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Old 16th April 2011, 06:17 AM   #1
rss388 is offline rss388  United States
diyAudio Member
Join Date: Dec 2007
Default Newbie question about a 300B amplifier

Hi all,

I was in China recently and on a whim, I bought a display unit of a 300B amplifier. When I brought it back, the tubes were taken out and packed separately. Now I have a problem, not knowing which tubes to put back where. The amp has a 5Z3P rectifier and two 300B tubes, which I was able to locate on the unit as labelled. Now comes the problem, the other 4 sockets have the same number of pins for two tube types but I am not sure about the labelling. Two of the tubes are dark coated and one had printed on it 6P6P and the other two are clear but no markings. I attach a couple of pictures of the unit. I can trace that the input signals go to the center tubes rather than the side ones immediately next to the 300B tubes. Do I have it right as in the picture or should I put the dark 6P6P tube in the middle and the two clear tube on the sides? Sorry for this newbie question. I feel so stupid. I did verify the unit was working before taking the tubes out. Your help much appreciates!
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File Type: jpg IMG00156-20110414-0817.jpg (217.0 KB, 100 views)
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Old 16th April 2011, 11:55 AM   #2
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azazello's Avatar
Join Date: Aug 2008
Location: Bulgaria
I don't know the schematic, but left picture is maybe right.
Central tubes are: 1 rectifier /big one/ and two clear tubes are maybe for stability
/they look like the same Russian СГ-4 for stability of U/.
/sorry for my bad English....!/
Can You make photo of back side, it's important to look the difference between 4 sockets?

Last edited by azazello; 16th April 2011 at 11:58 AM.
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