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Tam

With best regards
Tam HANNA

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On 2020. 04. 07. 21:05, Merchison Burke via wrote:
> Is it the video on the HP 419 meter? ""
>
> On 2020-04-07 11:35 a.m., Tam Hanna wrote:
>> Hello,
>>
>> a dude named CarlsonLabs has had a 2h video on replacing these neons.
>> Never sat through it all the way to the fartingsound, don?t have a
>> link handy but wanted to mention it. If there is interest I can go
>> hunt it down.
>>
>>
>> Tam
>>
>> With best regards
>> Tam HANNA
>>
>> Enjoy electronics? Join 15k7 other followers by visiting the Crazy
>> Electronics Lab at
>>
>> On 2020. 04. 07. 16:41, n4buq wrote:
>>> Same problem with neon-choppers as found in the 410C.? HP replaced
>>> that with a fully solid-state board towards the end of production.?
>>> I wonder if something similar could be done for the 334A?
>>>
>>> Thanks,
>>> Barry - N4BUQ
>>>
>>> ----- Original Message -----
>>>> From: "Chuck Harris" <cfharris@...>
>>>> To: [email protected]
>>>> Sent: Tuesday, April 7, 2020 8:52:18 AM
>>>> Subject: Re: [HP-Agilent-Keysight-equipment] Anyone out there fix a
>>>> partially working 334A I need desperately to get
>>>> it up and running!
>>>>
>>>> The killer problem I have found with 334A's, is they have an optically
>>>> driven chopper that relies on NE2 style neon bulbs, and CdS photo
>>>> resistors
>>>> to do the chopping.
>>>>
>>>> The problem is two fold:? First, the neons get smoky inside, and
>>>> don't put
>>>> out enough light to switch the photo resistors, and second, the CdS
>>>> photo
>>>> resistors sometimes fail.
>>>>
>>>> The neons used have a little radioactive material sintered into their
>>>> electrodes,
>>>> to make them dark fire reliably, and modern replacements don't.?
>>>> And, the
>>>> CdS photo resistors were selected and matched for maximum on/off
>>>> resistance
>>>> spread.? CdS photo resistors run afoul of the RoHS regulations
>>>> because of the
>>>> Cadmium, and are very expensive, if you can get them at all. It is
>>>> unlikely
>>>> you can find the super wide spread selected variety that HP used.
>>>>
>>>> All of the other problems I have seen have been simple capacitor
>>>> replacement
>>>> issues.? The 334A is stocked full of TE/30D style electrolytic
>>>> capacitors,
>>>> and
>>>> their rubber seals have pretty much all turned to stone by now.
>>>>
>>>> Replacing the capacitors won't have any real effect on calibration.
>>>>
>>>> -Chuck Harris
>>>>
>>>> Steve wrote:
>>>>> I have an Hp 334A that powers on and appears to function partially
>>>>> but I’m
>>>>> not sure what all could be wrong with it. If anyone fixes these
>>>>> units at a
>>>>> reasonable price I would be interested in having it put back in
>>>>> top notch
>>>>> shape with a good calibration. I restore vintage hifi and I need
>>>>> to get it
>>>>> up and going as quickly as possible.
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>>
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