I have just re-capped the power supply capacitors in a DX-40 with 40uf 450 VDC
Aluminum Electrolytics from NTE Electronics in New Jersey.

I have noticeable hum on the carrier. Measuring the ripple voltage with a 10
Megohm ac coupled meter shows 2.3+ volts [average/rms ... non-sinusoidal] on the
600 vdc line and 1.2 volts [average/rms ... non-sinusoidal] on the 300 vdc line.

It appears the RS of the capacitors is way too high.

What manufacturer or brand are others using with success? Does MOUSER carry
suitable replacements? If so, what brand/style?

Other sources?

TIA

DD, W1MCE

Dave wrote:
I have just re-capped the power supply capacitors in a DX-40 with 40uf
450 VDC Aluminum Electrolytics from NTE Electronics in New Jersey.

I have noticeable hum on the carrier. Measuring the ripple voltage with
a 10 Megohm ac coupled meter shows 2.3+ volts [average/rms ...
non-sinusoidal] on the 600 vdc line and 1.2 volts [average/rms ...
non-sinusoidal] on the 300 vdc line.

It appears the RS of the capacitors is way too high.

Your ripple values look ok to me. They calculate out to
be under 1%. (0.4% rms)

You probably have a problem elsewhere, such as a heater-cathode
leak, or short.

-Chuck

How do you know you have hum? Are you listening
on a local receiver? If so it could be a form of
"tuneable hum" caused by the AC in the house wiring
modulating the received signal. If you have a good
scope, try looking at the waveform directly; any
hum will show as modulation riding on carrier.

The amounts of ripple you're seeing are very minimal,
as others noted...

Pete

Is this hum on am or both am and cw. If it is only on am, then it would be
int he audio chain and not the power supply.

Colin K7FM

Dave wrote:
I have just re-capped the power supply capacitors in a DX-40 with 40uf
450 VDC Aluminum Electrolytics from NTE Electronics in New Jersey.

I have noticeable hum on the carrier. Measuring the ripple voltage with
a 10 Megohm ac coupled meter shows 2.3+ volts [average/rms ...
non-sinusoidal] on the 600 vdc line and 1.2 volts [average/rms ...
non-sinusoidal] on the 300 vdc line.

It appears the RS of the capacitors is way too high.

What manufacturer or brand are others using with success? Does MOUSER
carry suitable replacements? If so, what brand/style?

Other sources?

TIA

DD, W1MCE


Dave, Although I concur with the thoughts of others replying, FYI, I use
the Xicom series of electrolytics from Mouser with success on virtually
all projects that have been recapped, transmitters and receivers.

COLIN LAMB wrote:

Is this hum on am or both am and cw. If it is only on am, then it would be
int he audio chain and not the power supply.

Colin K7FM




No ripple on the audio power buss [400+ vdc. 0.001 vac] This bus has a RC
filter of 20K and 20 uf. It is clean.

It is in both the AM & CW mode. So, it has to be the rf string where the +600 is
common to the two 6CL6s [series connected] and the 6146. I'm beginning to
suspect heater/cathode coupling/short in one or more of those tubes.

I gave my scope away about 5 years ago ... :-(

I have an EE degree and 40+ years of design/management experience, so a little
trouble shooting is not a problem for me. But, I have no capability to measure
capacitor ESR.

Well, I'll keep playing.

Thanks for suggestions.

DD, W1MCE

thanks

K3HVG wrote:

Dave wrote:

I have just re-capped the power supply capacitors in a DX-40 with 40uf
450 VDC Aluminum Electrolytics from NTE Electronics in New Jersey.

I have noticeable hum on the carrier. Measuring the ripple voltage
with a 10 Megohm ac coupled meter shows 2.3+ volts [average/rms ...
non-sinusoidal] on the 600 vdc line and 1.2 volts [average/rms ...
non-sinusoidal] on the 300 vdc line.

It appears the RS of the capacitors is way too high.

What manufacturer or brand are others using with success? Does MOUSER
carry suitable replacements? If so, what brand/style?

Other sources?

TIA

DD, W1MCE


Dave, Although I concur with the thoughts of others replying, FYI, I use
the Xicom series of electrolytics from Mouser with success on virtually
all projects that have been recapped, transmitters and receivers.

Dave wrote:
I have just re-capped the power supply capacitors in a DX-40 with 40uf 450 VDC
Aluminum Electrolytics from NTE Electronics in New Jersey.

Who makes them? NTE does not make capacitors, they rebadge them.

I have noticeable hum on the carrier. Measuring the ripple voltage with a 10
Megohm ac coupled meter shows 2.3+ volts [average/rms ... non-sinusoidal] on the
600 vdc line and 1.2 volts [average/rms ... non-sinusoidal] on the 300 vdc line.

It appears the RS of the capacitors is way too high.

What manufacturer or brand are others using with success? Does MOUSER carry
suitable replacements? If so, what brand/style?

I have been using the Panasonics from Digi-Key for years with no problem.
Always go for 105'F types, even for lower temperature applications. The
BCC ones are fine also.

I am surprised you would have any issue with the NTE ones, though... even
the cheapest caps today have better ESR than the caps of the sixties. I
might look elsewhere first, like a bad rectifier.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Dave wrote:
I have just re-capped the power supply capacitors in a DX-40 with 40uf
450 VDC Aluminum Electrolytics from NTE Electronics in New Jersey.

I have noticeable hum on the carrier. Measuring the ripple voltage with
a 10 Megohm ac coupled meter shows 2.3+ volts [average/rms ...
non-sinusoidal] on the 600 vdc line and 1.2 volts [average/rms ...
non-sinusoidal] on the 300 vdc line.

It appears the RS of the capacitors is way too high.

What manufacturer or brand are others using with success? Does MOUSER
carry suitable replacements? If so, what brand/style?

Other sources?

TIA

DD, W1MCE

I guarantee it's not the caps

"Dave" wrote in message
. ..
I have just re-capped the power supply capacitors in a DX-40 with 40uf
450 VDC Aluminum Electrolytics from NTE Electronics in New Jersey.

I have noticeable hum on the carrier. Measuring the ripple voltage
with a 10 Megohm ac coupled meter shows 2.3+ volts [average/rms ...
non-sinusoidal] on the 600 vdc line and 1.2 volts [average/rms ...
non-sinusoidal] on the 300 vdc line.

It appears the RS of the capacitors is way too high.

What manufacturer or brand are others using with success? Does MOUSER
carry suitable replacements? If so, what brand/style?

Other sources?

TIA

DD, W1MCE

Sounds like a earth loop.....