Hello!

I have a Hallicrafter-combo, SX-117 + HT-44, with a well-built
powersupply.
After not having activated the TX for say abt 10 years , 2 years
ago I tried a contact on 80, however got a report of very severe hum,
switched off, suspecting the PS-HT-capacitors, took them out,
measured too low resistances, started to ´rejuvenite´ them but not
trusting them anyway bought some new ones, but! roughly
the same voltages and capacitances are contained in a volume
abt 20% of the originals, what happens with heat dissipation,
are modern cap´s really so lowlossy? Can I use them, don´t
want any explosions in my basement!!
What´s the experts verdict!

73 / Per/ sm7aha

pegge wrote:

I have a Hallicrafter-combo, SX-117 + HT-44, with a well-built
powersupply.
After not having activated the TX for say abt 10 years , 2 years
ago I tried a contact on 80, however got a report of very severe hum,
switched off, suspecting the PS-HT-capacitors, took them out,
measured too low resistances, started to ´rejuvenite´ them but not
trusting them anyway bought some new ones, but! roughly
the same voltages and capacitances are contained in a volume
abt 20% of the originals, what happens with heat dissipation,
are modern cap´s really so lowlossy? Can I use them, don´t
want any explosions in my basement!!
What´s the experts verdict!

Yes, modern capacitors are MUCH smaller than the old ones. It's wonderful!

If possible, you should use the capacitors rated for 105'C use. They will
last much longer than the originals.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

but! roughly
the same voltages and capacitances are contained in a volume
abt 20% of the originals, what happens with heat dissipation,
are modern cap´s really so lowlossy? Can I use them, don´t
want any explosions in my basement!!
What´s the experts verdict!

The newer types are much more efficient. Most of the gain is due to the
improvements in materials science and chemistry. I haven't any catastrophic
failures in many rebuilds and replacements, but that's not saying it could
never happen. Do be sure to get the polarity right the first time.

The possibility of something going "boom" is always there with old tube gear.
Isn't that what makes it fun? I tell people running a vintage transmitter is a
lot like operating a steam locomotive. You aren't allowed many mistakes.

"pegge" wrote in message
...
Hello!

I have a Hallicrafter-combo, SX-117 + HT-44, with a well-built
powersupply.
After not having activated the TX for say abt 10 years , 2 years
ago I tried a contact on 80, however got a report of very severe hum,
switched off, suspecting the PS-HT-capacitors, took them out,
measured too low resistances, started to ´rejuvenite´ them but not
trusting them anyway bought some new ones, but! roughly
the same voltages and capacitances are contained in a volume
abt 20% of the originals, what happens with heat dissipation,
are modern cap´s really so lowlossy? Can I use them, don´t
want any explosions in my basement!!
What´s the experts verdict!

73 / Per/ sm7aha

Per -

The new capacitors are much smaller -- and allow for "restuffing" older
sized components (when required).
Here are some good web pages to review for replacing capacitors (bookmark
for future reference).

Tim Reese's great article
http://www.nmr.mgh.harvard.edu/~reese/electrolytics/

ABCs of capacitors
http://www.justradios.com/captips.html

Phil Nelson's "Replacing Capacitors in Old Radios"
http://www.antiqueradio.org/recap.htm

Rebuild an Electrolytic (2 photos demos - R390A and AC-4)
http://r-390a.us/filter_capacitors.htm

http://www.wb4hfn.com/DrakeArticles/...Rebuilding.htm

Need an axial? (and only have radials)
http://www.wb4hfn.com/DrakeArticles/...elacements.htm

Worried about looks for a historical restoration (Smithsonian caliber) ?
http://www.earlytelevision.org/capreplace.html

Finding modern HV capacitors for restorations
http://www.justradios.com/capacitors.html

Tnx gentlemen for info and views, I decided to try and use the new type of
capacitors, however during the ´burn-in´ test I will carry ear plugs and
safety-glasses! [8^
If problems arise I´ll be back!! ;-)

73 es regards / per / sm7aha


"pegge" skrev i meddelandet
...
Hello!

I have a Hallicrafter-combo, SX-117 + HT-44, with a well-built
powersupply.
After not having activated the TX for say abt 10 years , 2 years
ago I tried a contact on 80, however got a report of very severe hum,
switched off, suspecting the PS-HT-capacitors, took them out,
measured too low resistances, started to ´rejuvenite´ them but not
trusting them anyway bought some new ones, but! roughly
the same voltages and capacitances are contained in a volume
abt 20% of the originals, what happens with heat dissipation,
are modern cap´s really so lowlossy? Can I use them, don´t
want any explosions in my basement!!
What´s the experts verdict!

73 / Per/ sm7aha