- Radiation Alert, Monitor 4 repair - 1 Update
- Hantek - 1 Update
- Bose AWRC-1P - 1 Update
| William Beaty <billb@eskimo.com>: Dec 25 02:08AM -0800 Monitor 4, "Radiation Alert" S. E. International Inc, Summertown TN These little GM counters have a typical failure: the 500VDC voltage falls low, as the zener regulation diodes become damaged. In the power supply circuit on the PCB, three zeners in series are used as feedback reference: one of 1N5272 at 110V, and two of 1N5281 at 200V (to create a 510V zener.) I found that all three were damaged and leaky, resembling resistors of value between 1M and 4M. They still checked out as diodes. But they were conducting at much lower voltages than their rating. They caused the -HVDC value to be around -260V, so the geiger tube wasn't counting. On the PCB, the first diode is connected between a 470K resistor and a 4.7M resistor which leads to the GM tube. All three diodes are in series. I didn't have any 1N5281 on hand, so I tried a 1N5279 (180V, not 200,) and the unit woke up and worked fine. It might not give calibrated meter readings though, since the energy of each pulse might be down to ((510-40)/(510))^2, or 85% (since the HV supply is down by about 8%, if low by 20+20=40V) Note that there's a trimmer pot on the PCB. Possibly for meter calibrate? I didn't change its setting, measured at 362 ohms. |
| Cursitor Doom <cd@notformail.com>: Dec 25 01:40AM On Mon, 23 Dec 2019 18:45:50 -0500, Ralph Mowery >I bought a Hantek a few years back. Was going to go with a Rigol, but >overheard a couple of men at a hamfest talking scopes and they said the >Hantek was a better scope. I think you'd best delete that comment before JL reads it. ;) -- "When constituencies are small their elected representatives must concern themselves with the local interests of their constituents. When political representatives are distant and faceless, on the other hand, and represent vast numbers of unknown constituents, they represent not their constituents, but special interest groups whose lobbyists are numerous and ever present. Typically in Europe a technocrat is an ex-politician or a civil servant. He is unelected, virtually impossible to dislodge during his term of employment and has been granted extensive executive and even legislative power without popular mandate and without being directly answerable to the people whose interests he falsely purports to represent." - Sir James Goldsmith (Member of the European Parliament) 1933 - 1997 |
| tiger56usmc@gmail.com: Dec 24 12:09PM -0800 > Did you ever get a schematic because I need one for mine too. > Can you send me one via email pdf > sanfy@netease.com HEY I NEED A SCHEMATIC ALSO NO SOUND REPLACED BIG IC's and small caps still no sound ANYONE HAVE A diagram of parts |
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