Hello to all!

I just got on the forum, I am French and I am passionate small assemblies regenerative receiver!

On the attached diagram I want to replace the tubes and 6SK7 6Q7 by miniature tubes, tubes I have 9001, 9002, and 9003 or 954 955 acorn tubes and 956!

But I do not know how to calculate the new plate resistors of the two tubes!

The high voltage is 200v general!

Thank you for the info beaucoop!

cordially

tech

Tech,

I think that the original plate resistors should be OK to use with the new tubes.

The 6SK7 and 6SQ7 stages both employ "grid leak" bias. This does not result in a very predictable plate current, anyway, so it would be difficult to calculate new values for the plate resistors. I would try the circuit with the present parts values, then possibly adjust the grid leak resistor values to get 60 to 120 V on the plates.

A higher value grid leak resistor should result in reduced plate current, and increased plate voltage.

Note that the 6SK7 is shown connected to act as a triode, so you could use a triode in its place.

You seem to have a number of antique parts. Do you really plan to use a field coil speaker?

Please keep us informed about your progress on this project.

Ted

Hello!

Thank you for your answer!

Yesterday, I found the following diagram with a tube 955, the high voltage is 90v requested, so you have reason high voltage between 90 and 100V for the first tube!

What I do not understand is the high value of 200k for the tubes 6Q7??!

I also recovered datasheet tubes 9001, 9002, and 9003, and I also found that they are equivalent to the acorn tubes 954, 955 and 956, I also have these tubes and I think I will use because it is funny!

I'm going to put a tube 955 or 956 input, and place the tube 6Q7 I do not know, maybe a tube 955, and a 6AQ5 output tube!

Otherwise I made the coils to receive longwave and shortwave, photos attached below!

I will keep you informed!

Thank you!

Tech

Hello!

On the datasheet of the tube 956 is the plate current of 6.7 mA, the screen current is 2.7 mA!

If I mount the tube triode is it necessary to add these two to calculate the current load resistance??

If the tube 956 is supplied with 100V plate (triode) is that the flow rate remains the same for the plate and the screen??

http://frank.pocnet.net/sheets/049/9/956.pdf

Thank you!

Tech

Well, yes and no. The shown plate curves are with screen fixed at 100V and when wired triode that will no longer apply so those curves don't tell you how it will behave in triode mode. You need the triode curves which, unfortunately, they do not provide.

That "6.7 mA" is at a specific grid bias and will be lower with grid more negative (look at the bottom graph on that page). They pick that point because, as a general rule, gm increases with current (within limits) and a lower current would not look as good in the specs but you don't have to operate it there.

To answer a previous comment, 220k is not a particularly 'large' value for the 6SQ7 and I've seen radios use over 1 Meg. It depends on the bias which, as someone else mentioned, is always a grid leak (as high as 10 Meg)

At the vertical line where plate is 100V, since screen is fixed at 100V, the 'triode current' will be the sum of the plate and screen currents you see in the graph. But that is the only place that will 'match' because at all others plate and screen are at different voltages.


http://frank.pocnet.net/sheets/049/9/956.pdf

Btw, the 956 is a remote cutoff pentode and you might be better off using the 954 in pentode mode per their 'class A' amplifier 'typical'.

Ok thank you very much!

I'll get a tube 954 instead of 955 and a tube 6SK7 instead of 6Q7 leaving the current values, and I'll see how does the editing, I would make some voltage measurements and I will change resistors plate if necessary!

Tech

It might be worth noting that in the original schematic the 6SK7, operating triode mode (screen tied to plate), is the 'regenerative receiver' (the 350 pF being the regen control) and the rest is just an audio amplifier not involved in the 'regen' function.

Looks like that is the "Carolina 96" http://www.leradiodisophie.it/Landoni/carolina96.pdf and if the translation was correct the tubes were picked because he likes octal tubes or had them on hand.

http://www.leradiodisophie.it/Carolina96.html

Hello!

Yes it is the receiver 96 Carolina!

I already built the original receiver, it works really well!

Tech

Hello to all!

After several hours of assembly and testing, the receiver works really well with two acorn tubes 955 and 6AQ5 final!

I made myself the windings to receive large waves and small waves!

These small acorn tubes are great, the enclosed diagram if someone want to make!

Thank you all!

Tech

Great tubes !!!!!!!!!!!

Tech

Lovely job on the coils. Would you please post pictures of your coil winder?

Hello!

Here are some pictures of my machine!

Tell me if the link is active for you?

http://www.monalbum.fr/Album=SELQXZCQ

Tech

Beautiful machine! Wow, that thing is BUILT!

Thanks. I couldn't enlarge the photos, but I got the gist of it!

Hello!

Thank you for sharing!

This machine actually works really well, but she asked a lot of work!

Tech

Very nice work.

Are these solder joints coated for corrosion protection?

Hello!

Thank you!

It's just a can of enamel paint to solidify the departure of litz wire, and this is cleaner!

Tech

Very nice work!

Thank you very much !!

Again new coils !!

Tech