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Reviews For: GU78B

Category: Electron Tubes

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Review Summary For : GU78B
Reviews: 1MSRP: $500
Description:
Russian ceramic tetrode
Product is not in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0012
LY1O Rating: 2020-08-01
unreliable and hopeless Time Owned: 6 to 12 months.
I have a GU-78B tube in my PA. After 1000 hours of work, a short circuit occurred between the first grid and the cathode. This happens when the GU-78B heats up. "Treatment" was applied. Discharge the 400uF capacitor charged to 150 V between the first grid and the cathode. It helped, but so far only for the next 50 hours of work. Again, "treatment", this time discharging 800 uF and 200 V, helped. We'll see what comes next. In the meantime, the spare GU-78B arrived. Unfortunately it didn't work. High voltage explosion from anode to cathode. By the way, the amplifier was slightly damaged. I sent it back. A good tube while it works, but it's very unreliable.
Review update:
A few months ago OM Power sent me a spare tube GU-78B. The lamp worked without any problems for over 100 hours according to the amplifier's operating time counter. This obliges to raise the tube rating.