DX-100B Restoration Questions

[WB8VCM]

I am the new owner of a DX-100B. I have no history on the radio, so I am
carefully trying to examine it by comparison with the manual before applying
any power. So far so good, no major items missing, but a couple items stand
out.

First, someone has applied red tape under the entire outline of the
modulation transformer (part 51-22). It does not appear to be a good enough
job to electrically isolate the transformer from the chassis. Could this be
to mechanically isolate the transformer from the chassis and limit
audio-induced vibration?

Second, under the chassis near the modulation transformer, my rig has a big
cylindrical component resembling a modern electrolytic. It's about 1 3/4"
in length by 1" diameter. It has a "C-D" logo on it, with a part number
CP28AIEH203K. From the schematic, it should be an 0.02 uf @ 1600V across
the transformer secondary, but the size of the component is huge, at least
compared to a modern component with these ratings. There is also an 0.001
uf at 3 KV disc ceramic tacked on in parallel with the big capacitor. Is
anyone familiar with this big capacitor ?

Thanks,

Bruce
WB8VCM

[Michael Black]

"WB8VCM" ) writes:
>
> Second, under the chassis near the modulation transformer, my rig has a big
> cylindrical component resembling a modern electrolytic. It's about 1 3/4"
> in length by 1" diameter. It has a "C-D" logo on it, with a part number
> CP28AIEH203K. From the schematic, it should be an 0.02 uf @ 1600V across
> the transformer secondary, but the size of the component is huge, at least
> compared to a modern component with these ratings. There is also an 0.001
> uf at 3 KV disc ceramic tacked on in parallel with the big capacitor. Is
> anyone familiar with this big capacitor ?
>
"C-D" could certainly be well-known capacitor manufacturer Cornell-Dubilier


It's a high voltage capacitor, with relatively high (for the voltage
rating) capacitance. It's likely oil-filled. It's fifty years old,
and they've learned a lot since then about making capacitors. (I
have a 10,000uF 16V capacitor I got about 1973 at a hamfest, and it
was big time then. It's also the size of a Coke can. The same
value electrolytic is now far smaller, and it's easy to get them
with a higher voltage rating.)

Michael VE2BVW

[Doug]

On Wed, 24 Jan 2007 18:40:38 -0500, "WB8VCM" >
wrote:

>I am the new owner of a DX-100B. I have no history on the radio, so I am
>carefully trying to examine it by comparison with the manual before applying
>any power. So far so good, no major items missing, but a couple items stand
>out.
>
>First, someone has applied red tape under the entire outline of the
>modulation transformer (part 51-22). It does not appear to be a good enough
>job to electrically isolate the transformer from the chassis. Could this be
>to mechanically isolate the transformer from the chassis and limit
>audio-induced vibration?
>
>Second, under the chassis near the modulation transformer, my rig has a big
>cylindrical component resembling a modern electrolytic. It's about 1 3/4"
>in length by 1" diameter. It has a "C-D" logo on it, with a part number
>CP28AIEH203K. From the schematic, it should be an 0.02 uf @ 1600V across
>the transformer secondary, but the size of the component is huge, at least
>compared to a modern component with these ratings. There is also an 0.001
>uf at 3 KV disc ceramic tacked on in parallel with the big capacitor. Is
>anyone familiar with this big capacitor ?
>
>Thanks,
>
>Bruce
>WB8VCM
>


I can't help you with those caps but do have a question.

I just picked up a DX100B.
I've got a schematic for the "A" version but not the "B".

Do you have the schematic.
If so, would you be willing to pass along a copy?

I've not been able to find the "B" version schematic online.

tnx,

Doug/WA1TUT

[COLIN LAMB]

Is the CD component across the secondary? I would unsolder one side of it
and determine what the value is. If it is across the secondayr, it is
likely an oil filled high voltage cap.

The tape is likely to prevent a mechanical resonance. However, examine it
carefully. If the screws are insulated, it could be to correct a short to
case, which could make the case hot.

There is a lot of information on DX-100 rigs on the internet. They sounded
good before people started converting them. Electrolytics may need
replacement, but it shouldc be a smooth operation to put back on the air.

73, Colin K7FM

[M. J. Powell]

In message .net>,
COLIN LAMB > writes
>Is the CD component across the secondary? I would unsolder one side of it
>and determine what the value is. If it is across the secondayr, it is
>likely an oil filled high voltage cap.
>
>The tape is likely to prevent a mechanical resonance. However, examine it
>carefully. If the screws are insulated, it could be to correct a short to
>case, which could make the case hot.
>
>There is a lot of information on DX-100 rigs on the internet. They sounded
>good before people started converting them. Electrolytics may need
>replacement, but it shouldc be a smooth operation to put back on the air.

I found that mine was very sensitive to contact resistance on the Morse
key.

It chirped like mad sometimes, then I had to clean the contacts.

Mike
--
M.J.Powell

[WB8VCM]

Hi Colin,

Yes, it is across the secondary. Thank you to everyone who suggested it
might be an oil filled capacitor. I'm going to replace it with something
"modern" during my initial efforts to reach "stock" configuration.

I looked at the transformer and it is bolted in with metal hardware and no
insulating washers. Hopefully it was taped up for mechanical resonance
reasons, but I'll do some testing to make sure the case is not hot.

Thanks,

Bruce

[COLIN LAMB]

Hello Mike:

That is a high voltage point, so be sure the voltage rating is high enough.
I have plenty of boat anchors - many of which were more expensive than the
DX-100 when new. But, over a period of time, I have come to appreciate how
wonderful the DX-100 is. The Collins rigs are excellent - but they are
harder to work on and do not cover 160 meters. The Johnson Viking series is
nice - but does not have a vfo.

In short, the DX-100 is a very nice boat anchor.

Colin K7FM

[w9gb]

"WB8VCM" > wrote in message
...
> Hi Colin,
>
> Yes, it is across the secondary. Thank you to everyone who suggested it
> might be an oil filled capacitor. I'm going to replace it with something
> "modern" during my initial efforts to reach "stock" configuration.
>
> I looked at the transformer and it is bolted in with metal hardware and no
> insulating washers. Hopefully it was taped up for mechanical resonance
> reasons, but I'll do some testing to make sure the case is not hot.
>
> Thanks,
>
> Bruce
HOPEFULLY, you have the Heath kit assembly manual for this radio --- make
life MUCH EASIER for your investigation and "kit rebuilding". QST also
featured the DX-100 (eBay acquisition) in a rebuild article a couple of
years ago (total rebuilt including replating the copper chassis and parts)

gb