Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Zenith 9S262 antenna issue
#1

Totally recapped the chassis, replaced the out of tolerance resistors, with all strong tested tubes and the radio plays but with low sensitivity. No change in volume or signal strength by touching the antenna terminal, and only very slight eye tube movement (yes, the 1 meg resistor was changed). The RF coil was replaced as one section was open.

Here's what I've found:


No change in signal strength moving from the local to distant position on the off/on control (but did verify the switch itself is working and grounds out on the distant position).

The entire chassis is very sensitive...if I touch the chassis, the volume drops some.

The 6K7 RF tube is not conducting. I get zero volts on the plate (pin 3).  92 volts on pin 4

Antenna primary measures 22.4 ohms across the ANT to GND terminals. I get two ohm readings across the terminals of the ANT coil, but measuring across it I get 1.5 meg ohms which seems suspect.

I get 262 volts on the plate of the 6L7  & 94 volts on pin 4

If I connect my external antenna to the grid cap of the 6L7, bypassing the 6K7 RF tube the radio plays normally on all bands with strong sensitivity. Eye tube functions as it should but still no change in signal strength from local to distant position. The chassis also is no longer sensitive and volume doesn't drop if I touch it.

If I connect my external antenna directly to the plate pin of the 6K7 RF tube the radio also plays strong and the same as it did by connecting the antenna to the grid cap of the 6L7 tube. Again, the eye tube works as it should but no change in signal strength from local to distant. The chassis also is no longer sensitive and volume doesn't drop if I touch it.

It seems to point to an open section of the ANT coil but if anyone could give me any other possible causes to the zero plate voltage on the 6K7 RF tube and the lack of response from the ANT terminal please let me know.

Thanks. Here are the schematic pages for reference:

   

   

Greg V.
West Bend, WI
Member WARCI.org


Messages In This Thread
Zenith 9S262 antenna issue - by NostalgiaRadioTime - 01-30-2021, 08:11 PM
RE: Zenith 9S262 antenna issue - by morzh - 01-30-2021, 09:29 PM
RE: Zenith 9S262 antenna issue - by morzh - 01-30-2021, 09:47 PM
RE: Zenith 9S262 antenna issue - by morzh - 01-30-2021, 10:24 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Need to purchase some accessories for restoration of my Old Philco Radio
Here is a list of resources found in our online library that you might find useful. Mike's Gobs of Knobs email addres...klondike98 — 01:46 PM
First Radio restoration
Hi Tubeman, Welcome to the Philco Phorum.  Phamily Phriendly Pfun with Phine Pholks Phull of Philco Phacts. (See a p...MrFixr55 — 12:33 PM
First Radio restoration
You could post in the WANTED ADs section here on the Phorum and see if anyone has an RF generator that they want to sell...klondike98 — 11:55 AM
Zenith H725
Good ideas, thank you Arrange and Rich. I have the adhesive aluminum foil already and can try that immediately. More ...EdHolland — 10:18 AM
Graphics for majestic 1050 dial glass.
Murf; I found this thread on the ARF, the first photo has a pretty good view of the dial glass. Regards ArranArran — 01:12 AM
Zenith H725
hello Ed, how about that speacial tape used for ducting it's like foil or how about thin piece of aluminum roof flash...radiorich — 12:19 AM
Zenith H725
Ed; One material that I have seen, but never tried for this was material for making exhaust gaskets, it's similar to ...Arran — 11:42 PM
Zenith H725
I just remembered, I have some hi temp silicone rubber material which could do the trick. Or a piece of FR4 laminate. Th...EdHolland — 08:39 PM
Zenith H725
The PSU filter cap arrived today (thank you USPS!) so I will work on that later. Meanwhile, I have the dial, speaker...EdHolland — 06:42 PM
Philco 610B oscillator wiring
Thanks Terry. After checking my notes I think I recorded about -10v at the 6A7 G4/control grid. The screen grid (G3 &...Tubester — 05:59 PM

[-]
Who's Online
There are currently no members online.

>