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.
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.
An externally hosted image should be here but it was not working when we last tested it.
The potentiometer is here for fine-tuning purpose only and will be replaced with fixed resistor later.
Comments please.
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...
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.
Some people use them as is, some use 4 Ohm tap for 8 Ohm. What is really needed, some heatsinks on anode pins.
Oеhers prefer GU-29.
Also, I know about triode connected GU-50 used there.
110W in those transformers, lets assume they are the same as in the 75W version, that is still a lot more than designed for. I know Russians didn't have a shortage of copper but I still don't want to grill them.
And yes these are quite low impedence transformers for the output...
yes, your fave .....
mind to share your schematic of Priboi with ГУ-50 ?
It was not me; it was Sergey Sergeev, from Irkutsk, Siberia
Sergeev's site about Priboy modifications
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tnx W.
You are W., but he got 25W from it only in triode mode!
I would use, of course, in pentode mode with parallel feedbacks around output tubes. Or, stick with GU-19 or GU-29. GI-30 is another option, it is GU-29 with higher cathode emission. The story is, after new equipment was designed for Hall of Congress in USSR, around GU-19 and GU-29 tubes, then Minister got an order to design civil version of the tube. 6R3S-1 was born as the result, birth defected.
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Let's agree to disagree. I can make a nice amp from Priboy using EL34 tubes.
This old discussion has been mostly about replcement tubes in the Priboi amp, like the GU-19.
I have a few questions that is too related to this thread to require a new thread.
Under my bed, I have stored my Priboi (in good company with a Dynaco PAS3 and some hundred tubes - I sleep good at night
). Many years ago I modified it to Likhnitsky's schematic, but as I have ended up with loads of amp projects around or below 10W I started to consider do a new remake, getting som more watts from it.So, IF I am to switch to other tubes, what tubes can be used? Likhnitsky mentioned that he had tried EL34 with good result before redesigning.
And what's the maximum power that the components (power transformer + OP transformers can provide)?
I have been thinking of EL34 or 6L6, or even parallell 6L6, but I also have a pair of EL156 and KT120 - could these be used? Or is maybe KT88 or KT90/KT100 a better choice?
There was a Priboi-UM75 with 6R3S in parallell, that, according to the name was capable of 75W/channel, but I dunno if there were other and heavier transformers for that model.
yes
mind to share your schematic of Priboi with ГУ-50 ?
Зачем вам ГУ-50? Генераторные лампы сами по себе не предназначены для УНЧ.
Используя генераторные лампы в Прибой УМ, можно легко убить выходные трансформаторы.
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