IS my PSU problematic?

[Osvaldo de Banfield]

OK, 10.04‼

 

[youknowyou]

ok, sorry for the delay!

so 100k and 470r installed

its similar results:

8 ohms with input signal 1 Khz.

V4-1 et V4-6 120v p-p before distortion
V2-3 et V3-3 200v p-p with distortion

Output Transfo T2 20v p-p. we have about 4.5Wrms output

 

[Osvaldo de Banfield]

Well, slowly it goes good. What about cathode bypass in the first stage? What about increasing still more both (anodes and CCS) resistors proportionately?

 

[youknowyou]

what should I try first?
so I can go from 100 k to 200k and 470r to 940r?

 

[youknowyou]

What about bypassing the cathode resistor of the first stage (220R) with a large capacitor, say, 1000µF 25V

should I also do this?

 

[Osvaldo de Banfield]

Try both, but one at a time, and check intermediate results. Keep us posted.

As a general rule, never use such low plate resistor values with many valves/tubes, mainly in preamplifier/driver stages. Suggest to read the article at #38.

 

[youknowyou]

What about increasing still more both (anodes and CCS) resistors proportionately?

sorry for long hiatus. my tech is super busy

I need to order resistors. what is the maximum resistor at both the anode and CCS resistors i could install?
can I go from 100k to 400k and 470r to 1880r without any risk for example?

for bypassin the cathode resistor of the first stage, should I order other values then the 1000uf to experiment?

 

[Osvaldo de Banfield]

Yes, maintaining the ratio between resistors, any pair will work fine, the increasing load resisto, the increased gain, to the point where the load resistor is about ¼ the following grid resistor. Then, any further increase will be even
and even unnoticeable.

Respect to the cathode bypass, 100 to 220µF is sufficient, although 100 is better.

 

[youknowyou]

Yes, maintaining the ratio between resistors, any pair will work fine, the increasing load resisto, the increased gain, to the point where the load resistor is about ¼ the following grid resistor. Then, any further increase will be even
and even unnoticeable.

Respect to the cathode bypass, 100 to 220µF is sufficient, although 100 is better.

k for the cathode resistors

im confused, didnt you suggest to install a 1000uf cap for the bypass? so i should rather order 100uf 25v over 1000uf?

 

[Osvaldo de Banfield]

Sorry, I made a typo. I suggested 1000µF although 100µf is a good start. As you said that you need to order one of 1000µF, but you have at hand somewhat about 100 to 220, it can work for the test without spending money nor time.

 

[youknowyou]

ok ill order 100 uf, 200 uf and 1000uf.

thanks!

 

[Osvaldo de Banfield]

As you want‼

 

[youknowyou]

my tech redid the test and for some reason realized he had made mistake in the measurements with V5 bypass 220 ohms with 1000uF-25v.


input is constant for all values with 1v p-p and a charge of 8ohm

he retested
V4 15K x 2 (anode) and 75 ohms (LM317), then 47K (anode) et 220 ohms (LM317), then 100K (anode) et 470 ohms (LM317).

he always get, more or less, the same result: OUTPUT 5v rms ----> 3.1 watts rms without distortion

the distortion appear around L1, V2 and V3

so it appears increasing the cathode resistor and css dont increase my power at all.