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19lz shadow meter - Printable Version

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+--- Thread: 19lz shadow meter (/showthread.php?tid=1158)


19lz shadow meter - philco phan - 05-31-2008

hi ron,i picked up the 19lz today.the grillcloth has been replaced with red diamond cloth and looks o.k. for now,i'll take care of that later.the cabinet has been very well refinished a few years ago i guess and is excellant.

i've rebuilt the power supply,tested/replaced tubes and resistors as needed and i've done a partial recap. my problem is no shadow meter action. the coil tests good but i don't understand how it works. is it controlled by a.v.c. voltage like an eye tube? if so i have no voltage at the centertap of volume control so is this the problem? any clues/help appreciated,phil

- Chuck Schwark - 05-31-2008

The Shadow Meter does, indeed, respond to AVC action, indirectly as the front-end tube's plate current swings. The meter is in the B+ line to these tubes. Therefore, unless the set is accurately aligned and has a suitable antenna, the average AVC voltage will not be lage enough to show a reasonable shadow movement. Also, due to age, the bias magnet in the shadow meter may be weak and also contribute to "weak" movement.


See the Service Tips page on the Shadow Meter on my site.

Chuck

- philco phan - 06-01-2008

hi chuck,thanks for the reply. i have completely recapped this radio with the exception of the 700pf cap and the 110pf caps as i'm out of stock,will those parts effect the meter?
the alignment is done and i'm on a 100ft longwire,reception/performance is outstanding,just gotta figure out the meter. i have almost 2 volts neg avc on a strong station,is that enough?
phil

- Ron Ramirez - 06-01-2008

The 110 pF caps will affect the AVC, while the 700 pF cap will affect the local oscillator.

I *think* you should have a bit more negative AVC voltage on very strong stations, more like -4 to -5 volts? Replacement of the 110 pF caps should correct this. The originals were wound paper, just like the larger value caps in bakelite block containers, and are probably leaky. Later replacement bakelite blocks used mica caps.

- philco phan - 06-01-2008

i'll replace those caps when i can restock next weekend,i found the meter's coil is open and has been jumpered to feed b+ to the front-end,would you like to rewind the coil for me?or do you have a good used for sale? let me know,phil
phil

- Ron Ramirez - 06-01-2008

philco phan Wrote:would you like to rewind the coil for me?

I wouldn't mind...but too many radios to fix here (for other people), not enough time...

Quote:or do you have a good used for sale?

Sorry, no, I don't have any good spares.

- Texasrocker - 06-04-2008

I have a spare tested & working shadowmeter I removed from a Canadian made Philco. If I remember correctly, the Canada Philco model was a 38-C9 ? .... which is equilavent to American made 38-8 "shoulder-tombstone" style cabinet vs Canadian made tabletop cab.
The shadowmeter I have is the "newer" style as shown on Chucks website. If it will work, PM me. The coil is good and I already replaced the wires with new, and added new bulb. It worked well on my bench in the Philco chassis I removed it from!
I was going to hang-on to it, but if it will help another restorer, I will sell it. This is the type shadowmeter, that uses the 2-spring type clips that *snaps-on*, & holds it behind the round Philco brass escutcheon assy.
Perhaps the one I have is a totally-different item altogether?
I work on so many different brands vintage radios for customers, I cant remember all the different brands particular items anymores without taking time to seek verification or looking closely at vintage part numbers on old schematics,etc. Just tryin to help my friends here if I have the spare parts you are seeking. Perhaps Ron or Chuck can help verify if my good vintage Philco spare shadowmeter will fit your application. Right now, Im into reworking another 1936 model tabletop Truetone for a customer,( popular brand amongst buyers),.. and am "focused" on getting that project done in my vast amount of spare-time. (Hee Hee, wish I had more hobby-time indeed)! My wife just brought in a another Philco mod 65 lowboy in great orig condition she found at a antique shop in Fredericksburg Tx. She purchased it for $40. SWEET orig condition! I have another Philco model 65 lowboy in our collection I restored a few yrs ago, and for TRF , it sounds great! I like the compact-size and styling of those early model 65 lowboy Philco consoles! Good luck with all your Philco restorations, and if I can help anyway, lemme know via PM. Icon_wink Sincerely, Randal

- philco phan - 06-04-2008

thanks for the offer randal but a member of another forum is doing the rewind,he has a rig to do it,thanks,phil