Something wrong with my repro 6100 HV build

Pimpbot5000

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I've recently put together one of Dezbaz's reproduction 6100 HV boards. Every component is brand new except the T900 transformer.

It works great for a minute. B+, measured at pin 5 of the P900 connector, starts at 180V when powered on. There's a nice picture on the screen. Pin 1 and 8 measure around 25.2V and -25.2V.

However, after a few minutes R901 starts to get very hot. B+ starts to drop drastically. At one point R901 got so hot it de-soldered itself before I could turn the monitor off.

I must have made a mistake somewhere, but I can't find it. Any help is appreciated.

vPWccLDSe_PZ6Mt-Jaid0pW9UpvXcbWxGAH7p3Fccg4GnyToX8An-NDBRj6Xe1fYWBqphrpR9SiHAyh7zig3qk5oWCJAHNvsqUuBIheMV2iKjyb0xUv_ufqMszt78qnyodBUInl31GNQL8rF9-rr5MbyEUuXvb0gLPRPMvBlHtZyx1nu3nI1bS4ml6dFxMw8V24pgAvkYQyOSw7CCd1LW3i2cKzZ1_3rp7CJKgvbYZ0qIr_7a9NaEZqqeD4Wme6m4wglZjljecD8tIlUocQMxOxAILmTwBOt2HO1iKj92Gs_kS6Mei3sEB0kClFvCatRqMOYa49elAwNr4OXmsKQ85t54dqjUbTEh9sL7bi-qO69WScUUwdaD7UAAsbAWNA7ShFD6hepc5T7hKO8QBxXZcC84cJ3UuCiPaLfO7NiAFf5nGg8hXDNFZKk3ip-4BEBO6Wi7_U7v-V17wXomiDTBfeG4SQqWoEhz9qdNaM_jO8UEvlZPBiGZR-q_SOjM8RuCceyXDREvXbEmYFtQbb2hFuoaAyAM5SluXOsoPQS-E6JgSiPInt_Ow7AhYXaNIIbW1MyLlpTj4vze-8lC7ZWWMb_Lhhgzeq_g3OdLtpH67_x5YWlmQ=w1399-h1049-no
 
Is your board fully populated? I see a few test points and the areas where two different parts can be used, which do not need to be populated, but should there be a fuse on the right side by Q905?

The Q transistors don't appear to be in backwards, but I cannot tell if most caps are from your picture (C901, 902, 910 and the near Q900)? Did you confirm no extra or unwanted solder on the solder side of the PCB? I will pull-out my comparable, bare Dezbaz HV PCB to see if I see anything else.

Scott C.
 
I ended up figuring out my problem. What I found is that the MJE340 transistor I used at Q905 is NOT a suitable replacement for the original 2N6557. After spraying various components with freeze spray I realized that Q905 was getting overheated, after which it would start failing and the HV would plummet. I tried adding a heat sink to it, but that just made it last a little longer before it started failing.

In the end I used an MPSW42G, and that has worked great.

Here's the repro HV unit and repro deflection board all together and working.
ie2Pi7GzaDU8Jq285cSBg-YzmhYowJUVkF7pMetk34VdX82KYtpTceUiW0z5Gk_Y0NcDUSLMOxbSLnN465mwmcBDgCssb5eClxsK1AZEvFw4itvwiUv8TmxGhxeBp2sgJ_g2lXEC7anA_BLyT4Av2fGyrrQknenaiywvJdZc2UJJyYnexQuql2L2HULabm_wBewEpXoh2_42eiy2GjeQGrBA-IKqBEoR1OUhlBpZtpTjssmdtpeqdRgZygoHM6sPnqB9YwswlOpzQBFa9xi51_tWEk_GHSI5vF9SpDoGWJPOQiH3Gw9Ag5x7EH3Qk5azCsBb-iYIiu0gJhytXENiW1L7bgz_5lJQdm7Fp43WVJxDGBfQEmc-r3L0IkX6J82_V0YjyVsV56PMaTJ5r4ia8FuNh0x8qPL7-amYLdISifmWtao6QdYuTwJIpeed0zF_4uVykAkKlLP15_oE2BaTDwWrtapix6LrP-Jif3MJvCA9LDai-vzh5NZ4TXpAi39ZCoKb35Y3k3VWLnA1AwAT07hPtCiZL01pDZWDQgj6D8Dvb3rDqMNzE06MM2FTA6O6qM_yRHr4s1NDqK-rCe4N9Te18LhPPzu-o0JDJ6NZHe4wy6JUYQ=w810-h1079-no
 
Working better than blkdog7's 6100 :)
I ended up figuring out my problem. What I found is that the MJE340 transistor I used at Q905 is NOT a suitable replacement for the original 2N6557. After spraying various components with freeze spray I realized that Q905 was getting overheated, after which it would start failing and the HV would plummet. I tried adding a heat sink to it, but that just made it last a little longer before it started failing.

In the end I used an MPSW42G, and that has worked great.

Here's the repro HV unit and repro deflection board all together and working.
ie2Pi7GzaDU8Jq285cSBg-YzmhYowJUVkF7pMetk34VdX82KYtpTceUiW0z5Gk_Y0NcDUSLMOxbSLnN465mwmcBDgCssb5eClxsK1AZEvFw4itvwiUv8TmxGhxeBp2sgJ_g2lXEC7anA_BLyT4Av2fGyrrQknenaiywvJdZc2UJJyYnexQuql2L2HULabm_wBewEpXoh2_42eiy2GjeQGrBA-IKqBEoR1OUhlBpZtpTjssmdtpeqdRgZygoHM6sPnqB9YwswlOpzQBFa9xi51_tWEk_GHSI5vF9SpDoGWJPOQiH3Gw9Ag5x7EH3Qk5azCsBb-iYIiu0gJhytXENiW1L7bgz_5lJQdm7Fp43WVJxDGBfQEmc-r3L0IkX6J82_V0YjyVsV56PMaTJ5r4ia8FuNh0x8qPL7-amYLdISifmWtao6QdYuTwJIpeed0zF_4uVykAkKlLP15_oE2BaTDwWrtapix6LrP-Jif3MJvCA9LDai-vzh5NZ4TXpAi39ZCoKb35Y3k3VWLnA1AwAT07hPtCiZL01pDZWDQgj6D8Dvb3rDqMNzE06MM2FTA6O6qM_yRHr4s1NDqK-rCe4N9Te18LhPPzu-o0JDJ6NZHe4wy6JUYQ=w810-h1079-no
 
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