Posts: 1,077
Threads: 43
Joined: Feb 2015
City: Roseville, MN
I'm doing research on using Y2 safety caps in the power transformer primary circuit without a third wire for chassis ground. Did a Phorum search and the first hit was the restoration of a Philco 47-1230 and on the second page was the power supply schematic with exactly the circuit in question. Does anyone know if this is effective or was this case a matter of a CYA?
http://www.nostalgiaair.org/resources/606/M0013606.htm
Posts: 1,407
Threads: 72
Joined: Oct 2007
City: Linn Creek, MO
The line caps will provide a ground path for the antenna circuit, a chassis ground will not improve reception.
Steve
M R Radios C M Tubes
Posts: 704
Threads: 8
Joined: Apr 2018
City: S. Dartmouth
State, Province, Country: MA
Replacement of the line capacitors with "safety" type would be effective in that if there is a failure the cap goes open.
In terms of the "Y" caps, they form an "X" across the line with a common chassis ground if that ground is used or not.
The point is CYA is included in the change out of the caps as well as improvement in an RF return to earth or "pseodo" earth.
When it comes to liability, the "CYA" (cover your ) issue, you worked on it, you changed it, if there is a loss because of the work you are responsible as the professional who did the service. No amount of disclaimer document will excuse... chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
(This post was last modified: 03-04-2021, 01:20 PM by
Chas.
Edit Reason: Clarification of anacronym
)
Posts: 142
Threads: 28
Joined: Dec 2016
City: portland, OR
RodB, take a look at this article. ABC's of SAFETY (Interference Suppression) Capacitors for Tube Radios
https://www.justradios.com/safetytips.html
pokey posted the link a while back -
https://philcoradio.com/phorum/showthread.php?tid=21549
Posts: 1,077
Threads: 43
Joined: Feb 2015
City: Roseville, MN
So if I connect one Y2 cap across the primary on a chassis not directly connected to earth is it the same as connecting two Y2 caps with the center connected to the chassis? Hence, the interference is suppressed to the Neutral side of the power line.
Posts: 704
Threads: 8
Joined: Apr 2018
City: S. Dartmouth
State, Province, Country: MA
No,
If the reference to the AC line via a center connection of two caps is lost, over all sensitivity may be suffer. The two caps in series still constitute a common mode bypass.
For my consoles I will install a Corcom filter next to the line cord. But, that is my choice, my radios.
Be sure use the value in mfd no greater than the one given in schema. Higher values of line bypass too much AC. The effect is cumulative with other bypassed device on the same circuit breaker. If it is a ground fault breaker there can be nuisance trips.
I'm not a capacitor salesman, inferring a "sense of security" by adding devices...
IMHO keep the current configuration, just replace the line caps with ones that do not fail shorted.
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
(This post was last modified: 03-04-2021, 01:21 PM by
Chas.)
Posts: 1,077
Threads: 43
Joined: Feb 2015
City: Roseville, MN
Thank you Chas. I was looking for the functionality answer and that seems to fit. Funny you should mention the "more is better" sales pitch. The set I'm working on is a "7" tube radio. The plate and cathode of the 6SQ7 triode is fastened to ground then the audio is sent to a separate tube to drive the output tube.
Posts: 16,250
Threads: 564
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
More value also increases "touch current", when you have no safety GND connection. It could become unsafe.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 125
Threads: 18
Joined: Jan 2018
City: Kingsville Ohio
Chas Could you explain further about the corcom filters. That sounds interesting especially since I have so much RFI in my house which can not be resolved because a lot of it comes from my Geothermal furnace. If I could weed out some of this trash my consoles would certainly sound better.
Dick
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
