Yet another Priboi thread...

[Zen Mod]

if you wait till tomorrow - I'll post measured data for Priboi OPTs

[artosalo]

I don't know what are they but I found one priboi transformer drawing with Primary (A1) 1200 ( +480V ) 1200 ( A2 ) Sec (GND) 105 ( 4ohm ) 25 ( 8ohm )

By calculating with these the impedance with 8 ohms load will be some 2700 ohms and with 4 ohms load some 2100 ohms.
These values seems too low. I expected some 5 kohms.

if you wait till tomorrow - I'll post measured data for Priboi OPTs

This would be great. Thanks.

[tchiwam]

Originally Posted by Zen Mod

if you wait till tomorrow - I'll post measured data for Priboi OPTs

Waiting eagerly ! Thank you in advance !

[Zen Mod]

sorry

xformers are in my workshop , and I had some work elsewhere

tomorrow is work day , again

[Zen Mod]

primary Rdc 87R
pry inductance 9,3H
measured a-a


secondary Rdc
0R8 for 4R winding
1R1 for entire winding (8R)

voltage ratio 18,4:1 ( measured full pry to full sec (8R tap and gnd tap)) , which means that Raa=2K7

[artosalo]

Thank You.

[artosalo]

I have continued the "remote-repair" project of a modified Priboi with 6550 output tubes. This means that an non-experienced newbie makes the measurements I try to explain him and then I try to understand the results.

So far it seems to me that the phase splitter (6N6P) with quite low supply voltage - only some 240 V - can not drive the output tubes "full" before the clipping occurs at the phase splitter itself.

Has anobody noticed this before ?

To improve the phase splitter, I try to take the supply voltage to 6N6P from the high voltage line ( 470 V).

I ended up to the circuit like this.



The potentiometer is here for fine-tuning purpose only and will be replaced with fixed resistor later.

Comments please.

[Wavebourn]

By the way, colleagues from Russia who had experience with Priboy said that GU-19 is a beast: it is something between 807 and GU-50, and a pair of them can deliver up to 110W and live long. One gentleman said, they worked 7 years, but started dying all together: some layer from inside of anode started peeling off making spark flashes.

[tchiwam]

Originally Posted by Wavebourn

By the way, colleagues from Russia who had experience with Priboy said that GU-19 is a beast: it is something between 807 and GU-50, and a pair of them can deliver up to 110W and live long. One gentleman said, they worked 7 years, but started dying all together: some layer from inside of anode started peeling off making spark flashes.

Interesting, could he expand a bit on the setup ? It is true that the GU-19 are really quality made tubes, ceramic insulators around each leg etc etc and they look good. They work as is in a Priboi at -15VDC but I know I need to adjust more than that. I now have the OPT values...

The GU-29 are on the other hand something out of this world...

[tchiwam]

Originally Posted by artosalo

I have continued the "remote-repair" project of a modified Priboi with 6550 output tubes. This means that an non-experienced newbie makes the measurements I try to explain him and then I try to understand the results.

So far it seems to me that the phase splitter (6N6P) with quite low supply voltage - only some 240 V - can not drive the output tubes "full" before the clipping occurs at the phase splitter itself.

Has anobody noticed this before ?

To improve the phase splitter, I try to take the supply voltage to 6N6P from the high voltage line ( 470 V).

I ended up to the circuit like this.

Interesting indeed, is this true for the current output tube too ?

How about going to a Shmid or long tail pair type phase spiller while playing with that ? There is already a good gain from the 1st stage... That's where I am heading for the GU-29.