Re: 576 curve trace scope problem [1 Attachment]


Bob Koller <testtech@...>
 

There is another way, one that I considered a few years ago. That is, design a complete SMPS that output -3250 and +225, and completely eliminate the existing transformer circuit. As I recall about 15 watts were required. The "new" transformer could output around 1Kv and drive a multiplier. This could be powered by the 100V DC supply as it has plenty of capacity, and would be designed using current technology. All of the existing CRT bias and control circuity would be utilized as-is, just powered from the new raw, regulated DC source.
I never pursued it as most of the demand dried up.


From: Chuck Harris
To: TekScopes@...
Sent: Sunday, May 19, 2013 11:04 PM
Subject: Re: [TekScopes] Re: 576 curve trace scope problem [1 Attachment]

 
Hi Dave,

Here is the 576 transformer winding sheet.

The biggest thing that keeps me from volunteering to
wind you a transformer using my manual machine is the
1400T of #40AWG wire. It is bad enough winding 733T
#38.

Don't even think about trying to wind this with level
winding. #40AWG can take even less voltage T-T than
#38. It will arc over.

-Chuck

drawding@... wrote:
> Chuck,
>
> Per your response below, it appears that you have access to the 576 HV transformer winding sheet. Would you be kind enough to send me a copy or let me know where you got it?
>
> Thank you,
> Dave
>
> --- In TekScopes@..., Chuck Harris wrote:
>>
>> I can do precise weights without problem, but I am somewhat concerned about
>> how the silicone resin handles exposure to the air. I read that it has a
>> definite shelf life, and that it gets much shorter after opening the can.
>>
>> I am game to try it, though.
>>
>> The other issue relative to the silicone RTV potting compound is whether it
>> is thin enough to penetrate the windings. In the 561 transformer, tek used
>> an epoxy varnish to impregnate the windings, and then potted the transformer
>> in an aluminum can filled with clear RTV silicone rubber. The 576 winding
>> sheet only says silicone resin and gives the part numbers:
>>
>> 252-0203-00 and 252-0214-00
>>
>> Anyone know what the commercial equivalent silicone resin is?
>>
>> I cannot imagine that beeswax transformers would have any problem at all in the
>> 576. It is all solid state, and there is plenty of room for ventilation in
>> the EHT compartment. Tek switched from beeswax to epoxy when they modularized
>> the HV section... prior to that they used either beeswax, or mineral oil. I think
>> the issue, mostly, is whether a beeswax transformer would be well received by
>> 576 owners...
>>
>> -Chuck Harris
>>
>> Bob Koller wrote:
>>> I have used the two component silicones as far back as the mid-'70's.. The mix is
>>> by weight (or was then), and small volume was not a problem. I think the silicone
>>> is preferable to prevent corona. Weren't most of the beeswax impregnated
>>> transformers enclosed in a clear plastic case? I foe one, wouldn't care as long as
>>> it works right.
>>>
>>>
>>>
>>>
>>>
>>> ________________________________ From: Chuck Harris To:
>>> TekScopes@... Sent: Tuesday, August 2, 2011 5:23 AM Subject: Re:
>>> [TekScopes] 576 curve trace scope problem
>>>
>>>
>>>
>>> The biggest issue for me, with winding 576 transformers, is the potting. If I am
>>> to do the replacements with a nice modern 2 part silicone RTV compound, that will
>>> raise the price somewhat... The 2 part RTV's are designed to only be used in full
>>> can quantities, and that means potting 10 to 20 coils at a time, with the
>>> attending need for a 10 to 20 molds, and a way to process 10 to 20 molds in the
>>> vacuum chamber at a time.
>>>
>>> The problem can be lessened if the 2 part RTV's can be safely and reliably used in
>>> smaller quantities... without jeopardizing the quality of the resulting product.
>>>
>>> Beeswax and paraffin are much less expensive in all respects, but would not make
>>> an identical transformer.... assuming that anyone cares.
>>>
>>> -Chuck Harris
>>>
>>> tom jobe wrote:
>>>> Hi Bob, Do you have any idea what color the later (good?) 576 HV transformer
>>>> potting might be? Or what S/N's might be effected? The 576 is such a wonderful
>>>> machine, it would be absolutely criminal to have to "part one out" for the lack
>>>> of an important part such as the HV transformer. tom jobe...
>>>>
>>>>
>>>>
>>>>
>>>> ----- Original Message ----- From: "Bob Koller"
>>>> To:<TekScopes@...> Sent: Monday, August 01, 2011 2:56 PM Subject:
>>>> Re: [TekScopes] 576 curve trace scope problem
>>>>
>>>>
>>>> Pull the cover off the HV section. If the transformer has brown potting, that is
>>>> almost certainly the culprit. Common on the older s/n's. Chuck Harris and I
>>>> discussed rebuilding these, and I provided the winding details to him, but have
>>>> I not pursued it further. Finding an original replacement can be quite
>>>> difficult..
>>>
>>>
>>
>
>
>
>
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