[volt-nuts] volt-nuts Digest, Vol 95, Issue 18
blackdog at dds.nl
Sat Jul 22 13:14:33 EDT 2017
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Onderwerp: volt-nuts Digest, Vol 95, Issue 18
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1. Re: Datron 4700 manual and options (Fred)
Date: Sat, 22 Jul 2017 09:27:16 +0200
From: Fred <pa4tim at gmail.com>
To: volt-nuts at febo.com
Subject: Re: [volt-nuts] Datron 4700 manual and options
Message-ID: <61b14813-7e68-278e-7d40-7ae4c88b1318 at gmail.com>
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The 4700 is fixed. The 400V issue was caused by missing -15V, That was
caused by a shorted tantalum on the Ohms board. It was less then 0,1 ohm
but not even discolored.
I was curious about the way they die. So a desoldered about 20 tantalums
and measured C, D and leakage current. New ones have a very low D, at 1
kHz well under 0,1. Capacitance did not decrease much like electrolytics
do, but D does increase over age. Leakage current is as good as zero,
(my best leakage tester has only 1 uA resolution so it can not measure
leakage in the nA's)
The worst D i found was 0.67.
They did not leak, so I think they go from good to short in one step.
capacitance does not seem to decrease. In electrolytics this is caused
by a decreasing oxidelayer caused by the decreasing electrolyte.
I replaced a few by electrolytics as a test. The D factor of the 10uF
low ESR panasonic FM caps was better as that of the new 10uF tantalums I
had. Most tantalums measured OK, a few had very high D, non of them
So I think (based on this to small number test) they get a high D, start
to dissipate and as a result of that develop a short.
On 07/21/2017 01:59 AM, Todd Micallef wrote:
> I used the same values and typically went up to the next higher voltage. I
> think most ended up as 35v since I bought them in quantity. Some people
> recommend the OS-CON family as replacements. Many of the failed tantalums
> fit in a tight space so I just stayed with the original type.
> Once the in-guard was repaired, I found a few other boards where the
> tantalums on the same rail also failed so don't be surprised if more start
> to fail.
> The 4708 service manual is here
> It is now uploaded to KO4BB. The 4808 service manual will be very close
> since the 4708 and 4808 share similar designs.
> The 4708 uses a LTZ1000 as the reference instead of the array of zeners
> used in the 4000 and the lower spec'd 4700. You will have yourself a good
> calibrator once it is brought back into service. Be careful around the
> displays as there is hardly any room between the glass and front panel.
> On Thu, Jul 20, 2017 at 12:55 PM, Fred <pa4tim at gmail.com> wrote:
>> Hi Tod,
>> I just pulled that board (i think) and found a burned 22uF tantalum.
>> Tantalum caps should have a very long life unless used on the wrong place.
>> I guess this is an example. I do not even stock them, the last bad one I
>> had to replace was in a G&M secutest 2 years ago. ( I repair around 10-20
>> Secutests a year and that was the only bad tantalum)
>> With what type/value cap did you replace them ?
>> I found the 4708 manual at KO4BB but that is a user manual without
>> The calibrator should be OK but before I try to start her I always like
>> check things like caps, connectors, solderjoints etc. It really looks like
>> new, not even a scratch or dust. It came with a new looking HP8640 and a
>> new looking HP counter 5248. Both from the same cal lab (part of a company
>> that stayed there) that cal-lab closed about 30 years ago, but all gear
>> stayed where it was (I already had received most of their gear a few years
>> ago). This were the last things because my friend retires.
>> On 07/20/2017 04:51 PM, Todd Micallef wrote:
>>> Shorted tantalums most likely. I had several on mine that went bad as
>>> quickly as I replaced them. I would start with the inguard supply board.
>>> I think the 4708 manual is available for download at KO4BB or xDevs. If
>>> not, I can dig up something. I have a set of the manuals.
>>> On Thu, Jul 20, 2017 at 10:01 Fred <pa4tim at gmail.com> wrote:
>>> Today a friend gave me a Datron 4700. It looks like new. It is stored
>>>> (working) for many years in the cal lab he works. He was allowed to
>>>> take it home (for me, in return I will repair his SA), He plugged it in,
>>>> Fail 1 on the display followed by a sound and a smell.
>>>> I opened it but nothing looks burned.
>>>> I can not find a service manual, does someone has one ?
>>>> On the back the label shows no options but if he remembers it well it
>>>> should have all or at least most options. All slots are filled with
>>>> pcb's. The "box" in the left upper corner is full and there is a very
>>>> small pcb next to it. There is not much room left. Just enough to store
>>>> a small multimeter between the huge transformer and that box.
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