Re: G05 HV troubles

On 08/23/2013 10:01 AM, Andrew Welburn wrote:
> I had a few in a drawer, just to be sure, i tried 3 other diodes and
> i get the same with each one, R901 still burns up.. :(
>
> any other ideas?
>
> Andrew Welburn
> http://www.andys-arcade.com
>

I'd put an ammeter in series with the input and use a variable power
supply to see what happens when it gets close to the regulating point. I
leave the HV diode off or put the HV lead in a ceramic cup and monitor
the 90 or 400 volts out.

R901 shows as a 47R 1/2W (flameproof might be a good idea) and I don't
know why it would burn up unless the thing is breaking into a weird
oscillation - 'scope the emitter of Q900 to make sure it is clean.

Have you replaced C902 yet?

John :-#)#

> On 23/08/2013 17:09, John Robertson wrote:
>> On 08/23/2013 5:16 AM, Jeffrey Matthews wrote:
>>> Andrew;
>>> Did you check/replace D904 leading to the anode cup?
>>> I had a R901 cooking and found that to be the culprit.
>>> Jeff
>>>
>> Indeed, the HV diode can cause all sorts of overheating problems. I see
>> that they are still being made by a few people and available from a
>> couple of suppliers:
>>
>> http://hvstuff.com/high-voltage-diodes-and-rectifiers
>>
>> And:
>>
>> http://www.americanmicrosemi.com/products/search/index.php
>>
>> Look for the 2CL73, 2CL74 and 2CL75
>>
>> John :-#)#
>>>
>>>
>>>
>>> On 8/23/2013 4:56 AM, Andrew Welburn wrote:
>>>> hi all..
>>>>
>>>> I've been fighting with a HV box from hell recently, and i've held
>>>> off posting to vectorlist until i was really stuck. I'm at that point
>>>> now.
>>>>
>>>> Its a G05-802...
>>>>
>>>> Right now, R901 is smoking up. I'm only getting 7.2kv at the anode,
>>>> and the HV adjust pot does not change the hv. I can only have it
>>>> running for 10 seconds before R901 really starts to cook off.
>>>>
>>>> The flyback was actually bad, as the HV was bouncing around from
>>>> nothing up to 7kv very erratically before, so i swapped that from a
>>>> known-good v2000 hv box. Now i get a steady HV, albeit low and r901
>>>> still burning up. (R901 was cooked crispy before the flyback swap
>>>> anyway)
>>>>
>>>> I have subsequently swapped _every_ diode and transistors in the
>>>> box, and it still acts the same, no improvements. I also changed the
>>>> electrolytics, and the HV adjust pot itself (R905).
>>>>
>>>> Can anyone think of a scenario that would let R901 burn up? any
>>>> pointers as to where i should be looking harder?
>>>>
>>>> thanks..
>>>>
>>>
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>>
>>
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