedup]

i have some that look like that, i'm pretty sure mine are 1 watt CC.