[Boatanchors] HP-8708A Synchronizer?

[David C. Hallam]

The +300V supply is used as a reference for the 25.6V supply.  The 
filter capacitor in the +300V is a dual section 120/40 uF twist lock.  
There is a 1/4 A fuse in the negative line which is grounded after the 
fuse.  I thought it was a little unusual in the fact that the negative 
of the capacitor was not connected to the can.  Since the can is 
isolated from the capacitor and it is mounted on a phenolic wafer 
anyway, I didn't see why the can should be insulated.  Try to find an 
insulated dual section can with the negative not connected to the can of 
the correct size to find in the existing mounting brackets!  I finally 
bought a suitable replacement from AES.  Reamed out the hole in the 
bracket enough to allow me to wrap the can with vinyl tape.  Since the 
can was mounted on a phenolic wafer anyway, I didn't worry about the can 
being the negative connection.

David
KW4DH

On 3/31/2014 1:05 PM, Richard Knoppow wrote:
>
> ----- Original Message ----- From: "David C. Hallam" 
> <dhallam at knology.net>
> To: <boatanchors at mailman.qth.net>
> Sent: Monday, March 31, 2014 8:15 AM
> Subject: Re: [Boatanchors] HP-8708A Synchronizer?
>
>
>> Ian,
>>
>> I have a 606B and a synchronizer.  Now that my 606B is working 
>> properly, I will get an idea of how well it works. I had to replace 
>> filter capacitors in the power supply. That was a PITA job as the 
>> capacitors are somewhat unusual.  The can is insulated and the 
>> negative is not connected to the can. The ripple was way out of spec 
>> and the 606B frequency wouldn't stabilize.
>>
>> I do have a manual for it.
>>
>> David
>> KW4DH
>>
>    I've seen isolated filter caps in other equipment such as some 
> Boonton Radio instruments. They are standard can caps but mounted on 
> phenolic wafers and have an insulating sleeve of plastic or cardboard 
> over them. In some intstruments the chassis is not at the supply zero 
> voltage. Its been too long since I've been into a 606A or B but -hp- 
> liked to use regulated supplies where one was used as a reference for 
> the other so that the voltage between them was very constant.
>
>
> -- 
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com
>

-- 
"I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them."
Thomas Jefferson


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