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Everything posted by joehpj

  1. I am not talking about modifying KGST. I was just thinking the output stage of BH=T2, and have been designed for over 20 years. KT150 was produced since 2010 as I know. Don't know about KT120. Maybe those will make a better output stage? How does those KTs compared to dht like 845? Even though 845 still has some NOS available, the cost is insane for a matched quad. The price are at same level for modern 845 and KT120.
  2. The amp was up and kept running 4hrs/day for 2 weeks. This amp is indeed very good. Being dynamic, detailed, and a bit of "tubby" sound, I like it very much. BTW, I some times wonder if it's possible to use the new-designed KT family as the output stage. BH use EL34 as triode. Though EL34 is pentrode and KT77 is beam tetrode, I thought they were almost identical(working). The new-designed KT120 or KT150 can handle a little bit higher voltage and much bigger current output. So if it's possible to use KT120/150 as output stage, maybe there's no need to use current amplification like ciclotron? Plus, using dht tube like 300B/845 may have humming problem. So maybe using KT family is better?(though the voltage is lower....)
  3. It was actually my amp. I had little experience of building high voltage things. After the first blown PSU, I contacted Peleus. Peleus was kind to help me and introduced a experienced technician to build the amp for me. After two days of run-in. The positive rail and the bias part blown again with very loud sound and light. The weather was very humid recently (rainy days and I live beneath a hill). I don't know if it was the reason of the short of the negative and the bias rail. There is no solder, no flux between the TP of the bias and the negative rail. The white sandy smoke around the TP and the short negative rail was more like something left by heat. The upper right corner of the TP was blown away with negative rail having two small dot of melted copper wire.After discussion on the local forum, we conclude it may caused by arcing between rails. It may because of the PCB quality, the weather, or something we don't know. The PSU just end up like this so the mod of the board was to eliminate any chance of arcing happening again.
  4. How about the 1N4007s? Those are a little bit hard to desolder. Anyway, thanks for replying. You guys are sooooo kind.
  5. learned a lesson. The PCB says 12V for the zeners and those were what I've bought from mouser. Later I found in this topic 24V would be a better choice. Then I bought the 24V zeners from a local store. Wrong decision. I believe that's why the PSU were fine at first then blown after several times of running, Should I replace all active components in case of safety reason?
  6. update: I thought it was the 10M90S so I carefully cleaned up the flux and made sure those was isolated. Ran for just 3 seconds and -400V exploded too. so scary. I found the 8N80C was short between either of the three pin on both +-400V. So I assume both 8N80C were dead? Though I didn't desolder those, I believe those shouldn't be short if those were normal even on board. Maybe those 24V zener bought from the local store are the murderer? Or it's because I didn't use any thermal grease for the 8N80C? I thought those were directly contacting the cooler so I didn't use any thermal grease.
  7. Thanks guys,I will fix the problem. I will report once the problem solved.
  8. the solder is noclean type so I didn't clean them up. Maybe it's because of flux? please don't hesitate to ask for more detailed pics. many thanks!
  9. Any suggestion for where to start checking from? I know little about schematic and electric things. What I could do is put the components on where it should be and solder it. BTW, the the 335VAC from the transformer reads about 350V when unloaded. I thought it was fine for an unloaded transformer. The zener besides the 8N80C was bought from an local store and I can't really remember if I bought the right spec as 24V/1W. Will it matter if the actual spec is 24v/0.5W? All other things are bought from mouser and the same as BOM. Double checked for the direction. I use metal screw for the 10M90S but I had them isolated with plastic washer extend in to ceramic thermal pad. I thought it should be right. I was thinking if I mistakenly put one thing in wrong direction, the problem should happen in one direction but not both +-400V supply. Thanks for replying!
  10. Hi guys, I'm newbie here. I've already built a KGST PSU. I hooked up 2X 335VAC and 18-0-18 at the same time for provisional. However, the 150-150-100 zener string for +400V exploded. Yep, exploded. After that, I was trying to figure out what's wrong about the zener string. I only hooked up the 335VAC for the -400V and found the zener string ran extremely hot. Even the solder melts! I turned off the power immediately, and luckily they looked fine.(hope so) The voltage should be 150-150-100. But actually they ran at about 180-180-110. So, could any one tell me what to check and how to make it right? Plus, I had run the PSU once about a weeks ago. It was fine at that moment( not sure if it's me that didn't notice some thing was going wrong) All the voltage include +-400V and +-15V was fine then. It was kinda weird.......
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